Bay Area Environments

AU 301-01 Bay Area Environments

Bay Area Microclimates Lab

1. The San Francisco Bay Area offers a significant variety of microclimates because the hills, mountains, and large bodies of water. It is important to understand the topography, the effects of fog and urban heat in the area to apprehend how these microclimates are formed and how it affects different communities in the Bay Area. The purpose of this study is to compare and contrast three different locations in the Bay Area to see how their geographic locations affect the temperatures in each location.

2. The Bay Area has strong microclimates, which is especially apparent in the summer months when San Francisco can be in the clouds for days and the peninsula is pumping hot.

1. There is also what is known as Urban heat in the Bay Area that can affect the temperatures. Many areas of San Francisco are known as urban heat islands. It is a term that describes built up areas that are hotter than nearby rural areas due to urbanization.  So in a crowded urban space like downtown San Francisco, all the buildings, asphalt, concrete, and other surfaces releases more heat, making the area a couple of degrees warmer than nearby rural areas. And due to the construction materials in urban heat islands, heat is slowly being released even after sunset and near dawn, creating a bigger disparity in the High and Low temperature of that area compared to more rural area.  
2. Basically the Pacific Ocean, basins and valleys are responsible for great weather disparity. On one side of the Bay Area, there is the Pacific Ocean. The ocean is relatively cold due to currents coming from the North Pacific. On the other side is the Central Valley. The Central Valley is hot in the summer and cold in the winter. The temperature differential between the ocean and the interior drive a lot of air movement. The hilly nature with gaps and peaks channels this movement with some areas getting a lot of cold wind, and others being protected from the cold wind. With this movement of wind, as it travels, it pushes the ocean fog over San Francisco, enveloping the majority of the city’s western neighborhoods in low lying clouds.  There are also many hills and mountains in the Bay Area. Hills such as the Sutro hill, which is over 900ft above sea level, prevents the fog from going over the east side of the hill.  Resulting in warming climate for areas such as the Mission.

3. Hypothesis 1: If mountains and hills create a barrier for the fog to pass through, and protects certain areas around it from wind, then the temperatures should be higher for locations that are on the east of hills and mountains. The high temperature for the city of Hillsborough should be higher than that of Daly City and SFSU Lakeside locations.

Hypothesis 2:  If there are very few trees and tree covers, and the area consists of buildings and other urban developments, this will create a urban heat effect where the location will still experience warmer temperatures into the night.  Out of the three locations, both SFSU and Hillsborough locations have trees and tree covers with Daly City location being the most urbanized location; thus, Daly City location will have the highest Low Temperature.

Hypothesis 3:  If it is hotter in the summer as you get to closer to the central valley and away from the Pacific Ocean, then Hillsborough location should have the highest temperature when compared with SFSU Lakeside location and Daly City location.

4. For this study, I have created a 5-days High and Low temperature charts for the three locations in the Bay Area. It is important to make this observations over 5-days because anything less would make it hard to get an accurate weather patterns for these three locations. I also chose Hillsborough location to be part of this location because I’ve always admired that location with the million dollar homes and I hope to live there one day. Please refer to the Table 1 and Figures 1-3 below for the 5-days observations of High and Low temperatures in SFSU/Lakeside location, Daly City location, and Hillsborough location.

Table 1: 5-Days High and Low temperatures for SFSU/Lakeside, Station Avenue/Daly City, and Edgehill/Hillsborough locations.

