The significant uncertainties of Black Carbon (BC) radiative forcing are becoming an obstacle to the evaluation of their impacts and mitigation measures. One of the crucial reasons for this uncertainty could be the poorly constrained BC vertical profile. The BC has a lifetime of a few days to weeks and there is a clear pointer that it can be vertically transported through convection besides the horizontal advection. The present study aims for the intercomparison between the BC mass concentrations obtained through the aircraft-based observations and that derived from the selected Copernicus Atmosphere Monitoring Service (CAMS) reanalysis data over the three different locations of India, which is one of the largest emitters of BC aerosols. The aircraft-based BC observations were conducted from 0.5 to 7 km altitudes using Aethalometer during CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement Experiment) Phase I campaigns from June to September 2009. The output of the present study suggests the CAMS reanalysis data significantly underestimated BC mass throughout the vertical profile with an average mass normalized mean bias of greater than -70% at all three locations. Furthermore, the vertical radiative forcing and heating rates of BC were also calculated for both observation and reanalysis data. The output depicts the net forcing due to CAMS simulated BC in all the layers were 1-12 folds lower over all the study regions compared with observed BC aerosols. Likewise, the estimated mean biases in heating rate were in the range of -0.001 to -0.190 K day(-1) for all the vertical layers over the study locations. The possible reasons for these disparities could be poorly constrained emissions, especially aircraft emissions and/or their transformation schemes in aerosol modules. The present study emphasized that the validation of the vertical profile is also an essential factor for better constraints of the BC aerosols in climate models.

With Tibetan Plateau higher than 4 km to the west, the location of Sichuan Basin is unique all around the world and provides a good platform to study air pollution in the urban agglomerations over the complex terrain. To fill in the blanks on vertical distributions of PM1 (the particles smaller than 1 mu m) and carbonaceous aerosols within the basin, by means of high topographic relief, PM1 were off-line sampled during 20 January to 2 February 2018 at eight sites with increasing altitudes from the basin to southeastern margins of the Tibetan Plateau. The regional potential sources for each site were revealed by Hybrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The lowest carbonaceous aerosol levels occurred at Lixian, while the highest OC (organic carbon) (EC, elemental carbon) was at Hongyuan (the altitude of 3500 m) (Ande, a rural site) due to more primary emissions. The pollutants inside the basin can be transported the altitudes from 2 km to 3 km by vertical dispersion, but they cannot be dispersed to higher altitudes. The vertical stratification of the pollutants was obvious and easily formed high-low-high pattern from Sichuan Basin to southeastern Tibetan Plateau, especially during highly polluted episodes. The regional potential sources significantly varied as the increased altitudes. Regional pollution was significant inside the basin. The sources at the altitudes from 2 km to 3 km originated from southeastern margins of the Plateau and surrounding cities, while those at higher altitudes were transported from southeastern margins of the Plateau. The impact of basic meteorological variables (temperature, wind speed and vapor pressure) on carbonaceous aerosols was opposite between the basin and Plateau sites. This study was essential to understanding formation mechanisms of severe pollution episodes and thus to making control measures for the urban agglomerations inside the mountainous terrain.

Limited by the scarcity of in situ vertical observation data, the influences of biomass burning in Southeast Asia on major atmospheric carbonaceous compositions in downwind regions have not been thoroughly studied. In this study, aircraft observations were performed to obtain high time-resolved in situ vertical distributions of black carbon (BC) as well as carbon monoxide (CO) and carbon dioxide (CO2). Four types of profiles were revealed: Mode I (from 2000 to 3000 m, the BC, CO and CO2 concentrations were enhanced), Mode II (with increasing altitude, the BC, CO and CO2 concentrations almost decreased), Mode III (inhomogeneous vertical BC, CO and CO2 profiles with BC peaks were observed from 2500 to 3000 m) and Mode IV (the BC, CO and CO2 concentrations increased above 1500 m). Furthermore, simulations were conducted to calculate radiative forcing (RF) caused by BC and study the heating rate (HR) of BC in combination with the vertical BC profiles. A larger BC distribution in the atmosphere re-sulted in a sharp RF change from negative to positive values, imposing a nonnegligible influence on the atmospheric temperature profile, with maximum HR values ranging from 0.4 to 5.8 K/day. The values of the absorption Angstrom exponent (AAE) were 1.46 +/- 0.11 and 1.48 +/- 0.17 at altitudes from 1000 to 2000 and 2000-3000 m, respectively. The average BC light absorption coefficient at the 370 nm wavelength (alpha BC (370)) accounted for 50.3 %-76.8 % of the alpha (370), while the brown carbon (BrC) light absorption coefficient at the 370 nm wavelength (alpha BrC (370)) contrib-uted 23.2 %-49.7 % to the alpha (370) at altitudes of 1000-2000 m. At altitudes of 2000-3000 m, alpha BC (370) and alpha BrC (370) contributed 43.8 %-88.2 % and 11.8 %-56.2 % to the alpha (370), respectively. These findings show that calculations that consider the surface BC concentration but ignore the vertical BC distribution could result in massive uncertainties in estimating the RF and HR caused by BC. This study helped achieve a deeper understanding of the influences of biomass burning over the region of Southeast Asia on the profiles of atmospheric carbonaceous compositions and atmospheric BC absorption and its warming effect.

