Climate Controls and Comparision to Seattle

Dublin’s weather is affected by a few climate controls, with one overlying control that completely changes the climate.  The main climate control is of course, the North Atlantic Ocean current.  This meso-scale climate control (meaning it affects regional climates) is the main contributor to the year round mild climate of Ireland.  Like I said in a previous blog, the North Atlantic Ocean current brings warm water from the Caribbean up the east coast of the US, across the Atlantic, to the UK.  This warm water current brings warm winters with little snow and cool summers with moderate rain unlike somewhere of similar latitudes such as Russia or the northern United States, where very cold and snowy winter are common.  Another climate control are the coastal mountains on the western coast of Ireland.  These coastal cliffs create strong winds, warmer temperatures, and more precipitation on the western part of the island.  

Picture of the meso-scale climate control (North Atlantic Ocean Current).

 

The temperatures of Dublin for the months of July and January stay fairly constant through 1985 to 2010.  Some years show a direct correlation between warm weather in July and warm weather in January.  In the late 1980’s you can see both July and January had above normal temperature and in the early 1990s both July and January have below normal temperatures.  There are a few cases in which July has above average temperatures while January has below normal temperatures, like in the early 2000s.

Graph showing the mean temperatures for the months of July and January

I have chosen to compare my blog to Seattle, Washington.  Seattle is a coastal city on the western coast of the United States.  I have chosen to compare Seattle because it is at a similar latitude, is coastal, has similar average temperatures, and gets a lot of precipitation.  The first aspect I will compare is how the temperatures differ more in Seattle than in Dublin even though they’re at a similar altitude.  The main reason is of course the North Atlantic Ocean current that brings warm water to Ireland causing warmer temperatures.  Next, I will compare the air masses that affect both Dublin and Seattle.  Both Seattle and Dublin are affect by Maritime Polar and Maritime Tropical air masses.  These are the only two that affect Seattle but Dublin is also affect by Continental Tropical, Continental Polar, and Maritime Arctic air masses.  These maritime air masses influence the mild temperatures and large amounts of precipitation that both Seattle and Dublin receive on a monthly basis.  Both locations also experience mid-latitude cyclones.  Both these location experience lows and highs that directly affect the weather and precipitation.  The reason I wanted to compare Dublin to Seattle was because of the stations being at similar latitudes.  I expected more of a difference between the two but after looking at the Seattle blog I realized they are more similar than I expected.  Both are affect by the same air masses, both have fairly mild temperatures, similar amounts of rain, and are both affected by mid-latitude cyclones.  After really thinking about it, it makes sense because both are coastal cities that have maritime climates and also have coastal cliffs and mountains surrounding them.

Air Masses and Frontal Systems of Dublin, Ireland

Picture showing the types of air masses that affect Ireland
and the rest of the UK
source: http://www.geography.learnontheinternet.co.uk/topics/uk_weather_climate.html

The isles of the U.K. are affected by 5 air masses throughout the year.  The types of air masses are arctic maritime (mA), polar continental (cP), polar maritime (mP), tropical continental (cT) and tropical maritime (mT).  These 5 main types of air masses can affect Ireland year round and influence the weather patterns seen on a day to day basis.  The mA air masses, originating in the Arctic, brings cold, snowy weather during the winter.  The cP air, originating from northwestern Europe, brings cold, dry air year round to the area.  The mP air masses coming from Greenland and Canada, brings cold, wet weather throughout the year.  The forth air mass is tropical continental which comes from southern Europe and north Africa, brings hot, dry weather in the summer.  The last air mass is tropical maritime which comes from the south west, brings warm, wet weather year round. 


Ireland is effected regularly by both warm and cold fronts.  The figure below shows a weather map of the U.K. for today, Friday, November 16th, 2012.  It shows an incoming cold front coming from the northwestern polar maritime air.  It also shows an incoming warm front coming from the southeastern tropical continental air mass.  The advancing cold front is pushing the warm air up rapidly causing precipitation and colder temperature (as seen in the five day forecast).  There could also possibly be a stationary front in the coming days if the cold and warm fronts meet.  If the stationary front does occur, clouds and precipitation could last for days in the area (also seen in the five day forecast 

The five day forecast for Dublin shows high chances
of rain with lots of clouds, which is typical
of a stationary front
Source:http://www.weather.com/weather/5-day/EIXX0014

Weather map of the UK showing a cold and warm
front coming toward Ireland
Source:METEOROLOGICA

There are a few factors that influence the weather patterns of Dublin, Ireland.  Like I stated in my previous post, the North Atlantic Ocean currents runs from the Caribbean, across the Atlantic Ocean, bringing warm moist air along with it.  This warm water current influences the tropical maritime air masses that bring precipitation to the rolling green hills of Ireland.  Also, strong winds on the western coast influence wetter weather on the west coast and the coastal mountains block Dublin from much of the rainfall that hits western Ireland.

