Earth:Tropical monsoon climate

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File:Koppen-Geiger Map Am present.svgAn area of tropical monsoon climate (occasionally known as a tropical wet climate or a tropical monsoon and trade-wind littoral climate) is a type of climate that corresponds to the Köppen climate classification category "Am". Tropical monsoon climates have monthly mean temperatures above 18 °C (64 °F) in every month of the year and a dry season. [1]:200–1 Tropical monsoon climates is the intermediate climate between the wet Af (or tropical rainforest climate) and the drier Aw (or tropical savanna climate). A tropical monsoon climate, however, has its driest month seeing on average less than 60 mm, but more than [math]\displaystyle{ 100-\left ( \frac{Total\ Annual\ Precipitation\ (mm)}{25} \right ) }[/math].[1] This latter fact is in direct contrast to a tropical savanna climate, whose driest month sees less than 60 mm of precipitation and also less than [math]\displaystyle{ 100-\left ( \frac{Total\ Annual\ Precipitation\ (mm)}{25} \right ) }[/math] of average monthly precipitation. In essence, a tropical monsoon climate tends to either see more rainfall than a tropical savanna climate or have less pronounced dry seasons. Additionally, a tropical monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the "winter" solstice for that side of the equator.[1]

Versions

There are generally two versions of a tropical monsoon climate:

  • Less pronounced dry seasons. Regions with this variation of the tropical monsoon climate typically see copious amounts of rain during the wet season(s), usually in the form of frequent thunderstorms. However, unlike most tropical savanna climates, a sizeable amount of precipitation also falls during the dry season(s). In essence, this version of the tropical monsoon climate generally has less pronounced dry seasons than tropical savanna climates.
  • Extraordinarily rainy wet seasons and pronounced dry seasons. This variation features pronounced dry seasons similar in length and character to dry seasons observed in tropical savanna climates. However, this is followed by a sustained period (or sustained periods) of extraordinary rainfall. In some instances, up to (and sometimes in excess of) 1,000 mm of precipitation is observed per month for two or more consecutive months. Tropical savanna climates generally do not see this level of sustained rainfall.

Distribution

Tropical monsoon climates are most commonly found in South and Central America. However, there are sections of South Asia, Southeast Asia, Africa (particularly West and Central Africa), the Caribbean, North America, and Australia that also feature this climate.

Factors

The major controlling factor over a tropical monsoon climate is its relationship to the monsoon circulation. The monsoon is a seasonal change in wind direction. In Asia, during the summer (or high-sun season) there is an onshore flow of air (air moving from ocean towards land). In the “winter” (or low-sun season) an offshore air flow (air moving from land toward water) is prevalent. The change in direction is due to the difference in the way water and land heat.

Changing pressure patterns that affect the seasonality of precipitation also occur in Africa though it generally differs from the way it operates in Asia. During the high-sun season, the Intertropical convergence zone (ITCZ) induces rain. During the low-sun season, the subtropical high creates dry conditions. The monsoon climates of Africa, and the Americas for that matter, are typically located along tradewind coasts.

Cities with a tropical monsoon climate

Charts of selected cities

Chittagong
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
5
 
 
26
13
 
 
28
 
 
28
15
 
 
64
 
 
31
19
 
 
150
 
 
32
23
 
 
264
 
 
32
24
 
 
533
 
 
31
25
 
 
597
 
 
30
25
 
 
518
 
 
30
24
 
 
320
 
 
31
24
 
 
180
 
 
31
23
 
 
56
 
 
29
18
 
 
15
 
 
26
14
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: BBC[2]
Conakry
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
1
 
 
32
19
 
 
1
 
 
33
20
 
 
3
 
 
33
21
 
 
22
 
 
34
22
 
 
137
 
 
33
21
 
 
396
 
 
32
20
 
 
1130
 
 
30
20
 
 
1104
 
 
30
21
 
 
617
 
 
31
21
 
 
295
 
 
31
20
 
 
70
 
 
32
21
 
 
8
 
 
32
20
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: HK[3]
Manaus
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
260
 
 
31
23
 
 
288
 
 
30
23
 
 
314
 
 
31
23
 
 
300
 
 
31
23
 
 
256
 
 
31
23
 
 
114
 
 
31
23
 
 
88
 
 
31
23
 
 
58
 
 
33
23
 
 
83
 
 
33
24
 
 
126
 
 
33
24
 
 
183
 
 
32
24
 
 
217
 
 
31
24
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: WMO[4] HK[5]
Miami
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
51
 
 
24
15
 
 
53
 
 
25
16
 
 
61
 
 
26
18
 
 
72
 
 
28
20
 
 
158
 
 
30
22
 
 
237
 
 
31
24
 
 
145
 
 
32
25
 
 
193
 
 
32
25
 
 
194
 
 
31
24
 
 
143
 
 
29
22
 
 
68
 
 
27
19
 
 
47
 
 
25
16
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: WMO[6]

References