Earth’s Weather and Climate EVSC 1300 Earth’s Weather and Climate

Composite Surface Maps warm fronts cold stationary occluded Precipitation type and intensity isobars pressure wind direction wind speed

Scales of Motion (pp. 230-231) Page: 230 FIGURE 9.1 Scales of atmospheric motion. The tiny microscale motions constitute a part of the larger mesoscale motions, which, in turn, are part of the much larger synoptic scale. Notice that as the scale becomes larger, motions observed at the smaller scale are no longer visible. (pp. 230-231)

Scales of Motion Increasing size Increasing duration (pp. 230-231) Page: 231 FIGURE 9.2 The scales of atmospheric motion with the phenomenon’s average size and life span. (Because the actual size of certain features may vary, some of the features fall into more than one category.) (pp. 230-231)

Scales of Motion (pp. 230-231) Page: 231 FIGURE 9.2 The scales of atmospheric motion with the phenomenon’s average size and life span. (Because the actual size of certain features may vary, some of the features fall into more than one category.) (pp. 230-231)

Mercury Barometer Page: 203 FIGURE 8.6 The mercury barometer. The height of the mercury column is a measure of atmospheric pressure.

Aneroid Barometer Page: 203 FIGURE 8.7 The aneroid barometer.

Barograph or Recording Barometer Page: 205 FIGURE 8.8 A recording barograph.

Time of frontal passage Barograph Trace Charlottesville Jan. 5–10, 2009 Time of frontal passage (4–6 p.m., Jan. 7)

Surface Map; Jan. 7, 2009; 7 a.m. EST

Surface Map; Jan. 7, 2009; 7 p.m. EST

Time of frontal passage Barograph Trace Charlottesville Jan. 5–10, 2009 Time of frontal passage (4–6 p.m., Jan. 7)

Sea-level pressure variations Page: 203 FIGURE 8.5 Atmospheric pressure in inches of mercury and in millibars.

resulting map of sea-level Station vs. Sea-level Pressure station pressure—barometer measurement correction factor for elevation FIGURE 8.9 The top diagram (a) shows four cities (A, B, C, and D) at varying elevations above sea level, all with different station pressures. The middle diagram (b) represents sea-level pressures of the four cities plotted on a sea-level chart. The bottom diagram (c) shows sea-level pressure readings of the four cities plus other sea-level pressure readings, with isobars drawn on the chart (gray lines) at intervals of 4 millibars. resulting map of sea-level pressure variations (surface map)

Sea-level Pressure Map Influence of topography (elevation) on pressure has been removed (pp. 200–207)

Change of Air Pressure and Density with Height Page: 11 FIGURE 1.9 Both air pressure and air density decrease with increasing altitude. The weight of all the air molecules above Earth’s surface produces an average pressure near 14.7 lb/in.2

Earth’s atmosphere is thin relative to the size of the planet.

Change of Air Pressure with Height atmosphere’s mass above 100 mb Page: 12 FIGURE 1.10 Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km, where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules. 100 mb 90% of atmosphere’s mass below 100 mb

500 mb Map (pp. 10–12) Upper air map showing winds and other variables at the “mid-point” of the atmosphere.

Quick Pressure Summary: pressure is the weight of the atmosphere per unit horizontal area pressure variations determine wind (speed and direction) High vs. low pressure determine clear vs. stormy weather pressure drops rapidly with height from sea level average surface pressure is about 1000 mb (1013.25 mb)

air molecules Number of air molecules determine surface pressure Page: 200 FIGURE 8.1 A model of the atmosphere where air density remains constant with height. The air pressure at the surface is related to the number of molecules above. When air of the same temperature is stuffed into the column, the surface air pressure rises. When air is removed from the column, the surface pressure falls. (In the actual atmosphere, unlike this model, density decreases with height.) Number of air molecules determine surface pressure (Note: Unrealistic example...constant density and fixed top)

TWO BAROMETERS L SAME TEMPERATURE D E N S Low Pressure High Pressure Air Column Air Column D E N S L SAME TEMPERATURE Low Pressure High Pressure Barometer Barometer At same temperature, dense air has higher pressure than less dense air

