Statistical investigation of long-term meteorological data to understand the variability in climate: a case study of Jharkhand, India

The present study was conducted to identify long-term (1901–2002) climatic trends for the state of Jharkhand. The meteorological data utilized in this study included maximum and minimum air temperatures, diurnal temperature (DTR) and rainfall for the state of Jharkhand. This data was evaluated on annual basis as well as for monsoon (June–September), winter (October–January) and summer (February–May) seasons respectively. A nonparametric statistical test (Mann–Kendall test) was employed to statistically analyze the aforementioned meteorological data. Prior to Mann–Kendall test, the time series data was processed using pre-whitening test to remove any serial correlation present in the data. An increasing trend in maximum and minimum temperatures was apparent during winter season and on annual basis for the period of study in Jharkhand at 1%, 5% and 10% significant levels. During monsoon season, all the districts exhibited decreasing trend in DTR at 1%, 5% and 10% significant levels except Giridih district where no trend was apparent at 0.0001% significance level. In winter season, no trend in DTR was apparent for all the districts at 0.0001% significance level except Pashchimi Singhbhum which exhibited decreasing trend at 10% significance level. No trend was observed in the annual DTR for most of districts except Dhanbad, Gumla, Kodarma, Lohardaga, Pashchimi Singhbhum and Ranchi. Rainfall exhibited a decreasing trend during monsoon season for all the district at 1%, 5% and 10% significant levels except Purbi Singhbhum district where the trend was not significant at 0.0001% level. A decreasing trend in annual rainfall was apparent for most of the districts at 1%, 5% and 10% significant levels. However, no significant trend was found in annual rainfall for Pashchimi and Purbi Singhbhum districts, respectively, at 0.0001% significant level. The change point test reveals that break years occured during the 1950 decade for annual maximum temperature and rainfall. Meanwhile, for minimum temperature, break years happened in 1920 decade, whereas a mix behavior was found for DTR. The findings of current study will be useful for the local resource managers and policy makers toward informed decision making.