Air masses, cyclones and anticyclones
A large volume of air in the troposphere over a big territory, with uniform temperature, humidity and clarity, is called an air mass. By the latitude of origin they are arctic, temperate, tropical and equatorial, and temperate and tropical masses also divide into marine and continental kinds. Arctic, temperate and tropical masses take part in forming Central Asia’s climate: arctic air is cold and dry, temperate air from the west is cool and often brings precipitation, and in summer a hot dry continental tropical air forms over the region itself. The boundary zone where different air masses meet is a front; at a cold front the temperature falls quickly and precipitation falls, at a warm front the weather warms gradually. A vortex with low pressure at the centre and rising air is a cyclone, with cloudy weather and precipitation; a vortex with high pressure at the centre and descending air is an anticyclone, with clear weather, hot in summer and cold in winter.
“Cyclone–anticyclone”: draw two vortices on paper with arrows (clockwise and counter-clockwise) and label “Low” or “High” pressure; then attach the matching weather card to each.