The Relationship between Diurnal Temperature Range (DTR) and Rainfall over Northern Thailand

Abstract

Since 1950, it has been found that the global diurnal temperature range (DTR), the difference between the minimum temperature (Tmin) and the maximum temperature (Tmax) of daily surface air temperature, has been temporally decreasing in several places all over the world. The aim of this study is to investigate the effect of DTR on the amount of total monthly rainfall (TRF) and the number of rainy days per month (RD), as well as to evaluate the possibility of using DTR as a parameter in the rainfall prediction process. The study area is in northern Thailand, which covers about one third of the total area of the country. The impact of DTR on rainfall over the studied area is evaluated from the relationship between DTR and TRF, as well as DTR and RD, by using long-term meteorological monthly data over 30 years (1978-2007). Besides, the relationships of RD, TRF, and the temperature of mean monthly Tmax and Tmin are also analysed. The significance of the correlation between the two parameters is identified by the coefficient of correlation. The possibility of using DTR is evaluated by estimating the relationships between DTR and a one month-lag time of RD and TRF. It is found that the DTR has a strong statistically significant ( > 99%) negative correlation with TRF and RD, as well as with the one month-lag time of TRF and RD. Therefore, it is possible to consider DTR as a significant parameter for rainfall prediction.