Radiative forcing of the aerosol-cloud interaction in seriously polluted East China and East China Sea

摘要

The radiative forcing caused by aerosol-cloud interaction (ACI) is one of the most critical factors that lead to climate research uncertainty. In East China and the adjacent sea areas, the severe air pollution makes the ACI effect stronger than in other regions, but few observational studies focus on the effect of different aerosol components. This study estimated the shortwave radiation effect at the top of the atmosphere (TOA) caused by the interaction between the increased aerosol and the warm liquid cloud in East China and the East China Sea by applying the multiple linear regression into two ACI effect calculating methods proposed by Quaas et al. (2008; Method 1) and Chen et al. (2014; Method 2). Four aerosol components, black carbon (BC), dust (DU), organic carbon (OC), and sulfate (SU), are included in this research. The total ACI radiation effect of the four aerosol components is -12.08 +/- 4.63 W m(-2) in Method 1 and - 9.25 +/- 10.44 W m(-2) in Method 2, respectively, indicating a cooling effect to the planet. The divergence in the two methods is probably because the higher aerosol loading increases the cloud property retrieval deviation, and the cloud droplet spectral dispersion is neglected in Method 1. The effect of different aerosol components has significant diversity, with OC and SU have a cooling effect, DU has a heating effect, and BC shows an obvious geographical distinction. Further analysis suggests that under a similar aerosol optical depth (AOD), the areas with high relative humidity (RH) and low-tropospheric stability (LTS) have a more significant cooling effect due to the suppression of droplet evaporation and entrainment. Regions with higher average cloud top height also have a stronger cooling effect, especially for BC and SU. The possible reason is that high cloud altitude reduces the aerosol concentration within the cloud, further alleviates the heating effect of absorbing aerosols, and reduces the cloud droplet evaporation caused by the over much cloud condensation nuclei. This research contributes to a better understanding of the aerosolcloud radiative effect and its mechanism in East China and the East China Sea.