Abstract
Atmospheric aerosols can interact with clouds and influence the hydrological cycle by acting as cloud condensation nuclei. The current study reviews the results obtained on aerosol-precipitation interactions over India and the surrounding oceanic regions. An analysis of aerosol and cloud characteristics over the Arabian Sea, India, and the Bay of Bengal during summer monsoon in the last decade reveals large regional, intraseasonal, and interannual variations. Aerosol optical depth (AOD) and aerosol absorbing index (AAI) in 2002 (a drought year) are higher over India when compared to normal monsoon years. Cloud effective radius (CER) and cloud optical thickness exhibit a negative correlation with AOD over India, which agrees well with the indirect radiative effects of aerosols. Over Bay of Bengal CER is positively correlated with AOD suggesting an inverse aerosol indirect effect. In future, observatories to measure aerosol characteristics (amount, size, type, chemical composition, mixing, vertical and horizontal distributions), and cloud properties (number and size) over several locations in India, and intense observational campaigns involving aircraft and ships are crucial to unravel the quantitative impact that aerosols have on Indian monsoon. Satellite remote sensing of aerosol distribution, their chemical composition, microphysical properties of clouds, solar irradiance, and terrestrial longwave radiation is important.
Highlights
Aerosols affect the earth-atmosphere radiation budget directly by scattering and absorbing the incoming solar radiation and indirectly by influencing the processes of formation of clouds and precipitation
Anomalies in Aerosol optical depth (AOD), absorbing aerosol index (AAI), cloud effective radius (CER), cloud optical thickness (COT), and rainfall corresponding to July for each year from 2001 to 2010 and for JJAS are calculated with respect to the 2001– 2010 mean of the respective parameters over the Arabian Sea, India, and the Bay of Bengal (Figure 1) and analyzed
AODs were higher in July than in January, April, and October (Figure 4) and were lower in northeast India and south India when compared to the other regions in India on an annual scale [2]
Summary
Aerosols affect the earth-atmosphere radiation budget directly by scattering and absorbing the incoming solar radiation and indirectly by influencing the processes of formation of clouds and precipitation. The Indian summer monsoon and the associated rainfall exhibit wide variability over spatial and temporal scales and comprise interactions between land, ocean (Arabian Sea and Bay of Bengal) (Figure 1), and atmosphere [4]. These aerosols can get transported to higher heights (2–4 km) because of prevailing strong convection and can give rise to a heating of >0.5 K/day [3] leading to a burn-off of clouds (semidirect effect) which can further suppress the rainfall, producing a feedback effect With such significant spatiotemporal variations in aerosol, cloud characteristics, rainfall, and orography India is an ideal region to undertake aerosol-precipitation interaction studies. The aerosol impacts on clouds and precipitation over India and the surrounding oceanic regions (Arabian Sea, Bay of Bengal, and northern Indian Ocean) have been investigated mostly using models. The analysis is performed for July and the entire monsoon season separately to determine whether the correlations between aerosols, cloud characteristics, and precipitation observed in the core rainy month of the monsoon season become stronger or weaker when their respective seasonal means are considered or vice versa
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
