Greetings to all,
Many thanks to Joe K, who forwarded to me an interesting article about the impact of an island on downstream oceanic currents; which appears to be even more profound than its impact on air currents. One of the intruiging aspects of the article was that the scientists studying the phenomena did not realize the extent of it until they were aboe to pull back and look at the big picture. I thought that for this posting I'd attempt to do the same thing. Whereas in my last post I took a brief look at meteorological impacts on an individual basis, this time I have chosen three examples of how weather events effect the bigger picture, from a medical standpoint. One is "ancient" history, the other two more recent. Please note however, how the ramifications of the historic weather are with us still.
The first case is explored at length in a fascinating book called "Catastrophe" by David Keys. To set the stage, in the year 542AD, the world situation is poised for change. Justinian is the ruler of the Eastern Roman Empire, headquartered in Constantinople and is ready to reabsorb the fallen Western Roman Empire, formerly run from Rome. Despite not being what it was, the Roman Empire, as reconstituted in the east, was still a world power with widespread trade relations; even as far distant as the coast of East Africa, where a thriving set of village ports exported foodstuffs from an interior that practiced labor intensive farming. On his Eastern frontier Justinian has to contend with one of the other two local powers, Persia. At the same time, in Yemen a fledgling but rising state is making use of dams and irrigation development to dominate the southern part of the Arabian Peninsula.
So what happened? Justinian failed, utterly to reconquer the West. The Persian empire dwindled into feebleness. The Yemenites vanished. And all this happened probably because of a change in the weather in East Africa. As Keys relates it, and I think he is on to something here, it was a classic example of meteorological cause and effect.
Approximately seven years earlier, probably the most massive volcanic eruption in the past fifty thousand years had blown a gigantic caldera into that portion of Indonesia known as Krakatoa. This eruption was many many times stroner than the 1990's eruption of Pinatubo, and it affected climat on a global scale for years afterward. One of the things it did was change the rainfall pattern in East Africa, bringing more rain to the region. Under wetter conditions, certain species of rats flourished. So did the disease carrying fleas that lived on the rats.
It is theorized that the rats migrated east towards the coast, changing the landscape as they went. Large numbers of the inhabitants died. The land use, because of a sudden labor scarcity, changed from labor intensive farming, to the pastoral cattle raisng tribes such as the masai of today.
Upon reaching the coast, a migration that took some years, the rats took cruises on the trade vessels, north to the Eastern Roman Empire. In their wake, the coastal villages died, having nothing more from the interior to trade and no one left to trade it. Along the way the rats might have looke out at the demise of the Yemenite civilization. The same unusually heavy rain pattern that had such an impact on East Africa had also fallen on Yemen; where it is speculated that the combination of too much rain for the dams, and a sickening population unable to maintain infrastructure, accounted for the failure and disappearance of a regional power. Finally, upon arrival in Constantinople, the rats and their flea(ing) passengers (sorry, couldn't help making that pun) spread out to cause what may have been the world's first pandemic. It was called the Plague of Justinian's, and killed an extraordinary number of the citizenry of the empire, dooming Justininian's hope of conquest of the west. Today we know the disease as bubonic plague, and it was to debilitate the local powers in waves for the next several decades.
So what, you might ask. All this was long ago and far away, and matters not at all now days. That might have been true, except for one additional little bit of history. All three of the power structure of the mid to late sixth century were enormously adveresely impacted by that changing climate pattern. Their debilitation, retreat, and or disappearance, left a vacuum in that part of the world, such that there was no regional power strong enough to stand against the rise of Islam, early in the 600's. And you need only look at today's headlines to know that the effects of that are still with us.
End of Part One - in Part Two I'll bring things up to date, in a manner of speaking.
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Justice Is Coming
For the Otherwise
Moderator: Super Moderators
-
Guest
Greetings to all,
In Part One I looked at an example of how a change in the weather pattern brought about a change in the epidemiological pattern and subsequently a change in history. In Part Two I'd like to look at a couple of more meteorological pattern changes, and examples of their impact on the biometeorological menu. The historic example I cited was brought about by a massive volcanic eruption, which changed the weather for the worse. However, it doesn't take as much as that to bring about change.
In 1993 a sudden rash of deaths took place on the Navajo reservation in the Four Corners area of the United States, where Utah, Arizona, New Mexico, and Colorado adjoin. The striking thing about most of these deaths was the swiftness with which they took place from appearance of initial effects, given that most of the victims were strong healthy young adults; usually the last group to succumb to any sort of disease, long after children and the elderly sicken and die. After intensive investigation, well detailed in "The Coming Plague" by Laurie Garrett, the Centers for Disease Control determined that the culprit was something called a hantavirus. I'll leave it to ou to read more about just what a hantavirus is, and turn instead to the question of why there, and why then. The answer turned out to be ultimately meteorological in origin.
As it happened, that particular hanta virus was associated with a rodent species called deer mouse. The local deer mouse population had recently boomed. Navajo tribal elders, who probably don't miss much of what goes on about them, had noted a previous increase in the nuts/seeds that constituted the main source of food for the mice. More food meant more mice, and more mice around, mostly outdoors, meant more possibility of exposure to them by the healthy members of the Navajo tribe who got out and about; hence the reason why the healthy young adult Navajo were more likely to contract the disease.
So why was there an increase in the mouse food supply? The answer to that question was that the normal local rainfall patterns had changed for a season, with much more rain falling than during the previous several "rainy seasons" in what is a dry part of the country. More rainfall meant more plant growth and consequently more mouse food. And the reason for the increase in the rainfall brings us to a term with which we've all become more familiar in recent years. El Nino.
In the April 2, 2002 issue of EOS, Transactions of the American Geophysical Union, there is another article on El Nino; this one with the title "El Nino Helps Spread Bartonellosis Epidemics in Peru". For those of you who don't know what bartonellosis is, and I'll confess I didn't, allow me to quote: "Bartonellosis is characterized by two well-defined clinical stages, including an acute pahse of life threatening anemia (Oroya fever), during which the death rate may exceed 40% in untreated patients; and a chronic form that manifests as blood filled wart-like skin lesions or subcutaneous nodules (verruga peruana)." Sounds grim, doesn't it? The vector, or carrier of this disease, is a species of sand fly.
