Regional climatesVariety of different scales of climatic investigations• macroclimate- largest area of study, area extends for 4 x 108 m2, up to 6000 m vertically

• (continental in scale)• mesoclimate- 103 m2 up to 4 x 108 m2 in area

• (sub continental in scale)• Local climate - a group of microclimates that characterize a specific region; 103 to 108 m2 in size

• Microclimate - the smallest category 1 to 104 m2 in area• An individual field or park

Schematic of climatic scales of study

Climate classification: What, Why and How?What:Organize regions with similar climatesWhy:Understand what causes the climate to be what it is and when to worry about departuresHow:Look at moisture, temperature, evaporation, transpiration, vegetation, altitude, latitude, etc. and decide on some value that sets the boundary (threshold)- commonly related to plants

Köppen climate classification schemeUses Monthly mean temps, monthly mean precipitation, and annual mean temps to establish major climatic zones• designated with capital letters

Widely used but frequently criticized• no agreement between plants and climate• variability in the factors that set boundary

= climate classification changes constantly

Class Class name SubcategorySubcategory nameKey characteristic for sub categorization

A Tropical humid Af Tropical wet No dry season

Am Tropical monsoonal

Short dry season; heavy monsoonal rains in other

months Aw Tropical savanna Winter dry season

B Dry BWh Subtropical desert Low-latitude desert BSh Subtropical steppe Low-latitude dry BWk Mid-latitude desert Mid-latitude desert BSk Mid-latitude steppe Mid-latitude dry

C Mild Mid-Latitude Csa Mediterranean Mild with dry, hot summer

Csb Mediterranean Mild with dry, warm

Cfa Humid subtropical Mild with no dry season, hot summer

Cwa Humid subtropical Mild with dry winter, hot summer

Cfb Marine west coast Mild with no dry season, warm summer

Cfc Marine west coast Mild with no dry season, cool summer

Köppen Climate table

summer

DSevere Mid-Latitude Dfa

Humid continental

Humid with severe winter, no dry season, hot summer

Dfb

Humid continental

Humid with severe winter, no dry season, warm summer

Dwa Humidcontinental

Humid with severe, dry winter, hot summer

Dwb Humid continental

Humid with severe, dry winter, warm summer

Dfc Subarctic

Severe winter, no dry season, cool summer

Dfd Subarctic

Severe, very cold winter, no dry season, cool summer

Dwc Subarctic Severe, dry winter, cool summer

Dwd Subarctic

Severe, very cold and dry winter, cool summer

E Polar ET Tundra Polar tundra, no true summer

EF Ice Cap Perennial ice H Highland

Climate zones of the worldDivided into alphabetic categories

A, B, C, D, E, H zones

KÖPPEN Climate classificationTropical climates designated with a capital “A”Based in part on vegetation zones that are sensitive to moisture and temperature

Tropical (A) Climates - All tropical climates are warmthe subdivisions are based on differences in rain Tropical Rainforest (Af) Climates located 0-15° N/S Lat. Diurnal temperature range is greater than the difference between the warmest and coolest months (annual range). Every month has precipitation and no month is deficient in rainfall. This high amount of rainfall keeps the soil moisture at capacity. EVT occurs at potential rate

Am- Tropical monsoonal climateDiurnal temperature range is greater than the difference between the warmest and coolest months (annual range). seasonal precipitation surplus and deficit Distinctive dry and wet season related to wind reversalAw- Tropical savanna climateDiurnal temperature range is greater than the difference between the warmest and coolest months (annual range). precipitation deficit much of the yearDistinctive dry and wet season

B climates - semi-arid to aridSeveral sub categories

All B-climates have less than 30” of annual precipitationBW climates are arid (less than 10”) and can be divided further based on latitude (temperature)

BWh- low latitude hot and dryBWk- mid latitude cool and dry

BWh is a function of Hadley cell circulation; occur between 18 and 32° N-S Latitude

BS climates are semi-arid (more than 10” but less than 30” of rain) and can be divided further based on latitude (temps)

BSh- low latitude hot and dryBSk- mid latitude cool and dry

A gradational change from A climates on either side of the B climates

C climates- Mesothermal temperate Warm summers (<10°C); Mild Winters (between -3 to 18°C)Annual moisture distribution determines subcategories

C-subcategoriesCf = moisture evenly distributed throughout the yearCw = 10x the amount of moisture in the summer as compared to the driest winter monthCs = 3x as much moisture in the winter as compared to the driest summer month; at least 1 month with less than 3 cm of precipitation

Csa= called Mediterranean climate• western edge of mid-latitude continents

Cfa= called a Humid subtropical climate• Southeastern edge of mid latitude continents

Cfb= called Marine west coast• Western edge of continents at higher latitudes

D climates- Severe Mid-latitudeAll have severe winters; short summers that range form hot in the south to cool to the north

E climates - Polar No true summerCold all year long

Köppen climate regions of North America

Köppen climate regions of the US

Trewartha climate classification scheme - a modified version of the Köppen system. Attempts to redefine the broad climatic groups in such a way as to be closer to vegetational zoning. Group A - this is the tropical climate group, defined as places which do not receive annual winter frosts (in maritime regions this corresponds closely to the Köppen boundary). Climates with no more than 2 dry months are classified Ar , while others are classified Aw . There is no specific monsoon climate identifier.Group B - this is identical to the Köppen scheme. Group C - in the Trewartha scheme this category includes subtropical climates only (8 or more months above 10 °C). The identifiers are the same as the first two letters of the Köppen identifier - the Mediterranean climate is denoted Cs and the humid subtropical climate, Cf or Cw .

Trewartha Climate scheme (Continued)Group D - this group represents temperate climates. Continental climates are represented as Dca (Köppen Dfa, Dwa, Dsa ) and Dcb (Köppen Dfb ,Dwb ,Dsb ). Maritime temperate climates (Köppen Cfb ,Cwb ,Csb ,Cfc ) are denoted Do in the Trewartha classification. The dividing point between maritime and continental climates is 0 °C in the coldest month, rather than the usual Köppen value of -3 °C.

Group E - this group is undivided and contains the continental subarctic climates (Köppen Dfc ,Dwc ,Dfd )

Group F - this is the polar climate group, split into Ft (Köppen ET ) and Fi (Köppen EF ).

Group H - Highland climates - in which altitude is the most important factor determining climate.

Other climate classification schemesThornthwaite-based his scheme on moisture effectiveness and temperature efficiency•mathematical relationships easy to identify from available meteorological data

•Also uses info on season when rain or snow falls

Genetic classificationIdentifies the “Why” of climates first and uses that information to establish each climatic zone

-which air mass dominates

Tropical wet

Tropical wet and dry

Tropical dry (desert)

Grp I

mid latitude wet

Mid latitude summer or winter dry

mid latitude dry (desert)

Grp II

Polar wet Polar wet and dry

Polar dry (desert)

GrpIII

Wet DryWarm

Cold

Air masses and climatic types

Climate zones determined by air mass

VegetationClosely linked to climateOften used as PROXY data for lack of climate data5 distinct veggie zones• Forests = trees; many different types of forests

• e.g., hardwood, conifer, rainforest• Deserts = discontinuous veggies; scrub brush; cactus, etc.• Grasslands = grasses• Taiga = cold; climate evergreen conifer forests• Tundra = cold; grasses sedges mosses and lichens