Table 4.2 Regional climates
a
Ko ¨ppen group and types
Ecoregion equivalents
A Tropical and humid climates
Humid tropical domain (400)
Tropical wet (Ar)
Rainforest division (420)
Tropical wet-dry (Aw)
Savanna division (410)
B Dry climates
Dry domain (300)
Tropical/subtropical semiarid (BSh)
Tropical/subtropical steppe division (310)
Tropical/subtropical arid (BWh)
Tropical/subtropical desert division (320)
Temperate semiarid (BSk)
Temperate steppe division (330)
Temperate arid (BWk)
Temperate desert division (340)
C Subtropical climates
Humid temperate domain (200)
Subtropical dry summer (Cs)
Mediterranean division (260)
Humid subtropical (Cf)
Subtropical division (230)
Prairie division (250)
b
D Temperate climates
Temperate oceanic (Do)
Marine division (240)
Temperate continental, warm
summer (Dca)
Hot continental division (220)
Prairie division (250)
b
Temperate continental, cool
summer (Dcb)
Warm continental division (210)
Prairie division (250)
b
E Boreal climates
Polar domain (100)
Subarctic (E)
Subarctic division (130)
F Polar climates
Tundra division (120)
Tundra (Ft)
Ice Cap (Fi)
Definitions and Boundaries of the Ko ¨ppen–Trewartha System
Ar
All months above 18
C and no dry season
Aw
Same as Ar, but with 2 months dry in winter
BSh
Potential evaporation exceeds precipitation, and all months above 0
C
BWh
One-half the precipitation of BSh, and all months above 0
C
BSk
Same as BSh, but with at least 1 month below 0
C
BWk
Same as BWh, but with at least 1 month below 0
C
Cs
8 months 10
C, coldest month below 18
C, and summer dry
Cf
Same as Cs, but no dry season
Do
4–7 months above 10
C, coldest month above 0
C
Dca
4–7 months above 10
C, coldest month below 0
C, and warmest month
above 22
C
Dcb
Same as Dca, but warmest month below 22
C
E
Up to 3 months above 10
C
Ft
All months below 10
C
Fi
All months below 0
C
A/C boundary ¼ Equatorial limits of frost; in marine locations, the isotherm of 18
C for coolest month
C/D boundary ¼ 8 months 10
C
D/E boundary ¼ 4 months 10
C
E/F boundary ¼ 10
C for warmest month
B/A, B/C, B/D, B/E boundary ¼ Potential evaporation equals precipitation
a
Based on the Ko ¨ppen system of classification (Ko ¨ppen 1931), as modified by G.T. Trewartha (1968) and Trewartha
et al. (1967)
b
Ko ¨ppen did not recognize the Prairie as a distinct climatic type. The ecoregion classification system represents it at the
arid sides of the Cf, Dca, and Dcb types
4.2 Types of Ecoclimatic Zones, or Continental Ecoregions
37
a
Ko ¨ppen group and types
Ecoregion equivalents
A Tropical and humid climates
Humid tropical domain (400)
Tropical wet (Ar)
Rainforest division (420)
Tropical wet-dry (Aw)
Savanna division (410)
B Dry climates
Dry domain (300)
Tropical/subtropical semiarid (BSh)
Tropical/subtropical steppe division (310)
Tropical/subtropical arid (BWh)
Tropical/subtropical desert division (320)
Temperate semiarid (BSk)
Temperate steppe division (330)
Temperate arid (BWk)
Temperate desert division (340)
C Subtropical climates
Humid temperate domain (200)
Subtropical dry summer (Cs)
Mediterranean division (260)
Humid subtropical (Cf)
Subtropical division (230)
Prairie division (250)
b
D Temperate climates
Temperate oceanic (Do)
Marine division (240)
Temperate continental, warm
summer (Dca)
Hot continental division (220)
Prairie division (250)
b
Temperate continental, cool
summer (Dcb)
Warm continental division (210)
Prairie division (250)
b
E Boreal climates
Polar domain (100)
Subarctic (E)
Subarctic division (130)
F Polar climates
Tundra division (120)
Tundra (Ft)
Ice Cap (Fi)
Definitions and Boundaries of the Ko ¨ppen–Trewartha System
Ar
All months above 18
C and no dry season
Aw
Same as Ar, but with 2 months dry in winter
BSh
Potential evaporation exceeds precipitation, and all months above 0
C
BWh
One-half the precipitation of BSh, and all months above 0
C
BSk
Same as BSh, but with at least 1 month below 0
C
BWk
Same as BWh, but with at least 1 month below 0
C
Cs
8 months 10
C, coldest month below 18
C, and summer dry
Cf
Same as Cs, but no dry season
Do
4–7 months above 10
C, coldest month above 0
C
Dca
4–7 months above 10
C, coldest month below 0
C, and warmest month
above 22
C
Dcb
Same as Dca, but warmest month below 22
C
E
Up to 3 months above 10
C
Ft
All months below 10
C
Fi
All months below 0
C
A/C boundary ¼ Equatorial limits of frost; in marine locations, the isotherm of 18
C for coolest month
C/D boundary ¼ 8 months 10
C
D/E boundary ¼ 4 months 10
C
E/F boundary ¼ 10
C for warmest month
B/A, B/C, B/D, B/E boundary ¼ Potential evaporation equals precipitation
a
Based on the Ko ¨ppen system of classification (Ko ¨ppen 1931), as modified by G.T. Trewartha (1968) and Trewartha
et al. (1967)
b
Ko ¨ppen did not recognize the Prairie as a distinct climatic type. The ecoregion classification system represents it at the
arid sides of the Cf, Dca, and Dcb types
4.2 Types of Ecoclimatic Zones, or Continental Ecoregions
37