Satellite Data Application

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Adv. Space Res. Vol. 13, No. 5, pp. (5)273(5)276, 1993 02731177)93 S 2 4 . I X IPrinted in Great Britain. Allrights reserved. C o p y r i g h t 1993 COSPAR

SATELLITE DATA APPLICATION IN THESTUDY OF VARIABILITY OF DATES OF

ONSET OF INDIAN SUMMER MONSOON ANDITS INFLUENCE ON YIELD OF CROPS

V. R. Mujumdar, V. R. Deshpande and D. K. Paul

IndianInstitute ofTropical Meteorology, Pashan, Pune-411008, India

ABSTRACT

Agriculture in India is strongly dependent on rainfall. Besides th e quantum of rainfall,

th e timely commencement of rainy season (onset of monsoon) ha s also dominating influence

on th e yield of crops. Timely sowing especially in case of crops g ro wn u nd er rainfed

condition gives b etter yields. It is therefore necessary that th e beginning of cropping

season is linked with t he f i rs t monsoon rainfall which would provide th e required moisture

f or th e sowing operations. Th e most variable nature of ons e t an d subsequent behaviour of

summer monsoon season makes th e task difficult f o r t he farmers an d planners to plan their

cropping strategies an d to estimate t he f i na l yield. Th e year to year variability of dates

of ons e t of monsoon over different parts of India have been s tu di ed b as ed on satellite

derived data. Th e yield of different crops under early, normal an d late ons e t ar e also

studied. Delayed onset, is f o u n d to have adverse effect on th e yields.

INTRODUCTION

An agriculture sector in India, today provides livelihood to about 70 percent of labourforce , contributes nearly 35 percent of ne t national product an d accounts f o r sizeable share

of t ot al value of countrys export /1/. B ut s i nc e mor e t han 70 percent of th e cultivated

land in th e country is nonirrigated, th e Indian farmers continue to depend on th e monsoonrainfall which gives nearly 70 percent of th e annual rainfall during th e f o u r months (June

September) of th e season assuring enough supply of moisture f o r t he kharif crops (rainfed

summer crops ). Irregularities in th e commencements of rainfall (onset of monsoon), its

c e s sa t io n , d u ra t io n , distribution an d intensity over any region results in th e variation

in th e crop yields. In many parts of India, after a long dr y period of ho t summer (April

May) a fe w spells of premonsoon thundershowers supply firs t moisture to th e soil.Thereaft e r with t he o n se t of th e monsoon th e region receives 4 to 5 days of sustained rainfall

supplying enough moisture f o r t he sowing operations of most of th e kharif crops / 2/ .

Depending upon th e kind of crop, soil type, terrain features an d occurrence of f i r s t s p el lof rainfall which could built up enough moisture in th e soil, Raman /3 / ha s determined th e

normal dates f o r commencement of sowing rains in th e district scales f o r Maharashtra state.

Th e fie ld experiments conducted by Singh et. al. at Ranchi / 4 / a nd by J os eph at K er al a /5 /ha s respectively observed that timely sowing of rice during t he o n se t of monsoon ha s

recorded a good growth of crop with high g ra in y ie ld a nd delayed transplanting of rice due

to late arrival of monsoon rains resulted into low yield of th e grain. Prior knowledge of

th e d at e o f commencement of monsoon rains would thus guide th e farmers in planning th esowing operations.

Fo r good yield o f c ro ps , critical conditions of weather s uc h a s rainfall, cloudiness or

sunshine ar e essential at various s tage s o f c ro p growt h . Heavy showers just aft e r sowing

or germination may compact th e soil aft e r drying or wash away t h e s e ed s, kill seedlings

by water logging or lessen th e fertility producing poor yield. Groundnut, a major kharif

c ro p i n Gujarat with life cycle of 1 1 0 to 1 40 days grows on warm an d moderately moist

climate, requiring abundant sunshine an d moderate r a in f a l l. T he critical period of moisture

requirement f o r t he crop is at th e initial stages of sowing an d germination bu t at th e time

of maturity or flowering prolonged ra in o r cloudy weather may r es ul t i n poo r yield /6/.

