Environmental stable isotopes of rainfall over Delhi and Bombay: some observations

Environmental stable isotope contents of selected monthly rainfall measured as δD and δ18O over Delhi and Bombay collected from IAE-WMO network are analysed statistically and interpreted in the light of other meteorological parameters. Analyses have been carried out for 11 years comprising six years (1961-66) plus five years (1973-77). It is observed that while the monthly δ- values (mean and weighted mean) of rainfall over Delhi are depleted with respect to those of Bombay, due to continental effect, respective δD-δ18O relationships for Delhi and Bombay give slopes of 6.80 and 7.63 showing the amount effect. Analyses of the data for individual months show both enrichment and depletion of values depending on temporal distribution of rainfall. In addition to δD and δ18O relationship, rainfall (P), vapour pressure (VP) and temperature (T) also have good correlation for some months among any of one or two of the parameters. These variations in respect of Bombay are discussed. (author). 8 refs., 5 figs