Seasonal Oscillation of the Diurnal Range of Temperature in India and neighbourhood

Abstract

The seasonal oscillation of the diurnal aperiodic amplitude of air temperature at 4 ft above ground has been studied with reference to the data of 167 climatological stations in India and neighbourhood.

                  It has been found that the annual and half yearly oscillations account for nearly 90-95 per cent of the variation except at a very few stations associated with special features.

                  The amplitude of the annual oscillation is largest (9-10°F) over a track extending from the Gulf of Cambay on the west to Bihar on the east and decreases towards the coast and towards the Himalayas. The maximum in the oscillation occurs generally in February; the notable exception being the southeast Peninsula where it is very much delayed being as late as May and over the Coromandel coast.

                   The half yearly amplitude is much smaller in magnitude with highest values of 4-5°F over the northwestern part of the country decreasing towards the coast and the Himalayas the maximum in the oscillation occurs generally in May advancing by two to three months in the south Peninsula outside the west coast.

                     Regression equations for representing distribution of the components of the two oscillations as linear functions of latitude longitude, and elevation have been derived. The fit of these representations has been found to be fairly good in the case of the annual and half-yearly amplitudes and genera angles of the annual oscillation. The significance of the gradients with respect to the positional co-ordinates have been discussed.