atmospheric vertical structure & thunderstorms
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Atmospheric Vertical Structure & Thunderstorms. Forecast Question: Will a severe thunderstorm develop today? Or not?. Having a solid understanding of atmospheric thermodynamics helps forecasters answer this question every day…. Atmospheric Vertical Structure & Thunderstorms. Outline: - PowerPoint PPT PresentationTRANSCRIPT
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Thermodynamics M. D. Eastin
Atmospheric Vertical Structure & Thunderstorms
Forecast Question:
Will a severe thunderstorm develop today? Or not?
Having a solid understanding of atmospheric thermodynamics helps forecasters answer this question every day…
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Thermodynamics M. D. Eastin
Atmospheric Vertical Structure & Thunderstorms
Outline:
Vertical Structure Thunderstorms
Single Cell Multicell Supercell
Importance of Thermodynamics
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• The vertical variability of pressure and density is much larger than the horizontal and temporal variations of these quantities
• Earth’s atmosphere extends >150 km above sea level
• Half the mass of the atmosphere lies within the lowest ~6.0 km above mean sea level (MSL)
• 99% of the mass lies within the lowest 30 km above MSL
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• Vertical distribution of temperature can be divided into four distinct layers
• The troposphere accounts for >80% of the mass, nearly all of the water vapor, clouds and precipitation in the Earth’s atmosphere
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• Relatively little mixing occurs between the ozone rich stratospheric air and the moist, ozone-poor tropospheric air
• The troposphere and stratosphere together account for 99.9% of the atmospheric mass
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• Mesosphere is the region where aurora borealis are sometimes observed
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• Temperatures in the thermosphere are highly dependent on solar activity (e.g. sunspots and flares) and can reach very high values
• The International Space Station maintains a stable orbit within this atmospheric layer (at ~350 km)
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Standard Atmosphere:
• The changes in temperature with height are very important for driving vertical motions in the atmosphere
• Below the tropopause, pressure and density decrease with height more rapidly in cold layers than in warm layers
• We will soon learn why soon
• These differences between cold and warm layers are critical for the development of thunderstorms
Atmospheric Vertical Structure
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Thermodynamics M. D. Eastin
Why do forecasters worry about thunderstorms?
• Flash Floods• Large Hail• Strong winds• Lightning• Tornadoes
Thunderstorms
• Change people’s daily plans• Damage homes and towns• Influence local economies
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Thermodynamics M. D. Eastin
What are the important ingredients for thunderstorm development?
Thunderstorms
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Thermodynamics M. D. Eastin
Why do thunderstorms differ in size, shape, and longevity?
Thunderstorms
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Thermodynamics M. D. Eastin
Three Primary Types:
1. Single Cell (or “air mass”)
2. Multi-cell (e.g., squall lines)
3. Supercells
Thunderstorms
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Thermodynamics M. D. Eastin
Thunderstorms
Single Cell Thunderstorms:
• Cumulus Stage (cloud dominated by updrafts)• Mature Stage (both updrafts and downdrafts present)• Dissipating stage (cloud dominated by downdrafts)
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Thermodynamics M. D. Eastin
Thunderstorms
Multi-Cell Thunderstorms:
• Composed of multiple single cells• Updrafts and downdrafts work in concert to regularly develop new single cell storms on a preferred flank of the storm• Warm updrafts rise rapidly• Cold downdrafts act as a wedge forcing warm moist air upward
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Thermodynamics M. D. Eastin
Thunderstorms
Multi-Cell Thunderstorms:
• Warm air can rise spontaneously above certain levels• Enormous quantities of moisture are condensed out of the air• Modify the large-scale environment by transporting moisture and heat• Often produce large hail and flash floods
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Thermodynamics M. D. Eastin
Thunderstorms
Supercell Thunderstorms:
• Strongest and most dangerous• Large Hail• Lightning• Strong Tornadoes
• Single rotating updraft• Two prominent downdrafts
• Occur when very warm air resides beneath very cold air
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Thermodynamics M. D. Eastin
Thunderstorms
Supercell Thunderstorms:
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Thermodynamics M. D. Eastin
Thunderstorms
Supercell Thunderstorms:
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Thermodynamics M. D. Eastin
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Thermodynamics M. D. Eastin
Importance of Thermodynamics
• All thunderstorms are driven by strong updrafts and downdrafts
• The magnitude and location of all vertical motions are the result of vertical temperature differences
• All thunderstorms “condense out” large quantities of water vapor, producing clouds and precipitation
• All thunderstorms impact society, and they do so on a daily basis
• Successful forecasts of thunderstorms requires a solid understanding of atmospheric thermodynamics…
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Thermodynamics M. D. Eastin
Atmospheric Vertical Structure & Thunderstorms
Summary:
• Vertical Structure (variations in density, pressure, and temperature)
• Thunderstorms (produce severe weather and impact daily life)• Single-cells• Multi-cells• Supercells
• Importance of Thermodynamics (critical to forecasts)
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Thermodynamics M. D. Eastin
ReferencesBluestein, H. B, 1993: Synoptic-Dynamic Meteorology in Midlatitudes. Volume II: Observations and Theory of Weather
Systems. Oxford University Press, New York, 594 pp.
Byers, H. R., and R. R. Braham, Jr., 1949: The Thunderstorm. Supt. Of Documents, U.S. Government Printing Office, Washington, D.C., 287 pp.
Houze, R. A. Jr., 1993: Cloud Dynamics, Academic Press, New York, 573 pp.
Lemon, L. R. , and C. A. Doswell, 1979: Severe thunderstorm evolution and mesocyclone structure as related to tornadogenesis., Mon. Wea. Rev., 107, 1184–1197.
Markowski, P. M., and Y. Richardson, 2010: Mesoscale Meteorology in Midlatitudes, Wiley Publishing, 397 pp.
Petty, G. W., 2008: A First Course in Atmospheric Thermodynamics, Sundog Publishing, 336 pp.
Tsonis, A. A., 2007: An Introduction to Atmospheric Thermodynamics, Cambridge Press, 197 pp. Wallace, J. M., and P. V. Hobbs, 1977: Atmospheric Science: An Introductory Survey, Academic Press, New York, 467 pp.
Weisman, M. L. , and J. B. Klemp, 1986: Characteristics of Isolated Convective Storms. Mesoscale Meteorology and Forecasting, Ed: Peter S. Ray, American Meteorological Society, Boston, 331-358.