Bangladesh
experiences a tropical monsoon natured climate characterised by hot, wet
summers and a prominent dry season in the cooler months. Bangladesh features a wide range of
seasonal variations in rainfall, moderately warm temperatures, and high humidity;
however the local climatic disparities throughout the country are very minimal.
Instead of having four distinctive seasons, Bangladesh has
only three; generally recognized as a hot, humid summer from March to June; a
cool, rainy monsoon season from June to October; and a cool, dry winter season
from October to March. Throughout the entire country the coolest month is
January with temperatures averaging near 26ºC and April being the warmest with
temperatures ranging anywhere from 33ºC to 36ºC. The typical climate of Bangladesh is
also one of the wettest in the world, with most areas receiving more than 1525mm
of rain a year and areas near the hills receiving 5080mm. However, most
rainfall occurs during the monsoon; from June to September and little in winter
from; November to February.
Bangladesh
has warm temperatures right through the year, with comparatively little
discrepancy from month to month. In Dhaka the
average January temperature is about 19°C, and the average May temperature is
about 29°C.
Winds
Winds throughout Bangladesh are mainly from the
north and northwest in the winter, gusting softly at one to three kilometers
per hour in northern and central areas and three to six kilometers per hour
near the coast. From March to May, aggressive thunderstorms, generate winds of
up to sixty kilometers per hour. Throughout the forceful storms of the early
summer and late monsoon season, southerly winds of more than 160 kilometers per
hour cause waves to peak as high as 6 meters in the Bay of
Bengal, which can bring devastating downpours to the coastal
areas.
Precipitation and
Humidity
Heavy rainfall is a distinctive feature of Bangladesh. With the exemption of
the comparatively dried out western region of Rajshahi, where the annual precipitation
is approximately 1600mm, the majority of the country receives at least 2000mm
of rainfall per year. Because the nations locality just south of the foothills
of the Himalayas, where monsoon winds turn west and northwest, the region of
Sylhet in north-eastern Bangladesh obtains the maximum average precipitation.
From the years of 1977 to 1986, annual rainfall in that particular region varied
between 3280mm and 4780mm per year. Average daily humidity ranged from March
lows of between 45 and 71 percent to July highs of between 84 and 92 percent.
Bangladesh
is one of the most flood-prone countries in the world. Basically, it's the
flood plain where the nation’s two largest rivers; the Ganges and the
Brahmaputra transmit spring snowmelt from the towering Himalayan Mountains
to the sea. Bangladesh
being mostly formed of the Gangetic delta will be severely impacted if
sea-levels rise as a result of the greenhouse effect.
Monsoon Season
About 80 percent of Bangladesh's rain falls throughout
the course of the monsoon season. The monsoons effect from the disparities
between low and high air pressure areas that result from discrepancy heating of
land and water. During the hot months of April and May hot air rises over the
Indian subcontinent, creating low-pressure areas into which hasten cooler,
moisture-bearing winds from the Indian Ocean.
This is the southwest monsoon, initiating in June and generally lasting through
until September. Dividing against the Indian island, the monsoon flows in two
branches, one of which strikes western India. The other travels up the Bay
of Bengal and over eastern India
and Bangladesh, crossing the
plain to the north and northeast before being turned to the west and northwest
by the foothills of the Himalayas.
Cyclones
Bangladesh
is prone to shattering cyclones, initiating over the Bay
of Bengal, in the periods of April to May and September to
November. These cyclones are often attended by swelling waves, which have been
known to cause great damage and loss of life. They can create winds with speed
of 161 to 241 kilometers per hour piling up the waters of Bay
of Bengal to crests as high as 20 feet that crash with remarkable
force onto the coastal areas and offshore islands. Since the early 18th
century, when records were first kept, more than one million people have been
killed in such storms. Between 1947 and 1988, thirteen relentless cyclones hit Bangladesh,
causing enormous loss of life and property. In May 1985, for example, a severe
cyclonic storm packing 154 kilometre-per-hour winds and waves 4 meters high flounced
into south-eastern and southern Bangladesh, killing more than 11,000 persons,
damaging more than 94,000 houses, killing some 135,000 head of livestock, and
damaging nearly 400 kilometers of critically needed embankments. The cyclone of
November 1970 however, in which about 500,000 lives were lost in Bangladesh, was
one of the worst natural disasters of the country in the 20th century.
Apart from Cyclones, other natural misfortunes, such as
floods, tornadoes, and tidal bores devastate the country, particularly on the
coastal belt, almost every year. Annual monsoon flooding results in the loss of
human life, damage to property and communication systems, and a deficiency of
drinking water, which leads to the spread of disease. In 1988 two-thirds of
Bangladesh's sixty-four districts attributed widespread flood damage in the
wake of curiously heavy rains that flooded the river systems. Millions were
left homeless and without potable water. Half of Dhaka, including the runways
at the Zia International Airport
was flooded. About 2 million tons of crops were reported destroyed, and relief
work was rendered even more challenging than usual because the flood made
transportation of any kind exceedingly difficult.
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