Heat Waves (4) A Climate Case Study:
Heat Waves (4) A Climate Case Study:
In the last article I wrote that the extreme events of 2011 were providing us with the opportunity to think about climate and how to cope with a warming world. The U.S. is experiencing an extreme heat event this week (Masters @ WU). This heat wave is the consequence of a strong, stationary high pressure system over the central U.S., and it will move to the east over the next few days. Back on July 14th The Capital Weather Gang did a nice write up on the forecast of the heat wave. At the end of this blog are links to my previous blogs on heat waves and human health.
When thinking about weather, climate, and extreme events an important idea is “persistence.” For example, a heat wave occurs when there are persistent high temperatures. Persistent weather patterns occur when high and low pressure systems get large and stuck; that is, they don’t move. In the Figure below, you need to imagine North America and the United States. There is a high pressure center over the proverbial Heartland. With blue arrows I have drawn the flow of air around the high pressure system, and in this case moist air. There is moisture coming from the Gulf of Mexico and, in fact on the date when this was drawn, from the Pacific. This is common in the summer to see both the Gulf of Mexico and Pacific as sources of continental moisture.
Figure 1: Schematic of a high pressure system over the central United States in July. While generic, this is drawn to represent some of the specifics of 2011. The green-shaded area is where there have been floods in 2011. The brown-shaded area represents sustained drought in the southern part of the nation.
At the center of this high pressure system there is a suppression of rain, because the air is moving downward. This sets up a situation where the surface heats from the Sun’s energy. There is not much mixing and cooling, because of the suppression of the upward motion that produces rain. Hence, if this high pressure system gets stuck, then there is persistent heat. This is a classic summer heat wave.
Let’s think about it some more. There is lot of moisture being drawn around the edge of the high pressure system, and this moisture contributes to the discomfort of people. People – just a short aside about people: if we think about heat and health, then we are concerned about people’s ability to cool themselves. It is more difficult to cool people when it is humid because sweat does not evaporate. Suppose that in addition to this moisture, there is a region where the ground is soaked with water from flooding. Then on top of already moist air coming from the Gulf, there is local evaporation into the air being warmed by the Sun. If on the interior of the high, where the rain is suppressed, there is hot, wet air, then it becomes dangerous heat.
It’s not easy to derive a number that describes dangerous heat. But in much of the eastern U.S. a number that somehow combines temperature and humidity is useful. Meteorologists often use the heat index. It’s the summer time version of “it’s 98 degrees, but it feels like 105.” For moist climates, the heat index is one version of the “it feels like” temperature. Jeff Masters tells me that in Newton, Iowa yesterday, July 17, 2011, the heat index was 126 degrees F. (see here, and 131 F in Knoxville, Iowa on July 18)
Another measure of heat and humidity is the dew point; that is, the temperature at which dew forms, and effectively limits the nighttime low. The dew points in Iowa, South Dakota, Minnesota, and Wisconsin are currently very high and setting records. Here is a map of dew point for July 19, 2011.
Figure 2: Exceptionally high dew points centered on Iowa.
Now if I was a public health official, and I was trying to understand how a warming planet might impact my life, then here is how I would think about it. First, the Gulf of Mexico and the Pacific are going to be warmer, and hence, there will be more humid air. This will mean, with regard to human health for the central U.S., heat waves will become more dangerous, without necessarily becoming hotter. It is also reasonable to expect heat waves will become more frequent and last longer, because those persistent, stuck high pressure systems are, in part, forced by the higher sea surface temperatures. If I am a public health official here is my algorithm – heat waves are already important to my life, and they are likely to get more dangerous, more frequent, and of longer duration. But by how much? Do I need to know by how much before I decide on a plan for action?
If I think about the air being more humid, then I might expect to see trends in the heat index. I might expect to see trends in dew points, and trends in the nighttime minimum temperatures getting higher. (That’s where a greenhouse effect really matters.) I worry about persistent heat, warm nights, and the inability of people and buildings to cool themselves. I worry about their being dangerous heat in places where people and emergency rooms are not used to dangerous heat – not acclimated to heat – not looking for heat-related illness.
