ESTIMATING CONTRIBUTION OF WATER FLOW COMPONENTS TO KAMENG RIVER BASIN USING HYDROLOGICAL MODELLING

We present the 3-D distribution of atmospheric aerosols and highlight its variation with respect to longitudes over the Indian mainland and the surrounding oceans using long-term satellite observations and realistic synthesised data. The atmospheric heating due to the 3-D distribution of aerosols is estimated using radiative transfer calculations. We believe that our findings will have strong implications for aerosol–radiation interactions in regional climate simulations.

Global maps of aerosol absorption were generated using a multi-satellite retrieval algorithm. The retrieved values were validated with available aircraft-based measurements and compared with other global datasets. Seasonal and spatial distributions of aerosol absorption over various regions are also presented. The global maps of single scattering albedo with improved accuracy provide important input to climate models for assessing the climatic impact of aerosols on regional and global scales.

We show that the Atlantic Ocean is the major driver of interannual variability in dust over South Asia since the second decade of the 21st century. This is a shift from the previously important role played by the Pacific Ocean in controlling dust over this region. Following the end of the recent global warming hiatus, anomalies of the North Atlantic sea surface temperature have remotely invoked a weakening of the South Asian monsoon and a strengthening of the dust-bearing northwesterlies.

Vertical distributions of atmospheric aerosols across the Indo-Gangetic Plain (IGP) and their ability to form clouds have been studied based on airborne measurements during the SWAAMI field campaign. The ability of the aerosols to act as cloud-forming nuclei exhibited large spatial variation across the IGP and strong seasonality with increase in this ability with increase in altitude prior to the onset of monsoon and decrease with increase in altitude during the active phase of the monsoon.

We have estimated the aerosol radiative forcing (ARF) by employing the assimilated, gridded aerosol datasets over the Indian region. The present ARF estimates are more accurate and certain than those estimated using the currently available, latest satellite-retrieved aerosol products. Therefore, the present ARF estimates and corresponding assimilated aerosol products emerge as potential candidates for improving the aerosol climate impact assessment at regional, subregional and seasonal scales.

We have developed quality-enhanced, gridded datasets for aerosol optical depth (AOD) and absorption AOD by assimilating highly accurate measurements from the dense network of ground-based stations, with respective satellite-retrieved datasets. The assimilated datasets demonstrate improved accuracy and reduced uncertainties as compared to respective satellite products. Thus, these assimilated products emerge as important tools to improve the accuracy of climate impact assessment of aerosols.

Recent studies have shown that simulation of monsoons can be improved with an exact representation of SST–precipitation relationship. The vertical structure of precipitation with SST is distinctly different over the Arabian Sea than over the Bay of Bengal. The reflectivity profiles show variation with SST over the Arabian Sea and do not show considerable variation with SST over the Bay of Bengal. The variations in reflectivity profiles seem to originate at the cloud formation stage itself.

We show substantial improvements in the near-surface BC mass concentrations simulated by a regional chemistry transport model, WRF-Chem, over the Indian region, upon scaling up the CMIP5 equivalent anthropogenic BC emissions by 3 and introducing a diurnal variation to those. The diurnality in emissions alone significantly controls the simulated near-surface BC mass concentration, with a mean delay of 3–4 h. The simulated AOD, however, is still underestimated.

Our study, for the first time, presents measurements of aerosol chemical composition and physical characteristics across northern India in the pre-monsoon and monsoon seasons of 2016 using the FAAM BAe-146 UK research aircraft. Across northern India, an elevated aerosol layer dominated by sulfate aerosol exists that diminishes with monsoon arrival. The Indo-Gangetic Plain (IGP) boundary layer is dominated by organics, whereas outside the IGP sulfate dominates with increased scattering aerosol.

The paper focusses on utilizing freely disseminated SAR data for estimating ice-thickness and mass changes in the Himalayan terrain. The state-wise water loss estimates for the Himalayas has not been performed before. This information gives an idea as to how each state is performing in terms of water-sustainability on a global scale.

Multiple satellite retrieval algorithms are used to counter problems, such as cloud contamination, faced by sensors with large pixel sizes. This work uses one such algorithm to retrieve a parameter (single scattering albedo) over the oceans. It was found that the joint algorithm performed better than the original when aerosols were present near the surface. Discrepancy between the measurements was seen when elevated aerosols were present which might not have been detected by cruise instruments.

The knowledge on the realistic state of mixing of aerosols is inevitable for climate studies. Our paper unravels the existing uncertainties regarding the morphology and mixing state of aerosols, hitherto unexplained. To the best of our knowledge, this is a first-of-its kind study over the Indian region, coupling realistic aerosol observations, advanced spectroscopic, microscopic and image processing techniques on atmospheric aerosols at single particle resolution.