Weather Review 2 Los Angeles The clear skies of Los Angeles Previous slide shows how pollutant passes from two stages of chemical reactions. In first stage pollutants like nitrogen oxides, hydrocarbons (volatile organic compounds) and carbon monoxide by using sunlight energy combine to form nitrogen dioxide (intermediate cyclic chemical) In second stage nitrogen dioxide reacts further to produce smog chemicals.(ozone (0 3 ), aldehyde and ketone) Roof tiles designed to remove the chemicals that react with sunlight and produce ozone (smog) Barometers measure atmospheric pressure. Here is a diagram of what the original barometer might have looked like. The standard pressure at sea level is inches of mercury. Changes in air pressure are an important indicator of changing weather. When pressure is falling, the weather is getting bad clouds and precipitation are likely. A rising barometer iis a fair weather indicator. High Pressure Clockwise in N-Hemisphere Sinking air Spreads out Fair weather Low Pressure Counterclockwise in N-Hem Rising air gathers and rises clouds form stormy weather Overhead, air above High pressure area Is converging (coming together) Similarly, overhead, Air above low pressure Is diverging (spreading apart) Air always moves from region of high pressure to region of low pressure on large scales as well as very small scales (in your bathroom when hot shower is running) Ridges aligns with high pressure at surface Troughs aligns with low pressure at surface Wind Belts on the Earth India has wet and dry seasons. Known as monsoon weather. During dry season higher pressure in mountains and lower pressure over Indian Ocean and Arabian Sea. Winds at this time of year shown in red. During wet season lower pressure in mountains and higher pressure over Indian Ocean and Arabian Sea. Winds at this time of year shown in blue.