Climate & Weather Malaysia
The characteristic features of the climate of Malaysia are uniform
temperature, high humidity and copious rainfall and they arise mainly
from the maritime exposure of the country. Winds are generally light.
Situated at the equatorial doldrum area, it is extremely rare to have a full
day with completely clear sky even in periods of severe drought. On the
other hand, it is also rare to have a stretch of a few days with completely
no sunshine except during the northeast monsoon seasons.
Wind flow in Malaysia
Though the wind over the country is generally light and variable, there
are, however, some uniform periodic changes in the wind flow patterns. Based
on these changes, four seasons can be distinguished, namely, the southwest
monsoon, northeast monsoon and two shorter inter monsoon seasons.
The southwest monsoon is usually established in the later half of May or
early June and ends in September. The prevailing wind flow is generally
south westerly and light, below 15 knots.
The northeast monsoon usually commences in early November and ends in
March. During this season, steady easterly or north-easterly winds of 10 to
20 knots prevail. The more severely affected areas are the east coast states
of Peninsular Malaysia where the wind may reach 30 knots or more during
periods
of intense surges of cold air from the north (cold surges).
The winds during the two inter monsoon seasons are generally light and
variable. During these seasons, the equatorial trough lies over Malaysia.
It is worth mentioning that during the months of April to November, when
typhoons frequently develop over the west Pacific and move westwards across
the Philippines, south-westerly winds over the northwest coast of Sabah and
Sarawak region may strengthen reaching 20 knots or more.
As Malaysia is mainly a maritime country, the effect of land and sea
breezes on the general wind flow pattern is very marked especially over days
with clear skies. On bright sunny afternoons, sea breezes of 10 to 15 knots
very often develop and reach up to several tens of kilometer inland. On
clear nights, the reverse process takes place and land breezes of weaker
strength can also develop over the coastal areas.
Rainfall Distribution
The seasonal wind flow patterns coupled with the local topographic
features determine the rainfall distribution patterns over the country.
During the northeast monsoon season, the exposed areas like the east coast
of Peninsular Malaysia, Western Sarawak and the northeast coast of Sabah
experiences heavy rain spells. On the other hand, inland areas or areas
which are sheltered by mountain ranges are relatively free from its
influence. It is best to describe the rainfall distribution of the country
according to seasons.
Seasonal Rainfall Variation in Peninsular Malaysia
The seasonal variation of rainfall in Peninsular Malaysia is of three
main types:
(a) Over the east coast districts, November, December and January are the
months with maximum rainfall, while June and July are the driest months in
most districts.
(b) Over the rest of the Peninsula with the exception of the southwest
coastal area, the monthly rainfall pattern shows two periods of maximum
rainfall separated by two periods of minimum rainfall. The primary maximum
generally occurs in October - November while the secondary maximum generally
occurs in April - May. Over the northwestern region, the primary minimum
occurs in January - February with the secondary minimum in June - July while
elsewhere the primary minimum occurs in June - July with the secondary
minimum in February.
(c) The rainfall pattern over the southwest coastal area is much affected
by early morning "Sumatras" from May to August with the result that the
double maxima and minima pattern is no longer discernible. October and
November are the months with maximum rainfall and February the month with
minimum rainfall. The March - April - May maximum and the June -July minimum
are absent or indistinct.
Seasonal Rainfall Variation in Sabah and Sarawak
The seasonal variation of rainfall in Sabah and Sarawak can be divided
into five main types:
(a) The coastal areas of Sarawak and northeast Sabah experience a
rainfall regime of one maximum and one minimum. While the maximum occurs
during January in both areas, the occurence of the minimum differs. In the
coastal areas of Sarawak, the minimum occurs in June or July while in the
northeast coastal areas of Sabah, it occurs in April. Under this regime,
much of the rainfall is received during the northeast monsoon months of
December to March. In fact, it accounts for more than half of the annual
rainfall received on the western part of Sarawak.
(b) Inland areas of Sarawak generally experience quite evenly distributed
annual rainfall. Nevertheless, slightly less rainfall is received during the
period June to August which corresponds to the occurence of prevailing
southwesterly winds. It must be pointed out that the highest annual rainfall
area in Malaysia may well be found in the hill slopes of inland Sarawak
areas. Long Akah, by virtue of its location, receives a mean annual rainfall
of more than 5000 mm.