Where El Nino comes into play is, once again, by changing the local temperature and rainfall patterns. Increased rainfall and an increased minimum temperature, associated with El Nino development, is particularly conducive to Peruvian sand fly population explosions. Efforts are presently underway to better forecast the ecology and mechanism of bartonellosis epidemics, with the goal of providing two to three month forecast lead times; or enough time to take action to mitigate the severity of any forecast epidemic. Good luck, I struggle sometimes to get tomorrow's forecast accurate.
I think the length at which I've written should suffice for now as an introduction to things biometeorological. As always I welcome your feedback. I'd hoped to finish this post with some particularly witty quip but nothing comes to mind. Meanwhile, Maryals is summoning me, so I'd better bug out for now.
Rainmaker
------------------
Justice Is Coming
In Part One I looked at an example of how a change in the weather pattern brought about a change in the epidemiological pattern and subsequently a change in history. In Part Two I'd like to look at a couple of more meteorological pattern changes, and examples of their impact on the biometeorological menu. The historic example I cited was brought about by a massive volcanic eruption, which changed the weather for the worse. However, it doesn't take as much as that to bring about change.
In 1993 a sudden rash of deaths took place on the Navajo reservation in the Four Corners area of the United States, where Utah, Arizona, New Mexico, and Colorado adjoin. The striking thing about most of these deaths was the swiftness with which they took place from appearance of initial effects, given that most of the victims were strong healthy young adults; usually the last group to succumb to any sort of disease, long after children and the elderly sicken and die. After intensive investigation, well detailed in "The Coming Plague" by Laurie Garrett, the Centers for Disease Control determined that the culprit was something called a hantavirus. I'll leave it to ou to read more about just what a hantavirus is, and turn instead to the question of why there, and why then. The answer turned out to be ultimately meteorological in origin.
As it happened, that particular hanta virus was associated with a rodent species called deer mouse. The local deer mouse population had recently boomed. Navajo tribal elders, who probably don't miss much of what goes on about them, had noted a previous increase in the nuts/seeds that constituted the main source of food for the mice. More food meant more mice, and more mice around, mostly outdoors, meant more possibility of exposure to them by the healthy members of the Navajo tribe who got out and about; hence the reason why the healthy young adult Navajo were more likely to contract the disease.
So why was there an increase in the mouse food supply? The answer to that question was that the normal local rainfall patterns had changed for a season, with much more rain falling than during the previous several "rainy seasons" in what is a dry part of the country. More rainfall meant more plant growth and consequently more mouse food. And the reason for the increase in the rainfall brings us to a term with which we've all become more familiar in recent years. El Nino.
In the April 2, 2002 issue of EOS, Transactions of the American Geophysical Union, there is another article on El Nino; this one with the title "El Nino Helps Spread Bartonellosis Epidemics in Peru". For those of you who don't know what bartonellosis is, and I'll confess I didn't, allow me to quote: "Bartonellosis is characterized by two well-defined clinical stages, including an acute pahse of life threatening anemia (Oroya fever), during which the death rate may exceed 40% in untreated patients; and a chronic form that manifests as blood filled wart-like skin lesions or subcutaneous nodules (verruga peruana)." Sounds grim, doesn't it? The vector, or carrier of this disease, is a species of sand fly.
Where El Nino comes into play is, once again, by changing the local temperature and rainfall patterns. Increased rainfall and an increased minimum temperature, associated with El Nino development, is particularly conducive to Peruvian sand fly population explosions. Efforts are presently underway to better forecast the ecology and mechanism of bartonellosis epidemics, with the goal of providing two to three month forecast lead times; or enough time to take action to mitigate the severity of any forecast epidemic. Good luck, I struggle sometimes to get tomorrow's forecast accurate.
I think the length at which I've written should suffice for now as an introduction to things biometeorological. As always I welcome your feedback. I'd hoped to finish this post with some particularly witty quip but nothing comes to mind. Meanwhile, Maryals is summoning me, so I'd better bug out for now.
Rainmaker
------------------
Justice Is Coming
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eliza_nightvoice
- Pirate
- Posts: 1814
- Joined: 01-20-2002 03:00 AM
Hi, Rainmaker, have a question that I haven't seen addressed in any of my 'net searches.
What factors influence the northern jet stream? This winter the stream didn't drop down across the mid states like it usually does and a result was that we didn't get many "Alberta Clippers" and warm air was pumped up from the Gulf of Mexico. All contributing to our freakily warm winter.
Now, with the high number of record breaking high temps as far north as Minnesota, it appears that the stream may be retreating further north, and I don't really want to see what happens this summer. If it's in the 90's in April around here, I'm going to have to figure out how to make my refridgerator a studio apartment!
What factors influence the northern jet stream? This winter the stream didn't drop down across the mid states like it usually does and a result was that we didn't get many "Alberta Clippers" and warm air was pumped up from the Gulf of Mexico. All contributing to our freakily warm winter.
Now, with the high number of record breaking high temps as far north as Minnesota, it appears that the stream may be retreating further north, and I don't really want to see what happens this summer. If it's in the 90's in April around here, I'm going to have to figure out how to make my refridgerator a studio apartment!
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Cherry Kelly
- Pirate
- Posts: 12852
- Joined: 07-29-2000 02:00 AM
- Contact:
Jet streams are strange - and when they touch down close to earth cause all kinds of havoc (see Pahrump, NV reports and others from that area where 70mph sustained winds were reported).
We need rain - ponds, rivers, lakes and streams are very low. Too low! We went from winter to summer with perhaps a week of what could be called "normal spring" if that.
We need rain - ponds, rivers, lakes and streams are very low. Too low! We went from winter to summer with perhaps a week of what could be called "normal spring" if that.