Owing to a lack of vertical observations, the impacts of black carbon (BC) on radiative forcing (RF) have typically been analyzed using ground observations and assumed profiles. In this study, a UAV platform was used to measure high-resolution in-situ vertical profiles of BC, fine partides (PM2.5), and relevant meteorological parameters in the boundary layer (BL). Further, a series of calculations using actual vertical profiles of BC were conducted to determine its impact on RF and heating rate (HR). The results show that the vertical distributions of BC were strongly affected by atmospheric thermodynamics and transport. Moreover. Three main types of profiles were revealed: Type I, Type II, Type III, which correspond to homogenous profiles (HO), negative gradient profiles (NG), and positive gradient profiles (PG), respectively. Types I and II were related to the diurnal evolution of the BL, and Type III was caused by surrounding emissions from high stacks and regional transport. There were no obvious differences in RF calculated for HO profiles and corresponding surface BC concentrations, unlike for NG and PG profiles. RF values calculated using surface BC concentrations led to an overestimate of 13.2 W m(-2) (27.5%, surface) and 18.2 W m(-2) (33.4%, atmosphere) compared to those calculated using actual NG profiles, and an underestimate of approximately 15.4 W m(-2) (35.0%, surface) and 16.1 W m(-2) (29.9%, atmosphere) compared to those calculated using actual PG profiles. In addition, the vertical distributions of BC HR exhibited dear sensitivity to BC profile types. Daytime PG profiles resulted in a positive vertical gradient of HR, which may strengthen temperature inversion at high altitudes. These findings indicate that calculations that use BC surface concentrations and ignore the vertical distribution of BC will lead to substantial uncertainties in the effects of BC on RE and HR. (C) 2020 Elsevier B.V. All rights reserved.

Black carbon (BC) exerts important radiative effects over regions with intensive emissions. This study presents in-situ aircraft measurements of BC vertical profiles including mass loading, size distribution and mixing state, spanning a range of pollution levels in both warm and cold seasons over Beijing. The development of planetary boundary layer (PBL) influenced the properties of pollutants at low levels, and regional transport from the southwest elevated the pollution at higher altitudes. Thicker coatings of BC were associated with higher pollution in the PBL, where interactions between BC and other substances intensively took place. Considering the mixing state of BC, the absorption efficiency could be potentially increased by up to 86% and 60% in the PBL and lower free troposphere, respectively. Including a columnintegrated absorption enhancement, the in-situ constrained absorption aerosol optical depth at wavelength 870 nm (AAOD(870)) improved the agreement with AERONET by 28%, but the in-situ measurement remained 19% lower. A radiative transfer model finds a BC heating rate of 0.1-0.3 K/d and 0.5-3.1 K/d for less and more polluted environments respectively, and the BC coating effect could positively introduce a +0.1-4.2 Wm(-2) radiative forcing. The presence of aerosol layer enhanced the positive vertical gradient of heating rate by redistributing the actinic flux. In particular, this gradient was further enhanced by introducing thickly-coated BC at higher level during the regional transport events, which may promote the temperature inversion and further depress the PBL development on polluted days. (C) 2020 Elsevier Ltd. All rights reserved.