This paper attempts to study th e yield of Groundnut a nd i t s relation with th e time of ons e t

of monsoon a nd i ts further development during th e season over Gujarat based on satellite

derived dat a s uc h as Outgoing Longwave Radiation (OLR) or cloud imageries during monsoon

season with t h e yie ld of groundnut in the state of Gujarat.

DATA AND METHODOLOGY

Th e ons e t date f o r well distributed stations over th e country have bee n analysed f o r t heperiod of 33 years (19601992). T h e y i el d of groundnut during th e monsoon seasons of 1 96 5

through 1 987 ha s been calculated from th e data published by Government of India /7, 8/. The

J A S R 1 3 : 5 S

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(5)274 V. R . Mujumdar et al.

e 70 75E25 N ~ ~~t JUN 25N

DSA

SAH M

VVL

20 D M N 20

BMB

I I I I I

70 75E

Fig. 1 . Normal ons e t dates of summer monsoon over Gujarat

daily OLR d at a a t 2.5~ latitude/longitude intersections from NOAA Polar orbiting satellite

obtained f o r period 1 97 4 1986 from th e Climate A nalysis C entre, US A were averaged f o r

th e latitudes 2O~to 25~Nan d longitudes 7O~to 75~E to analyse th e various spells of

rainfall, cloudiness or bright s un s hi ne o ve r Gujarat. In 1 987 in absence of OLR data th e

percentage of c lo u d c o ve r over Gujarat region was estimated by visually inspecting th e

cloud imageries received from INSAT1B. It wa s then plotted an d analysed to determine

epochs of dr y and we t periods during monsoon over Gujarat.

DISCUSSION AND RESULTS

Onset a nd T h e Yield of Groundnut

Normally th e onset of monsoon over Kerala, the Southern ti p of India occurs on 1 June,

which further advances northward across th e southern peninsula an d covers th e entirecountry by 15 July / 2/ . Th e rainy season commences at th e Southern en d of Gujarat near

Dahanu (2ON, 7 2 E) j u st aft e r 10 June an d passing over Ahmedabad (23.2N, 72.5~E) o n J un e14 it reaches D e es a ( 2 4. 2 N, 72.5~E) near northern boundary of Gujarat b ringing nearly

80 % of t he s ta te under th e influence of monsoon on June 21 an d covers th e entire state

by 1 July (Figure 1 ) . Th e analysis of th e standard deviation of date o f onsets over Indian

stations show maximum y ea r t o y e ar variation over Gujarat region of 9 to 10 days

compared to 7 to 8 d ay s o ve r re st of th e country. Th e withdrawal of th e monsoon seasons tart s fro m northwestern parts of India from September 1 onwards, an d hence a delay in

th e onset of monsoon over Gujarat (b y mor e t han 2 weeks) does affect t he t o ta l duration

a n d t he amount of seasonal rainfall significantly leading t o poo r yield of crops / 9/ .

F or t he years 1 96 5 to 1 987 th e m ap s o f northern limits of monsoon which gives t he d ay today position of advance of monsoon over various parts of th e country during t he o ns et

phases w er e us ed to determine the o ns et d at es f or the Gujarat state during th e various

y ears . W e define ons e t date f o r t he s ta te when more than 7 0 % of t he s ta te h as been covered

by th e monsoon rain. T hu s 2 0 June is th e dat e by which monsoon normally covers aro un d 7 0

percent of th e entire state. Th e correlation between th e yield of groundnut in Gujarata nd t he o n se t date o ve r th e s ta te f o r th e year ha s shown th e inverse relationship

(correlation coefficient 0.55, significant at 1% level) signifying that th e delay in

ons e t of monsoon adversely affects th e yield of groundnut in t h e s t at e (Figure 2).