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Guest
Greetings to all,
This post will be in response to your questions and comments about the jet stream. I don't know that it will answer all your questions because, for one thing, I am not sure I have all the answers. However, I might be able to clear up a few misconceptions. I'll know in your responses. (Note to Joe K - Maryals did pass your message/site recommendation on to me. Many thanks, again, for it. I thought I mentioned that in the previous post)
Nightvoice has asked what factors influence the "northern jetstream", a question to which there is no simple answer. So, I'll start with the basics, fluid dynamics 101. That is the starting point because the atmosphere acts like a fluid, obeying those laws of fluid dynamics, with certain comparatively minor differences; and also because, unlike surface fluids such as rivers, the atmosphere and it's jet streams are not constrained by river banks. Thus the meandering effect of a gaseous jet stream is much greater than that of a surface stream.
Another important point here is that this ocean of air is on the surface of a rotating planet, subject to centrifugal forces and differential heating. What this means is that the thickness of the layer of gas will vary with it's proximity to the equator, and the temperature/pressure combinations accorded to a specific portion of that gas will vary according to whether it is north, south, sunlit, or dark. With these points in mind we can continue to basic fluid dynamics 102.
Since the atmosphere is affected by the spin of the earth, it is thickest at the equator, most thin in the polar regions. We are speaking of the lower layer of the atmosphere here, known as the troposphere. And while it seems like you would have a smooth decline in height with latitude, that isn't really the case. Rather there are what might be described as overlapping leaves of atmosphere, with the point of overlap at the juncture between the troposphere and the stratosphere. Anytime there is a dsicontinuity in the atmosphere there is generally a transfer of energy at that point. The jet stream represents a major transfer of energy at the atmospheric leaf overlap points.
What that gives us in the northern hemisphere (and the southern) are not one continuous jet stream, but instead, several discontinuous ones, dependent upon latitude, etc. Near the equator you've got a high level equatorial jet. In the mid latitudes, including the continental U. S. the major player is know as the polar jet, and is responsible for a tremendous latitudinal transfer of energy, generally in the form of heat. Those of us in Alaska not only get the effects of the polar jet but we also have it's northen cousin, the arctic jet, to contend with. Polar jets may be found around thirty to forty thousand feet up depending again on how close to the equator you are. Arctic jets are about ten thousand feet lower in the thinner atmosphere of the arctic regions. There are also some special cases of seasonal jet streams, and also a low level jet associated with severe weather, but these are not pertinent to our
discussion here.
For now, let's stick with the polar jet. If you go back to one of my earlier posts, you'll recall that I wrote at length about the meteorological phenomena known as semi permanent pressure systems and long wave patterns. To refresh your memory, at any given time there are several large semi permanent quasi stationary pressure systems (the Bermuda High is an example) active in the northern hemisphere. They can be delineated by what is called the long wave pattern, a pattern of three to seven troughs of deep low pressure that move slowly about the globe. So, you have a large high pressure system bordered by a low pressure trough. The high pressure waxes and wanes, and some even vanish temporarily, allowing the troughs to advance or retrograde (retreat). This is important because the undulating movement of the polar jet stream is linked to the movement of those long wave troughs.
A good example of this has taken place the last several days here in Alaska, where a long generally cold winter has been reluctant
to let go. We had a large continental high pressure system anchored along the Canadian border, providing us with sunny days and clear cold nights. Here in Anchorage the temperature would drop down into the single digits, well below normal for this time of year. In the past three days however, that pattern has changed entirely. The high advanced to the east, weakened to the west where Alaska is in reference to it. A long wave trough has advanced such that most of Alaska's weather is now being driven in from the southwest, out of the Pacific Ocean. Our temperatures climbed into the 40s, with 20s and 30s at night, plus we've clouded over, and gotten some light rain. This long wave trough is associated with a strong jet stream that stretches all the way back to Japan, so we can expect this Seattle like weather for quite some time to come. Similar mechanisms, as explained, are responsible for seasonal patterns in the continental U.S. where a lot of what any particular season is like depends on what particular part of the long wave pattern and associated jet stream oscillates across your location at a given time.
I'll conclude this with a couple of more important notes. First, to correct a misconception, with the exception of Mt. Washington, New Hampshire and a few other high mountain locations, the jet stream does not touch down to the surface of the earth. There are almost certainly more mundane explanations (horses not zebras) as to the recent winds referenced in Nevada. In point of fact, most meteorologists don't start looking at winds aloft as being in the category of jet stream until they approach ninety to one hundred knots.
The other point to remember here is that nature abhors a vacuum and always seeks a balance. To those I work with who complained of the late cold "spring" we are enduring here I suggested that their warmth wishes would come true in the form of a cloudy rainy summer. So for those of you thinking of converting refrigerators into studio apartments, you may want to also keep open the option of remaking your icebox into a covered hot tub.
Rainmaker
------------------
Justice Is Coming
This post will be in response to your questions and comments about the jet stream. I don't know that it will answer all your questions because, for one thing, I am not sure I have all the answers. However, I might be able to clear up a few misconceptions. I'll know in your responses. (Note to Joe K - Maryals did pass your message/site recommendation on to me. Many thanks, again, for it. I thought I mentioned that in the previous post)
Nightvoice has asked what factors influence the "northern jetstream", a question to which there is no simple answer. So, I'll start with the basics, fluid dynamics 101. That is the starting point because the atmosphere acts like a fluid, obeying those laws of fluid dynamics, with certain comparatively minor differences; and also because, unlike surface fluids such as rivers, the atmosphere and it's jet streams are not constrained by river banks. Thus the meandering effect of a gaseous jet stream is much greater than that of a surface stream.
Another important point here is that this ocean of air is on the surface of a rotating planet, subject to centrifugal forces and differential heating. What this means is that the thickness of the layer of gas will vary with it's proximity to the equator, and the temperature/pressure combinations accorded to a specific portion of that gas will vary according to whether it is north, south, sunlit, or dark. With these points in mind we can continue to basic fluid dynamics 102.
Since the atmosphere is affected by the spin of the earth, it is thickest at the equator, most thin in the polar regions. We are speaking of the lower layer of the atmosphere here, known as the troposphere. And while it seems like you would have a smooth decline in height with latitude, that isn't really the case. Rather there are what might be described as overlapping leaves of atmosphere, with the point of overlap at the juncture between the troposphere and the stratosphere. Anytime there is a dsicontinuity in the atmosphere there is generally a transfer of energy at that point. The jet stream represents a major transfer of energy at the atmospheric leaf overlap points.
