A Study of Climate and Forests in the Ranchi Plateau (Changes Over the Period: 1889-1943) Part-1

Statistical analysis shows that the climate of Ranchi is now (1944) warmer by day in the hot weather months or Mey(0.8°F), and June (2.3°F), June nearly significant and less so by night, (June: 0.5°F, not significant. The air, remains drier from January till June, calmissing a decrease of relative humidity by 5.8 points in June, which is significant. With reduced rainfall from March till June, the drop of 0.96' in May is significant and of 1.66' in June nearly so, and with less rainy days from March till June, the drop of (1.8 days in May is highly significant though June's 1.7 drop is not yet significant in the Monsoon the rainfall is heavier than formerly, the 3.65' excess in July being highly significant and the 2.145' excess of August being just significant. The number of rainy days is greater, the 2.3 excess of July being highly significant. Day temperatures are significant cooler in July and August (0.7°F and 0.5°F respectively and night retemperatures are significantly cooler from July till December. In the cold weather, days are cooler and drier with more rainfall; but these changes are not significant. The same pattern of climatic change is noticed is the Stations of Tamor and Kurdeg, sitnated closer to the disforested areas but more accentuated. In the hot weather rainfall losses(as might be expected) are greater, being 4.36 inches in May, highly significant, and 2.99 inches in June significant (c.f. Ranchi's 1.66 inches). Tamor's shortfall of 2.1 rainy days in June is also significant. In the monsoon, the excess rainfall of 2.88' for July is nearly significant while the four rainy days average excess of that month is highly significant. So also is Kurdeg's 3.8 excess rainy days of that month. In the cold weather Kurdeg's 1.59' excess in October is significant and its 2.3 excess rainy days highly significant, while Tamor's 0.9 excess rainy days of November is also significant; Ranchi further away from the forest showed on significant changes In these months. Seven other stations five on the plateau and two near it, are analysed but not tested for statistical ,significance, The annual rainfall average bas gone up in seven out of the tea stations examined, by 0.89' (Tamar) to a maximum of 8.27' (Chainpur) and has gone down in three stations by 0.42' (Kurdeg) to 2.99' (Khunti). They show the same general pattern of climatic change and point to the facts of rainfall losses in June and gains in July, greater nearer to the disforested areas than away from them. The geatest recorded loss is 5.62' at Khunti in June and the greatest gain 7.02 inches at Chainpur in July. The above changes 10 climate could have been due to (a) changes in vegetative cover or (b) weaker indraughts of moisture laden winds from the coast, or to a combination of both. In fact, the indraughts of moisture as measured by the rainfall at the Coastal Control Station were, if anything, slightly stronger than normal, in the critical pre-and early monsoon month of May and June. Thus, the desiccation in these months appears to have been brought about by the disapparance of forest or cutting back to scrub over extensive areas 24-38 miles east baa vollageand south of Ranchi, (156 square miles) and 68-100 miles away in the south west of the plateau (751 square miles). The same pattern of adverse climatic change is found in neighbouring; areas of Bihar, Chota Nagpur and Orissa, where also the change is greatest near the disforested areas.