Atmospheric and Climate Sciences, 2011, 1, 206-213
doi:10.4236/acs.2011.14023 Published Online October 2011 (http://www.SciRP.org/journal/acs)
Thermal Classification of Pakistan
Maida Zahid, Ghulam Rasul
Research & Development Division, Pakistan Meteorological Department, Islamabad, Pakistan
Received June 24, 2011; revised July 29, 2011; accepted August 15, 2011
Abstract
This research work is designed to carry out the annual and seasonal thermal classification of Pakistan to pro-
vide better understanding to all the stake holders like farmers and scientists etc. for obtaining maximum crop
yield. The data of Climatic Normal’s (1971-2000) has been used to calculate Thornthwaites’s Thermal effi-
ciency index for thermal classification of Pakistan. The results of annual thermal classification reveals that
Pakistan’s northern half experiences Tundra to Microthermal climate type and southern half experiences all
types of Mesothermal to Megathermal climate type. Seasonal analysis showed large variations like in winters
the whole country ranges from Frost to Microthermal type of climate except the extremely southern parts of
the country which have Mild Mesothermal climate. In spring the northern half of the country lies between
Tundra to Microthermal climate and southern half from Mesothermal to Megathermal climate. During dry
and wet (monsoon) summer season majority of the regions in the country experience Megathermal except
Northern areas which show Moderate Mesothermal to Mesothermal climate. The autumn season mostly have
Mild Meso- thermal to Tundra climate excluding southern half which showed Moderate Mesothermal to
Megathermal climate.
Keywords: Evapotranspiration, Thermal Efficiency Index, Tundra and Megathermal
1. Introduction
The formulation of climate classification system is very
complex. There are different climate classifications de-
veloped by various climatologists according to their own
criteria. “Climatic classification is merely a method of
arranging various climatic parameters either singly or
grouped into ranks or sets, so, as both to simplify the
mass of data and to identify analogies” [1]. There are
many approaches which have been used for climate clas-
sifications both for Pakistan and all over world wide.
Some of them are the qualitative portrayal of the climate,
whereas others are quantitative in nature. These climate
classifications are entirely different from each other on
the basis of their criteria’s. The world climate has been
first divided on the basis of solar concentration by Per-
manide a Greek philosopher. Then the other most well
known scientists who did the climate classification are
Supan (1896), Koppen (1846-1940), Thornthwaite
(1931-1948), Blair (1942), Rodoulf Geiger (1953),
Miller (1969) and Griffiths (1978). The former contribu-
tors are Kazi (1951), Shamshad (1956) and Nasarullah
(1968) who did climat e classi fi ca t i on of Pa ki st an [2].
The annual climate indices developed by Koppen [3]
are in use world wide, in spite of vast variation among
the zones themselves. Koppen classification was tem-
perature based therefore there was some lapse in it. In
1948 Thornthwaite introduce a climate classification on
the basis of effective rainfall and Potential Evapotran-
spiration (PET). This approach was adopted by various
regions of the world for classification. The climate of
Pakistan has been characterized by adopting Reddy
modified Thornthwaite approach using reference crop
evapotranspiration (ETo) instead of potential evapotran-
spiration (PET) [4]. Thornthwaite also developed thermal
efficiency index (TEI) for climate classification. The
thermal efficiency is a growth index which indicates the
thermal periphery and as well as water requirement in
different climate types. This approach has also been used
by various scientists around the globe [5-11].
The agro climatic classification for Asia and Africa
had been done by United Nations Environment Program
[12]. Pakistan has arid to semi arid climate with great
variability in temperature [13]. Pakistan has been classi-
fied into five regions (hot, warm, mild, cool and cold) on
the basis of temperature. The southern half experience

207 M. ZAHID ET AL.
high temperatures and decreases while heading towards
northern half of Pakistan. The eastern part of Pakistan
receives heavy rainfall in summers due to monsoon
while western parts receive heavy rain in winters due to
western disturbances. The most suitable area for crop
production lies between 33˚ N to 35˚ N due to rain fed
conditions. The agricultural production above and below
these latitudes is only possible if there is supplementary
conditions available for irrigation [13].
