Strong Aerosol Absorption and Its Radiative Effects in Lhasa on the Tibetan Plateau

Abstract

Knowledge of aerosol radiative effects in the Tibetan Plateau (TP) is limited due to the lack of reliable aerosol optical properties, especially the single scattering albedo (SSA). We firstly reported in situ measurement of SSA in Lhasa using a cavity enhanced albedometer (CEA) at λ = 532 nm from 22nd May to 11th June 2021. Unexpected strong aerosol absorbing ability was observed with an average SSA of 0.69. Based on spectral absorptions measured by Aethalometer (AE33), black carbon (BC) was found to be the dominated absorbing species, accounting for about 83% at λ = 370 nm, followed by primary and secondary brown carbon (BrCpri and BrCsec). The average direct aerosol radiative forcing at the top of atmosphere (DARFTOA) was 2.83 W/m2, indicating aerosol warming effect on the Earth‐atmosphere system. Even though aerosol loading is low, aerosol heating effect plays a significant role on TP warming due to strong absorbing ability.

Impact of Aerosols on the Macrophysical and Microphysical Characteristics of Ice-Phase and Mixed-Phase Clouds over the Tibetan Plateau

“…During MAM and JJA nights, in the low range of AOD values, aerosols may inhibit the vertical development of ice-phase and mixed-phase clouds, resulting in a decrease in the CT and CWP, and the semi-direct effect of aerosols may play a dominant role. Wang et al [91] also found in their observational study of aerosols in the Lhasa region that although the aerosol load is low over the Tibetan Plateau, the heating effect of aerosols due to strong solar radiation absorption is significant for warming the Earth-atmosphere system. In the high range of AOD values, aerosols may promote the vertical development of ice-phase clouds, leading to an increase in the CTH and the CBH, and the indirect effect and activation effect of aerosols may play a dominant role.…”

“…The stronger randomness may prevent the aerosol's first indirect effect from manifesting in all samples, resulting in small ACI values when considering different samples from many different time points and limited sampling areas. Additionally, it may be because aerosols in plateau regions have a strong solar radiation absorption capability, leading to strong heating effects [91], which enhances the semi-direct effect of aerosols and weakens the aerosol's first indirect effect. Furthermore, it may be because, at smaller time scales and limited spatial scales, compared to aerosols, clouds are more influenced by meteorological factors, resulting in small ACI values.…”