3/31/17. No CLASS FRIDAY. End of subsidence unit. Next up: SEVERE WEATHER. Video - Severe Weather (Tornadoes) #23 - Weather - Principles I

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1 No CLASS FRIDAY End of subsidence unit Next up: SEVERE WEATHER Exam 2: Wednesday April 5 th 7:15 PM, Loomis Web Exercise #4 (Landslides): Due Today 11:59 PM Writing Assignment Information will be posted tomorrow Video - Severe Weather (Tornadoes) #23 - Weather - Principles I Super Tornado Outbreak in 2011 (355 tornadoes), Remarkable F4 tornado that went through Tuscaloosa, AL on 4/27/11 (YouTube, 0-0:30, 2:30-3:00, 3:30-5:00, 6:40-6:50; Satellite view of tops of towering clouds that mark the top of the troposphere Weather vs. Climate Weather = daily changes in air temperature, precipitation, wind speed Climate = long-term atmospheric and surface conditions Sunny weather Importance of Weather Severe weather is most deadly and damaging of all categories of natural hazards (excluding drought and disease) Rainy weather World Climate Zones ATMS 120 (Severe and Hazardous Weather) 1

2 Deadliest Natural Disasters (excludes drought, disease, heat waves) From , hurricanes caused most deaths (41%) for natural hazards we re discussing, floods (link with severe rainstorms) caused third most deaths Globally, weather and climate-related hazards are most common ones; frequency and damage from weather and climate hazards are rising Trends in USA - Weather and Climate Disasters In US weather- and climate-related hazards are most common ones; frequency of weather (green) and climate (yellow) hazards is rising Frequency of Natural Disasters in US, Trends in USA - Weather Disasters Damage from weather disasters is rising in the US Average Number (red) and Average Cost (blue) of Billion-Dollar Weather Disasters in US, Extreme Weather Years - USA 2005 rising? Global warming, especially for heat waves, droughts, heavy rain, coastal flooding (not for hurricanes and tornadoes) 2

3 rising? Current global warming may have little impact on hurricanes, but future warming is more likely to affect hurricanes rising? More development More people rising? Negative impact of increased development, especially floods, storminduced landslides 2012 flood in Beijing, China Clicker Question Review: Why are deaths and/or damage due to weather- and climate-related natural disasters increasing? A. Population increase has increased the number of people on the planet. B. Climate change has made some disasters worse and/or more common. C. Increased economic development leads to greater cost of damage. D. All of the above landslide near Rio de Janeiro, Brazil Clicker Question Which of the following is NOT thought to be increasing in frequency due to climate change? A. Hurricanes B. Droughts C. Floods D. Heat Waves E. None of the above; ALL are increasing due to climate change. Trends in USA - Weather and Climate Disasters Which states have greatest weather and climate-related damage? Southeastern US Number of Billion-Dollar Weather/Climate-Disasters ( ) Why those states? Hurricanes - need warm ocean water nearby (also due to heat waves/drought) 3

4 Fundamentals of the Atmosphere - Definitions Atmosphere = envelope of gases surrounding Earth, extending <1 m below surface to ~10,000 km above Fundamentals of the Atmosphere - Layers Atmosphere has layered structure (defined by temperature, pressure, chemical composition). Lowest layer = troposphere, where all weather phenomena occur. Edge-on (limb) view of Earth s atmosphere as seen from International Space Station Top of troposphere marked by top of towering cumulonimbus cloud Fundamentals of the Atmosphere - Troposphere Fundamentals of the Atmosphere - Troposphere Temperature in troposphere: Warmest at the bottom, and decreasing upward Troposphere extends to altitude of km, contains ~ 90% of mass of atmosphere, ~all water vapor. Warmed at the bottom: Earth (incl. oceans) absorbs sunlight and is heated; this energy is then transferred to the atmos. Fundamentals of the Atmosphere - Stratosphere Finishing up class #23 Stratosphere contains ozone (O 3 ) layer; temperature in stratosphere increases upward due to O 3, absorbs UV radiation 4

5 Controls of Atmosphere - Pressure Atmospheric pressure (14.7 lbs/in 2 at sea level) due to weight of overlying air column. As you rise in atmosphere, pressure derceases (less atmosphere above). Solar energy absorbed by Earth depends on latitude: - Low latitudes (near equator) receive most solar energy per unit area (~vertical sunlight), making it hot. - High latitudes receive much less solar energy per unit area (low angle sunlight), makes it cold Controls of Atmosphere - Temperature Difference in air temperature causes circulation of atmosphere (wind). Hot air rises at low latitude Cold air sinks and high latitude CONVECTION CELLS Simplified representation of global winds due to differential heating alone. The actual atmosphere is more complex Controls of Atmosphere - Heat (Evaporation, Rain) Heat = motion of atoms; increasing (>) temperature = > atomic vibration Change from solid to liquid (melting), or from liquid to gas (evaporation) involves large increase in atomic vibration and requires large input of heat (latent heat). Controls of Atmosphere - Heat (Evaporation, Rain) Conversely, condensation of H 2 O gas to liquid water (rain) release lots of latent heat Clicker Question Thought question: Dry air near the equator becomes moist by evaporating water from the ocean. This air mass then moves to a cooler place and cools down, causing rain. Which of the following is true? A. Energy has been lost from the earth permanently, because the evaporation caused cooling of the ocean. B. Energy has been transferred, as latent heat, from near the equator to the cooler place. C. Energy has been transferred toward the equator, as latent heat, from the cooler area. D. None of the above. 5

6 Controls of Atmosphere - Humidity Humidity = amount of water vapor air mass can hold, depends on temperature; hot air can hold MUCH more water vapor (up to 4 wt. % H 2 O) than cold air. Absolute humidity = abundance of water vapor in atmosphere; Relative humidity = ratio of observed absolute humidity divided by maximum absolute humidity Dew point = temperature to which air must be cooled to reach saturation (100% RH) Controls of Atmosphere - Formation of Clouds Clouds form when air rises, expands, and cools. Cooling causes decreasing ability to hold water vapor; air eventually becomes fully saturated with water vapor (reach dew point), then cools even more (supersaturated) and condensation (rain) begins (Picture ignores heat exchange with surrounding air) Controls of Atmosphere - Formation of Clouds Diagram shows relationship between absolute and relative humidity for rising air; absolute humidity of rising air remains constant but relative humidity increases (to left) due to cooling, until air reaches dew point, get condensation and clouds Controls of Atmosphere - Descending Air Descending air is compressed and warms (adiabatic warming), increasing ability of air to hold water vapor favors evaporation (liquid water to water vapor) and sunny, warm, dry weather Controls of Atmosphere - Global Winds (Non-rotating Earth) Heated air near equator expands, becomes less dense, therefore rises and cools (creates rain with low-pressure zone at equator). At top of troposphere, air then flows toward poles, losing more heat (< temperature) due to radiation into outer space and condensation. As flow continues, dry air becomes denser (due to < temperature) + eventually will sink, get compressed (> P) and warmer. If Earth was not rotating, two giant convection cells. Clicker Question: As we just saw, rising air masses are very importantthey produce rain and snow. So. In the earth s atmosphere, which of these air masses has the greatest tendency to rise? a) A hot, dry air mass b) A cool, dry air mass c) A hot, most air mass d) A cool, moist air mas e) No difference- they are all the same. 6

7 Clicker Question: Review: In the earth s atmosphere, the troposphere is a) Usually moving (convecting) because it is heated at the bottom and heat escapes at the top b) Usually moving because the higher level winds push the air east to west c) Stratified because it is warmer near the top d) Stratified because the Coriolis effect does not operate there 7