Climatological study on maximum temperature trends and heat waves at Ludhiana

The temperature is the most important climatic factor that influences growth, development and yield of crops. During the summer season the maximum temperature in Punjab reaches upto 44–45ºC during April or May months and affecting the kharif crops in the region. Forty three years data (1970–2012) on maximum temperature of Ludhiana, located in the central plain region of Punjab state at an altitude of 247 m above msl for the month of April to June was collected and classified into various groups for interpretation. Results showed that the lowest and the highest maximum temperature recorded during the study period were 19.4 and 47.2°C for the months of April and May, respectively during different years. The Coefficient of Variation varied from 35–46 per cent and standard deviation of average temperatures varies from 3.2 to 3.6°C. Persistence in maximum temperature for five days was found to be minimum 36.2 to 46.2 per cent. Analysis indicated that maximum number of heat waves occurred during the month of June. A negative and linear relationship has been observed between rice yield and maximum temperature of different months but results indicated that maximum temperature has not much affect on rice yield during the period under study. The decade wise analysis of extreme temperature analysis showed that maximum number of extreme events occurred during the last decade (2000–2012) and it was also found that maximum number of extreme temperatures occurred during the month of May in all the categories of temperatures at Ludhiana.