Tuesday, November 15, 2011

Climate in Los Angeles compared to Lima, Peru

Both coastal cities on the Pacific Ocean, Lima and Los Angeles share many differences and similarities.

Although the seasons are variedbetween the north and south hemispheres, the temperatures in Los Angeles and Lima remain very steady and similar throughout their seasons.



(weather.com)

 Lima has a much lower precipitation rate due to the Andes Mountains. Los Angeles also experiences fairly low precipitation, but this is due to the dominance of the stable marine layer. Precipitation is rare between May and October and any rain that does occur is usually the result of isolated thunderstorms associated with subtropical moisture. During the remainder of the year the eastern Pacific high pressure ridge is displaced and Los Angeles finds itself on the southern margins of the northern hemisphere polar jet stream. With cold air aloft, the marine layer breaks down. Pacific storms, sometimes fed with subtropical moisture, often push cold fronts across California from northwest to southeast.(http://www.wrh.noaa.gov/lox/climate/climate_intro.php)

(weather.com)
 
Both Lima and Los Angeles experience weather due to maritime air masses, where both are influenced by polar air, Los Angeles is also greatly influenced by subtropical air.

Tuesday, November 1, 2011

Air Masses

 Los Angeles often experiences cool temperatures due to the onshore flow from the Pacific Ocean.



(image source : http://www.nc-climate.ncsu.edu/edu/k12/.breezes)

In Los Angeles upper air inversions develop because it is on the edge of the subtropical high pressure cell in the Pacific Ocean. Subsiding air from the high pressure cell is compressed by the increasing pressure of the surrounding air as it descends, so the air warms up as it subsides.  Combined with the cool air at ground level from onshore flow, there is also a general subsidence of warm air aloft. The inversion layer acts as a lid to prevent air at ground level from rising and dispersing.  The mountains inland also help trap the air.  
(image source: http://www.ec.gc.ca/air/default.asp?lang=En&n=AFF4D58F-1)

Any pollutants emitted build up in the trapped air.  The smog worsens in high temperatures and clears best with high winds.
(image source: http://www.huffingtonpost.com/2009/07/10/la-vows-to-be-coalfree-by_n_229832.html)

(http://daphne.palomar.edu/calenvironment/smog.htm)