(c) The northwest coast of Sabah experiences a rainfall regime of which
two maxima and two minima can be distinctly identified. The primary maximum
occurs in October and the secondary one in June. The primary minimum occurs
in February and the secondary one in August. While the difference in the
rainfall amounts received during the two months corresponding to the two
maxima is small, the amount received during the month of the primary minimum
is substantially less than that received during the month of the secondary
minimum. In some areas, the difference is as much as four times.
(d) In the central parts of Sabah where the land is hilly and sheltered
by mountain ranges, the rainfall received is relatively lower than other
regions and is evenly distributed. However, two maxima and two minima can be
noticed, though somewhat less distinct. In general, the two minima occur in
February and August while the two maxima occur in May and October.
(e) Southern Sabah has evenly distributed rainfall. The annual rainfall
total received is comparable to the central part of Sabah. The period
February to April is, however slightly drier than the rest of the year.
Temperature Distribution
Being an equatorial country, Malaysia has uniform temperature throughout
the year. The annual variation is less than 2°C except for the east coast
areas of Peninsular Malaysia which are often affected by cold surges
originating from Siberia during the northeast monsoon. Even there, the
annual variation is below 3°C.
The daily range of temperature is large, being from 5°C to 10°C at the
coastal stations and from 8°C to 12°C at the inland stations but the
excessive day temperatures which are found in continental tropical areas are
never experienced. It may be noted that air temperature of 38°C has very
rarely been recorded in Malaysia. Although the days are frequently hot, the
nights are reasonably cool everywhere.
Although the seasonal and spatial temperature variations are relatively
small, they are nevertheless fairly definite in some respects and are worthy
of mention. Over the whole Peninsula, there is a definite variation of
temperature with the monsoons and this is accentuated in the east coast
districts. April and May are the months with the highest average monthly
temperature in most places and December and January are the months with the
lowest average monthly temperature. The average daily temperature in most
districts to the east of the Main Range is lower than that of the
corresponding districts west of the Main Range. The differences in the
average values in the east and the west are due almost entirely to the low
day temperatures experienced in the eastern districts during the northeast
monsoon as a result of rain and greater cloud cover. At Kuala Terengganu,
for example, the day temperature rarely reaches 32°C during the northeast
monsoon and often fails to reach 27°C. A number of occasions have been
recorded on which the temperature did not rise above 24°C which is quite
frequently the lowest temperature reached during the night in most
districts. Night temperatures do not vary to the same extent, the average
usually being between21°C to 24°C. Individual values can fall much below
this at nearly all stations, the coolest nights commonly follow some of the
hottest days.
Relative Humidity
As mentioned earlier, Malaysia has high humidity. The mean monthly
relative humidity falls within 70to 90%, varying from place to place and
from month to month. For any specific area, the range of the mean monthly
relative humidity varies from a minimum of 3% to a maximum of about 15%. In
Peninsular Malaysia, the minimum range of mean relative humidity varies from
a low 84% in February to a high of only 88% in November. The maximum range
is found in the northwest area of the Peninsula (Alor Setar) where the mean
relative humidity varies from a low of 72% in February to a high of 87%. It
is observed that in Peninsular Malaysia, the minimum relative humidity is
normally found in the months of January and February except for the east
coast states of Kelantan and Terengganu which have the minimum in March. The
maximum is however generally found in the month of November.
As in the case of temperature, the diurnal variation of relative humidity
is much greater as compared to the annual variation. The mean daily minimum
can be as low as 42% during the dry months and reaches as high as 70% during
the wet months. The mean daily maximum, however, does not vary much from
place to place and is at no place falls below 94%. It may reach as high as
nearly 100%. Again, the northwest states of Kedah and Perlis have the
largest diurnal variation of relative humidity.
Sunshine and Solar Radiation
Being a maritime country close to the equator, Malaysia naturally has
abundant sunshine and thus solar radiation. However, it is extremely rare to
have a full day with completely clear sky even in periods of severe drought.
The cloud cover cuts off a substantial amount of sunshine and thus solar
radiation. On the average, Malaysia receives about 6 hours of sunshine per
day. There are, however, seasonal and spatial variations in the amount of
sunshine received. Alor Setar and Kota Bharu receive about 7 hours per day
of sunshine while Kuching receives only 5 hours on the average. On the
extreme, Kuching receives only an average of 3.7 hours per day in the month
of January. On the other end of the scale, Alor Setar receives a maximum of
8.7 hours per day on the average in the same month.
Solar radiation is closely related to the sunshine duration. Its seasonal
and spatial variations are thus very much the same as in the case of
sunshine.
Source - Malaysia
Meteorological Service
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