Lets review some climate controls from class today:
latitude-higher latitudes have colder weather (less intense solar radiation) and lower latitudes are warmer.
elevation- higher elevation colder temps
global winds- these winds move warm air towards the polar regions, the Sahara (fig 1, north Africa) and many of the worlds deserts are located at 30 degrees N and S latitude in the subtropical high. The dry-summer tropical climate is found Southern California.
vegetation- influences cloud formation, solar absorption and precipitation.
water- moderates the temperature of the air above the water.
topography- think mountains ( fig 2) windward side of mountains usually wetter than the leeward side. Fig 2 is Boulder CO, as you go east the landscape becomes very arid.
Friday, December 12, 2008
El Nino- the piling up of warm water in the eastern Pacific off the west coast of South America. This warm water does not allow the cold water upwelling ( source of nutrients for fish) along the west coast of South America. This El Nino phenomenon affects the economy and climate of not only SA but also the US, see diagram.
La Nina- is the opposite of El Nino. During La Nina colder than average water temperatures are experienced in the eastern Pacific.
Hurricanes- need warm, moist air to form. Hurricanes begin in the east Atlantic Ocean in tropical latitudes where the water temp is at least 80 degrees F. As hurricanes move over land they lose energy due to friction and the lack of warm moist air.
Photo credit-NASA/Jeff Schmaltz
Thursday, December 11, 2008
The major weather producer in the US is the mid-latitude cyclone/wave. This weather producer is shaped like a water wave and the greatest number of thunderstorms are associated with this weather producer along the cold front.
Key points: warm air is always forced upwards (less dense), heaviest precipitation associated with cold fronts, occluded fronts happen when a cold front overtakes a warm front- see diagram.
Tuesday, December 9, 2008
Lets look at today's weather map and review some terms:
low pressure- rotate counterclockwise, winds blow towards the center, rising air, also known as cyclones, move from west to east.
high pressure- rotate clockwise, winds blow out from the center, sinking air, also known as anticyclones, move from west to east.
prevailing westerlies- the consistent wind that blows from west to east across the US, remember winds are named from the direction they blow and wind speed is measured by an instrument known as an anemometer.
Notice the cold front extending from northern Mexico all the way north to the western side of New York state.
A cold front is symbolized by triangular points on one side and is the boundary between a warm and cold air masses. Behind this cold front is a cold air mass that originated in Canada and is known as a continental Polar (cP) air mass. Air masses take on the temperature and moisture characteristics from where they form.
Along the US/Canadian border, upstate New York, is a warm front. This warm front is identified by the semicircles extending from one side. Much of the warm air behind the warm front originates in the Gulf of Mexico and is a maritime Tropical (mT) air mass.