2. Methodology
The Climatic Normal of 1971-2000 (temperatures, rela-
tive humidity, sunshine hours and wind speed data) pre-
pared by Pakistan Meteorological Department (PMD) on
monthly basis were used to analyze the thermal clas-
sification of Pakistan. The ETo calculator has been used
to measure Evapotranspiration. ETo calculator is soft-
ware developed by Food and Agriculture Organization
(FAO). The main function of this calculator is to calcu-
late evapotranspiration (ETo) according to FAO stan-
dards. The ETo calculator measures evapotranspiration
using meteorological data with the help of FAO Pen-
man-Monteith equation. This method has been selected
by FAO as it results in most appropriate value of ETo at
certain location. The FAO Penmen Montieth method has
also been considered best method for Pakistan climate.
Evapotranspiration is the combination of two processes
commonly known as Evaporation and Transpiration. The
loss of water from vegetation both as evaporation from
soil and water surface and transpiration from aerial parts
of plants. The transpiration mostly takes place through
stomata present on the leaves. Both the processes
(evaporation and transpiration) occur simultaneously
therefore it is very difficult to distinguish between the
two processes. It determines the water requirement of
crops and as well as potential of agro-climate of a region
and suitability of crop varieties, which can possibly be
grown profitably with the best economic returns [14].
Annual and Seasonal Thermal Classification of Pakistan
has been done by ap plying Thornthwaite’s Ther mal Effi-
ciency Index. For seasonal thermal classification five
seasons have been considered during the study. These are
Winter Season (December-February), Spring (March-
April), Summer (May-June), Monsoon (July-September)
and Autumn (October-November).
Thermal efficiency index is a product of “Tempera-
ture” & calculated “Evapotranspiration”. It is not only a
growth index; it gives the idea of growth in terms of the
water required for growth (Thornthwaite, 1948). The
Thornthwaite climate types according to thermal effi-
ciency index were for large scale area. He defined nine
classes out of which Microthermal climate type was di-
vided in two categories i.e. Microthermal (C1 and C2)
while Mesothermal climate was divided into four climate
types like Mesothermal (B1, B2, B3 and B4). These cli-
mate types were difficult to understand therefore for
simplification and better understanding of these climate
types these were redefined in this study. The Thorn-
thwaites’s climate types according to thermal efficiency
index were downscaled and redefined according to the
geography and climate of different regions in Pakistan.
For example the Microthermal (C1) has been renamed as
Mild Microthermal Climate and Microthermal (C2) as
Microthermal climate. While Mesothermal classes were
modified into Mild Mesothermal (B1), Moderate Meso-
thermal (B2), Strong Mesothermal (B3) and Mesothermal
(B4) climate type. Table 1 shows both the original and
redefined classes for simplification climate types ac-
cording to Thornthwaites’s Thermal Efficiency Index.
T-E Index = T. ET
where, T = Temperature (˚C)
ET = Evapotranspiration (cm)
Table 1. Thermal climate types based on thornthwaites’s thermal efficiency index.
TE index Climate Type Redefined types for simplification
14.2 E' Frost/Ice Frost
28.5 D' Tundra Tundra
42.7 C1' Microthermal Mild Microthermal
57 C2' Microthermal Microthermal
71.2 B1' Mesothermal Mild Mesothermal
85.5 B2' Mesothermal Moderate Mesothermal
99.7 B3' Mesothermal Strongly Mesothermal
114 B4' Mesothermal Mesothermal
> 114 A' Megathermal Megathermal

M. ZAHID ET AL.
208
3. Results & Discussion
3.1. Annual Thermal Classification
Pakistan annual average thermal classification lies be-
tween Tundra (D) to Megathermal (A) according to
Thornthwaites’s Thermal Efficiency Index. The extreme
northern parts of the country like Gilgit, Skardu and
Gupis have Mild Microthermal (C1) while Bunji & As-
tore areas have Tundra (D) climate. The Microthermal
(C2) climate type can be observed in northern parts of
Khyber Pakhtoonkhwa including Parachinar, Kalat in
Balochistan and Azad Kahsmir. The Microthermal cli-
mate types are usually observed in humid areas. The
Mesothermal climate is divided into four categories by
Thornthwaite. The Mesothermal climate is found in sub
humid to semi arid environment. The Mild Mesothermal
(B1) climate is found in Chilas, northwestern areas (Chi-
tral & Drosh) & southern parts of Khyber Pakhtoonkhwa
and North western parts of Punjab. The distribution of
rest of the Mesothermal climate types can be seen in
northern and central Punjab, southern Khyber Pakhtoon-
khwa and central Balochistan. The Megathermal (A)
climate type is usually found in arid areas. The Mega-
thermal (A) climate covers most of the areas of southern
Punjab, north eastern and southern parts of Balochistan,
entire Sindh including coastal belt. In nutshell, Figure 1
shows that the northern half of the country has Tundra to
Microthermal climate types, central and southern half of
the country have clear distribution of all kind of Meso-
thermal to Megathermal climate types.
