Vergara - 1976 - Physiological and morphological adaptability of ri

52 ems-ran; AND arcs
Monsoonal activity and length of growing season
The rainfall in the Asian rnonsoonic region more often than not is characterized
by high spatial and temporal variability Eighty’ percent of the riee-grovring
areas of $outh and Southeast Asia are under rainfed farming. The onset of
monsoon determines the planting time, and the subsequent temporal distribution
of rainfall greatly influences the growth and development of the erop. The
filling of reservoirs, which are the source of supplemental inigation after the
rains cease, also depends on the activity of the preceding monsoon in any particular
year.
In the Indian region for example, the kharif sowing season in the south starts
early i11 J1me, and in the north does not begin until the middle of July when
monsoonal activity covers the entire country. The length of the khan-if growing
season depends on the withdrawal of the 11101150011 rainfall activity (F ig. l).
Localized showers of short duration. rather than the long persisting. drizzle-type
rain characteristic of the middle latitudes, predominate during the period. The
contribution from depressions and cyclonic storms to the rainfall of these areas
l I l I I
70° 7g’ 80° %° 90° 95°
30L
2y_
2s"-
|5°ooh
\ i’?
fiw
r l r r r t
pp
‘épi
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l. The southwest monsoon over India and neighborhood, The data on the letl-hand side of
each curve indicates the nonnal date of onset; normal time of withdrawal is shown on the right
side (compiled from maps published by India Meteorological lkpartment).