Spectral aerosol optical depth (AOD) measurements obtained from multi-wavelength radiometer under cloudless conditions over Doon Valley, in the foothills of the western Himalayas, are analysed during the period January 2007 to December 2012. High AOD values of 0.46 +/- A 0.08 and 0.52 +/- A 0.1 at 500 nm, along with low values of ngstrom exponent (0.49 +/- A 0.01 and 0.44 +/- A 0.03) during spring (March-May) and summer (June-August), respectively, suggest a flat AOD spectrum indicative of coarse-mode aerosol abundance compared with winter (December-February) and autumn (September-November), which are mostly dominated by fine aerosols from urban/industrial emissions and biomass burning. The columnar size distributions (CSD) retrieved from the King's inversion of spectral AOD exhibit bimodal size patterns during spring and autumn, while combinations of the power-law and unimodal distributions better simulate the retrieved CSDs during winter and summer. High values of extinction coefficient near the surface (similar to 0.8-1.0 km(-1) at 532 nm) and a steep decreasing gradient above are observed via CALIPSO profiles in autumn and winter, while spring and summer exhibit elevated aerosol layers between similar to 1.5 and 3.5 km due to the presence of dust. The particle depolarisation ratio shows a slight increasing trend with altitude, with higher values in spring and summer indicative of non-spherical particles of dust origin. The aerosol-climate implications are evaluated via the aerosol radiative forcing (ARF), which is estimated via the synergy of OPAC and SBDART models. On the monthly basis, the ARF values range from similar to -30 to -90 W m(-2) at the surface, while aerosols cause an overall cooling effect at the top of atmosphere (approx. -5 to -15 W m(-2)). The atmospheric heating via aerosol absorption results in heating rates of 1.2-1.6 K day(-1) during March-June, which may contribute to changes in monsoon circulation over northern India and the Himalayas.

A Tethered balloon-based field campaign was launched for the vertical observation of air pollutants within the lower troposphere of 1000 m for the first time over a Chinese megacity, Shanghai in December of 2013. A custom-designed instrumentation platform for tethered balloon observation and ground-based observation synchronously operated for the measurement of same meteorological parameters and typical air pollutants. One episodic event (December 13) was selected with specific focus on particulate black carbon, a short-lived climate forcer with strong warming effect. Diurnal variation of the mixing layer height showed very shallow boundary of less than 300 m in early morning and night due to nocturnal inversion while extended boundary of more than 1000 m from noon to afternoon. Wind profiles showed relatively stagnant synoptic condition in the morning, frequent shifts between upward and downward motion at noon and in the afternoon, and dominant downward motion with sea breeze in the evening. Characteristics of black carbon vertical profiles during four different periods of a day were analyzed and compared. In the morning, surface BC concentration averaged as high as 20 mu g/m(3) due to intense traffic emissions from the morning rush hours and unfavorable meteorological conditions. A strong gradient of BC concentrations with altitude was observed from the ground to the top of boundary layer at around 250-370 m. BC gradients turned much smaller above the boundary layer. BC profiles measured during noon and afternoon were the least dependent on heights. The largely extended boundary layer with strong vertical convection was responsible for a well mixing of BC particles in the whole measured column. BC profiles were similar between the early-evening and late-evening phases. The lower troposphere was divided into two stratified air layers with contrasted BC vertical distributions. Profiles at night showed strong gradients from the relatively high surface concentrations to low concentrations near the top of the boundary layer around 200 m. Above the boundary layer, BC increased with altitudes and reached a maximum at the top of 1000 m. Prevailing sea breeze within the boundary layer was mainly responsible for the quick cleanup of BC in the lower altitudes. In contrast, continental outflow via regional transport was the major cause of the enhanced BC aloft. This study provides a first insight of the black carbon vertical profiles over Eastern China, which will have significant implications for narrowing the gaps between the source emissions and observations as well as improving estimations of BC radiative forcing and regional climate. (C) 2015 Elsevier Ltd. All rights reserved.

