Diurnal asymmetry of the recent surface warming, reported for several continental areas, is believed to be related to changes in cloudiness, humidity, atmospheric circulation patterns, winds and soil moisture. This paper presents linear trend analyses of maximum and minimum temperature data at 121 stations in India during the period 1901–87. While the mean temperature trends over India are similar to the global and hemispheric trends, there are marked differences in their diurnal manifestation from those reported for other areas. The increase in the mean temperatures over India is almost solely contributed by the maximum temperatures, with the minimum temperatures remaining practically trendless, leading to an increase in the diurnal range of temperatures. These trends do not show any significant urban or altitude bias. There are some differences in the trends on smaller spatial and temporal scales, but the increase of maximum temperature is predominant over a major part of India, particularly in winter and post‐monsoon seasons.

SummaryA significant correlation between the seasonal rainfall over India and the southern oscillation index (SOI) illustrated by Walker is examined on the basis of a long series of 100 year data. The relationship is discussed in the light of recent applications of global interactions in the regional climatic change models through feedback processes. The years of large scale deficient/excess rainfall over India during June-August season are examined in relation to the concurrent SOI regimes. This aspect may be of importance in examining the large scale circulation features in association with severe droughts/floods over India. ZusammenfassungEinige Gesichtspunkte iiber eine Verbindung zwischen der siidlichen Oszillation und dem indischen Sommermonsun Eine signifikante Korrelation zwischen dem jahreszeitlichen Regen in Indien und dem Index der siidlichen Oszillation (SOI) nach Walker wird aufgrund einer hundertj~thrigen Reihe yon Beobachtungsdaten untersucht. Die Beziehung wird im Hinblick auf neue Anwendungen globaler Wechselwirkungen durch Rtickkoppelungsprozesse in regionalen Klimaschwankungsmodellen besprochen. Die Jahre mit groflr~iumigem Mangel oder ()berschui~ an Regen in Indien in der Zeit von Juni bis August wird in Beziehung zum gleichzeitigen SOI-Verlauf untersucht. Diese Gesichtspunkte k6nnen bei der Untersuchung gro~r~umiger Zirkulationsmerkmale in Verbindung mit starken Trockenheiten oder [2rberschwemmungen in Indien yon Bedeutung sein.

Long-term changes in the Indian monsoon rainfall on regional and local scales have important social and economic consequences. To present a comprehensive picture of such changes, the monthly rainfall data at 306 stations, well spread over India, have been analysed over 114 years (1871-1984), for long-term trends. The trends are quantified by linear trend for monthly as well as seasonal rainfall for each station. Some broad contiguous areas showing statistically significant trends have been identified. Areas of increasing trend in the monsoon seasonal rainfall are found along the west coast, north Andhra Pradesh and north-west India, and those of decreasing trend over east Madhya Pradesh and adjoining areas, north-east India and parts of Gujarat and Kerala.The subseasonal patterns indicate that the excess or deficiency of the monsoon rainfall is more frequently realized in the later half of the season. Monsoon rainfall tends to be more concentrated in August, over the west coast and central India.

An actively growing stalagmite collected from a cave located in the hills of the Western Ghats in the Uttar Kannada District of Karnataka, India, has been studied for stable isotope ratios of oxygen and carbon, width of growth layers and grey-level changes. Distinct carbonate layers, alternate coarse and compact, are seen in cross-section. Each couplet of compact and coarse layer is found to represent a single year. A total of 331 such couplets has been counted, indicating that the stalagmite started growing in AD 1666 and continued until it was sampled. Stable isotope ratios of oxygen (δ18O) and carbon (δ13C) show variations ranging from-13.6 to-7.9%° and from-2.7 to 1.6%°, respectively. We have reconstructed past rainfall changes of the cave site using the‘amount effect’ in &δ18O of rain. Speleothemδ18O and instrumental rainfall data from the associated climate subdivision show a significant correlation (r =-0.62, decadal average). Several sharp spikes of enrichment and depletion in 18O are indicative of the past deficiency and excess in rainfall. Most of the severe drought years recorded independently by meteorological observations are found registered in the stalagmite layers. During the 331-year-period, rainfall was highest at Añ 1666 and lowest around AD 1900. The stalagmite-generated past rainfall record can serve as a reasonable proxy for testing monsoon models.

Association between the all-India summer monsoon (June to September) rainfall and an index of the Southern Oscillation (SO) is studied in relation to the vagaries of the monsoon rainfall and the seasonal characteristics of the SO. The Southern Oscillation index (SOI) used is the difference of normalized sea surface pressure between Tahiti and Darwin, two stations located in the core regions of the circulation systems associated with the SO. The data length of 46 years from 1935 to 1980 is used in the detailed examination of the nature of association between these parameters.The SO1 values of different months and standard seasons show opposite tendencies during deficient and excess years of all-India monsoon rainfall. The correlation coefficients (CC) between the all-India monsoon rainfall series and the SOIs of summer monsoon (JJA), autumn (SON) and winter (DJF) minus spring (MAM) seasons are significant at the 1 per cent level. The correlations have been examined by dividing the series into two equal halves of 23 years and different sliding window widths of 10, 20 and 30 years. The least squares fit line is represented by the equation y (all-India monsoon rainfall) = 85.9 -2 . 7~ (DJF minus MAM, SOI), the variance explained by this line is about 13 per cent. In view of the large spatial variability of the summer monsoon rainfall the correlations are examined for the rainfall series of various meteorological subdivisions of the country. The CC between the monsoon rainfall of the subdivisions north of 16"N and west of 80"E and the SO1 series of DJF minus MAM is significant at the 5 per cent level or above.Potentialities of the SO1 of DJF minus MAM, an important premonsoon circulation parameter, are examined for the seasonal prediction of Indian summer monsoon rainfall, and the limitations of single parameter prediction models are discussed.