Time­less clues

Clouds have been used to pre­dict weather since an­cient times. The method has rekin­dled the in­ter­est of re­searchers

Down to Earth - - COVER STORY - Jigyasa Watwani

ADITYAT JAYATI VRISHTI (the sun gives birth to rain),” reads a line from the Bri­hat­samhita. Writ­ten by sixth cen­tury astrologer-math­e­ma­ti­cian Vara­hami­hira of Uj­jain, the line shows a deep un­der­stand­ing of cloud for­ma­tion and rain.

Clouds have al­ways been the key in­di­ca­tors of weather. Long be­fore satel­lites be­gan map­ping the earth, weather fore­cast­ing was based on in­for­ma­tion given in an­cient texts and lo­cal knowl­edge. There are enough ex­am­ples to cor­rob­o­rate this. The Upan­ishads, com­posed dur­ing 700300 BC, con­tain dis­cus­sions on cloud for­ma­tion. Bhadali, a 10th/11th cen­tury sa­vant from the Saurash­tra re­gion, wrote songs on 10 me­te­o­ro­log­i­cal in­di­ca­tors of the “ethe­real em­bryo” of rain: clouds, winds, light­ning, colours of the sky, rum­blings, thun­der, dew, snow, rain­bow and an orb around the sun/moon.

Tra­di­tional meth­ods of weather fore­cast­ing, which are based on me­te­o­ro­log­i­cal, bi­o­log­i­cal and as­tro­nom­i­cal in­di­ca­tors, have once again aroused the in­ter­est of cli­mate sci­en­tists, pro­fes­sors and agri­cul­tur­ists, and the lit­er­a­ture on these in­di­ca­tors has been in­creas­ing. For in­stance, a pa­per pub­lished in the In­dian Jour­nal of Tra­di­tional Knowl­edge in 2011 listed 25 bioindi­ca­tors of rain. The blos­som­ing of Cas­sia fis­tula (golden shower tree) ex­actly 45 days be­fore the on­set of the mon­soon, the un­usual chirp­ing and sand-bathing of birds im­me­di­ately be­fore rain, and na­tive frogs croak­ing near swampy ar­eas and hid­ing their eggs be­fore rain are some of the listed signs.

Parshotam Ranch­hodb­hai Kanani, pro­fes­sor and head, de­part­ment of agri­cul­ture ex­ten­sion, Ju­na­gadh Agri­cul­tural Univer­sity ( jau), Gu­jarat, says that about 50-60 per cent farm­ers in the state still de­pend on tra­di­tional fore­cast­ing meth­ods, par­tic­u­larly the Bhadali vakyas (sen­tences). Since 1994, jau has been or­gan­is­ing an an­nual sem­i­nar where farm­ers from the state gather to share data and pre­dict rains for the com­ing year us­ing tra­di­tional knowl­edge sys­tems. “We re­ward farm­ers whose pre­dic­tions have a 60-80 per cent suc­cess rate,” says Kanani.

Prime in­di­ca­tors

As tra­di­tional in­di­ca­tors of rain, clouds are by far the most pop­u­lar sign. In­dige­nous Rain Fore­cast­ing in Andhra Pradesh, a book by the Cen­tral Re­search In­sti­tute for Dry­land Agri­cul­ture ( crida) in 2008, doc­u­mented 14 phys­i­cal and bi­o­log­i­cal in­di­ca­tors of rain. Clouds ranked first and it was found that 16.7 per cent of the farm­ers in the state used clouds to pre­dict rain.

Sim­i­larly, in a 2009 pa­per by Anand Agri­cul­tural Univer­sity ( aau), Gu­jarat, re­searchers tested 16 “symp­toms” of rain—rainy clouds, blood­red colour of the east­ern sky 15-20 min­utes be­fore sun­rise, blood-red colour of the sky 1520 min­utes af­ter sun­set, squalls, wind di­rec­tion, roar­ing clouds, light­ning, gusty weather, traces of rain, rain­bow, ants car­ry­ing eggs, kite fly­ing, halo around the moon, halo around the sun, hot and hu­mid weather and haze—for their ac­cura-


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