Abstract

Aerosols significantly affect the Earth-atmosphere energy balance and climate change by acting as cloud condensation nuclei. Particularly, the susceptibility of clouds to aerosols is more pronounced when the aerosols are faint. However, previous methodologies generally miss these faint aerosols and their climate effect based on instantaneous observations because they are too optically thin to be detected. Here, we focus on retrieving faint aerosol extinction based on instantaneous observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Results show a good agreement between faint aerosol extinction retrieval of CALIPSO and Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III-ISS) product over June 2017 to 2019 during nighttime, with correlation coefficients (R) and root mean square error (RMSE) of 0.58 in logarithmic scale and 0.0008, respectively. The lower bound of retrieved aerosol extinction extended to 0.0001 km−1 product (0.01 km−1, much lower than the CALIPSO Level 2 Extinction). The CALIPSO retrieval during daytime has a positive bias and low agreement with SAGE III-ISS with R and RMSE of 0.16 and 0.0034, respectively, due to the low signal-to-noise ratio caused by sunlight. Additionally, the retrieval at 20 km resolution successfully capture the enhanced faint aerosol from Siberian fires in 2019 instantaneously, which are also shown by CALIPSO monthly-averaged aerosol product at much lower temporal-spatial resolution. It indicates a significant potential for improving the quantification of aerosol impacts on climate change through retrieving instantaneous faint aerosol.

Highlights

  • Aerosols significantly affect the Earth-atmosphere system through direct and indirect climate radiative forcing (Boucher et al, 2013)

  • 140 3 Results and analysis 3.1 Faint aerosols in wildfire cases Figure 3 shows a case with the retrieved faint aerosol combined with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) detected aerosol from wildfires in Australia that burned for several months

  • The smoke and dust transmission trajectory generated by the wildfires in Australia in August 2019 can be seen in the red dash boxed area of the Terra MODIS true-color image (Figure 3a)

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Summary

Introduction

Aerosols significantly affect the Earth-atmosphere system through direct and indirect climate radiative forcing (Boucher et al, 2013). Increased aerosol perturbs atmospheric radiative balance by directly interacting with solar radiation 30 (direct effect), and affects the cloud properties and precipitation by acting as cloud condensation nuclei and ice forming particles (indirect effect) (Dipu et al, 2013;Rosenfeld et al, 2014). Aerosols represent a major uncertainty in global climate change with a low scientific understanding (Schwartz and Andreae, 1996;Lee et al, 2016;Watson‐Parris et al, 2020). Discussion started: 16 February 2022 c Author(s) 2022.

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