Recent mean temperature trends in Pakistan and links with teleconnection patterns

摘要

Monthly, seasonal and annual trends in mean temperatures have been analysed in this study using data from 37 weather stations from the Pakistan Meteorological Department with records from 1952 to 2009. Statistical tests including Sen's slope and Mann-Kendall were applied to each of the 37 stations in order to determine the sign and slopes of trends and their statistical significance. The study reveals that the temperature has generally increased in Pakistan at all time scales analysed over the past few decades. March and the pre-monsoon season were the periods with the highest number of weather stations showing statistical significance, and also with the highest magnitudes of trends. Mean annual temperature increased around 0.36 °C/decade. This rise in temperature is slightly higher than other results found for Pakistan. The association between temperatures and certain teleconnection patterns, as well as the influence of the urban effect, might be among the causes of the trends found in this study. The largest number of correlations between mean temperatures and teleconnection patterns was found in March, April and May with NAO, ENSO and NCP, respectively. The North Atlantic Oscillation (NAO) may also have an influence on the temperatures of certain months in the monsoon season and particularly in August. At a seasonal resolution, NAO and NCP may control temperatures in the pre-monsoon season. The lowest number of sites exhibiting correlations was found in winter and in the post-monsoon seasons.