Temporal analysis of thermal bioclimate conditions between Kolkata (India) and its three neighbouring suburban sites

The study of human biometeorological conditions is becoming increasingly important in climate perception for the improvement of public health system. The present study investigates the long-term thermal bioclimate conditions in four stations of West Bengal, India. Kolkata, the capital city of West Bengal, and three suburban stations, namely, Dum Dum, Canning and Diamond Harbour, located in the adjacent districts of Kolkata, have been selected. The biometeorological conditions have been estimated by physiological effective temperature (PET) and modified physiologically equivalent temperature (mPET) at 1130 h and 1730 h (IST) based on 42 years of meteorological data. The initial purpose of this study is to present the monthly distribution of PET and mPET categories and further highlight the structure of each thermal index in four tropical climate locations. The results from this analysis reveal higher human thermal stress in Kolkata compared to other neighbouring stations during the period from 1979 to 2018. Reverse behaviour was observed from 2018 to 2020 indicating that Diamond Harbour and Canning are warmer in terms of human thermal stress compared to Kolkata and Dum Dum. The results captured has also been validated by mean monthly, mean seasonal PET and mPET index difference between Kolkata (urban station) and other three stations (suburban areas). During the past period (1979-2018), highest differences in PET and mPET were recorded in Canning and Diamond Harbour for the months September to November (SON), varying between 4 and 5 degrees C both at prenoon and evening. The second highest differences of indices ranging from 2.5 to 3.5 degrees C were observed during December to February (DJF). For the last two years (2018-2020), the seasonal differences of PET and mPET are negative, implying that Dum Dum, Canning and Diamond Harbour at 1130 h are warmer by a maximum of 2 degrees C in comparison to Kolkata. Finally, the mean annual thermal indices of each year show a growing trend in all the four stations with a variation of 0.4 degrees C to 0.7 degrees C and 1.1 degrees C to 1.3 degrees C in early noon and evening measurements respectively for 40 years.

Automated summary

The study investigated the long-term thermal bioclimate conditions in four stations of West Bengal, India using physiological effective temperature (PET) and modified physiologically equivalent temperature (mPET). It found higher human thermal stress in Kolkata compared to other stations, but a reverse behavior was observed in recent years. The monthly distribution and seasonal differences of PET and mPET indices were also analyzed.