Station Avenue/ Daly City
High	Low
Sept. 12	59.4	54.9
Sept. 13	77.7	52.2
Sept. 14	75.2	53.8
Sept. 15	59	54
Sept. 16	67.6	53.1
Average	67.78	53.6

SFSU/Lakeside
High	Low
Sept. 12	60.1	54.9
Sept. 13	73.2	52.3
Sept. 14	72.7	51.4
Sept. 15	60.1	53.8
Sept. 16	65.5	53.4
Average	66.32	53.16

Edgehill/ Hillsborough
High	Low
Sept. 12	65.3	49.1
Sept. 13	71.8	49.9
Sept. 14	78.3	51.8
Sept. 15	78.3	48.2
Sept. 16	79	49.1
Average	74.54	49.62

3.60 degrees respectivly.aly City average lows were perature, it gets much colder during the night compared to the other two lo

3.60 degrees respectivly.aly City average lows were perature, it gets much colder during the night compared to the other two lo

Figure 1: 5-Days High and Low Temperatures at SFSU/Lakeside  

Figure 2: 5-Days High and Low Temperatures at Station Avenue/ Daly City

Figure 3: 5-Days High and Low Temperatures at Edgehill/Hillsborough

5. When comparing the three charts, you can see that the three locations have different Highs and Lows temperatures even though they are all within a 10-mile radius.

1. From September 12-16, the Hillsborough location had the highest average High temperature of 74.54 degrees, with Daly City location coming in second warmest with the average high of 67.68 degrees and SFSU location with the lowest average high temperature of 66.32. Although Hillsborough location had the higher average high temperature, it gets much colder during the night compared to the other two locations.  The average lows for Hillsborough location was 49.62 degrees, while SFSU and Daly City average lows were much higher at 53.16 degrees and 53.60 degrees.
2. The geographic location of Hillsborough allows it to be warmer than both the SFSU location and Daly City location. This is evident when looking at the 5-days observations of the high temperatures.  On average, Hillsborough location is 6-8 degrees higher during the day than SFSU and Daly City.  This is due to the fact that Hillsborough is more inland, closer to central valley and farther away from the Pacific Ocean. It is also kept warmer due to fact that it is protected by the mountains and hills west from fog allowing more sunshine over the location.
3. Daly City on the other hand had the highest average lows out of the three locations. This can be due to the fact that Daly City is the most urban-like out of the three locations.  The location consists of many streets, housing and offices.  With little tree covers, the grid style streets and housing traps heat during the day and slowly releases the heat as the sun goes down.  As a result the average lows in Daly City is around 0.5 degree to 4 degrees higher than SFSU and Hillsborough locations.
4. Another way to see how urban heat really affects temperature at night is by looking at the readings for Hillsborough. Although Hillsborough is hotter than Daly City on average by about 7 degrees, it is significantly cooler at nights.  This is because houses in Hillsborough are much more spread out compared to houses in Daly City.  Also Hillsborough location has a lot more tree covers and long stretches of fields and lawns causing a more rapid cool down at night.

6. In conclusion, the Bay Area definitely has strong microclimates. The effects of the topography, advection fog, and urban heat are all very clear when looking at temperatures across the different locations in the Bay Area. One thing that surprised me during this study was how much urban heat can impact the temperatures during the night.  I expected Daly City to be cooler at night than SFSU and Hillsborough because of its proximity to the ocean but that was not the case.  But looking at the 5-days observations, it is not surprising that many people are often confused by the microclimates we have in the Bay Area, how a place that is about 15 minutes drive away be over 10 degrees warmer on some days?  This is why it is important to understand how the microclimates are formed and what is affecting the weather in the Bay Area.

Works Cited

Arrau, Camilo P., and Maroc A. Pena. "URBAN HEAT ISLANDS (UHIs)." URBAN HEAT ISLANDS (UHIs). N.p., 09 Sept. 2015. Web. 22 Sept. 2016.

"Climate of San Francisco Narrative." Golden Gate Weather Services. N.p., n.d. Web. 22 Sept. 2016.

Hirsch, By Daniel. "Street Science: Why the Mission Is Sunny." MissionLocal. N.p., 27 Aug. 2013. Web. 22 Sept. 2016.

"San Francisco Microclimates - SF MAC Team." SF MAC Team. N.p., 13 Nov. 2012. Web. 22 Sept. 2016.