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The relationship between precipitation and cloud properties in Southwest China are investigated by using the CLARA‐A2 cloud parameters data and TRMM‐3B43 precipitation data from 1998 to 2015. Ice water path (IWP) and cloud top height (CTH) are significantly and positively correlated with precipitation in all regions, indicating that ice‐phase processes and cloud development processes are the critical processes influencing precipitation. Precipitation is also directly associated with cloud fractional coverage (CFC) due to the significant positive correlation between CFC and precipitation in all regions except the Sichuan Basin (SCB). A positive correlation between liquid water path (LWP) and precipitation is found in the Eastern Tibetan Plateau (ETP) and Yunnan‐Kweichow Plateau (YKP), but not in the Western Tibetan Plateau (WTP) and SCB. Notably, the response of precipitation to LWP is not as good as that to IWP in SCB. Precipitation is significantly negatively correlated with ice effective radius (IREF) in WTP and ETP and positively correlated with liquid effective radius (LREF) in ETP, YKP and SCB. IREF and LREF are closely related to cloud microphysical processes. Specifically, small IREF could accelerate the Bergeron process and thus increase precipitation, while large LREF is closely related to the cloud droplets coalescence process. Results indicate that the difference in precipitation between the cold and warm seasons is related to convective available potential energy (CAPE) and low troposphere relative humidity (RH). High CAPE and RH favour the precipitation occurrence in Southwest China. The influence of CAPE and RH on precipitation is more significant in the ETP than that in the WTP, owing to the orographic lifting and moisture transport from the Indian Ocean. Thermodynamic and humidity conditions have a greater impact on precipitation by influencing LREF, LWP and IWP in YKP. In SCB, precipitation shows a strong dependence on CAPE, IWP and LREF, but not on RH. [ABSTRACT FROM AUTHOR]

The vertical distributions of BC mass concentration (m BC) during a winter pollution period in 2017 over Chengdu, a megacity in the Sichuan Basin, China, were measured by a micro-aethalometer equipped on a tethered balloon. This observation experienced severe air pollution with an averaged ground BC of 11.1 μg·m−3, which is higher than two times the annual mean in Chengdu for 2018. The available 68 BC vertical profiles are grouped in to five types: Type A (18%) is the uniform vertical distribution of BC with an unrecognizable mixing layer (ML) height; BC in Type B (26%) is also uniformly distributed in the ML while decreases rapidly above the ML; Type C (7%) is a unimodal distribution with BC peak within the ML when the suspended temperature inversion forms; BC in Type D (29%) is accumulated in the near-ground layer and quickly decreases with height; Type E (20%) is the bimodal or trimodal distribution with BC peaks around the top of ML. Types A and B dominate from noon to afternoon, and Types C–E play critical roles during the evening and night. The different vertical patterns of BC are mainly associated with the evolution of the ML and the local emissions. For all the five types, the calculated radiative forcing of BC (f BC) is negative at the surface but positive at the top of profile (TOP), indicating the net absorption of radiation by the atmosphere due to BC. The absolute values of f BC at the surface and the TOP are increased with the increase of columnar BC loading, and there is no significant difference in f BC at the TOP and the surface among different patterns when the same BC loading is considered. However, the vertical distribution of atmospheric heating rate contributed by BC (h BC) is highly related to BC's vertical profile. The uniform distributed BC can result in a positive gradient of h BC with altitude, and thus, enhance the stability of the atmosphere. The plateau terrain induced small-scale secondary circulation and relatively lower thermal inversion in the west of the Sichuan basin have an essential effect on the vertical distribution of aerosols and can contribute to an accumulation of aerosols at 0.8–1.4 km above ground level. This study would hopefully have a preliminary understanding of the vertical distribution of BC in the Sichuan Basin, and a vital implication for accurately estimating direct radiative forcing by BC in this region. • Vertical profiles of black carbon (BC) are measured by a micro-aethalometer equipped on a tethered balloon over Chengdu. • Five types of BC vertical profiles are grouped. • Vertical distribution of BC radiative forcing and heating rate for the five types of BC are calculated and compared. • The secondary circulation and low thermal inversion can contribute to the aerosol layer above the observation site. [ABSTRACT FROM AUTHOR]