What that gives us in the northern hemisphere (and the southern) are not one continuous jet stream, but instead, several discontinuous ones, dependent upon latitude, etc. Near the equator you've got a high level equatorial jet. In the mid latitudes, including the continental U. S. the major player is know as the polar jet, and is responsible for a tremendous latitudinal transfer of energy, generally in the form of heat. Those of us in Alaska not only get the effects of the polar jet but we also have it's northen cousin, the arctic jet, to contend with. Polar jets may be found around thirty to forty thousand feet up depending again on how close to the equator you are. Arctic jets are about ten thousand feet lower in the thinner atmosphere of the arctic regions. There are also some special cases of seasonal jet streams, and also a low level jet associated with severe weather, but these are not pertinent to our
discussion here.
For now, let's stick with the polar jet. If you go back to one of my earlier posts, you'll recall that I wrote at length about the meteorological phenomena known as semi permanent pressure systems and long wave patterns. To refresh your memory, at any given time there are several large semi permanent quasi stationary pressure systems (the Bermuda High is an example) active in the northern hemisphere. They can be delineated by what is called the long wave pattern, a pattern of three to seven troughs of deep low pressure that move slowly about the globe. So, you have a large high pressure system bordered by a low pressure trough. The high pressure waxes and wanes, and some even vanish temporarily, allowing the troughs to advance or retrograde (retreat). This is important because the undulating movement of the polar jet stream is linked to the movement of those long wave troughs.
A good example of this has taken place the last several days here in Alaska, where a long generally cold winter has been reluctant
to let go. We had a large continental high pressure system anchored along the Canadian border, providing us with sunny days and clear cold nights. Here in Anchorage the temperature would drop down into the single digits, well below normal for this time of year. In the past three days however, that pattern has changed entirely. The high advanced to the east, weakened to the west where Alaska is in reference to it. A long wave trough has advanced such that most of Alaska's weather is now being driven in from the southwest, out of the Pacific Ocean. Our temperatures climbed into the 40s, with 20s and 30s at night, plus we've clouded over, and gotten some light rain. This long wave trough is associated with a strong jet stream that stretches all the way back to Japan, so we can expect this Seattle like weather for quite some time to come. Similar mechanisms, as explained, are responsible for seasonal patterns in the continental U.S. where a lot of what any particular season is like depends on what particular part of the long wave pattern and associated jet stream oscillates across your location at a given time.
I'll conclude this with a couple of more important notes. First, to correct a misconception, with the exception of Mt. Washington, New Hampshire and a few other high mountain locations, the jet stream does not touch down to the surface of the earth. There are almost certainly more mundane explanations (horses not zebras) as to the recent winds referenced in Nevada. In point of fact, most meteorologists don't start looking at winds aloft as being in the category of jet stream until they approach ninety to one hundred knots.
The other point to remember here is that nature abhors a vacuum and always seeks a balance. To those I work with who complained of the late cold "spring" we are enduring here I suggested that their warmth wishes would come true in the form of a cloudy rainy summer. So for those of you thinking of converting refrigerators into studio apartments, you may want to also keep open the option of remaking your icebox into a covered hot tub.
Rainmaker
------------------
Justice Is Coming
RAINMAKER any idea on what caused the event here in pahrump nv?????????????? if so email or me on my radio show tonite [email protected]
7 pm pst turtle
ps are e mail on the pahrumpradio.com web page is screeeeewwwed upppppp use this one or call if u can
[This message has been edited by turtle101 (edited 19 April 2002).]
7 pm pst turtle
ps are e mail on the pahrumpradio.com web page is screeeeewwwed upppppp use this one or call if u can
[This message has been edited by turtle101 (edited 19 April 2002).]
Due to current economic conditions the light at the end of the tunnel has been turned off.
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Guest
Greetings to all,
And sorry Turtle that I did not respond to your request for a radio program appearance. I elected not to for several reasons, one being that our home computer is antiquated and mute, so I don't suppose I could have participated anyway. Second, to have done so would have pushed me uncomfortably close to the line of seeming to be an official spokeperson for the agency for which I work, which would have been strictly verboten. To get the answer you want as to what actually happened in Nevada you'd be better served by asking a local professional. I have not looked at the meteorological situation for the time in question and therefore can not tell you defniitively what the cause of the windstorm was. I'd only mentioned what I know for sure it was not, a jet stream scouring the earth's surface. However, in my capacity as whatever I am regarded as on this forum, I am willing to speculate in general terms as to what sorts of meteorological situations might cause straight line wind flow damage.
I use the term straight line, with respect to wind flow damage, to rule out such things as tornados and hurricanes. While the basic mechanism for cyclonic (curved) wind damage is the same as in straight line cases - pressure differential - the pattern of destruction of such events differs. That is why scientists will often go out after reports of wind damage and look at the damage pattern, straight line or curved, so as to narrow the determination of the meteorological cause.
So, let's revisit our previously discussed concept of pressure differentials. What we should be thinking of here is a question of scale. Nature is consistent and will seek to balance an inequality on any scale. The greater the imbalance, the greater the reaction, as per Newton's Laws. Likewise, in terms of time scale, since the prommpting question implied sustained winds, we will ignore in this post short term linnear events such as the passage of squall lines and gust fronts, which are generally of less than an hour's duration.
On a gentle local scale, anyone who lives near the coast can see such a law in effect every day. During the daytime heating period, land heats up more than water and the heated air over land rises. This creates a pressure imbalance with the adjacent body of water, so cooler air over the water moves in to replace the air that was over the land, creating a sea breeze. This cool air, in turn, is heated and rises, to be replaced by more cool air off the water. Meanwhile, the air that was heated earlier, propelled by the convective or heating process, and acquired what is referred to as positive bouyancy. What that means is that the air rose in the atmosphere to a point beyond where it might normally have stabilized in equilibrium with the surrounding air. It then spread out, cooled, acquired a negative bouyancy and started descending, ultimately to the surface to replace the cool air that was drawn over the land. Whallah, now you have a feedback loop. Another example of the same phenomena is common to mountainous areas, and results in mountain/valley breezes.
