Climate

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Climate
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Climate Extremes

• Highest temperature ever recorded in North
  America
• 57C (134F) at Greenland Ranch in Death Valley,
  CA
• Average max temp in July in Death Valley is
  116F!!
• Hottest urban area is Yuma AZ (high temps average
  108F in July)
• Hottest place in the world Dallol, Ethiopia -
  located south of the Red Sea
• Average annual temperature between 1960-1996 was
  94F !!
• One of the coldest spots in U.S. - International
  Falls, MN
• Average temperature in January of 3F
• Longest cold streak - Langdon, ND - winter of
  1936
• Temp remained below 0F for 41 consecutive days
• Coldest temperature reading in US - Rogers Pass,
  Montana
• -70F on 20 Jan, 1954
• Coldest areas of the North America
• Yukon and the Northwest Territories of Canada
• Coldest areas in N.H.
• Siberia and Greenland
• Coldest temperature ever recorded anywhere in the
  world
• -129F at Vostok, Antarctica

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• Defining climate
• Long-term statistical properties of the
  atmosphere for an area
• Climate classifications
• Express obvious properties
• Temperature and precipitation
• Also, air mass types, energy budget components,
  or water budget characteristics

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Climate Scales

• Climate can be defined on different spatial
  scales
• Microclimate - near the ground over your front
  yard
• Mesoclimate - over a field or few fields (a few
  square kilometers)
• Macroclimate - scale of a state or country
• Global climate - over entire earth
• We will focus on large-scale climate
• Indeed, climate extremes exist on the planet, so
  what controls climate?

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Climate controls

• Intensity of solar radiation and it's variation
  with latitude
• Distribution of land and water
• Ocean currents
• Prevailing winds
• Positions of semi-permanent high and low pressure
  systems
• Mountain barriers
• Altitude

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Earths Climate

• The Koeppen Classification
• Tropical Climates (A)
• Dry Climates (B)
• Mild Mid-latitude Climates (C)
• Severe Mid-latitude Climates (D)
• Polar Climates (E) and Highland (H)
• Based on mean monthly temperature and
  precipitation of regions of similar natural
  vegetation cover

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• Tropical Climates
• Warm annual temperatures and minimal seasonal
  temperature variation
• Differentiated on precipitation variations
• Tropical Wet (Af)
• Even precipitation through year
• High humidity
• Temperatures
• Highs low 30s C (80s F)
• Lows low 20s (70s F)

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Af climographs
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• Monsoonal (Am)
• Near tropical coastal areas
• Monthly precipitation variations
• Very high annual totals
• Small annual temperature variations

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Am climographs
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• Tropical Wet and Dry (Aw)
• Poleward tropical margins
• Distinct temperature and precipitation
  seasonality
• Low sun dry period
• Unreliable precipitation
• Sahel region
• Savanna vegetation

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Aw climographs
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• Dry Climates
• 30 of Earths land surface (Most of any type)
• Defined by water balance
• Potential evapotranspiration gt precipitation
• Subtropical Deserts (BWh)
• Largest deserts
• Western sides of continents
• Subsidence areas
• High diurnal temperature ranges

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BWh climographs
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High precipitation variability of BWh regions
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• Subtropical Steppe (BSh)
• High aridity
• High precipitation and temperature variability
• Large temperature ranges
• Extreme summer temperatures
• Summer precipitation

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BSh climographs
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• Mid-Latitude Deserts (BWk)
• Extreme continentality and/or rain shadows
• Asia and the Western U.S.
• Very high temperature ranges
• Summer temperatures very hot
• Nighttime and winter temperatures - very cool
• Higher humidity and precipitation

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BWk climographs
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• Mid-Latitude Steppe (BSk)
• A transition zone
• Higher annual average precipitation than true
  desert

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BSk climographs
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• Mild Mid-Latitude Climates
• Eastern continental areas
• 30o and 60o
• Varying precipitation regimes
• Mild winter temperatures
• Summer temperatures may be harsh

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• Mediterranean (Csa, Csb)
• Distinct summer dry period
• Subtropical high interactions
• Winter precipitation is variable
• Mild winter temperatures
• Mild to hot summers

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Csa, Csb climographs
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• Humid Subtropical (Cfa, Cwa)
• Eastern continental areas of the lower
  mid-latitudes
• High heat and moisture
• Abundant and even monthly precipitation
• Subtropical highs
• Mild winters
• Hot summers
• Moisture deficits

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Cfa, Cwa climographs
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• Marine West Coast (Cfb, Cfc)
• Poleward of Csb
• Cold ocean current influence
• Fog and/or low cloud cover
• Mild and even annual temperatures
• High frequency of rain days
• Low totals

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Cfb, Cfc climographs
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• Severe Mid-latitude Climate
• Very cold winters
• Large continental areas
• Continentality
• Evenly distributed annual precipitation
• Humid Continental (Dfa, Dfb, Dwa, Dwb)
• Eastern continents - 40o-55o N
• Warm to hot summers
• Cold winters
• Even and abundant annual precipitation

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Dfa, Dfb, Dwa, Dwb climographs
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• Subarctic (Dfc, Dfd, Dwc, Dwd)
• Poleward of humid continental climates
• Coniferous boreal forest (taiga)
• Warm, short summers
• Low annual precipitation
• Summer maximum

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Dfc, Dfd, Dwc, Dwd climographs
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Polar Climates

• Poleward of 70
• Subtypes
• Tundra (ET)
• Ground is permanently frozen to depths of
  hundreds of meters - called permafrost
• Meager annual precip
• Very cool summers - low sun angle
• Extremely cold winters
• Ice Cap (EF)
• Average T for each month is below freezing
• Interior ice sheets of Greenland and Antarctica
• Very meager precip - no moisture

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• Polar Climates
• Very high latitudes
• Very cold
• Tundra (ET)
• Tundra vegetation
• Harsh winters
• Mild summers of long days
• Permafrost region

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ET climographs
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• Ice Cap (EF)
• Constant ice cover
• Greenland and Antarctica
• Warmest monthly temperatures lt 0oC
• Katabatic winds
• Low precipitation

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EF climographs
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• Highland Climates (H)
• Governed solely by topography
• Vertical zonation
• Highly variable local climates