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Item Assessment of the predictability of seasonal rainfall in Ratnapura using the southern oscillation and its two extremes(National Science Foundation:Colombo, 1999) Punyawardena, B.V.R.; Cherry, N.J.Item Spatial interpolation of rainfall in the Dry Zone of Sri Lanka(NSF:Colombo, 1998) Punyawardena, B.V.R.; Kulasiri, D.One of the problems which often arises in climatology is either data at a given site is missing or the site is ungauged.In this study, a spatial interpolation model was developed to estimate the weekly rainfall of the Dry zone of Sri Lanka at ungauged sites assuming that the spatial continuity of rainfall at two neighbouring locations are exponentially correlated. Twenty years of weekly rainfall data from six stations located in the Dry zone was used in the study. To support the methodilogy, the results of the exponential model were compared with the other two methods of spatial interpolation techniques, namely,the local mean and the inverse distance methods.The results of the study indicates that the exponential correlation model is a promising candidate for estimating mean weekly rainfall of the Dry zone.However, the local mean and the inverse distance methods compare quite well along with the exponential model, indicating that more complex midels have no particular advantage over simple models for estimating rainfall in the Dry zone of Sri lanka .Nevertheless, the results point towards the relative importance of the exponential model as opposed to the other two models when the neighbouring locations do not have long series of historical records.Item Variation of surface winds at Hambantota from April 1990 to March 1991(NSF:Colombo, 1998) Zubair, L.Hourly measurements of surface winds have recently become available through the Ceylon Electricity Board Wind Energy Project.These records were used to characterise the structure of the wind velocity of the atmospheric surface layer at Hambantota in different seasons. The Surface winds at Hambantota are from the north-east from November to January.In the rest of the year,the winds are directed towards the south-west particularly intensely around July.The Von Karman log-law can approximate the velocity Profile.The velocity at heights between 10m and 20 m are highly correlated.There is a singnificant diurnal variation of wind velocity which averages 3-5 m/s from 2400 to 0800 h .Thereafter it peaksat 7-10m/s around 1530 h.The "Gustiness"of the wind as measured by the mean of the difference between maximum and average velocity is moderately greater during the monsoonal months.The average velocity is moderately greater during the monsoonal months.The average monthly wind velocity is correlated with precipitation.Theseseasonal variations of wind and precipitation in Sri Lanka are correlated with the latitude of the equatorial low pressure trough commonly called the Inter-Tropical Convergence Zone.Item Influence of El Nino/La Nina episodes on the rainfall regime of the DL1, region of the North Central Province of Sri Lanka(National Science Foundation:Colombo, 2004) Punyawardena, B.V.R.; De Silva, R.P.; Nijananthy, S.Item The climatic water balance approach for the identification of agroclimatological regions in the dry zone of Sri Lanka(National Science Council:Colombo, 1991) Weerasinghe, K.D.N.Item Possible differences in some characteristics of lightning in the tropics and in temperate latitudes as deduced from experiments with lightning flash counters (LFC's)(National Science Council:Colombo, 1982) Kannangara, M.L.T.