Humid Subtropical Climate

Geographic Distribution

Figure 9.24 Humid subtropical climate of North Carolina

The humid subtropical climate is found on the east coast of continents  between 20^o and 40^o N and S latitude. The humid subtropical climate can be found in the southeastern United States, southeastern South America; coastal southeast South Africa; eastern Australia; eastern Asia from northern India through south China to Japan.

Controlling Factors

The east coast location of the Humid Subtropical climate places it near the source region for maritime tropical air. Additionally, warm ocean currents paralleling  these coasts further enhance the instability of the air. These factors combine to produce moderate amounts of precipitation in most months of the year. The humid subtropical climate is subject to cold temperatures during the winter as cP air masses embedded in cyclonic storms pass through this region.

Figure 9. 25 Climograph for Memphis, TN Latitude/Longitude = 35o N; 90o W Average Annual Temperature (oC) = 17 Annual Temperature Range (oC) = 22 Total Annual Precipitation (mm) = 1222 Summer Precipitation (mm) = 536 Winter Precipitation (mm) = 686

Distinguishing Characteristics

Temperature

The humid subtropical climate is noted for its warm summer months, and relatively mild winters. Summer temperatures average between 21^o (69.8^oF) to 26^o C (78.8^oF) and no winter month has an average temperature below 0^oC (32^oF). Many days the temperature can hit 32^oC (90^oF) or higher.  Moving poleward through the various climates of the earth, one notices the distinct development of a seasonal cycle of temperature, especially toward the poleward limits of the climate. The high humidity experienced in the humid subtropical climate makes warm days feel oppressive. The daily temperature range tends to be very small as the evening does not cool down much during the summer. Winter temperatures will dip into the single digits with the relatively frequent invasions of cP air masses, especially on the poleward side of the climate.

Precipitation

The humid subtropical climate gets its name from the high humidity experienced in this environment. Dominance of the warm and moist maritime tropical air creates summers similar to the humid tropics. Precipitation is generally evenly distributed throughout the year. Annual precipitation varies from 254 cm (100 in) near the coast to 63.5 cm (25 in) inland. Frost is generally only a problem in winter when very cold cP air masses penetrate this region, a real hazard for fruit and vegetable growers in the southeastern United States. A monsoon influence is experienced in Asia.