3.2. Seasonal Thermal Classification
3.2.1. Winter
The average temperatures in winter range from 4˚C to
20˚C. Mercury sometimes falls well below freezing point
in Northern parts of the country. Thermal Classification
of Pakistan for winter season shows that it starts from
climate type Frost (E) and ends at Mild Mesothermal
(B1). The Northern areas including northern half & ex-
treme western parts of Khyber Pakhtoonkhwa, few areas
of Azad Jammu & Kashmir (Muzaffarabad & Kotli),
Northern Punjab (Murree & Islamabad) and Balochistan
(Zhob, Kalat and Quetta) have frost (E) climate in win-
ters. The Tundra (D) climate covers the entire central
Pakistan and extends up to the south western Balochistan.
The Sindh province shows variation in climate types
from Mild Microthermal (C1) to Mild Mesothermal (B1).
The upper Sindh is Mild Microthermal (C1), the central
Sindh is Microthermal (C2) whereas Lower Sindh have
Mild Mesothermal (B1) climate due to difference in tem-
peratures. The Balochistan depicts mark distribution in
climate types from frost (E) to Mild Mesothermal (B1).
In Figure 2 the north and south eastern Balochistan show
Mild Microthermal (C1) climate. The South western and
eastern border of Balochistan have Microthermal (C2)
climate whereas the coastal areas at the southern tip of
Balochistan shows Mild Mesothermal (B1) climate.
Figure 1. The annual average ther m al classification of Pakistan shows Tundra to Megathermal climate.

209 M. ZAHID ET AL.
Figure 2. Thermal classification of winter (December-February) in Pakistan shows Frost to Mild Mesothermal climate.
3.2.2. Spring
In spring season (March and April) the Northern parts of
Pakistan show variety of climate types from Tundra (D)
to Microthermal (C2) climate. The majority of Northern
areas clearly depict the Mild Microthermal climate (C1)
except Bunji which show Tundra (D) climate type and
Chilas have Microthermal (C2) climate type as shown in
Figure 3. The few stations of north western, south west-
ern Khyber Pakh toonkhwa and an isolated cell in cent ral
Balochistan also show Mild Microthermal climate (C1).
Whereas the north eastern parts of Khyber Pakhtoonk-
hwa along with adjoining areas of upper Punjab and
Azad Kashmir show Microthermal (C2) climate during
spring season. The central Pakistan covers from Mild
Mesothermal (B1) to Mesothermal (B4) climate type. An
isolated Megathermal (A) climate within Mesothermal
(B4) climate type can be observed at the border of south
eastern Punjab. The Balochistan covers almost all cli-
mates from Mild Microthermal (B1) to Megathermal (A)
conditions. The entire Sindh, south eastern and extreme
southern areas of Balochistan extend ing from Noku ndi to
Lasbella lie in Megathermal (A) climate type. The reason
can be that temperature start increasing in spring in
southern half of the country. The increase in temperature
will increase Evapotranspiration and ultimately thermal
efficiency index of the area. The water requirement of
flora starts increasing towards the southern half of the
country during spring.
3.2.3. Dry Summer
Summer season from May to June is extremely hot and
dry with relative humidity ranges from 25% to 50%. The
day-time temperature in this season remains 40˚C and
beyond in plain areas. In summers the day length and
temperature values show high degree of uniformity.
Figure 4 illustrates the thermal classification for sum-
mers lies between Moderate Mesothermal (B2) to
Megathermal (A) climate. The Moderate Mesothermal
(B2) climate is found in Astore and along North Eastern
border while strongly Mesothermal (B3) climate type is
found in Skardu and Gupis. The areas like Gilgit, Dir,
Parachinar, Murree and Kalat lie in Mesothermal (B4)
climate. The rest of the entire regions show Megathermal
(A) conditions. Therefore th e vegetation in the region s of
Megathermal climate remains under stress during dry
summer period.
