Blog Post #3

The close proximity to the Alps Mountain range is the biggest determining factor for the meso and micro scale climate in Zurich.  There is a high level of orographically determined precipitation and temperature.  Zurich is in a valley north of the Alps and the meso scale climate varies greatly from year to year but is typically the opposite of what the Southern Alpine Region is experiencing.  The air masses that move over the region determine which side of the mountains receive the precipitation.  If Zurich is rainy there is a high probability that the Southern Alps will be dry, and vice versa.  Several programs have been implemented to try to study the patterns of meso scale climate in Switzerland, the RAPHAEL program and the Mesoscale Alpine Programme are two examples.  Their aim was to be able to predict precipitation for the mitigation of flood risk.  They found incredibly varying levels of rain and snowfall, the variability, again, is orographic in nature.  They were able to attain accurate predictions of location of rainfall but the amounts proved impossible to predict.

In the winter Zurich has less precipitation because the air masses are largely from the south which means they drop their moisture in the south before flowing over the Alps.  In the summer the effect is the opposite as air masses are coming down from the north and dropping rain over the region.  As the air masses in the region shift the wind speeds and directions also shift, when they are moving east to west there can be devastating effects in the region.  The valley Zurich lies in is generally oriented east to west.  Therefore when air masses are moving this direction they pick up speed while moving along the mountain range.  Extreme wind events are very common.

Fig. 1: Wind gusts as a function of return period in Zurich-Fluntern. The blue curve represents the function calculated by means of statistical analysis. Wind gusts measured over the period 1981-2007 are depicted by black dots. See text for further details. Source: http://www.meteoschweiz.ch/web/en/climate/climate_reports/frequency_of_extreme_wind_speeds.html

On a micro scale the same forces are at work.  Zurich is also a large city, with a population of slightly over 1 million living in an area of 38.5 square miles.  There is most certainly an urban heat island effect happening on a micro, local level.  The main weather station that collects data for Zurich is located at the airport.  Airports are large plots of concrete which reflect a lot of heat.  This weather station is naturally going to reflect higher temperatures than a station located on top of a mountain nearby.

Historical data has been collected in Switzerland 1870, this data is currently being used to forecast impacts and determine the severity of climate change in the region.

Source: http://www.meteoschweiz.ch/web/de/forschung/publikationen/alle_publikationen/Das_Schweizer_Klima_im_Trend.html

 This graph shows the average winter temps recorded in Zurich from 1870-2000.  There is a clear upward trend indicating that temperatures have been steadily rising in the area.  This does not necessarily mean that climate change is the cause.  As mentioned earlier this is a highly urbanized area and some of this warming could be a result of an urban heat island effect.

Source: http://www.meteoschweiz.ch/web/de/forschung/publikationen/alle_publikationen/Das_Schweizer_Klima_im_Trend.html

This graph shows the average summer temperatures from 1870-2000.  The trend lines in this graph are far less impressive than the rise in temperatures for winter months further suggesting that climate change is probably not the only factor in changing temperatures.

Source: http://www.meteoschweiz.ch/web/de/forschung/publikationen/alle_publikationen/Das_Schweizer_Klima_im_Trend.html

This precipitation graph also shows very little historical change, there is a slight noticeable increase over the last 130 years but it is minimal and probably has more to do with reflection of anomalies over time.

Source: http://www.wunderground.com/history/airport/LSZH/1997/1/30/MonthlyHistory.html?req_city=NA&req_state=NA&req_statename=NA

This graph is based on temperatures recorded at the weather station in Zurich from 1996-2012, with the obvious exception of June 2012.  As in the graph above depicting historic summer temperatures there does not seem to be a clear indication of consistently rising temperatures.  Although 2003 was an incredibly unusually warm winter.

The Koppen-Geiger classification system was put in place by two Germans, it was created in 1928 and placed broad classifications on the continents based on observed climate patterns.  Switzerland is in an area that has a lot of diversity topographically and was clearly difficult to classify.

Source: http://en.wikipedia.org/wiki/File:Koppen_World_Map.png

Europe according to Koppen-Geiger

 This is obviously not an exact science and these borders cannot be clearly defined.  As this picture indicates Switzerland is full of flux climatically.  According to this graphic most of Switzerland lies in what Koppen-Geiger classify as tundra.  This means that there is at least one month of the year warm enough to melt snow but no full month with an average over 50F.  This has huge impact on the types of vegetation and wildlife that can exist in the area.  Tundra, or Alpine, environments perfectly fit the Swiss environment.

Source: http://www.bing.com/images/search?q=climograph+of+zurich&view=detail&id=FCD9125C92E11CA9E34E5EECA27B625EF0D3546F&first=0