This document discusses various climatological classification systems, focusing on Koppen's and Thornthwaite's classifications. Koppen's system classifies climates into 5 main groups (A through E) based on temperature and precipitation averages. Thornthwaite's system uses potential evapotranspiration and temperature effective indices to classify climates into humidity and temperature provinces. The document also briefly outlines Troll's classification system which differentiates tropical climates based on the number of humid months.

1. Climatological Classification

2. Introduction
• Classification of climate has been done by many scientists namely
koppen, Thornthwait, Troll, Hargreaves
• Koppen consider annual and monthly means of temperature and
precipitation
• Thornthwait consider PE index and TE index for classification
• Troll takes the account of temperature and humid months for
differentiation of climate
• Hargreaves took moisture difficiet for distinguish the climate

3. KOPPEN’S CLASSIFICATION
Koppen has taken annual and monthly means of temperature and also precipitation
for the classification of climate
Koppen classified climate into 5 group from A to E
A. Tropical rainy climate
B. Tropical dry climate
C. Mild temperate rainy climate
D. Cold snow climate
E. Polar climate

4. A. Tropical Rainy Climate
The average temperature of coolest month is more than 18oC , precipitation
is received in form of rain and rainfall is more than evaporation.
B. Tropical Dry Climate
The average temperature is more than 18oC and rainfall is less than
evaporation. It is sub-divided into Arid(BA) and Semiarid(BS) climate.

5. C. Mild Temperate Rainy Climate
The average temperature of coolest month is in the range of 18oC
to -3oC.
D. Cold Snow Climate
The average temperature of coolest month is less than -3oC and
precipitation is received in form of snow.
E. Polar Climate
The average temperature of warmest month is less than 10oC. It is
sub-divided into Tundra and Ice cap.

6. Key to the code system in the Koppen's system of classification
• A – Tropical Climate : Average temperature throughout the year is above 18
degrees Celsius
• B – Dry Climate : On average, potential evaporation exceeds precipitation
throughout the year
• C – Humid-mesothermal Climate (sub-tropical) :Average temperature of the
coldest month should be less than 18 degrees Celsius
• D – Humid micro-thermal climate : Average temperature of the coldest month is
less than –3 degrees celsius
• E – Polar Climate : Average temperatures of the warmest month is less than 10
degrees Celsius

7. LETTERS USED WITH A CLIMATES
 f - Moist; driest month has a mean precipitation of at least
60 mm
 m – monsoon; excessively heavy rainfall in some months
which compensates for one or more months of less than
60mm rainfall
 w -winter dry; driest month has less than 60 mm of rainfall.
Total rainfall is less than that required for monsoon month
 s – Well – defined summer dry season. It is not a common
phenomenon

8. LETTERS USED WITH B CLIMATES
 S – steppe; a semi- arid climate with about 380 mm to 760mm of
rainfall annually
 W – desert; annual rainfall is less than 250 mm

9. LETTERS USED WITH C AND D CLIMATES
 f – moist; precipitation is well distributed throughout the year
and not limited
 w – winter dry; mean precipitation of the driest month of the
winter half year is less than 1/10 that of the wettest month of
the summer half season
 s – summer dry; mean precipitation of the driest month of the
summer half year is less than 40 mm and less than 1/3 that of
the wettest month of the winter half year

10. LETTERS USED WITH B CLIMATES
 h – Dry hot; average annual temperature is above 18 degrees Celsius
 k– Dry cool or cold; Average annual temperature is below 18 degrees
Celsius

11. LETTERS USED WITH C AND D CLIMATES
 a– hot summer; average temperature of the warmest month is above 22
degrees Celsius. At least 4 months with an average temperature above 10
degrees Celsius
 b- warm summer; average temperature of the warmest month is below
22 degrees Celsius. At least 4 months with an average temperature above
10 degrees celsius
 c – Cool summer; average temperature of 1 to 3 months is above 10
degrees Celsius
 d– severe winter; average temperature of the coldest month is below –3
degrees Celsius

12. The B, C, and D climates are further divided into tertiary category by the addition of
a third small letter. These letters differentiate more variation of temperature
MAJOR TYPE SUB DIVISION DESCRIPTION
Humid tropical (A) Af Tropical wet
Am Tropical monsoon
Aw Tropical wet and dry
As Dry summer
MAJOR TYPE SUB DIVSION DESCRIPTION
Dry climate (B) BS
BSh Low latitude deserts (semi-
arid)
BSk Cool, semi-arid mid-latitude
steppe
BW
BWh Hot, dry , low latitude desert
(arid)
BWk Mid latitude desert (arid) ;cool
desert climate

