Study on Global Aerosol Direct Radiative Effect by Fast Calculation Methods for Satellite Observations

Aerosol direct radiative effect (ADRE) is an important uncertainty factor in climate change research. Large-range and long-term ADRE calculations based on massive data from satellite observations need considerable computational time. This article commences with an examination of the dependence of shortwave surface ADRE on aerosol optical properties, solar zenith angle (SZA), atmospheric conditions, and surface parameters. It then formulates a hybrid lookup table (LUT) method that integrates the optimized LUT with formulaic calculations of nonlinear parameters. We provide a low-frequency LUT utilization strategy based on the time-varying pattern of ADRE. The comparison of findings between the fast computation method and the libRadtran radiative transfer model revealed a coefficient of determination ( $R^{2}$ ) of 0.99. The fast calculation method requires approximately 1/8190 of the libRadtran, proving that our approach significantly boosts computational speed while maintaining high accuracy. We computed and examined the daily ADRE for the worldwide period from 2001 to 2020 using this method. The average ADRE was −12.8 W/m², indicating a cooling effect. In regions characterized by frequent dust storms and human activities, the cooling effect was elevated, exemplified by Eastern China (−33.61 W/m²) and Northern India (−27.52 W/m²). Between 2001 and 2020, the ADRE cooling effect showed a slight strengthening of −0.004 W/m²/year. Simultaneously, the enactment of environmental protection measures in diverse global locations has resulted in varying alterations in the trend of ADRE over the previous two decades. Over time, the cooling effects of aerosols at the surface have strengthened (2001–2010: −0.08 W/m²/year) and then weakened (2011–2020: 0.12 W/m²/year).