Discontinuities in temperature and contour heights resulting from change of instruments at Indian radiosonde stations

Abstract

In India, Chronometric (C) and Fan (F) type radiosondes which were used in the fifties and sixties, were gradually replaced by Audio Modulated (AM) type sondes in the late sixties. The change of instruments apparently resulted in discontinuities in the time series of monthly means of contour heights and temperatures. This aspect has been examined in detail by studying the mean monthly values of contour heights and temperatures of six Indian radiosonde stations for five standard isobaric levels for four representative months of the year by using the data for 1he period 1951- 84. It has been shown by rigorous statistical tests that contour heights and temperatures fell substantially at stations that used C-type initially and that the fall was less substantial in those that used F-type first. The differences between the measurements by the various instruments have been shown to be independent of location and season. Thereupon the standard differences and their standard errors for contour heights and temperatures have been computed for all the five levels.