Let’s go back to the figure. Rain is suppressed in the middle of the high pressure system, but around the edge of the high pressure system it will rain; there will be storms. (see Figure 3 at the end) The air around the edge of high is warm and very wet. Wet air is energetic air, and it is reasonable to expect local severe storms. (See Severe Storm on Lake Michigan) And if the high pressure is persistent, stuck, then days of extreme weather are possible. If this pattern sets up, then there is increased likelihood of flooding. If I am that public health official, then I am alerted to the possibility of more extreme weather and the dangers thereof. But, again, can the increase of extreme weather be quantified? Do I need to quantify it before I decide on a plan of action?
Still with the figure - what about that region of extended drought and the heat from the high pressure system? Dehydration becomes a more important issue. As a public health official, I start to see the relation of the heat event to other aspects of the weather, the climate. I see the relation to drought. I see the flood, and it’s relation to the winter snow pack and spring rains.
So what I have presented here is to look at the local mechanisms of the weather – what are the basic underlying physics responsible for hot and cold, wet and dry – for moist air? If I stick to these basic physics, and let the climate model frame the more complex regional and global picture, what can I say about the future? Do I have to have a formal prediction to take action? Here in 2011, I see drought and flood and hot weather and warm oceans that interact together to make a period of sustained, dangerous heat. It does not have to “set a record” to convey the reality of the warming earth. It tells me the type of event that is likely to come more often, of longer duration, and of, perhaps, of greater intensity. If I am a public health planner, then I can know this with some certainty. The question becomes, how do I use that information in my planning?
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Figure 3: Radar loop showing precipitation around the edge of the large high pressure system in the middle of the continent. July 19, 2011.
Previous Blogs on Heat Waves
Hot in Denver: Heat Waves (1)
Heat Waves (2): Heat and Humans
Heat Waves (3): Role of Global Warming
Reader Comments
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Here are three. The temperature increase is statistically meaningless:
Link
And Link
Hold on here you said the graphs represented cooling during this ten year time period. 3 of the 4 graphs show warming.Now you say temperature increase. You going by the one that shows slight cooling?
My brother! Many are the answers.
The key is that 'standard' does not equal 'same'. For example, having a small economy car instead of a large 4x4 would be the same 'standard' to most people in the world. It is not the 'same' however.
In my definition of standard, I have good clean air, water, land and sea. I have freedom to vote, to do what I want (so long as I don't pollute or brak other community standards), to live my life how I chose. I have a country that is financially stable and corruption free. I have freedom to travel, freedom of speech, etc.. I have my house, I have air conditioning on the really hot days, I have a huge refridgerator and heat in the winter. I enjoy foods from around the world and my kids are raised in a safe environment.
If your definition of standard includes driving heavy cars, buying products made by companies that can't compete without polluting, etc., probably not.
If we could stop pollution our standard of living would be much greater it would not be statusquo.
The only one that shows a statistically significant increase is the GISS graph and we know their history.
But you said the others show a decrease. Where is the decrease. I only see a decrease on one of the four.
I'll tell you what. Let's compromise What do we get if we average all four of them out? An Increase or a Decrease?
Finally he gets it!
1. Start with rationing fuel or simply raise the tax on fuel to around $3 per gallon with a 1$ per year increase after that. (Right off the bat I am not keeping the same standard of living but give me a transition period to get through and then return to our standard of living.) I'd do the same/equivilent thing with coal.
2. Require all factories, farms, mines, etc to meet pollution standards of zero runoff.
3. Increase junk mail costs, packaging costs and transportation costs on everything except personal movement. It's not good that my new TV is made in over there somewhere. Why isn't it made in Baltimore?
The goal of my little fantasy is:
1. Most transportation will done by electric bicycle, bicycle, skooter, eletric vehicle. Recharging for heavy vehicles is done by battery swap: i.e. join a battery club. If you need a battery, swap it out in a few minutes. Light vehicles can either recharge overnight/at work or have thier own private swap out system.
2. The charging power comes from mostly solar, wind, nuclear or wave power.
3. Note that the benefits of a light vehicle culture are far more than just the cost of oil. they include health benefits (no, really, look up the figures, it is amazing), less pollution, less infrastructure costs, and so on.
4. Insulation on buildings increases. For example, they have houses in Norway where breakfast cooking provides all the heat necessary for the entire day..in winter! Passive heating and cooling increases.