Large uncertainty in the direct radiative forcing of black carbon (BC) exists, with published estimates ranging from 0.25 to 0.9 W m(-2). A significant source of this uncertainty relates to the vertical distribution of BC, particularly relative to cloud layers. We first compare the vertical distribution of BC in Coupled Model Intercomparison Project Phase 5 (CMIP5) models to aircraft measurements and find that models tend to overestimate upper tropospheric/lower stratospheric (UT/LS) BC, particularly over the central Pacific from Hiaper Pole-to-Pole Observations Flight 1 (HIPPO1). However, CMIP5 generally underestimates Arctic BC from the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign, implying a geographically dependent bias. Factors controlling the vertical distribution of BC in CMIP5 models, such as wet and dry deposition, precipitation, and convective mass flux (MC), are subsequently investigated. We also perform a series of sensitivity experiments with the Community Atmosphere Model version 5, including prescribed meteorology, enhanced vertical resolution, and altered convective wet scavenging efficiency and deep convection. We find that convective mass flux has opposing effects on the amount of black carbon in the atmosphere. More MC is associated with more convective precipitation, enhanced wet removal, and less BC below 500 hPa. However, more MC, particularly above 500 hPa, yield more BC aloft due to enhanced convective lofting. These relationshipsparticularly MC versus BC below 500 hPa-are generally stronger in the tropics. Compared to the Modern-Era Retrospective Analysis for Research and Applications, most CMIP5 models overestimate MC, with all models overestimating MC above 500 hPa. Our results suggest that excessive convective transport is one of the reasons for CMIP5 overestimation of UT/LS BC.

During (the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) over India, I high-resolution airborne measurements of the attitude profiles of the mass concentrations (M-B) Of aerosol black carbon (BC) were made off Bhubaneswar (131311, 85.82 degrees E, 20.25 degrees N), over northwest B ay of Bengal, in the altitude region upto 3km. Such high-resolution measurements of altitude profiles of aerosols are done for the first time over India. The profiles showed a near-steady vertical I distribution of M-B modulated with two small peaks, one at 800 in and the other at similar to 2000 n(-1). High ) sonde (Vaisala) measurements around the same region resolution GPS (Global Positioning System onboard the research vessel Sagar Kanya (around the same time of the aircraft sortie) revealed two convectivelv well mixed layers one from ground to similar to 700m with an inversion at the top and the other extends from 1200 in to similar to 2000 in with a second inversion at similar to 2200 in and a Convectively stable region in the altitude range 700-1200 m. The observed peaks in the M-B profile are found to be associated with these temperature inversions. In addition, long-range transport from the Indo-Gangetic Plain (IGP) and deserts lying further to the west also influence the vertical profile of BC. Latitudinal variation of M-B Showed a remarkable land ocean contrast at the 500 in altitude (within the well mixed region) with remarkably lower values over oceans, suggesting the impact of strong In,sources over the mainland. However, above the ABL (at 1500m), the latitudinal variations were quite weak, and this appears to be resulting from the impact of long-range transport. Comparison of the altitude profiles of M-B over BoB off BBR, with those obtained during the earlier occasion over the inland stations of Hyderabad and Kanpur showed similarities above similar to 500m, with M-B remaining around a steady value of similar to 1 mu g m(-3). However, large differences are seen within the ABL. Even though the observed M-B values are not unusually high, their near constancy in the vertical column will have important implications to radiative forcing.

[1] Chemical, physical, and optical measurements of aerosol particle properties within an aged biomass-burning plume were performed on board a research aircraft during a profile descent over a ground-based site in northeastern Greece (40degrees24'N, 23degrees57'E; 170 m asl) where continuous measurements of the spectral downwelling solar irradiance (global, direct, and diffuse) are being made. The aerosol optical depth measured at the ground during the time of overflight was significantly enhanced (0.39 at a wavelength of 500 nm) due to a haze layer between 1 and 3.5 km altitude. The dry particle scattering coefficient within the layer was around 80 Mm(-1), and the particle absorption coefficient was around 15 Mm(-1), giving a single scattering albedo of 0.89 at 500 nm (dry state). The black carbon fraction is estimated to account for 6-9% of the total accumulation mode particle mass (<1 mu m diameter). The increase of the particle scattering coefficient with increasing relative humidity at 500 nm is of the order of 40% for a change in relative humidity from 30 to 80%. The dry, altitude-dependent, particle number size distribution is used as input parameter for radiative transfer calculations of the spectral short-wave, downwelling irradiance at the surface. The agreement between the calculated irradiances and the experimental results from the ground-based radiometer is within 10%, both for the direct and the diffuse components (at 415, 501, and 615 nm). Calculations of the net radiative forcing at the surface and at the top of the atmosphere (TOA) show that due to particle absorption the effect of aerosols is much stronger at the surface than at the TOA. Over sea the net short-wave radiative forcing (daytime average) between 280 nm and 4 mu m is up to -64 W m(-2) at the surface and up to -22 W m(-2) at the TOA.