13. MAJOR TYPES SUB DIVISION DESCRIPTION
Humid mesothermal climates
(C)
Cw (moist summer, dry
winter)
Cwa Hot moist summer, dry winter
Cwb Warm moist summer, dry
winter
Cs (Moist winter, dry
summer)
Csa Hot, moist winter, dry summer
Csb Warm, moist winter, dry
summer
Cf (All months moist)
Cfa Hot summer, all months moist
Cfb Warm summer, all months
moist
Cfc Cool summer, all months moist

14. MAJOR TYPES SUB DIVISION DESCRIPTION
Humid microthermal climates
(D)
Dw ( dry winter)
Dwa Dry winter, hot summer
Dwb Dry winter, warm summer
Dwc Dry winter, cool summer
Dwd Dry and severe winter, short
and cool summer
Df (all months moist)
Dfa Summer long, warm
continental
Dfb Summer long and cool
Dfc Summer short and cool
Dfd Short, cool summer, severe
winter, all months moist
MAJOR TYPES SUB DIVISION DESCRIPTION
Polar climates (E) Et Very short summer
Es Perpetual ice and snow

15. Thornthwaite classification

16. Thornthwaite classified climate based on PE index ,TE
index and seasonal distribution of rainfall
PE index = precipitation of effective index =P/E x 100
P – annual precipitation
E – annual evaporation

17. Based on PE index he classified the
climate into 5 groups as shown below
Symbol Humidity province Vegetation PE index
A Wet Rainforest 128 and above
B Humid Forest 64-127
C Sub-humid Grassland 32-63
D Semiarid Steppe* 16-31
E Arid desert <16
*steppe –dry ,grassy,treeless uncultivated area

18. Per Humid( A) region of India:
•Western Ghats
•Most parts of the NorthEastern States
Humid(B) region of India:
•Adjoining region of the Perhumid
region
Moist Sub Humid(C1) climatic
region
•Narrow belt Adjoining region of
the humid region of Western Ghats.
•Eastern India comprises of West
Bengal and Orissa

19. Dry Sub Humid(C2) regions:
•Northern Narrow belt of the Ganga
basin.
•Part of Uttar Pradesh, Bihar, MP,
Chhattisgarh, Jharkhand
•Western Maharashtra and Southern
Gujarat
Semi-Arid(D) climatic region:
•Part of Punjab and Haryana
•Eastern part of Rajasthan, Maharashtra,
Karnataka, Telangana
•Western Part of Tamilnadu.

20. Arid climatic( E) region of India:
•Western Rajasthan
•Western Himalaya
•Rainshadow zone of Western Ghats

21. TE index (temperature effective index) = ∑¹²i=1 (T-32/4)
where T = mean monthly temperature in ◦F
Based on TE index , the climate is divided into six temperature
provinces as shown below :
symbol Temperature
province
TE index
A’ Tropical 128 and above
B’ Mesothermal 64-127
C’ Microthermal 32-63
D’ Taiga 16-31
E’ Tundra 1-15
F’ Frost 0

22. Subsequently, seasonal distribution of rainfall is also
included in the classification as shown below.
For example, the climate in Southern India can be grouped under
DA’s in thornthwaite classification which means semiarid
tropical with rainfall in summer.
symbol Seasonal distribution
r Rainfall adequate in all
seasons
s Rainfall deficit in summer
w Rainfall deficit in winter
d Deficit in all seasons

23. Troll’s classification
Troll took tempature and humid months as parameters for
distinguishing different climates.
In this classification ,tropical region is the one where mean
monthly temparature of coolest month is more than 18 degree
celcius.
Tropical region is sub divided into five groups based on
humid months.
A humid month is one in which monthly precipitation
exceeds monthly potential evapotranspiration.

24. TYPE OF CLIMATE TYPE OF VEGETATION NUMBER OF HUMID
MONTHS
Tropical rainy climate Evergreen forest 12-9.5
Tropical humid summer Evergreen forest 9.5-7.0
Tropical humid winter Half decidious 9.5-7.0
Tropical wet dry Rain forest dry wood 7.0-4.5
Tropical dry climate Thorny,succulant,wood 4.5-2.0
Tropical dry climate with
humid months in winter
4.5-2.0
Tropical semi-desert and
desert climate
<2.0

25. Similar to tropical region , temperate and polar regions are
subdivided .
Troll classification has been used by ICRISAT as a
workable system of defining the geographical extent of
semiarid tropics (SAT). Using Troll system, areas having 2 to
7 humid months in the warm season (5 to 10 arid months)
are classified as semiarid.

