The March-April edition of WeatherWise magazine has an interesting article in it regarding UHI (Urban Heat Island) effects of enhancing thunderstorm formation in the downwind heat plume. It Stems from this paper (PDF) published in the Bulletin of the American Meteorological Society. I saw a similar study presented in August 2007 when I attended Dr. Roger Pielke’s land use conference presented by Dr. William Cotton on the enhancements modeled in St. Louis, MO. Read that paper here
Excerpts from WeatherWise Magazine:
The Atlanta Thunderstorm Effect
by Mace Bentley, Tony Stallins and Walker Ashley
Although nearly everyone is fascinated by lightning, some of us are terrified, while others are drawn to its elusive beauty. Lightning is one of the most photogenic of all atmospheric phenomena, but also one of the least understood. For all of its beauty, lightning is a major cause of weather-related deaths in the United States and accounts for more deaths than hurricanes and tornadoes combined. Nearly 40 percent of all lightning deaths occur when a person is involved in some form of outdoor recreation.
Now, new evidence suggests that lightning and its parent thunderstorms might actually be enhanced by cities. Urban areas are literally hotbeds for producing heat and lift, two important ingredients for thunderstorm formation. At the same time, throughout the world people are continuing to migrate to cities for employment opportunities and the search for a better life. Eighty percent of the U.S. population now lives in cities. City growth has increased the amount of urbanized land cover in the United States to nearly the size of Ohio! In the United States, many of our cities in the south are growing rapidly due to their location in a more temperate climate. However, a temperate climate also means cities are more prone to thunderstorms. Could all of these factors together combine to increase risk of lightning and other thunderstorm hazards to urban communities around the world?
The Urban Heat Island
The first step in unraveling the question is to understand the interaction between the land and atmosphere. It is currently thought that several processes in this complex interaction are likely at work in altering thunderstorm distributions around cities.
The first is the urban heat island effect, perhaps the most well-known atmospheric phenomenon produced by a city. An urban heat island occurs when the city registers higher temperatures than the surrounding rural areas. Cities heat up because of all the “activity” in them. Cars, air conditioning units, idling engines, and miles of asphalt and concrete all either produce or retain heat. The most notable feature of an urban heat island is the lack of cooling during late afternoon and evening after temperatures normally reach their highest. When compared to the rural countryside, urban corridors have much less area exposed to open air and instead have many warm buildings facing each other. Less heat is lost, and higher nighttime temperatures result. After sunset, city-to-countryside temperature differences grow quickly and can reach, in some cases, more than 10°F. The greatest city-to-countryside temperature differences occur during the long, hot days of summer when daylight is maximized.
…
Caption: Radar climatology illustrating the clustering of strong thunderstorm days directly over and immediately surrounding Atlanta, Georgia.
Caption: Plot of lightning events during periods of westerly flow illustrating downwind enhancement east of Atlanta, Georgia.
The Atlanta Case
The 10-year study of lightning, rainfall, and thunderstorm activity in Atlanta in the summer months showed that enhanced thunderstorm activity was found to shift due to prevailing winds. For example, westerly winds produced a distinct increase in lightning activity east of downtown Atlanta. Evidence suggests that thunderstorms developing over the city center, as well as storms along the periphery, were being directed by the westerly winds to the east side of the city and suburbs. The Atlanta enhancement, particularly for lightning, was well developed for westerly and northwesterly winds that carried thunderstorms east and southeast of downtown. Thunderstorm enhancement can occur in all directions around downtown Atlanta, directed primarily by the prevailing wind direction.
