|
AVIATION TECHNOLOGY 12
|
|
Air Masses and Associated Weather A. Definitions 1. Air Mass - a large section of the troposohere with uniform temperature and moisture charactaristics in the horizontal, formed when an extensive area of the troposphere is in contact with a uniform surface i.e, continents, oceans 2. Front - boundary zone between air masses at the surface - takes its name from the colder air mass - above the surface the boundary is usually referred to as the fromtal surface note: Most wearther phenomena are air mass or front related B. Classification and Properties of Air Masses 1. Classification by temperaturs a) A Arctic - very cold b) P Polar - intermediate c) T Tropical - very warm 2. Classificationby moistures contant a) c Continental - dry, fron passage over land b) m Maritime - moist from passage over water note: of the sic passible comvinations of the preceding classifications, opnly four are found in Canada. These are: 1. cA - Continental Arctic - from the polar ice cap 2. mA - Maritime Arctic - from cold arctic oceans 3. mP - maritime Polar - from temperate oceans 4. mT - Maritime Tropical - from equatorial oceans i.e. Gulf of Mexico C. Factors determining Weather in an Air Mass 1. moisture content 2. cooling or warming process operating 3. stability of the air mass D. Properties of Air Masses in Canada 1. cA - deep inversion in the lower levels 2. mA - moist and unstable 3. mP - moist with varying stability 4. mT - very moist and warm, unstable with daytime heating E. Fronts 1. Cold Front a) front along which the cold air is advansing to replace warmewr air, OR the leading edge of an advancing cold air mass b) cold air becomes deeper over a station as cold air advances c) rapid movement and frictional drag cause a cold front to have a slope of 1 mile in 50 miles 2. Warm Front a) front along which the cold air is retreating, OR the trailing edgs of a retreating cold air mass b) cold air diminishes in depth as warm front approaches c) slope is flatter than that of a cold front. It is 1 mile in 200 miles 3. Stationary Fron (also referred to as a Quasi-stationary front) a) cold air is almost motionless with no overall movement b) poor bisibility 4. TROWAT, ( line of intersenction of two air masses (above the ground) 5. Upper Fronts a) occur when cold air advances faster on the surface than at upper levels b) occur when a pool of air is trapped in a valley and a front passes F. Definitions 1. Frontogenesis -frontal formation 2. Frontolysis - frontal weakening |