Now then, let's step up in scale to phenomena which are not so gentle. Note though, the primary difference is one of scale, not mechanism. So, what we will examine are large scale pressure differentiations which are capable of producing high winds and associated damage. Two scenarios come to mind, and both are possible in Nevada, as well as many other parts of the country, and indeed the world.
Scenario one is simple to explain and has produced some colorful local terms. Basically, what happens here is that a large high pressure system will be in close enough proximity to a deep strong low pressure system, for a sustained wind to blow from the high to the low. The greater the pressure differences between the systems, the faster the wind speed. This is common during certain times of the year in the Southwestern U.S., when high pressure over the elevated interior of Nevada, Arizona, etc. drives wind into a low pressure system in coastal California, producing the famed Santa Anna winds. Other names for this wind might be a chinook, or a foehn.
Two other points to note about these sorts of winds. One, they are comparatively low level atmospheric phenomena and therefore may be enhanced by the effects of terrain. Mountains will have the effect of damning pools of air which will then move with even greater force through passed and down valleys, etc. There is a law of physics (Bernoulli's, if I remember correctly including the spelling of his name) which governs movement of fluidic substances in enclosed spaces. But a simple show and tell of what we are trying to envision here is to turn on a garden hose and put your thumb partway over the nozzle whereupon you should be able to feel the increased force and see the greater speed at which water departs the nozzle. Second, there are instances in which the weight of the air itself, generally very cold air, pooling in high cold locations, promotes an increased windspeed when this air finally starts spilling down the mountains. In these special cases, a gravity feed is the mechanism at work; and it has been known to result in what are called katabatic winds in excess of 100 miles per hour off the Greenland and Antarctic ice caps.
The second scenario that comes to mind is also the reult of a pressure differential. here though it works a little bit differently though. What happens is a thunderstorm develops, in proximity to other thunderstorms. When the outflow boundaries of these storms collide, that in turn breeds still more thunderstorms. Given the right conditions you can ultimately wind up with a comples of thunderstorms the size of a state like Iowa. Outflow from these systems -remember the descending cool air from the sea breeze, same mechanism here - can produce long lived straight line winds of seventy miles per hour with even higher gusts, even at a distance many miles from the thunderstorms themselves. The name given to this phenomena is "derecho".
The elucidation of the derecho is a comparatively new discovery in meteorology, within the past twenty years. I've had to learn about it since it was unknown at the time I entered into the career. Proof positive for the doubters among you that even an old dog of a meteorologist can learn new tricks.
Rainmaker.
------------------
Justice Is Coming
And sorry Turtle that I did not respond to your request for a radio program appearance. I elected not to for several reasons, one being that our home computer is antiquated and mute, so I don't suppose I could have participated anyway. Second, to have done so would have pushed me uncomfortably close to the line of seeming to be an official spokeperson for the agency for which I work, which would have been strictly verboten. To get the answer you want as to what actually happened in Nevada you'd be better served by asking a local professional. I have not looked at the meteorological situation for the time in question and therefore can not tell you defniitively what the cause of the windstorm was. I'd only mentioned what I know for sure it was not, a jet stream scouring the earth's surface. However, in my capacity as whatever I am regarded as on this forum, I am willing to speculate in general terms as to what sorts of meteorological situations might cause straight line wind flow damage.
I use the term straight line, with respect to wind flow damage, to rule out such things as tornados and hurricanes. While the basic mechanism for cyclonic (curved) wind damage is the same as in straight line cases - pressure differential - the pattern of destruction of such events differs. That is why scientists will often go out after reports of wind damage and look at the damage pattern, straight line or curved, so as to narrow the determination of the meteorological cause.
So, let's revisit our previously discussed concept of pressure differentials. What we should be thinking of here is a question of scale. Nature is consistent and will seek to balance an inequality on any scale. The greater the imbalance, the greater the reaction, as per Newton's Laws. Likewise, in terms of time scale, since the prommpting question implied sustained winds, we will ignore in this post short term linnear events such as the passage of squall lines and gust fronts, which are generally of less than an hour's duration.
On a gentle local scale, anyone who lives near the coast can see such a law in effect every day. During the daytime heating period, land heats up more than water and the heated air over land rises. This creates a pressure imbalance with the adjacent body of water, so cooler air over the water moves in to replace the air that was over the land, creating a sea breeze. This cool air, in turn, is heated and rises, to be replaced by more cool air off the water. Meanwhile, the air that was heated earlier, propelled by the convective or heating process, and acquired what is referred to as positive bouyancy. What that means is that the air rose in the atmosphere to a point beyond where it might normally have stabilized in equilibrium with the surrounding air. It then spread out, cooled, acquired a negative bouyancy and started descending, ultimately to the surface to replace the cool air that was drawn over the land. Whallah, now you have a feedback loop. Another example of the same phenomena is common to mountainous areas, and results in mountain/valley breezes.
Now then, let's step up in scale to phenomena which are not so gentle. Note though, the primary difference is one of scale, not mechanism. So, what we will examine are large scale pressure differentiations which are capable of producing high winds and associated damage. Two scenarios come to mind, and both are possible in Nevada, as well as many other parts of the country, and indeed the world.
Scenario one is simple to explain and has produced some colorful local terms. Basically, what happens here is that a large high pressure system will be in close enough proximity to a deep strong low pressure system, for a sustained wind to blow from the high to the low. The greater the pressure differences between the systems, the faster the wind speed. This is common during certain times of the year in the Southwestern U.S., when high pressure over the elevated interior of Nevada, Arizona, etc. drives wind into a low pressure system in coastal California, producing the famed Santa Anna winds. Other names for this wind might be a chinook, or a foehn.
