Past, Present, and Future

 100 Million Years Ago

100 million years ago Los Angeles was a much different place.  It was underwater!  The water was much warmer than it is today.  Today the water temperature off the coast is around 60 degrees Fahrenheit; 100 million years ago the water temperature was much warmer somewhere around 80 degrees Fahrenheit.  Los Angeles is underwater so it would have had a steady temperature pretty much year-round.  Since the climate was much more tropical it can be assumed that the average amount of precipitation was much greater than it is currently.  Right now LA averages less than 20 inches of rainfall each year; 100 million years ago this number was probably three times that amount or 60 inches plus a year.

 

Current Average Temperatures (weather.com)

Current Average Precipitation

Past Average Temperatures

In the future it looks as though Los Angeles will once again be underwater.  Not only will it be under water but it will have moved closer to the equator.  So the water temperature will be even warmer.  My guess would be about 85 degrees Fahrenheit.  The earth will be in a warming period so it stands to reason that the water temperature will be much warmer and being located closer to the equator will only amplify this.  The average annual precipitation will be much greater than it is today probably 60 or more inches each year.  This is due to the tropical nature of the climate and the new location (closer to the equator).

The Future?

Future Average Temperatures

Comparison of the Climate in LA to the Climate in Milan, Italy

I based this comparison on the Milan, Italy weather blog by Alina Yurievna Shemetova.

Koppen-Geiger Classification

Los Angeles is classified as a dry-summer subtropical climate. This means that the area has rainy winters and mild dry summers. This is due to the relatively cold ocean currents that are present off the California coast.  Milan is classified as a oceanic climate.  This means that the area has cool summers but relatively mild winters.

                                    (Source: http://koeppen-geiger.vu-wien.ac.at/)

 

Meso-scale

The climate in Milan is affected by its proximity to a large body of water, the Mediterranean (specifically the Adriatic and Ligurian seas).  This plays a major role in the amount of precipitation that Milan receives as well as helps to moderate the temperature.  In addition, the Alps are located just to the north which can also influence the precipitation and climate.  LA is similarly situated with the Pacific Ocean to the west and the San Gabriel Mountains to the east.

Micro-scale

The urban heat island effect is quite strong in Milan.  There is a marked difference in temperatures between 1997 and 2011 according to the data in Alina's blog.  LA has a similar heat island in the Valley.  In addition LA experiences the seasonal Santa Ana winds.

LA Climatology

Koppen-Geiger Classification

Under this classification Los Angeles would be classified as a dry-summer subtropical climate. This means that the area has rainy winters and mild dry summers. This is due to the relatively cold ocean currents that are present off the California coast.

                                    (Source: http://koeppen-geiger.vu-wien.ac.at/)

Climate Controls

Meso-scale influences for Los Angeles include its close proximity to the Pacific Ocean (west) and the San Gabriel Mountains (east).

Micro-scale influences include the Valley where the central portion of the city is located, as well as the seasonal Santa Ana winds. In addition, the urban heat island effect can be quite strong in the Valley.

Comparison of the Weather in LA to the Weather in Milan, Italy

I based this comparison on the Milan, Italy weather blog by Alina Yurievna Shemetova.

Los Angeles is located on the coast of California while Milan is located in the interior of Italy.  Both cities are in close proximity to mountains.  The San Gabriel Mountains just east of Los Angeles and the Alps located just north of Milan.  Due to the geography of the two cities, they experience inversions along with smog from the pollution.

 Los Angeles is generally warmer than Milan on average.

 (Source: weather.com)

 Milan averages more precipitation than Los Angeles on average.

(Source: weather.com)  

  

Maritime Tropical and Maritime Polar are the air masses that affect the weather in Los Angeles.  Milan on the other hand is affected by many different air masses: Maritime Tropical, Maritime Polar, Maritime Arctic, Continental Tropical, and Continental Polar.

Milan will commonly experience snow in the winter while snow is relatively uncommon in Los Angeles.  Milan is located at a higher latitude and is affected by much colder air masses than Los Angeles.

Air Masses Affecting LA

Los Angeles is affected by the cooler air masses that come inland off the Pacific Ocean and the warmer air masses coming from the desert.  This often leads to an inversion layer.  The marine atmospheric boundary layer forms with the inversion in place.  The marine layer is a layer of cool, moist maritime air with the thickness of a few thousand feet immediately below a temperature inversion.  The inversion layer traps the carbon emissions from the city and this causes the smog that is often associated with Los Angeles.

(Source: http://www.theweatherprediction.com/weatherpapers/109/index.html)

Source: http://rst.gsfc.nasa.gov/Sect14

 Marine Layer at LAX

My personal photo taken October 23, 2011

In addition, Los Angels is affected by the seasonal Santa Ana winds that blow in the fall, winter, and spring, peaking in December.  The wind usually has its origin when cold air spills southward into the Great Basin, trapped between the Rockies to the east and the Sierras and Southern California coastal range to the west. This cold air mass is characterized by unusually high pressure near the land surface. Winds are driven into Southern California when the pressure of this interior air mass exceeds the pressure along the California coast.

(Source: http://meteora.ucsd.edu/cap/santa_ana.html)

Source: http://meteora.ucsd.edu/cap/santa_ana.html

LA Climate Basics

Los Angeles is located on the west coast of California.  It is the largest city in California and the second largest in the United States.  The climate is moderate due to the city’s close proximity to the Pacific Ocean.  The temperatures are generally cooler along the coast and warmer in the Valley.  Mornings are generally foggy or overcast (especially along the coast) and the afternoons are sunny.

La Cienega Blvd & Santa Monica Blvd                                                           LAX (headed to Lot C)

                                                                   La Cienega Blvd (Northbound)

                                               My personal photos taken on October 17, 2011.

Monthly Averages for Los Angeles, CA

Month

Avg. High

Avg. Low

Mean

Avg. Precip

Record High

Record Low

Jan

68°F

48°F

58°F

3.12 in.

95°F (1971)

28°F (1949)

Feb

69°F

49°F

59°F

3.92 in.

95°F (1995)

25°F (1911)

Mar

70°F

51°F

61°F

2.43 in.

98°F (1988)

35°F (1976)

Apr

73°F

54°F

64°F

0.91 in.

106°F (1989)

39°F (1975)

May

74°F

57°F

66°F

0.26 in.

102°F (1967)

43°F (1922)

Jun

78°F

60°F

69°F

0.09 in.

112°F (1990)

49°F (1999)

Jul

83°F

64°F

74°F

0.01 in.

107°F (1985)

53°F (1909)

Aug

84°F

64°F

74°F

0.04 in.

105°F (1983)

51°F (1933)

Sep

83°F

63°F

73°F

0.24 in.

110°F (1988)

50°F (1921)

Oct

79°F

59°F

69°F

0.66 in.

108°F (1987)

41°F (1971)

Nov

73°F

52°F

63°F

1.04 in.

100°F (1966)

38°F (1978)

Dec

68°F

47°F

58°F

2.33 in.

92°F (1938)

24°F (1944)

Source: The Weather Channel – weather.com