Climate Of Bangladesh

Topics: Climate, Precipitation, Monsoon Pages: 69 (2805 words) Published: April 11, 2015
Climate of Bangladesh
Climate is the average weather of
30-year time period for a particular
region. Climate is not the same as
weather, but rather, it is the
average pattern of weather for a
particular region. Weather
describes the short-term state of
atmosphere.

The Tropic of Cancer passes through
the center of Bangladesh and the
country's climate can be described as
tropical monsoon type - warm and
humid in the summer, dry and cool in
the winter. The dominant climatic factor
for Bangladesh is the monsoon - the
distinct change between the wet
(warmer) and dry (cooler) periods.
Three main meteorological seasons are
recognized:

• (a) Hot or summer season (March-May).
This pre-monsoon season is generally
hot and sunny with high evaporation
rates. April is normally the hottest month
when the maximum temperature may
exceed 40°c in the western part of the
country. About 15% of the annual rainfall
occurs in this season, mainly from
thunderstorms or 'norwesters'.

b) Rainy or Monsoon season
(June-October). This is the
period of highest rainfall,
humidity and cloudiness. Nearly
80 % of the annual rainfall
occurs during this season, and
in June, the temperature drops
due to the cooling effect of the
rains.

(c) Cool (winter) and dry season
(November-February). This season
is characterized by low temperature,
low humidity and high solar
radiation. January is normally the
coldest month when minimum
temperature of 5° C may be
recorded in the northern part of the
country. Only about 5% of the
annual rainfall occurs during this
season.

Mean annual temperature in
Bangladesh is about 25°C. Mean
monthly temperatures vary from
about 18° C in winter to around
30'C in the pre-monsoon period,
while extreme temperatures range
between about 5°C and 43° C
except near the coast where the
sea provides the moderating
influence.

On average, the country annually
receives about 2300 mm of rainfall,
varying from 1250 mm in the west to
5500 mm in the extreme northeast. The
rainfall, however, is variable from year to
year, both in total amount as well as in
terms of the beginning and departure
schedule of the rainy season. Ironically,
this variability often causes problems of
both drought and floods.

The coastal areas of Bangladesh are hit
by tropical cyclones, accompanied by
storm surges, almost every year in the
pre-monsoon months of April-May and
post-monsoon months of OctoberNovember. Some of these cyclones develop into hurricanes with wind velocity
exceeding 120 km per hour. The country
exhibits certain seasonal and spatial
variations in climate. These can be best
understood through an insight into the
main climatic elements.

Norwesters
The norwesters are so called
because these thunderstorms
frequently approach a place from
the northwesterly direction, though,
in fact, they may come from any
direction. These storms occurring
in the Bengali month of Baishakh
(April-May) are locally known as
Kalbaishakhi.

• The frequency of norwesters is
generally highest in April, but they
are also common in late March and
early May. The special features of
the norwesters are their rapid
formation and movement against
the direction of the surface
currents. The most frequent time of
occurrence is afternoons or early
evenings.

They are usually of a short duration
with rainfall of high intensity, but wind
speed often exceeds 100 km/hr. The
storms are accompanied by thunder,
lightning, hailstones (often more than a
centimeter in diameter) and convective
cumulo-nimbus clouds. There is a
sharp fall in temperature following the
storm. The norwesters are triggered by
a variety of factors.
 

However, the principal conditions
which favour the development of
norwesters in Bangladesh are a
steady drift of cool, dry air from
the northwest at altitudes of over
two kilometers, and a warm, moist
southerly or southwesterly current
along...
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