Two other points to note about these sorts of winds. One, they are comparatively low level atmospheric phenomena and therefore may be enhanced by the effects of terrain. Mountains will have the effect of damning pools of air which will then move with even greater force through passed and down valleys, etc. There is a law of physics (Bernoulli's, if I remember correctly including the spelling of his name) which governs movement of fluidic substances in enclosed spaces. But a simple show and tell of what we are trying to envision here is to turn on a garden hose and put your thumb partway over the nozzle whereupon you should be able to feel the increased force and see the greater speed at which water departs the nozzle. Second, there are instances in which the weight of the air itself, generally very cold air, pooling in high cold locations, promotes an increased windspeed when this air finally starts spilling down the mountains. In these special cases, a gravity feed is the mechanism at work; and it has been known to result in what are called katabatic winds in excess of 100 miles per hour off the Greenland and Antarctic ice caps.
The second scenario that comes to mind is also the reult of a pressure differential. here though it works a little bit differently though. What happens is a thunderstorm develops, in proximity to other thunderstorms. When the outflow boundaries of these storms collide, that in turn breeds still more thunderstorms. Given the right conditions you can ultimately wind up with a comples of thunderstorms the size of a state like Iowa. Outflow from these systems -remember the descending cool air from the sea breeze, same mechanism here - can produce long lived straight line winds of seventy miles per hour with even higher gusts, even at a distance many miles from the thunderstorms themselves. The name given to this phenomena is "derecho".
The elucidation of the derecho is a comparatively new discovery in meteorology, within the past twenty years. I've had to learn about it since it was unknown at the time I entered into the career. Proof positive for the doubters among you that even an old dog of a meteorologist can learn new tricks.
Rainmaker.
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Justice Is Coming
-
Guest
Greetings to all,
In this psting I'd like to summarize an interesting item from the latest issue of EOS, Transactions of the American Geophysical Union. I suspect this publication is not on the must read list for most of you.
This particular article is called "Ezekiel and the Northern Lights: Biblical Aurora Seems Plausible" by George L. Simcoe, Samuel M. Silverman, and Kieth D. Siebert. The authors suggest that some 2600 years ago, in approximately the year 593BC, it would have been possible for a person at Nippur, about 100KM south of Babylon (when and where Biblical scholars place Ezekiel at the time of his vision) to have witnessed an aurora. As the author's put it, "After careful consideration, there appear to be no geophysical showstoppers to an auroral interpretation of Ezekiel's vision".
In other words, the following set of questions had to be answered in tha affirmitive: "Can auroras be seen at Ezekiel's latitude? More important, can they reach a coronal stage of development, which is what the vision requires? Was the tilt of the dipole axis favorable? Was the general level of solar activity favorable?" It was also necessary to determine if a larger dipole moment in Ezekiel's time would have a favorable effect on the possibility of auroral activity. In answer to the latter question, it turns out that paleomagnetic studies suggest that 2600 years ago the dipole strength was 50% stronger than present day. That being the case, Ezekiels vision might possibly have been of an auroral display of the sort currently most often witnessed by those of us living in latitudes of Alaska.
Evidence supporting the author's conjectures is found in carbon 14 analysis of tree rings for long term variablity of solar activity. That is, the more activity the rings indicate, the greater the probability of sunspots, flares, etc. and thus the greater the chance for a major auroral display. This analysis looks at a broader scale than the eleven year sunspot cycle. As it happens, Ezekiel's vision of circa 593BC came during the greatest C14 readings in the past four millenia.
There have been other explanations ascribed to Ezekiel"s vision, including tornado's, solar halos, sandstorms, (horses all) as well as a true epiphany or even a UFO (zebra's both). The addition of the possibility of an auroral explanation to the horse herd of reasonings is a prime example of scientists attempts to find natural explanations for supernaturally suggested events.
Rainmaker
------------------
Justice Is Coming
In this psting I'd like to summarize an interesting item from the latest issue of EOS, Transactions of the American Geophysical Union. I suspect this publication is not on the must read list for most of you.
This particular article is called "Ezekiel and the Northern Lights: Biblical Aurora Seems Plausible" by George L. Simcoe, Samuel M. Silverman, and Kieth D. Siebert. The authors suggest that some 2600 years ago, in approximately the year 593BC, it would have been possible for a person at Nippur, about 100KM south of Babylon (when and where Biblical scholars place Ezekiel at the time of his vision) to have witnessed an aurora. As the author's put it, "After careful consideration, there appear to be no geophysical showstoppers to an auroral interpretation of Ezekiel's vision".
In other words, the following set of questions had to be answered in tha affirmitive: "Can auroras be seen at Ezekiel's latitude? More important, can they reach a coronal stage of development, which is what the vision requires? Was the tilt of the dipole axis favorable? Was the general level of solar activity favorable?" It was also necessary to determine if a larger dipole moment in Ezekiel's time would have a favorable effect on the possibility of auroral activity. In answer to the latter question, it turns out that paleomagnetic studies suggest that 2600 years ago the dipole strength was 50% stronger than present day. That being the case, Ezekiels vision might possibly have been of an auroral display of the sort currently most often witnessed by those of us living in latitudes of Alaska.
Evidence supporting the author's conjectures is found in carbon 14 analysis of tree rings for long term variablity of solar activity. That is, the more activity the rings indicate, the greater the probability of sunspots, flares, etc. and thus the greater the chance for a major auroral display. This analysis looks at a broader scale than the eleven year sunspot cycle. As it happens, Ezekiel's vision of circa 593BC came during the greatest C14 readings in the past four millenia.
There have been other explanations ascribed to Ezekiel"s vision, including tornado's, solar halos, sandstorms, (horses all) as well as a true epiphany or even a UFO (zebra's both). The addition of the possibility of an auroral explanation to the horse herd of reasonings is a prime example of scientists attempts to find natural explanations for supernaturally suggested events.
Rainmaker
------------------
Justice Is Coming
-
Guest
Greetings to all,
For this posting I'd like to briefly revisit and update a couple of recently discussed topics, contrails and dust storms.
In the current edition of BAMS, the Bulletin of the American Meteorological Society, David Travis of the University of Wisconsin -Whitewater - and Andrew M Carleton and Ryan Lauritsen (no affiliate provided), described an interesting, if unintential, experiment they conducted on the impact of contrails. It starts with the presumption that every day, at any given moment, thousands of aircraft are aloft over the continental United States. Many of these aircraft are presumed to produce contrails. However, within a three hour period, on September 11, 2001, every single commercial and general aviation plane was grounded. No aircraft presumes no contrails. The authors took a look at what changes might have been caused by this singular lack of contrails.