In-situ measurements were carried out to study the size-resolved hygroscopic behaviour of submicron aerosols during pollution and fireworks episodes in winter from late January to February 2019 in Chengdu, a megacity in Sichuan Basin, using a hygroscopicity tandem differential mobility analyser (H-TDMA). The H-TDMA data were acquired at 90% relative humidity for dry aerosol diameters between 40 and 200 nm. Aerosol particles were usually externally mixed and consisted of nearly hydrophobic mode (NH), less hygroscopic mode (LH) and more hygroscopic mode (MH) in the urban area. The average ensemble mean hygroscopicity parameter values (κ Mean) over the entire sampling period were 0.16, 0.19, 0.21, 0.23 and 0.26 for aerosols with diameters of 40, 80, 110, 150 and 200 nm, respectively. These averages were lower than those in Shanghai and Nanjing. κ Mean for aerosols larger than 110 nm, however, were higher than those in Beijing and Guangzhou during winter. Distinct diurnal patterns for all measured sizes were observed for aerosol hygroscopicity and mixing state because of the photochemical reactions and the activities of the planetary boundary layer (PBL). The number fractions of the NH (NF NH) was low, but κ Mean was high, and more aerosols were internally mixed during daytime. The number fraction of LH (NF LH) for the 40-nm diameter aerosols in clean periods (CPs) was larger than that in the pollution episodes (PEs) because of the increasing amount of SOA formation. More aerosols of diameters larger than 80 nm were internally mixed during CPs and pollution accumulation period, resulting in higher κ Mean values. More strong hygroscopic components of fireworks were found in the larger aerosols during the fireworks episode (FE). The average κ Mean values of 0.19, 0.19, 0.21,0.23 and 0.27 for the 40, 80, 110, 150 and 200-nm diameter aerosols, respectively, during the FE were higher than those during the pre- and post-FE periods. The findings of this study contribute to the preliminary understanding of the hygroscopic behaviour of urban aerosol particles in the Sichuan Basin, which are essential for understanding the formation and evolution of severe haze events in the Sichuan Basin. • H-TDMA measurements was carried out in a megacity of the Sichuan Basin. • The hygroscopicity (κ) was higher than that in Beijing and Guangzhou during winter. • κ during the fireworks episodes were higher than those in the rest of the campaign. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosol is an important influence factor of global climate change, which can absorb visible light and part of infrared light strongly and affect climate change. Black carbon aerosol is also one of the main components of PM2.5. It can adsorb some toxic and harmful substances, affecting human health. Black carbon aerosol can participate in atmospheric chemical processes and affect the composition of the atmosphere. Sichuan Basin lies in the southwest China, there are two mega-cities of Chengdu and Chongqing. Due to the unique topographic conditions and the rapid development of urbanization, the pollution diffusion condition in Sichuan Basin is poor, which often results in the accumulation of pollutants, especially in winter time.In order to investigate the BC concentration evolution and its variations and impacts in this special region, surface BC concentration was observed using AE33 instrument from September 2017 to August 2018 in CUIT (Chengdu University of Information Technology) campus located in western surburb of Chengdu and vertical structures were monitored using MA200 multiband black carbon micro-instrument in December 2017 in Jianyang city of Sichuan Province. The distance between CUIT station and Jianyang station is about 60 km. The observation data showed that, the annual concentration of BC is 5.88±2.49µg/m3. The concentration of BC in winter was much higher (8.16±3.19µg/m3) than other seasons, BC concentration in summer was relative low (2.77±1.17µg/m3), in spring and autumn BC was about 5.20±2.41µg/m3. The diurnal variation of BC concentration was also obvious due to the local meteorological conditions and anthropogenic activities. It appeared that BC high peak value in the morning and night and low value in the afternoon. The experiment data showed that the vertical distribution of BC concentration varied with different weather patterns and boundary layer structures. Usually BC concentration was high from surface to about 500m height, the value was relative low (about 3~6µg/m3) at normal days. When stable weather and inversion temperature occurred in lower layer, BC concentration within 200m could be very high more than 12 µg/m3, as well as the PM2.5 was high resulting heavy pollution. In Sichuan basin, the ratio of BC and PM2.5 was about 0.08, which means BC account for 8 percent of PM2.5 on average. The further deep investigation in the source of BC and PM2.5 and their formation process, impact on local and regional weather and climate and their effect on human health will be conducted. [ABSTRACT FROM AUTHOR]

Abstract: Biomass energy is the main energy source in rural China. The low per capita cropland in China makes it impractical to convert cropland to energy crop cultivation as in other countries; development of energy crops must not compete with food and other cash crops for prime cropland. Mulberry planted on marginal lands like land risers, land boundaries and waste slopelands in Ningnan County of China''s southwestern Sichuan Province not only yielded enough leaf biomass to support a production of over 6000t of cocoons in 2005, but also produced large amounts of woody biomass through annual pruning. Mulberry planted on marginal lands would not be replaced by food or other cash crops if cocoon prices drop. The average annual dry matter biomass of pruned mulberry branches is 1.7kg/plant, or approximately 17.0–22.5t/ha, which is high compared to the annual biomass growth of many fast growing trees and perennial herbaceous energy crops. Mulberry prunings exceed household needs for fuelwood because household energy requirements are met with multiple sources. Income from cocoons is the major driving force for the expansion of mulberry planting on marginal land, as lack of incentives has accounted for slow development of firewood in China. Large scale development of marginal land-based planting of mulberry can also help reduce greenhouse gas emissions to the atmosphere, conserve forests and promote biodiversity. [Copyright &y& Elsevier]