Intraseasonal Variations in OLR an d Yield of Groundnut

Th e time series analysis of average O LR values over Gujarat ha s been used to study th eda y to day variations in weather conditions over Gujarat. Followir~Kripalani et . al. / 1 0 /

a da y is considered to be a rainy da y when OLR value is 22 0 W/ m or less. Table 1 givest he o n se t dates, percentage departures of seasonal rainfall from n o rm al , t he number of

rain spells during th e season a nd t he yield of groundnut f o r Gujarat in Kg/hectare produced

during th e typical years of 1 97 5 , 1 97 9, 1 98 0, 1 982 an d 1 987 .

In 1975 a bumper yield o f groundnut reaching upto 1240 kg/hectare was obtained in Gujarat.

Figure 3a s h ows that along with normal onset of monsoon around 20 June with a good spellof rainfall as s ee n fro m lo w O LR values ha s probably built up enough moisture in soil

during the germinating stage o f the crop. Subsequently four well distributed alternate

spells of rainfall an d sunshine appears to properly match th e requirements of variousstages o f c ro p growth probably resulting into a bumper yield. Though 1 97 9 wa s a drought

year f o r I nd ia as a whole, three good spells of rainfall aft e r little delayed onset, with

Intermittant breaks ha s g iv en f ai rl y b et te r y ie ld (Figure 3b). Th e fluctuations in OLR


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(5)276 V.R.Mujumdar et aL

: is jL ;V : I \v r~W ISO ____________________________________________ 60

~32U ~ 320~ C c ) 980 C d ) 982

~~T-::T1i~-0 20 30 0 2 0 3 0 9 IS 29 5 5 25 0 20 30 0 20 30 9 IS 21 5 II 25JuNE JULY LU G I .~UN6 LUG

Fig.3. Mean OLR values over Gujarat (2O~25Nand 7O~75~E)during June to

September f o r t he years a) 1 97 5 b) 1 97 9 c) 1 980 an d d) 1 982

various spells of weather patterns i n t he s ea so n, b e t une d with the typical weatherconditions required at various growth stages of th e crop. Satellite data (OLR) is f o u n d

to be very much useful in monitoring year to year variability in the daily patternso f weather sequences.

The study shows that the various epochs o f sunshine, cloudiness or rainfall during monsoon

over different parts o f India ca n be monitored by analysing satellite derived data a nd t he

information when matched with th e requirements at various growth s tage s o f a certain crop

it is possible to estimate th e final yield which may be of vital importance to th e farmers

an d planners. A further study of long term satellite data over various parts o f the country

may also provide a guideline as to which crop will give a b et te r y ie ld in a particular

region.

REFERENCES

1. INDIA, A Reference Annual, Ministry of I & B, Govt. of I n di a ( 1 9 8 8 8 9 )

2. India Meteorological Department, Climatological Atlas for Airmen in India (1943)

3 . C.R.V. Raman, Scientific Report No. 216, India Meteorological Dept. (1974)

4. R.S. Singh, D.C. Ghosh and V.C. Srivastava; Indian Journal of Agronomi,36(2) 159164, ( J un e 1 9 9 1)

5 . Kamalan Joseph, Indian Journal of Agronomi, 36(1) 8386 (March 1991)

6 . J.R. Kakade, Agricultural Climatology, New Delhi Metropolitan (1985)

7 . Area Production of Principal Crops in India Directorate Economics and Statistics;

Department of Agriculture and Cooperation; Ministry of Agriculture, Govt. o f India

(198485)

8. India Data Base, The Economy Annual Time Series Data Vol. II

9. V.R. Mujumdar, V.R. Deshpande, P.V. Puranik, V.V. Bhide and D.K. Paul

Book by M/s Tata Mc Graw Hill on TROPMET92 in press

10. R.H. Kripalani, S.V. Singh and P.A. Arkin, Beitr. Phys. Atmosphere 159168 (August

1991).

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