Abstract View
General Circulation Model Estimates of Aerosol Radiative Effects and Its Implication to Hydrology over the Hindu Kush-Himalayan (HKH) Region
SAUVIK SANTRA, Amit Kumar, Shubha Verma, Indian Institute of Technology Kharagpur
Abstract Number: 401
Working Group: Aerosols, Clouds and Climate
Abstract
We present an analysis of aerosol transport simulations carried out in the Laboratoire de Me ́te ́orologie Dynamique (LMD-ZT) General Circulation Model (GCM) over the Hindu Kush Himalayan (HKH) region. The seasonal mean of GCM estimated aerosol optical depth (AOD) and single scattering albedo (SSA) were found to be consistent with the measured values. The pre-monsoon mean AOD was estimated to be 20% higher than that of the winter mean. About 75% of the simulated AOD was found to be from anthropogenic emissions and was mostly constituted of sulfate (45-65%), followed by organic carbon (OC) (40-50%), and black carbon (BC) (4-8%). One of the prominent features was the discrete spatial gradient in the distribution of sulfate and BC aerosols, thereby indicating their origin from different source regions. A substantial variation was seen in the spatial distribution of SSA between the HKH region and the neighboring regions of IGP. Aerosol radiative forcing was found to be positive at the top-of-atmosphere (TOA), indicating a net warming effect. Notably, the value of aerosol radiative forcing at TOA during pre-monsoon was about 4-6 times the value during the winter season. A strong influence of transport from far-off regions, which contributed as high as 60% of the total positive radiative effects, was inferred. Furthermore, the relative percentage of snow albedo reduction (SAR) and the annual increase in surface runoff due to deposition of both anthropogenic and natural aerosols were found to be significantly high, with their values being 13-15% and 3-12 cm of water equivalent respectively. The radiative transfer calculations are further used as input to a hydrological model, and sensitivity studies of surface runoff to aerosol deposition is carried out and validated with available observational data.