This document discusses various extreme weather events in India and their impact on agriculture. It defines extreme weather as unusual, severe, or unseasonal events that are outside the historical range for a particular location. Some key extreme weather events discussed are droughts, floods, heat waves, cold waves, thunderstorms, hailstorms, dust storms, cyclones, and excessive or defective sunlight. The document provides details on specific drought and flood years in India's history. It also explains how different extreme weather events can negatively impact crop yields and cause losses, particularly for food grains, mangoes, guavas, and other crops during heat waves, cold waves, or periods of low sunlight.

1. EXTREME WEATHER EVENTS-
HISTORICAL PERSPECTIVE IN
INDIA AND ITS RELEVANCE TO
AGRICULTURE.

2. EXTREME WEATHER INCLUDES
UNUSUAL, SEVERE OR
UNSEASONAL WEATHER; WEATHER
AT THE EXTREMES OF THE
HISTORICAL DISTRIBUTION- THE
RANGE THAT HAS BEEN SEEN IN
THE PAST.

3. THE METEOROLOGICAL OR
STATISTICAL DEFINITION OF
EXTREME WEATHER EVENTS ARE
EVENTS AT THE EXTREMES (OR
EDGES) OF THE COMPLETE RANGE
OF WEATHER EXPERIENCED IN THE
PAST.

4.  Droughts and floods
 Heat and cold waves
 Excessive or defective insolation
 Thunderstorms, lightning and hailstorms
 Dust storms
 Cyclones and anticyclones
 High winds
 Forest fire outbreaks
 Ice and snowstorms
 Sea level size
The weather abnormalities which can affect crops adversely in India
are as follows:

5. DROUGHT:
 Drought is a relative term used universally with reference to deficiency of
rainfall when compared to normal rainfall of a given location.
 The summers of 1983 and 2004 were declared as disastrous drought years.
 During these periods the major part of plantation crop production was
adversely affected over Kerala.

6. FLOODS:
 The years in which actual rainfall is above the normal by twice the mean
deviation or more is defined as years of floods or years of excessive rainfall.
 Like droughts, the definition of floods also varies from one situation to
another and from one region to other.
 Some of the flood years based on monsoon rainfall in India are 1878, 1892,
1917, 1933, 1942, 1956, 1959, 1961, 1970, 1975, 1983, 1988 and 2007.
 Kannur received 370mm of rainfall on 14 October 2002, which was the
highest single day rainfall received since 1924.

7. THE IMPACT OF
DROUGHT ON FOOD
GRAINS IS FELT MUCH
MORE WHEN COMPARED
TO THAT OF FLOODS.

8. HEAT WAVES:
 As per Indian convention, the departure of the maximum temperature to the
order of 60 Cto 70C above normal is termed ‘Moderate Heat Wave’, and, that
to 80 C and above 80C is called ‘Severe Heat Wave’.
 Heat wave develops over Rajasthan and Punjab due to their being in the
interior. Also in Orissa and AP.
 The maximum heat wave incidence is in May and June.
 In July and August, southeast Chennai becomes another centre of high
frequency of heat waves.
 The Heat Wave that occured during March 2004 over Himachal Pradesh
devastated several temperatures. Huge crop loss was estimated.

9. COLD WAVES:
 Cold Wave is defined with respect to the normal minimum temperature
experienced over a given area.
 Every year a number of deaths are reported during cold wave spells.
 Nearly 75% of the cold waves in the country occur during January to February.
 The years in which some of the worst cold waves appeared were 2002, 2003
and 2008.
 The worst affected states are UP, Bihar, Northwestern parts and areas further
North.
 Ground frost in low-lying areas caused for loss of crops like mango, guava,
pineapple, boro rice and maize. However temperate crops like apple, peach
and cherry flourished.

10. EXCESSIVE INSOLATION:
 During clear days in summer, soil temperature in the equatorial and tropical
regions reach very high levels, particularly on days when air movement is
weak.
 High soil temperature in the coconut root zone in the absence of soil moisture
during summer may restrict root activity and the same is true for almost all
the crops.
 The crops grown under sandy soils are the worst hit, as the temperature is
higher in sandy and sandy loam soils when compared to that of the laterite
soils.
 Places like Pune suffer this effect.

11. DEFECTIVE INSOLATION:
 During damp days in winter, soil temperature in the equatorial and tropical
regions fall at very low levels, particularly on days when air movement is
swift.
 It may retard the crop growth and yield, while the same weather conditions
become favourable for the incidence of crop pests and diseases.
 Cloudiness is injurious to crops during certain critical phases like flowering.
 In the humid tropics like Kerala, insolation is less during rainy season (June-
September) for about 120 to 150 days depending upon locality.

12. THUNDERSTORMS, LIGHTENING, HAILSTORMS AND
DUST STORMS:
 These are comparatively local in character but are often associated with depressions
affecting larger areas.
 The relatively more violent ones usually occur in the pre monsoon and post
monsoon seasons.
 There is similarity between dust storms, thunderstorms and hailstorms in their
fundamental mechanism.
 In the absence of sufficient moisture in the atmosphere Dust storms occur.
 When enough moisture is present a thunderstorms results.
 The hailstorm is a particularly violent thunderstorm.
 These are common over Delhi, Jammu, Haryana, Punjab, Rajasthan, UP, MP and
Bihar.

13. CYCLONES AND ANTICYCLONES:
 The more serious cyclonic storms usually form in the Bay of Bengal and the
Arabian Sea in the transition months (April to May and October to
November).
 Their effects are most severe in the coastal areas.
 The east coast of India is affected more frequently when compared to that of
the west coast.
 The anticyclone that forms in the upper atmosphere over western Rajasthan
is one of the reasons for not getting enough rainfall in Rajasthan during the
rainy season (June to September).

14. References:
 Agricultural Meteorology by
G.S.L.H.V.Prasada Rao.
 Agrometeorology and
Contingent Crop Planning by
S.C.Panda.

15. THANK YOU.
Expounded By:
Chandini S (2013-009-005)
R Durga Devi (2013-009-006)