The five main air masses that affect Ireland can be seen almost year around.  The temperature and precipitation are directly influenced by these five air mass types.  Like most places in the mid-latitudes, Ireland experiences all types of frontal systems which also affect the weather patterns.  There are also a few geographical factors that influence the weather.  All these factor directly shape the mild weather and climate of Ireland. 



Sources: 

http://nsidc.org/arcticmet/factors/pressure.html

http://www.weather.com/weather/5-day/EIXX0014

http://coolgeography.co.uk/GCSE/Year11/Weather,Climate/Air%20masses/air_masses.htm

Average Weather and Climate

Source:http://www.ecology.com/2012/03/17/ireland-emerald-isle-nasa/

Month	Min(°F)	Max(°F)
Jan	36.5	45.7
Feb	36.5	45.5
Mar	37.6	49.1
Apr	39.9	52.5
May	44.2	57.6
Jun	49.3	63.0
Jul	52.5	66.0
Aug	52.0	65.5
Sep	49.3	61.9
Oct	45.7	56.7
Nov	39.6	49.6
Dec	37.8	47.1

The city of Dublin rests on the eastern side of the island of Ireland.  Ireland resides in the Northern Atlantic Ocean northwest of the European Continent and just west of England.  Due to the North Atlantic Ocean current, Dublin enjoys a very mild climate with monthly highs only changing from around the 40s in the winter to the mid 60s in the summer.  The amount of monthly precipitation also doesn’t vary much with an average of 2-3 inches per month with slightly higher values coming in the later months of the year.  The western side of Ireland is exposed to westerly winds causing more change in the average temperatures and rainfall while Dublin’s position on the east side of the island make it less exposed to the same extremes shared by the rest of the island. 

Graph showing monthly temperature together
with average monthly rainfall
Source:http://www.world-climates.com/city-climate-dublin-ireland-europe/

Graph showing monthly highs and lows for Dublin, Ireland
Source:http://en.allmetsat.com/climate/europe.php?code=03969

 

The geography of Ireland is mostly rolling plains covered in green grass year round due the consistently high humidity from warm, moist air coming from the tropics via the North Atlantic Ocean current.  There are few mountainous regions on the island with steep coastal cliff on the western coast of Ireland leading to high winds and higher extremes in temperatures and precipitation.

Koppen Climate Map showing the climate of Ireland to be Cfb, meaning it is temperate,
without a dry season, and has warm summers
Source:http://people.eng.unimelb.edu.au/mpeel/koppen.html

The North Atlantic Ocean current is the main influencer in the climate of Ireland.  The warm waters that travel across the Atlantic to islands of the United Kingdom give the islands a temperate maritime climate with cool summers and mild winters.  This is why this area, being at the same latitudes as the northern United States or Russia, experiences fairly warm winters with little snow while the northern United States and Russia experience very cold and snowy winters.  The climate of Dublin is very similar to that of southern parts of continents in the southern hemisphere, which we associate more with hotter temperatures and less moisture.

Picture of the North Atlantic Ocean Current bringing warm water from the Caribbean up the east coast of the US, across the Atlantic to Greenland and northern Europe
Source:http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html

 

Bowen ratios are used to determine how net radiational heating is partitioned between the sensible and latent heat fluxes.  The sensible heat flux means the amount of heat conducted from the Earth’s surface to the atmosphere.  This mean the more landmass in an area, the higher the sensible heat.  Latent heat refers to the amount of heat conducted through water meaning coastal areas will have higher latent heat than sensible.  In terms of the Bowen ratio, moist areas will have lower ratios and dry areas will have high ratios because moist regions, usually being coastal, have more moisture available giving higher latent heat levels while areas in the interior of continents are much dryer because land is much greater than water.  In terms of the Bowen ratio for Dublin, I would estimate the ratio to be low, around 0.20-0.30 because Ireland is a coastal landmass, giving it a low sensible heat level, with a lot of available moisture, giving it a high latent heat flux, making the Bowen ratio relatively low.