Abstract
Changing patterns in aerosol concentrations over the Asian region is well documented with a concurrent increase over India and a marked reduction over China. However, aerosol vertical distribution in the changing climate is not fully understood. By combining long-term satellite observations from MODIS and CALIOP, here we show rapid changes in the aerosol vertical distribution over the South and East Asia covering India and China. A statistically significant decreasing (increasing) trend in the boundary layer (free troposphere) aerosol concentrations is noticed over India. ERA-Interim reanalysis model suggests that this increase in free tropospheric aerosol concentrations are due to the lifting of boundary layer pollutants through an increase in convection (and vertical velocity) in a changing climate. In contrast, a consistent decreasing trend is observed over China irrespective of the altitude. Interestingly, a decreasing trend in Aerosol Optical Depth is observed over the northwest India and we relate this to an observed increase in precipitation leading to increase in the vegetation. It is also found that long-term oscillations like QBO, ENSO and solar cycle significantly affect the aerosol concentrations. Thus, it is prudent to conclude that background meteorology and dynamics play an important role in changing patterns of aerosol vertical distribution.
Highlights
For investigating the vertical distribution of aerosols, we made use of CALIOP on-board CALIPSO measurements obtained during 2006–2018
Consistent with earlier reports (Samset et al.), dipole pattern in AODs i.e., statistically significant increasing trends (0.1 AOD/decade) over India and decreasing trends over China are observed in long-term MODIS o bservations[5]
Several earlier studies reported higher aerosol loading over the IGP region than any other parts of India but the present study reveals a significant increase in the aerosol loading over central India in recent periods (2014–2018)
Summary
For investigating the vertical distribution of aerosols, we made use of CALIOP on-board CALIPSO measurements obtained during 2006–2018. Version 3 products had lot of ambiguity in choosing the lidar ratio and it is resolved in Version 4 through extensive upgrades in the retrieval algorithms[45]. This data will produce the best results that are more representative of the actual condition of the atmosphere. Still, this algorithm has compromised by the low Signal to Noise Ratio (SNR) during day time measurements that may lead to weaker backscatter signals. Since the near surface AOD estimation from CALIOP has large uncertainty due to strong attenuation of backscattering signals in the boundary layer, we have discarded measurements of the first few range bins (< 200 m) while estimating the AOD within the boundary laye
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
