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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 (BrCpriand 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. The Tibetan Plateau (TP) has experienced rapid warming over the past decades, but the key factors affecting TP climate change haven't yet been clearly understood. Aerosol single scattering albedo (SSA) is a key optical parameter determining aerosol warming or cooling effect; however, reliable SSA measurement is scarce in TP. This study firstly reported in situ measurement of SSA in Lhasa and explored the direct radiative effect of aerosol on TP warming. Strong aerosol absorption, mainly contributed by black carbon (BC), was observed with an average SSA value of 0.69 in this city. Besides Lhasa, other sites over TP were also reported with low SSA (≤0.77) from surface measurement. The strong aerosol absorption could cause heating effect on the Earth‐atmosphere system. To relieve TP warming, reasonable pollutant emission control strategies should be taken urgently to weaken aerosol absorbing ability. Unexpected low aerosol single scattering albedo was observed in Lhasa via in situ measurement of multiple optical parameters simultaneouslyBlack carbon was the dominant contributor (∼83%) to aerosol absorption at 370 nm, followed by primary and secondary brown carbonThe strong absorption in Lhasa exerted positive direct aerosol radiative forcing (warming effect) at the top of atmosphere Unexpected low aerosol single scattering albedo was observed in Lhasa via in situ measurement of multiple optical parameters simultaneously Black carbon was the dominant contributor (∼83%) to aerosol absorption at 370 nm, followed by primary and secondary brown carbon The strong absorption in Lhasa exerted positive direct aerosol radiative forcing (warming effect) at the top of atmosphere

A novel instrument based on broadband cavity-enhanced absorption spectroscopy has been developed using a supercontinuum broadband light source, which showcases its ability in simultaneous measurements of the concentration of NO2and the extinction of particulate matter. Side-by-side intercomparison was carried out with the reference NOx analyzer for NO2and OPC-N2 particle counter for particulate matter, which shows a good linear correlation with r2> 0.90. The measurement limits (1σ) of the developed instrument were experimentally determined to be 230 pptv in 40 s for NO2and 1.24 Mm–1for the extinction of particulate matter in 15 s. This work provides a promising method in simultaneously monitoring atmospheric gaseous compounds and particulate matter, which would further advance our understanding on gas–particle heterogeneous interactions in the context of climate change and air quality.

Biological aerosols represent a diverse subset of particulate matter that is emitted directly to the atmosphere in the form of (but not limited to) bacteria, fungal spores, pollens, viruses, and plant debris. These particles can have local air quality implications, but potentially play a larger climate role by acting as efficient ice nucleating particles (INPs) and cloud condensation nuclei. We have deployed a Wideband Integrated Bioaerosol Sensor on the NASA DC‐8 aircraft to (1) quantify boundary layer (BL) variability of fluorescent biological aerosol particle (FBAP) concentrations in the Southeast United States (SEUS), (2) link this variability explicitly to land cover heterogeneity in the region, and (3) examine the vertical profile of bioaerosols in the context of convective vertical redistribution. Flight‐averaged FBAP concentrations ranged between 0.1 and 0.43 scm−3(cm−3at standard temperature and pressure) with relatively homogeneous concentrations throughout the region; croplands showed the highest concentrations in the BL (0.37 scm−3), and lowest concentrations were associated with evergreen forests (0.24 scm−3). Observed FBAP concentrations are in generally good agreement with model parameterized emission rates for bacteria, and discrepancies are likely the result of fungal spore contributions. Shallow convection in the region is shown to be a relatively efficient lofting mechanism as the vertical transport efficiency of FBAP is at least equal to black carbon aerosol, suggesting that ground‐level FBAP survives transport into the free troposphere to be available for INP activation. Comparison of the fraction of coarse‐mode particles that were biological (fFBAP) suggested that the SEUS (fFBAP= 8.5%) was a much stronger source of bioaerosols than long‐range transport during a Saharan Air Layer (SAL) dust event (fFBAP= 0.17%) or summertime marine emissions in the Gulf of Mexico (fFBAP= 0.73%). The southeast USA region is a significant source of bioaerosolsShallow convection allows vertical transport of bioaerosolsEmission rates from different land types are relatively homogeneous

Extensive profiling of aerosol optical, chemical, and microphysical properties was performed in the Washington DC/Baltimore MD region in July 2011 during NASA DISCOVER‐AQ. In situ extinction coefficient (σext,in‐situ) measurements were made aboard the NASA P3‐B aircraft coincident with remote‐sensing observations by the High‐Spectral Resolution Lidar (HSRL; σext,HSRL) aboard the NASA UC‐12 aircraft. A statistical comparison revealed good agreement within instrumental uncertainty (σext,in‐situ= 1.1 σext,HSRL− 3.2 Mm−1, r2= 0.88) and demonstrated the robust nature of hygroscopicity measurements (f(RH)) necessary to correct observations at dry relative humidity (RH) to ambient conditions. The average liquid‐water contribution to ambient visible‐light extinction was as much as 43% in this urban region. f(RH) values were observed to vary significantly from 1.1 to 2.1 on a day‐to‐day basis suggesting influence from both local and transported sources. Results emphasize the importance of accounting for the RH dependence of optical‐ and mass‐based aerosol air‐quality measurements (e.g., of PM2.5), especially in relation to satellite and remote‐sensing retrievals. Independent observations demonstrate robustness of f(RH) relationshipSignificant variability of aerosol hygroscopicity is observed in an urban area