General Physical Science

Transcription

1 General Physical Science Chapter 20 Atmospheric Effects Condensation and Precipitation Supercooled (supersaturated) air Cooled below dewpoint without condensation Condensation will occur rapidly in the presence of condensation nuclei Hygroscopic species Water loving Clean dust not effective Condensation and Precipitation Updrafts Allow droplets to grow Fall when size is to big to be carried up by updrafts 2 methods for drop formation Coalescence Collision of particles to form drops 1

2 Condensation and Precipitation Bergeron Process Three components Ice crystals in upper portion of cloud Lower portion is supercooled Mixing Supercooled air causes ice crystals to grow larger Drops will melt/coalesce as they fall Rainmaking Cloud Seeding AgI Hygroscopic Mimics ice crystals Can be released on the ground or in the air by burning. Dry Ice Sublimes, cooling the surroundings Triggers ice crystal formation Also helps set up convection Rain Snow Types of Precipitation Sleet Freezing rain Hail Dew Frost 2

3 Frost Direct formation of ice from water vapor NOT frozen dew Frost patterns (hexagonal) Formation of frost on leaves is triggered by the presence of certain bacteria Work is being done to genetically modify the bacteria to delay the formation of frost Condensation and Precipitation Learning Goals Explain how precipitation is formed Distinguish among the various types of precipitation Questions: 1, 2 Air Masses Large bodies of air with similar physical characteristics Temperature Moisture Content Names come from source region Air masses move Become modified by area moving over Cold/Warm relative to surface area 3

4 Classification of Air Masses Surface type Maritime (m) Continental (c) Latitude Arctic (A) Polar (P) Tropical (T) Equatorial (E) Classification of Air Masses Air Masses Source region indicates moisture content Latitude indicates temperature Movement is predicted by general circulation patterns for the Earth (Chap 19) Normally movement is west to east for the US Front Boundary between air masses 4

5 Fronts Warm Front Movement about mph Slides over the top of colder air Precipitation usually occurs after front passage Fronts Cold Front Pushes warmer air up and over Usually driven by a high pressure system mph Sharp vertical boundary Precipitation usually before passage v v v v v Fronts Occluded Front 1 v 1 v 1 v 1 v 1 v Occurs when one front catches up to a second Usually a cold front catches a warm front Pushes the warm front up and out of the way Temperature inversion 5

6 Air Masses Stationary front Warm front and cold front collide Very little movement Low pressure areas Indicative of unstable air generally poor weather High pressure areas Stable air - good weather Weather Map El Niño Variation in typical temperature from source region Unusually warm weather off of Pacific Coast of South America in December (every 3-5 yr) Caused by relaxation of trade winds Increases precipitation in South America, drought in Indonesia, Australia, and to a lesser extent - USA 6

7 Opposite of El Niño USA Effects La Niña Warmer than normal in SE Cooler than normal in NW Lower than normal precipitation in CA and SE US. Learning Goals Air Masses Define air masses and tell how they are classified. Identify fronts and their effect on local weather. Questions: 3-6 Exercises: 1-5 odd Storms Two broad categories of storms Local Frontal (Airmass) Rainstorm Thunderstorm Rainstorm with lightning 7

8 Types of Lightning Intracloud Cloud to Cloud Cloud to Air Cloud to Ground Most concerns us! The higher an object, the more likely it is to be struck by lightning DON T HIDE UNDER TREES!!! Lightning Lightning strike affects a relatively wide area South African soccer players Heat lightning Typically C-C or IC lightning too far away to hear the thunder Lightning Safety Stay away from Open windows Fireplaces Other electrical conductors (sinks, stoves, ) Avoid using (corded) telephone Don t use electrical equipment Seek shelter Building Ditch/Ravine Car 8

9 Thunder Superheated air explosively expands Closer to the source, the sharper the sound Typically cannot be heard more than 16 mi from the source. Judge distance from lightning by timing Sound travels 1 mile in about 5 sec Ice Storms Storms Liquid rain falls and freezes on contact with surface less than 0 O C. Excess weight of ice causes much structural damage Tree limbs Power lines Snowstorm Storms Snow falls Hexagonal ice crystals Blizzard Snowstorm with high winds White-out conditions Causes disorientation Leads to death due to exposure 9

