Meteorological variables controlling the forest fire over the Himalayas

Forest fire is the main disturbance for the Himalayan ecosystems, which impacts the regional and global carbon cycle, climate, forest succession, and tree density. Forest fires can occur due to both natural processes and anthropogenic factors. The fires over the Himalayas are mostly observed in the summer and pre-monsoon season, with large interannual variability. The primary objective of the present study is to identify the main meteorological drivers controlling forest fires over the Himalayas from March to June. The study performed statistical analysis on the daily and monthly observed/reanalysis climate data between 2001-2016. We used precipitation (P), temperature (T), and soil moisture (SM) from the climate prediction center and Vapor Pressure Deficient (VPD) from ECMWF-ERA5. The three satellite-based datasets for the Burned Area (BA) are accessed from Global Fire Emissions Database version 4 (GFEDs), Collection 6 Moderate Resolution Imaging Spectroradiometer (MODIS C6), and the European Space Agency Fire Climate Change Initiative version 5.1 (FireCCI51 – CEDA archive). The preliminary results show that all three BA has significant spatial and temporal/interannual variability. Meteorological variables such as P, T, SM, and VPD indicate strong interannual variability with rising slopes throughout the study period. Among these, P and SM indicate a significant trend over the central and northeast parts of the Himalayas. The VPD has a maximum significant positive correlation with BA for all three datasets (highest for GFED). The daily climatology suggests that VPD drops with an increase in P and follows the peaks of increasing T. The VPD rises until the end of April and starts falling from May due to pre-monsoon showers. The study observed that the varying amount of BA follows the peaks of high VPD, high temperature, and dry days (P_Threshold < 1mm). The northeast part of the Himalayas experiences major fires in March-April because of the substantial number of dry days and reduces in May-June due to pre-monsoon showers. In the northwest part, the amount of BA is high in May-June, despite having a smaller number of high VPD and dry days over the region. In the future, the study will focus on the impact of Himalayas forest fires on the atmospheric dust loading at a high temporal scale which can potentially trigger forest fires in adjacent regions.