Los Angeles Part 3

Climate Controls

Meso-scale climate controls of Los Angeles include the Pacific ocean to the west and the San Gabriel Mountains to the east. Typical fronts associated with Los Angeles are generally cold front during the winter months. The air masses that effect Los Angeles, as explored before, are maritime polar, mP, and maritime tropical, mT, air masses.

Micro-scale climate controls of Los Angeles include the Valley which is due NW of the weather station studied and the Santa Ana winds that come over from the desert regions and bring hot and dry air into the area. Since the weather station is located in downtown by USC the urban heat island effect is strong and there is not much influence due to vegetation or irrigation.

Historical Data Trends

Data Source: NCDC Monthly Averages (MMXT, MMNT) (January) 1985-2016

While not able to put a trendline for the low temp (MMNT) it follows the same pattern.

Data Source: NCDC Monthly Averages (MMXT, MMNT) (July) 1985-2015

Same issue as above

The above graphs show historical temperature data for Los Angeles for the months of January and July. An interesting note is that for January the temperature trend is increasing while for July it appears to be decreasing however slight it might be for both instances.

Comparison to another Blogger

I chose to look at the blog by Seth Nance on Kansas City, Missouri to compare the two stations. There are more differences than there are similarities when comparing Kansas City to Los Angeles and the first and foremost is climate controls. Los Angeles is affected by a large body of water and surrounding mountain ranges while according to Seth Kansas City is a flat land with no topographic or maritime features surrounding the area. Elevation is also a role as Los Angeles sits slightly above sea level while Kansas City is about 800 to 900 feet in elevation. Diurnal and seasonal temperature variation is more pronounced in Kansas City than it is in Los Angeles and precipitation occurrences differ between the two locations as Los Angeles sees most of its precipitation in the winter months due to the Mediterranean climate while Kansas City gets most of its precipitation in the summer months.

One of the similarities that I observed within both climates was that they are both affected by mT air masses while another similarity is that both locations are effected by cold fronts although during different times of the year. Other than that according to both blogs that is about it when it comes to similarities... maybe that they are both located in the same country? These two blogs show just how much climate can vary on a given continent.

Los Angeles Part 2

Since Los Angeles is a city in close proximity to the coast, a Mediterranean climate (Mediterranean climate and Köppen Climate Classification System: http://www.eoearth.org/view/article/162272/), and surrounded by mountains, Santa Monica and San Gabriel, the two air masses that affect the region are maritime tropical in the summer and maritime polar in the winter. The picture below shows the path the air masses take but as one can discern the only two that actually travel towards southern California are the maritime air masses. The Continental Tropical air masses may travel into southern California by means of the Santa Ana winds during the colder seasons.

Source: http://www.geog.ucsb.edu/~joel/g110_w08/lecture_notes/midlat_surface/agburt09_01.jpg

One interesting note is that as the mP air mass travels over the San Gabriel mountains it loses its moisture and that is one reason why the eastern side of southern California generally varies greatly in temperature than the western side. (http://classroom.synonym.com/air-mass-influences-weather-pacific-coast-other-6144.html) Los Angeles is generally affected by cold fronts in the winter which would be responsible for the, somewhat, cold and wet climate around that time. Taking a look at a accuweather.com surface map (http://www.accuweather.com/en/us/national/weather-surface-maps) showing frontal system for the US for the next few days one notices that Southern California is due for another cold front by Friday which would probably bring some cold and wet weather. 

Source: http://www.intellicast.com/National/Surface/Mixed.aspx

This map shows surface analysis and clouds over the continental United States. Looking at Los Angeles, the red star, one would notice minimal cloud coverage as well as a neighboring low pressure system in Arizona as well as an approaching cold front approaching due to a mid-latitude pacific cyclone (Raphael, Marilyn, and Gerald Mills. "The Role Of Mid-Latitude Pacific Cyclones In The Winter Precipitation Of California.")

The San Gabriel mountain range is also responsible for the Santa Ana winds, strong winter winds that bring plenty of heat. As high pressure builds over the deserts they bring strong and cool winds over the mountains that heat adiabatically as they cross the mountains which can sometimes drive temperatures in Los Angeles to 90F in December or January. These winds generally only happen during the colder months because the LA basin in warmer than the deserts during fall and winter and are responsible for most of the wild fire season in Southern California. (http://people.atmos.ucla.edu/fovell/ASother/mm5/SantaAna/santa_ana_faq.html)

Source: http://cnap.ucsd.edu/santa_ana.html

Los Angeles

The station for this blog is Los Angeles, CA around the LAX area. Los Angeles as many people know is located in Southern California and is a fairly coastal urban city. Looking at the graph below one notices that the average high temperature never goes below 60 degrees Fahrenheit and the temperature difference between the high and low stays around 20 degrees Fahrenheit year round. It also does not rain very much in Los Angeles as the highest amount they receive in a month during the year is about 3.5in.

Source: http://www.rssweather.com/climate/California/Los%20Angeles%20County/

Source: http://www.rssweather.com/climate/California/Los%20Angeles%20County/

Los Angeles is located near the coast so most of the temperatures are relatively stable. LAX is located far more inland and experiences higher average temperatures than a city somewhere closer closer to the coast such as Santa Monica. Los Angeles does not sit that high in elevation, about 200 or so ft, and lacks any large features in the surrounding areas helping the weather and climate maintain predictability. Most of Southern California is not affected by jet streams because of how close the area is to the tropics. 

Source: http://cbsnews2.cbsistatic.com/hub/i/2014/04/30/24ac29d5-6d7e-4505-ad06-10a3ec5d34bc/f2b7e4e956933f20e86047e1ad8df734/stations-los-angeles-international-airport-map.jpg

This map shows that LAX, where the station is located, lies in close proximity to the ocean but still quite a ways inland which would suggest that the city is more or less maritime with some elements of being continental. Since there is some variation in monthly temperature, from 65 to about 85 for the high from January to August and about 50 to 65 for the low for the same time, as opposed to a more coastal city such as San Diego which has less seasonal variation in temperature suggests that since LAX has more seasonal variation in temperature it exhibits elements of both being maritime and continental. The Bowen Ratio for Los Angeles has most likely changed over the last 25 years or so because of the tremendous drought the state has been going through the last several years which effects the latent heat and increases sensible heat. An interesting tidbit about this is how Los Angeles tried to combat rising evaporation rates by dumping black shade balls into reservoirs to absorb incoming sunlight.