In particular the authors looked at the diurnal temperature range, that is the daily range between high an low tempertures; after determining that - according to satellite imagery, and logically enough - there were virtually no contrails from September 11-13, other than those from a few military aircraft. The authors determined that the reduction in contrails corresponded to a reduction in cirrus cloud cover over those areas subject to the heaviest high level air traffic. In turn, it is speculated that the lack of cirrus cloud cover produced diurnal temperature anomalies in those areas. That is, the daily temperatures were warmer than might have been expected, the night time temperature were cooler. The reason behind the anomolies is that the ice crystals composing cirrus clouds, during the day, reflect and scatter incoming sunlight/solar radiation and so less of it reaches the surface to heat it. Fewer clouds means more direct sunlight, and hence warmer surface temperatures. At night the same cirrus clouds act to block and retain outgoing terrestrial long wave infrared radiation - the greenhouse effect - thus keeping it close to home and heating the surface. With no cirrus clouds less radiation was blocked, more escaped to outer space, and thus surface temperatures were cooler.
The consequences of this unintended experiment indicate that there is no necessity for the intentional introduction of artificial aerosols into the atmosphere, as was suggested by some folks in other venues, and previously discussed here. Rather, we are doing a pretty good, if unintentional, job of modifying the climate already.
As to the subject of dust storms, the topic has come up at a scientific conference I am currently attending. The subject of the conference is the operational impact of volcanic eruptions and ash dispersal in the atmosphere. Where the subject of dust storms comes in is that sometimes the dust storms have a high sulfer dioxide content, just as certain types of volcanic ash does. The presence of one, the dust, can mask the presence of the other, the ash, on certain types of satellite imagery, with operational impacts for aviation, health, and other interests. An example of this is where dust from Saharan storms reaches the Caribbean Sea and has interacted with ash from volcanic eruptions of a Montserrat volcano.
The net result is that trying to distinguish the ash from the dust can sometimes be likened to trying to pick out a polar bear in a blizzard.
Another point, emphatically made in the conference, is that dust from springtime storms in the Gobi Desert of Mongolia, does indeed sometimes make it as far as the west coast of the U.S. the process takes about ten days, with as yet undetermined health impacts for residents of California, Oregon, etc. The trajectory of the dust flow generally splits around the semi permanent Pacific high, with a northern branch reaching Alaska. However, the impact here in Alaska is much mitigated due to extensive springtime precipitation of a frequency and sometimes of a sort not common in lower latitudes.
Rainmaker
------------------
Justice Is Coming
For this posting I'd like to briefly revisit and update a couple of recently discussed topics, contrails and dust storms.
In the current edition of BAMS, the Bulletin of the American Meteorological Society, David Travis of the University of Wisconsin -Whitewater - and Andrew M Carleton and Ryan Lauritsen (no affiliate provided), described an interesting, if unintential, experiment they conducted on the impact of contrails. It starts with the presumption that every day, at any given moment, thousands of aircraft are aloft over the continental United States. Many of these aircraft are presumed to produce contrails. However, within a three hour period, on September 11, 2001, every single commercial and general aviation plane was grounded. No aircraft presumes no contrails. The authors took a look at what changes might have been caused by this singular lack of contrails.
In particular the authors looked at the diurnal temperature range, that is the daily range between high an low tempertures; after determining that - according to satellite imagery, and logically enough - there were virtually no contrails from September 11-13, other than those from a few military aircraft. The authors determined that the reduction in contrails corresponded to a reduction in cirrus cloud cover over those areas subject to the heaviest high level air traffic. In turn, it is speculated that the lack of cirrus cloud cover produced diurnal temperature anomalies in those areas. That is, the daily temperatures were warmer than might have been expected, the night time temperature were cooler. The reason behind the anomolies is that the ice crystals composing cirrus clouds, during the day, reflect and scatter incoming sunlight/solar radiation and so less of it reaches the surface to heat it. Fewer clouds means more direct sunlight, and hence warmer surface temperatures. At night the same cirrus clouds act to block and retain outgoing terrestrial long wave infrared radiation - the greenhouse effect - thus keeping it close to home and heating the surface. With no cirrus clouds less radiation was blocked, more escaped to outer space, and thus surface temperatures were cooler.
The consequences of this unintended experiment indicate that there is no necessity for the intentional introduction of artificial aerosols into the atmosphere, as was suggested by some folks in other venues, and previously discussed here. Rather, we are doing a pretty good, if unintentional, job of modifying the climate already.
As to the subject of dust storms, the topic has come up at a scientific conference I am currently attending. The subject of the conference is the operational impact of volcanic eruptions and ash dispersal in the atmosphere. Where the subject of dust storms comes in is that sometimes the dust storms have a high sulfer dioxide content, just as certain types of volcanic ash does. The presence of one, the dust, can mask the presence of the other, the ash, on certain types of satellite imagery, with operational impacts for aviation, health, and other interests. An example of this is where dust from Saharan storms reaches the Caribbean Sea and has interacted with ash from volcanic eruptions of a Montserrat volcano.
The net result is that trying to distinguish the ash from the dust can sometimes be likened to trying to pick out a polar bear in a blizzard.
Another point, emphatically made in the conference, is that dust from springtime storms in the Gobi Desert of Mongolia, does indeed sometimes make it as far as the west coast of the U.S. the process takes about ten days, with as yet undetermined health impacts for residents of California, Oregon, etc. The trajectory of the dust flow generally splits around the semi permanent Pacific high, with a northern branch reaching Alaska. However, the impact here in Alaska is much mitigated due to extensive springtime precipitation of a frequency and sometimes of a sort not common in lower latitudes.
Rainmaker
------------------
Justice Is Coming
-
Guest
Greetings to all,
For this posting I'd like to briefly revisit and update a couple of recently discussed topics, contrails and dust storms.