“Pollution can alter how a thunderstorm forms”
“As water droplets collide and freeze onto hail and other ice particles, negative charges are removed from the updraft and added to the downdraft of the thunderstorm”
The rainfall and lightning characteristics of thunderstorms developing in and around Atlanta were also detected when examining radar reflectivity. Over the 10-year study, high radar reflectivity “hotspots” were persistently found along and north of downtown Atlanta and immediately east of the central business district. Towering cumulonimbus clouds containing high concentrations of water droplets and ice crystals reflect significant amounts of microwave radiation back to the radar antenna. On weather radar displays, highly reflective areas are thunderstorms, which are typically color-coded in hot colors (i.e., reds, oranges) to make it easy to identify their size and location. Radar-identified thunderstorms were found to be greatest over the downtown with a general decrease moving outward from the city center. A similar pattern was found over other southern U.S. cities. It appears that the Atlanta urban heat island and associated buildings may combine to produce the downtown thunderstorm radar “hotspot,” while the urban heat island-produced circulations on the fringes of the city lead to increases in suburban thunderstorms, lightning, and rainfall.
“Radar-identified thunderstorms were found to be the greatest over the downtown”
Although less important, the terrain might also be linked to the lightning and rainfall patterns surrounding Atlanta. Winds from the northeast off the Appalachians and the focus of rainfall and lightning activity on the upwind side of Atlanta suggest that elevation changes across the metro area may interact with the urban heat island circulation and focus lightning and rainfall on the north side of the city. One explanation is that air flowing downhill from the Appalachians will be forced to rise once it encounters the buildings on the northern edge of Atlanta. This is distinct from other prevailing wind directions, where lightning activity was found to intensify over and downwind of the city center.
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As far back as the 1960s, Tony Chandler gave his inaugural Professorial Lecture at the University of London on the London heat island. At much the same time, Bruce Atkinson, a geographer specialising in boundary layer climates, was discussing the effect of urban pavements on increased thunderstorm activity. I think some of this was published – I’ll see if I can track it down.
Air hits tall building, travels up, expands, cools, forms clouds, rains.
Interesting. I’ve always felt that cities effect wind patterns as well. As the city of Sydney has grown, 7 miles from here, North East sea breezes have weakened, to the point that a strong NE sea breeze is rare here now. 15 miles further North they are unchanged. On the other side of the city they have strengthened. (I’ve been windsurfing for many years)
Anthony,
Seems like the UHI has alarmism in all sides. I wonder, when the cooling will REALLY begin in 5 years, if Al Gore will start talking about our “soot footprint” and how we cause Global Cooling. Like Al Gore doesn’t have enough money becuase of his fraud corruptions.
OT. Sound of millisecond pulsars can be found here:
http://www.jodrellbank.manchester.ac.uk/research/pulsar/Education/Sounds/
Slam dunk proof of negative feedback.
Must avoid outdoor recreation.
Anthony,
Another thing, Check THIS alarmist scream on http://www.global-warming.accuweather.com. You may want to check it out for your latest post.
So much desinformation and distortion has been said above about what the article is really talking about.
Go back in time, and you will find many papers stating what is the real impact from the solar activity fluctuation on earth temps and climate. No one is arguing there’s none, but it’s not that big and already accounted – it does’nt make a big difference on the outcome , it’s marginal.
Answer to G. Karst:
They are not trying to predict the next minimum. It’s not even about that. Your usual distortion to make a point.
Answer to Dr. Science:
Again, your out of the subject (the subject here is Solar Activity impact – not Al Gore). Your usual junk and vomitting about Al Gore. You have the right to say whatever you want about the guy, still do it at the right place and in the right subject. Usually Brett post something about him every three months – use that opportunity to bash all your soul, but please stay in the subject.
Answer to Gary :
They know about the other factors such as El Nino and others. They were looking for the impact of the sun activity fluctuation, and that’s what they are talking about. They are not predicting the climate, they’re saying the sun fluctuation will account for that amount of cool/warm output.
To SVBOR :
As usual, your linking a subject talking about the sun activity fluctuation with something else. At least you could have linked it to a paper saying otherwise. Always on the confusion, please spare us from what you see on your screen. I’m sure we can do better than that. And if you close your system, don’t look at the screen – the reflection is quite ugly.
To Grumpy Old Man:
Your twisting a little bit what they said. Short terms cycles cannot explain long term trends.
