Spatio-temporal variability of near-surface air temperature in the Dokriani glacier catchment (DGC), central Himalaya

Abstract

Air temperature is one of the most important meteorological factors that affect melting of glaciers, distribution of snowfall and rain at higher altitudes in the Himalaya. However, studies on spatio-temporal variability of air temperature in the central Himalaya are limited. In the present study, seasonal and annual characteristics (July 2011 to December 2015) of near-surface temperature and lapse rate in the Dokriani glacier catchment (DGC) of the central Himalaya are investigated using data from three automatic weather stations (AWSs). An attempt is also made to quantify 0 °C isotherm and temperate sustainability over the glacierized area. The results reveal that the average near-surface temperature lapse rate (NSTLR) of the catchment varies from 4.6 to 7.5 °C km−1 during all measurement seasons, suggesting that the standard environmental lapse rate (SELR, 6.5 °C km−1) is not a promising input for realistic glacio-hydrological modeling. The seasonal variability of the NSTLR indicates that the monsoon (warm and humid period) lowers the temperature lapse rate in this catchment due to the presence of high moisture content in the air. The steepest lapse rate is investigated during the pre-monsoon season due to clear and drier weather conditions. In addition to this, the results reveal strong variability in NSTLR at diurnal and sub-diurnal levels, with high variability in the day time and low in the night-time hours. A higher air temperature is examined in the ablation zone of the Dokriani Glacier during the monsoon season (i.e., JJAS: June, July, August, September), while other seasons (pre-monsoon, post-monsoon, winter) show both higher as well as lower temperatures. A large variation in 0 °C isotherm is also observed ranging from 5000 to 5500 m asl during 2012–2015. The present work emphasizes that the study of monthly, seasonal, and annual variability of the NSTLR are very important for glacio-hydrological research in the central Himalaya.