26. Two further subclasses are proposed : dry savanna belt having 4.5 to 7
humid months, generally, referred to as wet-dry semiarid tropics and the
thorn savanna belt with 2 to 4.5 humid months called dry tropical
climate areas.
According to Troll approach, Bikaner and Jodhpur are classified as
arid and other 8 stations (Ludhiana, New Delhi, Agra, Allahabad,
Ahmedabad, Hyderabad, Mumbai and Sholapur) in India as semiarid. It
is important to note that Mumbai, which receives a mean annual rainfall
of 2,099 mm, is also classified as SAT.

27. The SAT of India as classified by Troll shows that most of the
areas of Rajasthan, Gujarat and part of Madhya Pradesh are
falling in 2 to 4.5 months humid zone dry SAT. This area
constitutes 26 per cent of the total area of tropical India and
represents 47 per cent of the SAT India as defined by Troll.
The wet-dry zone having 4.5 to 7 humid months forms a 200-
500 km wide strip running from northwest to south of India
around the dry semiarid zone. It constitutes 30 per cent of total
area of tropical India and 53 per cent of semiarid area of the
country.

28. The total SAT area works out to be 56 per cent of the total
tropical India, a figure very close to the 54 per cent estimate made
by economic group. The IMD in 1967 published 30 year (1931-
60) normals for over 200 meteorological stations. Monthly PET
values were published in 1971.

29. Modification of Troll’s Classification
Based on the climatic data of about 300 locations,scientists of ICRISAT
revised troll’s classification.
According to this,88% of geographical area of india is under tropics.
The regions with mean annual temperature or average temperature of
coolest months exceeding 18°c are identified as tropics.
Dry semiarid tropics constitute 57% of geographical area of india

30. Climatic regions of india(modified troll’s)
Climate Number of humid
months
%of geographical
area of India
Arid <2.0 17.00
Semiarid-dry 2.0-4.5 57.17
Semiarid-wet 4.5-7.0 12.31
Humid >7.0 1.10

31. Frequency of humid months at
selected Indian location.
Location Latitude Annual
rainfall(mm)
% frequency of number of
humid months
<1 2 >3
Arid areas
Hissar 29 10 400 85 13 2
Jodhpur 26 18 383 80 13 7
Ahmednagar 19 05 617 47 35 18
Sholapur 17 40 755 40 13 47
Bijapur 16 49 565 60 32 8
Average 544 62 21 16

32. Location Latitude
0 1
Annual
rainfall(mm)
% frequency of number of humid months
<1 2 >3
Semi-arid
areas
Jaipur 26 49 669 20 53 27
Udaipur 24 35 686 06 50 44
Dohad 22 55 805 11 26 63
Indore 22 43 1001 0 17 83
Anand 22 34 909 13 27 60
Hyderabad 17 27 783 16 33 51
Mahboobnaga
r
16 44 831 10 24 66
Average 812 11 33 56

34. Moisture Deficit index
All India Coordinated Research Project on dryland agriculture of Indian Council
of Agricultural Research adopted classification based on moisture deficit index.
Moisture deficit index (MDI) :To determine the magnitude of water deficiency in
these regions ,the moisture deficit index has been evaluated for dryland stations
in India.
The MDI is usually determined on the basis of annual precipitation and annual
potential evapotranspiration.

35. MDI = P-PET X 100
PET
Where,
P=annual precipitation(cm)
PET=potential evapotranpiration

36. Based on MDI ,the climate is divided into three
regions as shown below.
T
Type of climate MDI
Subhumid 0 to -33.3
semiarid -33.3 to -66.6
Arid > - 66.6

37. Hargreaves Method (1971)
This method is based on the degree of moisture deficit for
agricultural production and defines moisture availability index (MAI)
as a ratio.
 According to this method; MAI = PD/ PE
; Amount of rainfall at 75% probability/Potential evapo-transpiration

38. Climatic classification based on the moisture availability
index(MAI) at 75% probability of rainfall;
Range of MAI Duration Type of
climate
Crop planning
0-0.33 All months Very arid Not suitable for rainfed
0.34 and above 1-2 months Arid Limited suitability for
0.34 and above 3-4 months Semi arid Limited suitability for
0.34 and above 5 or more consecutive
months
Wet Suitable for crops of 5
months or more duration

39. Hargreaves(1975) proposed the following moisture
deficit classification for all types of climates;
Range of MAI Type of climate
0.00-0.33 Very deficit
0.34-0.67 Moderately deficit
0.68-1.00 Somewhat deficit
1.00-1.33 Adequate moisture
>=1.34 Excessive moisture

40. Thank you