In the current edition of BAMS, the Bulletin of the American Meteorological Society, David Travis of the University of Wisconsin -Whitewater - and Andrew M Carleton and Ryan Lauritsen (no affiliate provided), described an interesting, if unintential, experiment they conducted on the impact of contrails. It starts with the presumption that every day, at any given moment, thousands of aircraft are aloft over the continental United States. Many of these aircraft are presumed to produce contrails. However, within a three hour period, on September 11, 2001, every single commercial and general aviation plane was grounded. No aircraft presumes no contrails. The authors took a look at what changes might have been caused by this singular lack of contrails.
In particular the authors looked at the diurnal temperature range, that is the daily range between high an low tempertures; after determining that - according to satellite imagery, and logically enough - there were virtually no contrails from September 11-13, other than those from a few military aircraft. The authors determined that the reduction in contrails corresponded to a reduction in cirrus cloud cover over those areas subject to the heaviest high level air traffic. In turn, it is speculated that the lack of cirrus cloud cover produced diurnal temperature anomalies in those areas. That is, the daily temperatures were warmer than might have been expected, the night time temperature were cooler. The reason behind the anomolies is that the ice crystals composing cirrus clouds, during the day, reflect and scatter incoming sunlight/solar radiation and so less of it reaches the surface to heat it. Fewer clouds means more direct sunlight, and hence warmer surface temperatures. At night the same cirrus clouds act to block and retain outgoing terrestrial long wave infrared radiation - the greenhouse effect - thus keeping it close to home and heating the surface. With no cirrus clouds less radiation was blocked, more escaped to outer space, and thus surface temperatures were cooler.
The consequences of this unintended experiment indicate that there is no necessity for the intentional introduction of artificial aerosols into the atmosphere, as was suggested by some folks in other venues, and previously discussed here. Rather, we are doing a pretty good, if unintentional, job of modifying the climate already.
As to the subject of dust storms, the topic has come up at a scientific conference I am currently attending. The subject of the conference is the operational impact of volcanic eruptions and ash dispersal in the atmosphere. Where the subject of dust storms comes in is that sometimes the dust storms have a high sulfer dioxide content, just as certain types of volcanic ash does. The presence of one, the dust, can mask the presence of the other, the ash, on certain types of satellite imagery, with operational impacts for aviation, health, and other interests. An example of this is where dust from Saharan storms reaches the Caribbean Sea and has interacted with ash from volcanic eruptions of a Montserrat volcano.
The net result is that trying to distinguish the ash from the dust can sometimes be likened to trying to pick out a polar bear in a blizzard.
Another point, emphatically made in the conference, is that dust from springtime storms in the Gobi Desert of Mongolia, does indeed sometimes make it as far as the west coast of the U.S. the process takes about ten days, with as yet undetermined health impacts for residents of California, Oregon, etc. The trajectory of the dust flow generally splits around the semi permanent Pacific high, with a northern branch reaching Alaska. However, the impact here in Alaska is much mitigated due to extensive springtime precipitation of a frequency and sometimes of a sort not common in lower latitudes.
Rainmaker
------------------
Justice Is Coming
For this posting I'd like to briefly revisit and update a couple of recently discussed topics, contrails and dust storms.
In the current edition of BAMS, the Bulletin of the American Meteorological Society, David Travis of the University of Wisconsin -Whitewater - and Andrew M Carleton and Ryan Lauritsen (no affiliate provided), described an interesting, if unintential, experiment they conducted on the impact of contrails. It starts with the presumption that every day, at any given moment, thousands of aircraft are aloft over the continental United States. Many of these aircraft are presumed to produce contrails. However, within a three hour period, on September 11, 2001, every single commercial and general aviation plane was grounded. No aircraft presumes no contrails. The authors took a look at what changes might have been caused by this singular lack of contrails.
In particular the authors looked at the diurnal temperature range, that is the daily range between high an low tempertures; after determining that - according to satellite imagery, and logically enough - there were virtually no contrails from September 11-13, other than those from a few military aircraft. The authors determined that the reduction in contrails corresponded to a reduction in cirrus cloud cover over those areas subject to the heaviest high level air traffic. In turn, it is speculated that the lack of cirrus cloud cover produced diurnal temperature anomalies in those areas. That is, the daily temperatures were warmer than might have been expected, the night time temperature were cooler. The reason behind the anomolies is that the ice crystals composing cirrus clouds, during the day, reflect and scatter incoming sunlight/solar radiation and so less of it reaches the surface to heat it. Fewer clouds means more direct sunlight, and hence warmer surface temperatures. At night the same cirrus clouds act to block and retain outgoing terrestrial long wave infrared radiation - the greenhouse effect - thus keeping it close to home and heating the surface. With no cirrus clouds less radiation was blocked, more escaped to outer space, and thus surface temperatures were cooler.
The consequences of this unintended experiment indicate that there is no necessity for the intentional introduction of artificial aerosols into the atmosphere, as was suggested by some folks in other venues, and previously discussed here. Rather, we are doing a pretty good, if unintentional, job of modifying the climate already.
As to the subject of dust storms, the topic has come up at a scientific conference I am currently attending. The subject of the conference is the operational impact of volcanic eruptions and ash dispersal in the atmosphere. Where the subject of dust storms comes in is that sometimes the dust storms have a high sulfer dioxide content, just as certain types of volcanic ash does. The presence of one, the dust, can mask the presence of the other, the ash, on certain types of satellite imagery, with operational impacts for aviation, health, and other interests. An example of this is where dust from Saharan storms reaches the Caribbean Sea and has interacted with ash from volcanic eruptions of a Montserrat volcano.
The net result is that trying to distinguish the ash from the dust can sometimes be likened to trying to pick out a polar bear in a blizzard.
Another point, emphatically made in the conference, is that dust from springtime storms in the Gobi Desert of Mongolia, does indeed sometimes make it as far as the west coast of the U.S. the process takes about ten days, with as yet undetermined health impacts for residents of California, Oregon, etc. The trajectory of the dust flow generally splits around the semi permanent Pacific high, with a northern branch reaching Alaska. However, the impact here in Alaska is much mitigated due to extensive springtime precipitation of a frequency and sometimes of a sort not common in lower latitudes.
Rainmaker
------------------
Justice Is Coming
