Chapter 9 Meteorology

Section A, Weather Factors §Atmosphere l Comprised of: Oxygen - 21% Nitrogen - 78% Other gases - 1% l 99.9% of Atmosphere is within 30 miles

Section A, Weather Factors §Atmosphere is classified by thermal characteristics l Troposphere Lowest level contains most weather varies in altitude from 24,000’ to 50,000’ with about 36,000’ to 37,000’ in mid-latitudes characterized by a decrease in temp with increase in altitude

Section A, Weather Factors l Tropopause above troposphere characterized by an abrupt change in temp lapse rate About 36,000 l Stratosphere Severe thunderstorms may extend Tops about 160,000’

Section A, Weather Factors §Atmospheric circulation l Weather changes are caused by uneven heating l Every process of weather is the result of or is accompanied by a heat exchange l The sun is directly over the Tropic of Cancer on June 21

Section A, Weather Factors §Pressure and wind patterns l Pressure Highs - Center of high pressure, peak of hill Lows - Center of low pressure, bowl Cols - area between 2 highs, or lows Ridges - elongated area of high pressure Troughs - elongated area of low pressure

Section A, Weather Factors §Highs are usually associated with l Good visibility l Light winds l Few clouds l Good weather l Characterized by descending air

Section A, Weather Factors l Lows are usually associated with precipitation cloudiness poor visibility bad weather turbulence Wind characterized by rising air Example of lows are hurricanes and tornadoes

Section A, Weather Factors §Air tries to flow from high to low l At higher altitudes, Coriolis force makes the wind flow parallel with isobars l At lower altitudes, surface friction weakens Coriolis force and flows across the isobars l This airflow is wind

Section A, Weather Factors §In the northern hemisphere l Air flows counterclockwise around a low (cyclonic) l Air flows clockwise around a high (anticyclonic) l If one were to fly directly to the center of a low, the winds would come from the left and get stronger as one got closer

Section A, Weather Factors §Local wind patterns l Unequal heating of land and water Land and sea breezes l Mountain and Valley breezes On a larger scale these are Katabatic winds.

Section A, Weather Factors §Water l Solid - ice l Liquid - water l Gas - water vapor Odorless Colorless l Changes states by: Evaporation, Sublimation, Condensation, Deposition, Freezing and Melting

Section A, Weather Factors §Relative Humidity l Measure of how much moisture is present for a a parcel of air at a temperature. l If a parcel of air has a RH of 100%, it is saturated. The temperature that it is at is called the dewpoint. If this parcel were cooled more, water vapor would clouds, fog, dew or frost

Section A, Weather Factors §Precipitation - condensation nuclei l Drizzle l Rain l Snow l Ice pellets l Hail l Ice crystals

Section A, Weather Factors §For a heavy rain to occur, clouds must be at least 4000’ thick. §Virga §Wet snow §Ice Pellets

Section A, Weather Factors §Stability l Dry adiabatic lapse rate l Saturated adiabatic lapse rate §Condensation Level l Temperature dew point spread by 4.4F or 2.5C l Condensation nuclei l nimbus

Section A, Weather Factors §Families of clouds l Low l Middle l High l Extensive vertical development

Section A, Weather Factors §Airmass l Continental l Maritime l Polar l Tropical

Section A, Weather Factors §Fronts l Cold l Warm l Stationary l Occluded

301. I21 COM Every physical process of weather is accompanied by or is the result of A. a pressure differential. B. a heat exchange. C. the movement of air.

301. I21 COM Every physical process of weather is accompanied by or is the result of B. a heat exchange.

302. I21 COM What is the standard temperature at 10,000 feet? A. +5 °C. B. -5 °C. C. -15 °C.

302. I21 COM What is the standard temperature at 10,000 feet? B. -5 °C.

304. I22 COM What are the standard temperature and pressure values for sea level? A. 15 °C and 29.92" Hg. B. 15 °C and Mb. C. 59 °F and " Hg.

304. I22 COM What are the standard temperature and pressure values for sea level? A. 15 °C and 29.92" Hg.

306. I23 COM What causes wind? A. Pressure differences. B. Air mass modification C. The Earth's rotation.

306. I23 COM What causes wind? A. Pressure differences.

307. I23 COM In the Northern Hemisphere, the wind is deflected to the A. left by Coriolis force. B. right by Coriolis force. C. right by surface friction.

307. I23 COM In the Northern Hemisphere, the wind is deflected to the B. right by Coriolis force.

308. I23 COM Why does the wind have a tendency to flow parallel to the isobars above the friction level? A.Friction of the air with the Earth deflects the air perpendicular to the pressure gradient. B. Coriolis force acts perpendicular to a line connecting the highs and lows. C.Coriolis force tends to counterbalance the horizontal pressure gradient.

308. I23 COM Why does the wind have a tendency to flow parallel to the isobars above the friction level? C.Coriolis force tends to counterbalance the horizontal pressure gradient.

309. I23 COM The wind system associated with a low-pressure area in the Northern Hemisphere is A. a cyclone and is caused by Coriolis force. B. an anticyclone and is caused by Coriolis force. C. an anticyclone and is caused by descending cold air.

309. I23 COM The wind system associated with a low-pressure area in the Northern Hemisphere is A. a cyclone and is caused by Coriolis force.

312. I23 COM While flying cross-country, in the Northern Hemisphere, you experience a continuous left crosswind which is associated with a major wind system. This indicates that you A. cannot determine weather conditions without knowing pressure changes. B. are flying toward an area of generally unfavorable weather conditions. C. have flown from an area of unfavorable weather conditions.

312. I23 COM While flying cross-country, in the Northern Hemisphere, you experience a continuous left crosswind which is associated with a major wind system. This indicates that you B. are flying toward an area of generally unfavorable weather conditions.

313. I23 COM Which is true with respect to a high- or low-pressure system? A. A high-pressure area or ridge is an area of descending air. B. A low-pressure area or trough is an area of descending air. C. A high-pressure area or ridge is an area of rising air.

313. I23 COM Which is true with respect to a high- or low-pressure system? A. A high-pressure area or ridge is an area of descending air.

314. I23 COM When flying into a low- pressure area in the Northern Hemisphere, the wind direction and velocity will be from the A. left and decreasing. B. left and increasing. C. right and decreasing.

314. I23 COM When flying into a low- pressure area in the Northern Hemisphere, the wind direction and velocity will be from the B. left and increasing.

317. I24 COM Moisture is added to a parcel of air by A.evaporation and sublimation B.sublimation and condensation C.evaporation and condensation

317. I24 COM Moisture is added to a parcel of air by A.evaporation and sublimation

325. I25 COM What are the characteristics of stable air? A. Good visibility; steady precipitation; stratus clouds. B. Poor visibility; steady precipitation; stratus clouds. C. Poor visibility; intermittent precipitation; cumulus clouds.

325. I25 COM What are the characteristics of stable air? B. Poor visibility; steady precipitation; stratus clouds.