Having said that, you’re also out of the subject. Of course, you have’nt found a response on the net for this story, so you have to come here with another one.
TO FRANKOK:
The image is from the same source many skeptical articles are using to say it is cooling because we’re (or were) in a solar minimum. No photoshop needed, it’s available online.
To Paul:
The pleasure you have in bashing Al Gore is your right, but this paper is not about him nor it is if the sun is heating or not the earth. It’s kind of obvious that if they are looking at the fluctuation of the sun, they are looking at what heat it does during the cycle. As i said to someone else, if you want to bash on Gore, choose the right subject.
To The Wizard:
The impact of the sun’s fluctuation is known and documented – going up or down it counts for about 13% of whatever warms this place. They are talking about ”FLUCTUATION” – not the all of the sun’s energy – only the fluctuation part. I know it’s confusing for someone who does’nt know the subject.
To Stephan :
That’s not what they said. But if it’s the way you understand things, i know why see the earth is flat and the sun is circling the earth everyday.
To Anonymous, Oops, no it’s Robert :
They got the data from the past, and they’re using models for what can be the future with multiple scenarios. They also challenges their models with the data from the past. What’s your point, they did exactly what you’re asking for, but it’s still not good for you. What do you want.. Ok i see, you needed to bash on someone even if you’re prooven wrong.
To Sean2829:
Who the hell told you that? Must be Joe. Still it’s not relevant to this subject.
To MarkB :
You got it (at last).. It should’nt be much of an influence as stated in the 2007 paper (more or less 6% of the raise and not a straight line – it’s a cycle).
To Pete28 (again):
You are wrong, climate’s prediction can already be challenge even if we’re not in 2100. If you choose the coolest of the scenario, currently we’re already above the predictable average. If you choose the warmest scenario, we’re quite short of it globally. So what you said is wrong and showing you don’t understand what GW theory is. Please read the report on the possible climate scenario on temps.
To Oakden Wolf:
Welcome in the club. You’re another one who is finding it is quite easy to debunk SVBOR with all the lies he’s always linking to. Have fun, you’re about to become the next name calling victim of M. Cut and Paste.
To Caleb:
El Nino has a large impact, but it is still a local one. At some places it’s not felt, and at others it’s about +8c. But more than that, El Nino is not alone. You got many oscillation playing with the weather and what you can feel and get at any place in the world. I don’t know anyone who claimed – and please go back to the archives – ”that the sun had no effect whatsoever”. What you’ve been told is that the impact was marginal and already accounted in the figures. Read the IPCC report, it’s there. The feedback from the sun’s fluctuation is about 6%.
On the models, i agree with you, some are good – some are bad. But given the documented assumptions , show me where the climate models are wrong. You can still argue with the assumptions, but much less about the models.
Derek Cummins : same argument as Caleb – same answer. You are twisting what has been said in the past. In fact what they are saying today is about the same thing as 10 years ago. The sun’s fluctuation has very little to do with the climate warming or cooling. The cycle is just to short to have an impact on climate. Still it can have an impact on the weather for a specific year. But don’t say it’s something new… It has been said over and over on this site, it’s written in the IPCC report, and written in numerous scientific paper for the past 150 years. Please come back with more accurate informations if you want to put a story.
And you add : ”The sun is entering a long phase of being quiet, and as a result we can expect to cool for the next 30 years”. Where the hell are you coming from? The minimum is ending. We’re heading for the next maximum in about 3-5 years, and then it will start to go down. Don’t you know , it’s 11 years cycle. Just where do you get such stupid informations (i’m not calling you stupid, i’m saying that the arguments you copied is).
Spring is here, snow is gone, flowers are emerging already.. About a month in advance, but SBVOR told me it was the ice age beginning.
Quickly, Igor, pack up the lab equipment! We’re moving to Atlanta!
