Aerosol-Cloud-Interaction Variability Induced by Atmospheric Brown Clouds during the 2009 Indian Summer Monsoon Drought

Abstract

Contrasting monsoons of 2008 and 2009 provided a test bed to enhance the understanding of the aerosol variability and aerosol-cloud interaction. Vertical aerosol profiles derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are used to delineate the aerosol properties during the two contrasting Indian summer monsoons. We observed a 30-40% increase in the aerosol occurrence frequency (AOF) in lower altitudes (below 6 km) in 2009 and a 5-8% enhancement in AOF at higher altitudes in 2008. The cloud occurrence frequency also showed more deep convective clouds in 2008 (13-15%) than in 2009. Cloud Fraction, Aerosol Optical Depth and TRMM precipitation data sets have been also used to investigate the aerosol-cloud interaction. We define the microphysical effect as the increase in cloud fraction with increase in aerosols (CCN) and the radiative effect as the decrease of cloud fraction with increase in aerosol loading. We observe a stronger microphysical effect than the radiative effect in 2008 as compared to 2009. In 2009, atmospheric brown clouds were observed from March to September, which slowed down the microphysical effect and enhanced the radiative effect. This resulted in a 30% reduction in the total cloud fraction that may have reduced precipitation, and invigorated the drought conditions during 2009.

South Asian summer monsoon breaks: Process‐based diagnostics in HIRHAM5

“…Wild and Roeckner [] found systematically underestimated atmospheric shortwave absorption along with overestimated surface shortwave absorption at low latitudes in ECHAM5 and related these errors to the crude aerosol climatology used in the physical parameterization package, which does not take into account high regional and seasonal loadings of absorbing aerosols. During the past few decades, direct surface radiation measurements observed continuous and steady dimming in India associated with tremendous aerosol emissions due to rapid urbanization and population growth [ Wild et al , ], and more recent studies with satellite observations noticed increased aerosol loadings over central India especially during break conditions [e.g., Manoj et al , ; Bhawar and Rahul , ]. Since the ECHAM5 aerosol climatology is also implemented in HIRHAM5, we assume that anomalous high‐simulated incoming surface shortwave radiation flux during breaks is perhaps partly due to weak atmospheric aerosol absorption.…”

Double blanket effect caused by two layers of black carbon aerosols escalates warming in the Brahmaputra River Valley

“…The atmospheric radiative heating due to BC increases the atmospheric stability leading to a change in the precipitation patterns282930 and when such heating occurs over glaciers/ice, it enhances the melting rate as proved in a recent study31. Several studies about the aerosol variability and the associated heating have been conducted over the Himalayan region3233343536 and BC induced heating rates greater than 2 K/day have been reported over different Indian regions1637.…”

Variability of Aerosols and Clouds Over North Indian and Myanmar During the COVID-19 Lockdown Period

“…An increase in anthropogenic activity has led to an increase in aerosol emissions at a global scale, which led to an increase in cloud condensation nuclei (CCN) and ice nucleating particles (INP) (Seinfeld et al, 2016). However, the increase in CCN does not lead to enhanced precipitation, indicating complex microphysical processes affecting the precipitation (Koren et al, 2008;Bhawar and Rahul, 2013). Previous studies reported an adverse effect of aerosol increase and thereby giant CCN formation on precipitation (Posselt and Lohmann 2008).…”