3.2.4. Wet Summer (Monsoon)
In Monsoon (JAS) Pakistan thermal classification is found
between Moderate Mesothermal (B2) to Megathermal (A)
climate. The Hilly areas like Gilgit, Gupis, Astore, Para-
chinar, Dir and Kalat show Mesothermal (B4) climate
while an isolated cell of strongly Mesothermal (B3) cli-
mate around Skardu can be seen. The Chilas and Bunji

M. ZAHID ET AL.
210
Figure 3. Thermal classification of spring (Mar c h-April) in Pakistan show s Tundra to Me gather mal climate .
Figure 4. Thermal classification of summer (May-June) in Pakistan shows Moderate Mesothermal to Megathermal climate.

211 M. ZAHID ET AL.
both are having desert like climate so their aridity and
increase in thermal efficiency force them to fall in
Megathermal (A) climate type as shown in Figure 5. The
areas which are under the affect of monsoon rainfall belt
show mark variation in climate type from Moderate
Mesothermal (B2) to Mesothermal (B4) climate. This
variation is because of low temperatures due to more
rainfall. Secondly these areas are of Humid to Sub humid
climate therefore reduce the rate of Evapotranspiration
and hence the thermal efficiency index. The rest of the
country lies in Megathermal (A) climate zone. Although
during monsoon Pakistan receive a lot of rainfall but still
temperatures remain high in almost all over the country
affecting plants growth and health.
3.2.5. Autumn
The autumn season (October to November) thermal clas-
sification lies from Megathermal (A) to Tundra (D) cli-
mate. Tundra climate (D) covers almost all the Northern
areas and an isolated cell around Dir of Khyber
Pakhtoonkhwa. The majority of the stations of Khyber
Pakhtoonkhwa and adjoining areas of upper Punjab and
Kalat in Balochistan have Mild Microthermal (C1) cli-
mate. The few stations of southern Khyber Pakhtoonk-
hwa, northern Punjab, north western Balochistan includ-
ing Dalbandin have Microthermal (C2) climate during
autumn. Southern Punjab, D.I Khan of Khyber
Pakhtoonkhwa and Khuzdar of Balochistan show Mild
Mesothermal (B1) climate. An isolation around Baha-
walnagar area, Eastern Balochistan, including Panjgur
and Lasbella and northern Sindh lie in Moderate Meso-
thermal (B2) climate. The southern Sindh and Balochis-
tan fall between strongly Mesothermal (B3) to Megather-
mal (A) climate. The Megathermal (A) area can be seen
within Mesothermal (B4) climate in western Balochistan
and southern Sindh in Figure 6.
4. Conclusions
Pakistan experiences variety of thermal zones from Frost
(very cold/ice) to Megathermal (very hot/arid) climate
type. The annual thermal classification ranges from Mild
Microthermal (C1) to Megathermal (A) climate. It is
concluded on the basis of annual thermal classification
that Pakistan’s northern half experience Tundra (D) to
Microthermal (C2) climate type and southern half has all
types of Mesothermal (B1, B2, B3, B4) to Megathermal (A)
climate type. Seasonal analysis shows a lot of deviation
in thermal zones throughout the country. In winters, al-
most the whole country experiences from Microthermal
Figure 5. Thermal classification of monsoon (July-September) in Pakistan shows Moderate Mesothermal to Megathermal
climate.

M. ZAHID ET AL.
212
Figure 6. Thermal classification of autumn (October-November) in Pakistan shows Me gather m al to Tundr a c limate.
(C2) to Frost (E) Type of climate except the extreme
southern parts of the country which has Mild Mesother-
mal (B1) climate. During spring season the northern half
of the country lies between Tundra (D) to Microthermal
(C2) climate. The central parts show Mild Mesothermal
(B1) to Mesothermal (B4) climate types while Southern
half of Pakistan show Mesothermal (B4) to Megathermal
(A) climate. In summer, almost the majority of the re-
gions of Pakistan fall in Megathermal (A) climate type
excluding Northern areas which show Moderate Meso-
thermal (B2) to Mesothermal (B4) climates. During
monsoon, again most of the country show Megathermal
(A) climate. Northern areas including some parts of
northern half of Pakistan which are under the influence
of monsoon rain show demarcation from Moderate
Mesothermal (B2) to Mesothermal (B4) climate. In au-
tumn, the entire country experience Mild Mesothermal
(B1) to Tundra (D) climate with the exception of south-
ern half which has Moderate Mesothermal (B2) to
Megathermal (A) climate.
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