“On weather radar displays, highly reflective areas are thunderstorms, which are typically color-coded in hot colors (i.e., reds, oranges) to make it easy to identify their size and location”
I believe the color coding is for temperature of the cloud tops, the “hot” reds really being colder cloud tops. The temps are used to determine the height of the cloud tops, higher being colder. I also seem to remember reading that clouds must grow to a height greater than 20,000 feet in order to produce lighting but I am not sure.
Thunderstorms are weather events. Local influences as described by PielkeSr. are very real but are they altering the local climate through some local/regional weather patterns or the world climatic evolution?
I think there are a lot of extra electrons left over from all those TV sets and they get together and draw the lightning.
What? That’s at LEAST as good a theory as that global warming stuff!!!
Not that many airports are being built these days, but this does suggest that commercial airports should be placed upwind from cities. DFW, for instance, is downwind from Ft. Worth, and has an interesting record of thunderstorms and microbursts.
A recent example may have been the massive hailstorm a week or so ago in the Melbourne Suburbs – the massive hail storm (up to 100mm hail, smashing roofing tiles & car windscreens & panels) – The bad hail was some 30-40kms downwind from Melbourne CBD. Upwind & CBD areas received more “normal” hail (10mm)
“Thousands of private cars were also pummeled, showing evidence of glass damage and dimpled panels over a wide area, from Nunawading to Belgrave in the Dandenong Ranges.”
I had not considered the fact that urban heat would extend so far out into the surrounding countryside. Have any of the rural vs urban station analyses considered the impact of the direction of the rural station from the nearest large heat island? Based on that map above, it would appear to extend for a pretty good distance downwind.
I had heard several years ago how the mega-city Tokyo generates thunderstorms. So basically they are now finding out that other large cities can do so as well.
Love this bit:
The first is the urban heat island effect, perhaps the most well-known atmospheric phenomenon produced by a city. An urban heat island occurs when the city registers higher temperatures than the surrounding rural areas.
Jones, Hansen, Mann et al might have a slight objection to that statement. 😉
O/T It has been rumored that the Queensland Dept of Education (DET) has filtered out Watts and McIntyre’s Climate Audit, but kept in Real Climate and Deltoid.
Winston Smith would be amused.
One doesn’t have to live very long on the East Coast of Florida in order to observe this “phenomena” on a daily basis. The daily thunderstorm cycle in the warmer months offers a great insight as to the “Urban Effect” on local weather. I have actually seen clouds form and ascend from large parking lots as humid air races in from the West (interior) portions of the state. These clouds tend to form huge thunderstorms within 3-5 miles of the coast. This is where most of the urban effect is located. In areas where there is not a great degree of urbanization these storms usually form at or East of the coast itself.
Interesting.
When I lived in metro Atlanta for 20-odd years, I was quite familiar with a different effect. When a storm front with a line of thunderstorms would approach Atlanta from the west, they would die out as they hit the Atlanta UHI, then regenerate once they passed the metro area. But then I never really paid much attention to where thunderstorms bubbled up during an ordinary hot summer day, though it wouldn’t surprise me to see that the lift from the UHI would have an effect on storm location, intensity, and frequency.
Since I was living on the western perimeter, it was quite frustrating during a hot, dry spell to see thunderstorms approach with much needed rain, only to see them dissipate short of Atlanta.
I can testify as any other motorcycle rider can…Once your outside of the city limits and enter the rual area…temps drop dramatically..Especially in Spring and Fall…I was out today for the first time..I’m from the country and drove into a town…One can feel the difference…It was 67 today, full sun and no wind. Perfect day to ride!!!
“Eighty percent of the U.S. population now lives in cities. ”
I don’t know why,,, but I’ve never read that statistic before. I’m sitting here stunned! Must go look for my jaw! I think I may have kicked it under my desk somewhere. I feel foolish that I didn’t know this,,,,,,,,,,,,,,,
I thought UHI did not matter according to AGW LOL
Must be those CO2 domes ; )
Paul @ur momisugly 15:28:19
Greenhouse gas forcing fails cointegration with insolation forcing and temperature.
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You see, nature is taking care of us.
Nothing to worry about.