Impact of Heating and Cooling on Pressure Reference Level denser less dense Page: 201 FIGURE 8.2 Illustration of how variations in temperature can produce horizontal pressure forces. (Note that for simplicity, this model assumes that the air density is constant with height, whereas in the actual atmosphere, density decreases with height.) (a) Two air columns, each with identical mass, have the same surface air pressure. (b) Because it takes a shorter column of cold air to exert the same surface pressure as a taller column of warm air, as column 1 cools, it must shrink, and as column 2 warms, it must rise. (c) Because at the same level in the atmosphere there is more air above the H in the warm column than above the L in the cold column, warm air aloft is associated with high pressure and cold air aloft with low pressure. The pressure differences aloft create a force that causes the air to move from a region of higher pressure toward a region of lower pressure. The removal of air from column 2 causes its surface pressure to drop, whereas the addition of air into column 1 causes its surface pressure to rise. (The difference in height between the two columns is greatly exaggerated.) Warming or cooling air can induce pressure changes. Pressure change can produce air motion—wind!

Pressure and Density Same temperature at both locations Page: 204 FIGURE 1 Air above a region of surface high pressure is more dense than air above a region of surface low pressure (at the same temperature). (The dots in each column represent air molecules.) Same temperature at both locations Denser air produces higher surface pressure (Chap. 8; pp. 200–207)

Wind Direction (16-point compass) Page: 255 FIGURE 9.43 Wind direction can be expressed in degrees about a circle or as compass points. Wind is defined based on the direction from which it is coming.

Surface High = ANTICYCLONE Cyclones and Anticyclones Page: 223 FIGURE 8.35 Winds and air motions associated with surface highs and lows in the Northern Hemisphere. Surface Low = CYCLONE (counter-clockwise winds) Surface High = ANTICYCLONE (clockwise winds) (N. Hemisphere)

Cold vs. Warm Air Parcels Page: 32 FIGURE 2.1 Air temperature is a measure of the average speed (motion) of the molecules. In the cold volume of air, the molecules move more slowly and crowd closer together. In the warm volume, they move faster and farther apart. Cold air is denser that warm air (at the same pressure)

Surface Air Temperature Variations (pp. 32–34) Page: 34 FIGURE 2.2 Comparison of Kelvin, Celsius, and Fahrenheit scales, along with some world temperature extremes. (pp. 32–34)

Quick Summary—Ideal Gas Law: relates pressure, temperature, and density with 3 variables, you can’t determine how one will affect another unless the third variable is held constant cold air is denser than warm air (at the same pressure) temperature changes can induce pressure changes between two locations (pressure “gradients”) that cause the wind

Composition of Atmosphere Permanent Variable Greenhouse Gases TABLE 1.1 Composition of the Atmosphere near the Earth’s Surface

(removal from atmosphere) SOURCE (to atmosphere) SINK (removal from atmosphere) Fixed by (incorporated into) soil bacteria Fixed by ocean phytoplankton Lightning N2 Denitrification by anaerobic bacteria in wet soil Aerobic bacterial processes Combustion Respiration (oxidation: food to energy) O2 Ocean phytoplankton Photosynthesis Vis. light 6 CO2 + 6 H2O C6H12O6 + 6 O2 Photosynthesis Fixation by ocean phytoplankton Dissolved directly into ocean surface CO2 Respiration Combustion STORAGE: limestone sediments, marine shells, fossil fuels

(removal from atmosphere) SOURCE (to atmosphere) SINK (removal from atmosphere) Anaerobic processes (wetlands, rice paddies) Bovine flatulence Termites Biomass burning Interaction with hydroxyl in atmosphere Soils CH4 CH4 + OH CH3 + H2O Bacteria in soils/oceans (nitrification) Combustion (cars, biomass) Fertilizers Stratospheric photochemistry (converted to NOx) N2O O2 + O O3 O3 + uv O2 + O O3 Also chlorine, bromine, NOx Evaporation from open water Sublimation (from ice) Transpiration (through plants) Condensation onto surfaces Precipitation Deposition H2O (pp. 6–10)

Average vertical temperature structure of atmosphere (pp. 12–17) Page: 13 FIGURE 1.11 Layers of the atmosphere as related to the average profile of air temperature above Earth’s surface. The heavy line illustrates how the average temperature varies in each layer. (pp. 12–17)

Variation of Tropopause Height by Latitude Page: 275 FIGURE 10.11 Average position of the polar jet stream and the subtropical jet stream, with respect to a model of the general circulation in winter. Both jet streams are flowing from west to east. Tropopause is higher over equator and lower over poles