Seattle's Unique Insulation
Seattle offers itself as one of the best climatic conundrums. If one were to analyze the climatic composition based on any of the dominant climatic classification systems, a perfect fit would be impossible. This is largely due to the meso-scale physical attributes that dictate overall climate controls for the region. The two most important physical attributes insulating Seattle from more severe climatic fluctuations experienced at similar latitudes are the presence of mountains and the ocean. As the image below depicts, the Olympic Range flanks Seattle to the west, and to the east lay the Cascade Range. Both ranges help temper air masses moving into the region. The image below also draws distinction to the maritime nature of Seattle’s location on the Puget Sound. The influence of the oceanic dynamic insures moderate moisture levels a majority of the year.
 |
| Image courtesy of MetEd https://www.meted.ucar.edu/training_module.php?currentPage=10&tab=3&id=499
While Seattle's most prominent air mass affliction is caused by Maritime Polar (mP) air masses originating in the Gulf of Alaska, two other systems play a key roll in shaping the seasonal climatic characteristics. During the summer Maritime Tropical (mT) systems bring tons of moisture and strong winds to the greater Seattle area. Occasionally during this same time, massive mid-latitude cyclones are created out at sea and threaten Seattle with volatile weather. These cyclones are formed by the convergence of temperature differences found between 30 and 60 degrees north. These temperature differences provide the energy for these storms which will eventually dissipate as northerly cold fronts overtake the warm fronts, thus creating low-pressure systems. Pineapple Express storms also bring wind and heavy rain as the jet stream dips into tropical regions then reorients across western Washington. In the winter months, Continental Polar (cP) air masses can sometimes breach the Cascade Range bringing a deep chill. However, most times the cold air mass just sneaks into the Puget Sound region through lowland depressions like the Skagit River Valley, which is to the north-northeast of the city. The valley pictured below is just one of numerous micro-scale attributes that assist in the cold air drainage that affects Seattle. (Office of Emergency Management, Seattle)
|
 |
| Image courtesy of WestCoastWord http://westcoastword.wordpress.com/2012/07/27/losing-your-natural-self/ |
 |
| Image courtesy of twotwothree06 http://www.ar15.com/archive/topic.html?b=8&f=15&t=418764 |
It’s safe to think
that Seattle’s climate changes with the season’s right? Wrong, regardless of
the earths orbital dynamics and axis inclination of the earth during the course of a
year, Seattle doesn’t experience seasons like other regions with similar
latitudes. This is due to the profound impact that meso-scale and micro-scale topological
features play in insulating the city.
Due to the more southernly location of the weather station I chose to observe (SeaTac), with respect to downtown Seattle, there is no major micro-scale influences that affect the overall data. While Seattle does experience the affects of an Urban Heat Island due to it's built infrastructure and the roll of albedo, reflectivity, absorption and emissivity, as well as the change in its urban ecology; my station location just a few miles south of the city does not.
Interestingly, while my station location is largely unaffected by many of the micro-scale influences cause by anthropogenic sources, something interesting is being revealed by the data. There is an every so slight and incredibly hard to distinguish constant increase in temperature average maximum and minimum temperatures since the 1960. Below are two graphs I compiled of seasonal averages for the months of January and July over the course of 50 years. What is telling about the historical data is that the average highs are slowly but gradually increasing for both January and July. There are still yearly fluctuations caused by larger global components that must be taken into account, but one can't dismiss the increase in average historical highs! Many climatologists contribute these trends to increasing levels of carbon dioxide from anthropogenic sources.
Average Historical Highs & Lows in July
Average Historical Highs & Lows in January
| Graph compiled by George L. Humphries II Data courtesy of wunderground.com http://www.wunderground.com/history/airport/KSEA/2012/7/1/MonthlyHistory.html?req_city=NA&req_state=NA&req_statename=NA&MR=1 |
| Graph compiled by George L. Humphries II Data courtesy of wunderground.com http://www.wunderground.com/history/airport/KSEA/2012/7/1/MonthlyHistory.html?req_city=NA&req_state=NA&req_statename=NA&MR=1
To better address the roll that topography and geographical local plays in a regions climatic composition, I will draw on the specific attributes affecting weather and climate outcomes in Charlwood, England. Charlwood is located within a southern district called Surrey, about 40 kilometers south of London. Charlwood is geographically situated at 51 degrees N latitude, just a few kilometers west of the prime meridian. It's geographical position is similar to that of Seattle's which rests at just over 47 degrees N latitude. Charlwood's weather is much like Seattle's, it receives it's greatest amount of precipitation during the winter (November - February), and a similar number of rainfall days per month. Charlwood's temperature profile is also very similar to Seattle's, however winters are just slightly cooler by a few degrees. The summers are also a few degrees cooler during the months of July and August. Below are average temperature graphs for both Seattle and Charlwood, respectively.
Image courtesy of The Weather Channel
http://www.weather.com/weather/wxclimatology/monthly/graph/USWA0395
Image browed from T.J. Bacon's Blog
http://weatherandclimateassignmentpost1.blogspot.com/
Both Charlwood and Seattle are afflicted by Maritime Polar (mP), Continental Polar (cP), and Maritime Tropical (mT) air masses. What sets Charlwood apart from Seattle with respect to air mass influences is determined by Britain's geographical location. Being a high mid-latitud island with few topographical barriers, the influence of Arctic (A) has an impact on Charlwood during the winter. Continental Tropical (cT) air masses also influence the climatic composition of the parish due to the size and proximity of Africa. In closing, both cities have incredibly similar climates regardless of the diversity of meso and mico-scale influences. What's important to realize when addressing specific climatic dynamics is that traditional classification systems can only address so much!
-Here is the link to T.J. Bacon's blog about Surrey England. Just copy and paste it into your browser.
http://weatherandclimateassignmentpost1.blogspot.com/
|
