Trends in cooling and heating degree-days overtimes in Bangladesh? An investigation of the possible causes of changes

An understanding of the trend in cooling and heating degree-days acts as a driving force for building energy demand under climate change conditions. However, little is known about the spatiotemporal trend patterns in cooling and heating degree-days in recent times and their possible causes in Bangladesh. Therefore, we explored the trend and variability of cooling degree-days (CDD) and heating degree-days (HDD) and their possible reasons for variation for the study period 1980-2017 based on daily temperatures datasets from 27 sites in Bangladesh. The results show that the highest annual mean CDD and HDD were identified in the southwestern and central climatic regions of Bangladesh. The CDD trend has significantly increased in Bangladesh, and the HDD trend has increased but non-significance. The outcomes of detrended fluctuation analysis (DFA) and R/S analysis exhibit that CDD and HDD will continue their contemporary trend direction in the future. Land-Ocean Temperature Index (LOTI) had a significant positive influence on CDD; however, there was no significant correlation between HDD and atmospheric circulation indices. The importance analysis from the random forest (RF) model showed that the LOTI is the highest contributing variable for CDD and East Asian Summer Monsoon Index (EASMI) is the largest influential variable for HDD affecting climate variability in Bangladesh. ECMWF ERA5 reanalysis datasets depict that higher summer geopotential height, an anticyclonic center, enhanced relative humidity, declined total and high cloud covers, decreasing surface solar radiation, and high skin temperature fluxes might have influenced on CDD and HDD variations in Bangladesh.