(sub continental in scale) Regional climates Variety 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 climates Why:Understand what causes the climate to be what it is and when to worry about departures How: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 scheme Uses 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

Köppen Climate table Key characteristic for Class Class name Subcategory Subcategory name sub categorization A Tropical humid Af Tropical wet No dry season Short dry season; heavy monsoonal rains in other Am Tropical monsoonal 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 Mild with dry, warm summer Csb Mediterranean Mild with no dry season, Cfa Humid subtropical hot summer Mild with dry winter, hot Cwa Humid subtropical summer Mild with no dry season, Cfb Marine west coast warm summer Mild with no dry season, Cfc Marine west coast cool summer

Humid with severe Severe Mid-Latitude Humid continental winter, no dry D Dfa season, hot summer Humid with severe winter, no dry Humid continental season, warm Dfb summer Humid with severe, Humid continental dry winter, hot Dwa summer Humid with severe, Humid continental dry winter, warm Dwb summer Severe winter, no dry season, cool Dfc Subarctic summer Severe, very cold winter, no dry Dfd Subarctic season, cool summer Severe, dry winter, Dwc Subarctic cool summer Severe, very cold and dry winter, cool Dwd Subarctic summer Polar tundra, no true E Polar ET Tundra summer EF Ice Cap Perennial ice H Highland

Climate zones of the world Divided into alphabetic categories A, B, C, D, E, H zones

KÖPPEN Climate classification Tropical 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 warm the 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 climate Diurnal 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 reversal Aw- Tropical savanna climate precipitation deficit much of the year Distinctive dry and wet season

B climates - semi-arid to arid Several sub categories

All B-climates have less than 30” of annual precipitation BW climates are arid (less than 10”) and can be divided further based on latitude (temperature) BWh- low latitude hot and dry BWk- 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 dry BSk- 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-subcategories Cf = moisture evenly distributed throughout the year Cw = 10x the amount of moisture in the summer as compared to the driest winter month Cs = 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-latitude All have severe winters; short summers that range form hot in the south to cool to the north

E climates - Polar No true summer Cold 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 schemes Thornthwaite-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 classification Identifies the “Why” of climates first and uses that information to establish each climatic zone -which air mass dominates

Air masses and climatic types Wet Dry Warm 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) III Cold

Climate zones determined by air mass

Closely linked to climate Vegetation Closely linked to climate Often used as PROXY data for lack of climate data 5 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