5. The US becomes locally self sufficient for most things. Things like maple syrup that are local can still be sent but are more expensive.
6. This still leaves manufacturing as an energy cost but I think it is a start.
The goal of my little fantasy is that we all are able to live the important parts of our lives the way we want. Those parts that are not important, like driving across town to buy a specific brand of ice cream (I just did this for someone) are lost.
I'd also like to see small towns and communities return and see telecommuting centers/internet community centers installed in them to provide local revenue required and provide that contact with the larger society that is required.
I know it is a fantasy but without writing novels, that is my best attempt at describing the transition method and the goal. Imagine waking up and breathing clean air, being debt free and being able to walk (bike) to a downtown of a community that you know and care about. I think it is worth fighting for.
You can still have cycles up and down even in a warming trend upward. Can you understand that? Perfect example here: Look at the Co2 trending upwards. It too has a cyclic up and down cycle but the over all trend is still upward.
Gulfstream kinetic energy beats them all.
Here, try this on for size :)
IMPACTS OF LAND USE/LAND
COVER CHANGE ON CLIMATE
AND FUTURE RESEARCH
PRIORITIES
Bonus ~
Land use/land cover changes and climate: Modeling
analysis and
observational evidence
Price of Seafood is going up hence there is less of it.
Your point?
Houston is in a drought hence there is little rain.
Your point?
Some of it is caused by asphalt. However not all of it is caused by asphalt.
Your point?
Could be more warming in NYC than Idaho.
Your point?
It is more than Co2 and Asphalt causing the warming.
Your point?
How much warming does a pool cover create for a swimming pool?
At night it prevents the heat from escaping to the atmosphere. It can weigh much less than the .039% of all the pool water but it still traps all that heat like a blanket. How can something that small and thin do that?
You think it can't but it does.
However,the same cover used in daytime would actually cool the pool by blocking the sunlight.
Never forget who and where you are folks !
We should spend more time on the + side of it .......
Rusty, you devote probably 30% of your posts to saying that CO2 at just 0.039% of the atmosphere can't possibly have any effect on things. But the thing is, even most denialists themselves understand that CO2 is a greenhouse gas, and what that means. They may disagree on how much there is and/or how much of an impact it's had and/or where it came from--but they do understand. Here's a great primer on climate science; I politely suggest that you read it to help get you over this one particular hump.
Cheers!
Also,you can present them overwhelming scientific evidence from many universities supported by NOAA/NASA and the denialist's still are totally oblivious that the whole World around them is changing. They are no different than the frog in the pot of boiling water.
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well this presents a problem, at least in my mind.
where are the other private entities that blast weather satellites into space?
all of the observation data are from govt. funded and regulated agencies.
those with the authority to launch satellites have a clear advantage in holding data. if a private "denialist" entity wanted to put their own satellites in orbit, they would not be able to get off the ground due to the govt's grip on what goes into orbit.
this presents a bias.
overwhelming?
1979-2011 may be rapid to a human, full aware of their mortality..thus the existence of graveyards, but may not be to a 4.6 billion year old space cookie.
through geological investigation, we can theorize Earth has seen its levels of CO2 rise and fall in its history. that to me points in the direction of cyclical nature dictated by random events of physics and chemistry. it seems odd to me that evidence of change in the past is today ignored because of agenda.
the AGW CO2 complex is theoretical. overwhelming only to a creature with moods and emotional motives, but not likely so overwhelming to just one of probably several billion trillion trillion planets, each unique, in the universe.
the Earth's current climate scenario may be influenced by the progress of humans. but I'm not sure its CO2 that is the end-all-be-all reason behind such changes.
heat afterall is an engine of life. past history shows extinction events are influenced by radical drops in temperature within a timeframe.
the last great extinction event 65 million years ago is theorized now to be somewhat of a global double-whammy, large space impact combined with geological alterations caused by tectonic activity, producing a change to climate.
Every event plays a roll in the climate future.
whether by the hands of man or by nature, the Earth is constantly vulnerable to change.
there is just not enough time for man to understand all he sees and experiences. For every million things that effect one large thing, there are a trillion other things that effect the million things effecting that one large thing.
its deep, i know.
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