Page 321 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 10 Global Climate Systems 285
▼Figure 10.5 Tropical savanna climate. [(b) Blaine Harrington III/Corbis.]
Station: Arusha, Tanzania Lat/long: 3° 24′ S 36° 42′ E Avg. Ann. Temp.: 26.5°C Total Ann. Precip.: 119 cm
Elevation: 1387 m Population: 1 368 000 Ann. Temp. Range: 4.1 C° Ann. Hr of Sunshine: 2600
Subtropical high
0
(a) Climograph for Arusha, Tanzania; (intense dry period).
humid subtropical hot-summer
Climates
Humid subtropical hot-summer climates either are moist all year or have a pronounced winter-dry period, as occurs in eastern and southern Asia. Maritime tropical air masses generated over warm waters off eastern coasts influence these climates during summer. This warm, moist, unstable air produces convectional showers over land. In fall, winter, and spring, maritime tropical and continental polar air masses interact, generating frontal activity and frequent midlatitude cyclonic storms. These two mechanisms produce year-round precipitation, which averages 100–200 cm a year.
In North America, humid subtropical hot-summer climates are found across the southeastern United States. Columbia, South Carolina, is a representative station (Figure 10.6), with characteristic winter precipi- tation from cyclonic storm activity (other examples are Atlanta, Memphis, and New Orleans). Nagasaki, Japan, is characteristic of an Asian humid subtropical hot- summer station (Figure 10.7), where winter precipitation is less because of the effects of the East Asian monsoon.
ITCZ
35.0 32.5 30.0 27.5 25.0 22.5 20.0 17.5 15.0 12.5 10.0
7.5 5.0 2.5
38 32 27 21 16 10 4
0 –1
–7 –12 –18 –23 –29 –34 –40
Nairobi
Mt. Kilimanjaro
Arusha
TANZANIA
MASAI STEPPE
0 50 KM
KENYA
Mombasa
Tanga 5°
40°
JFMAMJJASOND Month
(b) Characteristic landscape in the Ngorongoro Conservation Area, Tanzania, near Arusha with plants adapted to seasonally dry water budgets.
However, the lower precipitation of winter is not quite dry enough to change the climate category to humid subtropical winter-dry. Nagasaki receives more overall annual precipitation (196 cm) than similar climates in the United States, owing to the monsoonal flow pattern.
humid subtropical Winter-Dry Climates
Humid subtropical winter-dry climates are related to the winter-dry, seasonal pulse of the monsoons. They ex- tend poleward from tropical savanna climates and have a summer month that receives 10 times more precipita- tion than their driest winter month. Chengdu, China, is a representative station in Asia. Figure 10.8 demon- strates the strong correlation between precipitation and the high-summer Sun.
Large numbers of people live in the humid subtropical hot-summer and humid subtropical winter-dry climates, demonstrated by the large populations of north-central India, southeastern China, and the southeastern United States. Although these climates are relatively habitable for humans, natural hazards exist; for example, the in- tense summer rains of the Asian monsoon cause flooding
Precipitation (cm)
Temperature (°C)