this lecture discusses the climate controls that form the settings for the different climate classes the climates of the northern hemisphere from the tropics poleward are very diverse these are called extra-tropical because they're outside the tropics there are many different factors that contribute to the climate settings in north america there are many local controls like lakes and changes to topography in Europe latitudes are more poleward and the land mass moving into Russia is substantial that results in the development of extreme high and low pressure cells Asia grapples with extreme topography and extreme monsoonal flows d climates are only found in the northern hemisphere for the extra-tropical southern hemisphere will consider Oceania and Antarctica Oceania is a term used to encompass the land masses that comprise Australia New Zealand Indonesia and the other small island chains and countries South America and Africa are dominated by tropical climates as our most locations in Oceania however water has a much larger influence on oceanic climates additionally much of Australia is dry with B climates C climates in Australia are found along the coasts and are dominated by moist flow from circulations around pressure cells Oceania is also strongly influenced by El Nino Southern Oscillation Antarctica has some of the most extreme climates due to its lack of insulation southern hemisphere climates are influenced by the perihelion during summer in the southern hemisphere more incoming radiation is received than in the northern hemisphere a desert is defined in many ways but the most common definition relates to lack of precipitation specifically less than 10 inches precipitation annually precipitation in a desert environment is typically highly variable and deserts can be located in hot and cold locations for example Antarctica is considered a desert because it receives less than 10 inches of precipitation annually deserts are formed where there's a lack of storm activity and the main control for deserts usually is the descending branch of the Hadley or polar cell where air descends and moves under high pressure the parcel moves away from saturation and is less likely to form clouds other controls to desert formation depend on geography and quite often more than one control affects a desert rain shadow deserts form on the leeward side of mountains continental deserts form far away from any moisture sources coastal deserts are typically influenced by the cold ocean currents found on the west side of many continents sea climates are modified by water they're typically found under the influence of on land flow they can be found next to a warm ocean current or adjacent to a subtropical high pressure cell in North America and Australia mid-latitude cyclones with associated fronts are a regular part of a sea climatic setting sea climates are moderate climates because higher dew point temperatures help to modify their climate that also evenly distributes precipitation through the year while sea climates do experience freezing days they're rare snow may fall in the winter season but it's unusual and will usually shut down an urban center for example Atlanta Georgia will get a snow event every two or three years but roads and schools will shut down D climates are poleward of C climates their higher latitudes so they received less incoming radiation and have lower sun angles they're only found in the northern hemisphere because continentality plays a large role in the climatic setting of D climates continentality brings larger diurnal and annual temperature ranges precipitation is usually evenly distributed through the year but might increase slightly during the summer season d climates also include the sub Arctic climates that include the boreal forests a boreal forest is a slow growing coniferous forest and is the second most extensive climate setting after desert climates eke limits are controlled by latitude and water high latitudes have very low Sun angles and day lengths are highly variable from 24 hours to 0 hours winter temperatures are extremely low glaciated and snow-covered locations have a high albedo which reflects a good amount of incoming radiation precipitation is very low so much that many climates could be considered cold deserts some heat is transferred from the ocean but when the ocean is frozen with sea ice during the winter heat transfer is essentially eliminated