10 Tornado General movement from southwest to northeast. Linear movement mph Wind speeds mph F scale F1 F6 (never observed an F6, but OKC was 1 mph away from this category!) Highest concentration of energy of any type of storm Caused by rising air circulating around a localized low pressure area Fujita Scale (F-scale) Tornado 10

11 Tornado Tornado Watch Conditions are such that the formation of a tornado is possible Cover a broad area Tornado Warning Tornado has been spotted Either by spotter or by radar TAKE COVER IMMEDIATELY! Much smaller area than warning Tornado Safety SEEK SHELTER FAST Basement or storm shelter (above or below ground) NO shelter, then interior of structure Avoid glass and chimneys Cover your head If you live in a mobile home RUN AWAY!!! 11

12 Tropical Storms Hurricane most energetic Greater than 74 mph winds Cover a large surface area More total energy than a tornado, but not as concentrated Gains energy from the source region Warm water evaporates in the low pressure area and feeds the circulation Eye of the storm is relatively calm Hurricanes Storm Surge Associated with water pushed by the winds Responsible for 9/10 deaths from hurricane! Dies away from source region Land Cold water 12

13 Watch Hurricanes Broad area (similar to tornado watch) hour warning (dissimilar) Warning Smaller area Imminent (within 24 hours) Saffir-Simpson Hurricane Scale Learning Goals Storms Identify various types of local and tropical storms. Describe the aspects of lightning safety and tornado safety. Questions:

14 Atmospheric Pollution Atypical contribution to the environment resulting from human activity. Documented since the 1200 s Certain types of coal were heavily taxed or banned in London because of pollution problems! 2 main sources Combustion, industrial Atmospheric Pollution Smog Combination of SMoke and fog First documented in London Temperature Inversion Warm air layer trapped over a cooler layer Puts a lid on the air - can t rise through the warm layer. Temperature Inversion Most common is Radiation Inversion Ground cools air relatively close to it Upper air not cooled as rapidly Leads to radiation fog Fog along low-lying areas Valley fog Subsidence Inversion High pressure causes air to sink, compresses the air and heats it. 14

15 Fossil Fuels Gasoline, Oil, Natural Gas, Coal Complete combustion leads to the release of CO 2 Incomplete combustion - CO IC engines very favorable for CO formation NO X Brown Haze associated with LA pollution Photochemical smog (LA smog) Photochemical Smog Sulfur Atmospheric Pollution Contaminant in fossil fuels Coal Fuel oil (Diesel) Reacts to form SO 2 and SO 3 Acid Rain Formed by reaction of precip with SO X and NO X 15

16 Acid Rain Atmospheric Pollution Learning Goals Identify the major atmospheric pollutants. Explain some pollutant effects, such as smog and acid rain. Questions: Pollution and Climate Climate Long term average weather conditions Believed that pollution has and will change climate Have been dramatic changes in the Earth s climate previously Ice Age Probably due to our orbit around the Sun 16

17 Pollution and Climate Variations also occur on a smaller scale average temperature of the Earth increased by 1.1 O C present average temperature decreased by 0.55 O F It is believed that these variations affect global winds/weather patterns. Frost and Ice boundaries have shifted. Pollution and Climate Greenhouse gas emission Atmospheric CO 2 content has increased tremendously. Should lead to increase in the average temperature of the Earth Particulate pollution Leads to decrease in insolation More condensation nuclei Particulate Pollution Tambora eruption in cubic miles of debris The year without summer Frost in New England in June and July! Mt. Pinatubo Tremendous SO 2 release Forms aerosol of H 2 SO 4 May lead to thinning of the ozone layer 17

18 Pollution and Climate Stratospheric Pollution SST No washout of pollutants in stratosphere What s really going to happen??????? Atmospheric Pollution Certainly, little comfort can be found in this speculative, counterbalancing pollution cycle. There are too many unanswered questions on the effects of pollution, which has occurred over a relatively short time, and on the natural interacting cycles of the atmosphere and the biosphere, which have taken millions of years to become established. Pollution and Climate Learning Goals Define climate and identify climatic changes. Explain the possible effects of atmospheric pollutants on climate. Questions: Key Terms; Matching, Multiple Choice, and Fill-in-the-Blank Questions; Visual Connection and Applying your Knowledge 18

19 General Physical Science Chapter 20 Atmospheric Effects 19