基于飞机观测不同天气条件下北京地区黑碳气溶胶的垂直分布及其混合态特性

利用机载单颗粒黑碳光度计(SP2)针对北京地区不同天气条件下黑碳(BC,black carbon)气溶胶的垂直分布特征进行了10次的飞机探测研究。结果显示,在霾和非霾条件下BC气溶胶的浓度都是随着高度升高而减小,而且浓度变化在1500 m高度存在明显的分界线。在1500 m以下,BC气溶胶浓度变化梯度均较大,霾条件下的BC气溶胶浓度约为非霾条件下的4.3倍,在1500 m以上,BC气溶胶浓度变化梯度均较小,霾条件下的BC气溶胶浓度约为非霾条件下的2.5倍。BC气溶胶粒子谱都呈单峰分布,霾条件下峰值粒径主要要集中在0.16µm在非霾条件下峰值粒径主要集中在0.18µm在近地面,霾条件下的平均内混比远远高于非霾条件下,越往高空两种条件下的BC气溶胶的平均内混比越接近。通过CAMx模拟了不同条件下的BC气溶胶,发现霾污染天气下模拟的结果差异较大,在非霾条件下的模拟结果要优于霾条件下的模拟结果,这主要是由于在大部分模式中,很少考虑黑碳的老化状态。

华北中部夏季气溶胶垂直分布及其与云凝结核和云滴转化关系的飞机观测研究

气溶胶的时空分布及其核化成云的转化过程是云降水物理研究的重点,也是气候变化中气溶胶间接效应关注的热点问题。利用2013~2014年期间在华北中部山西地区开展的9架次夏季晴天和积云天气情况下的气溶胶、云凝结核(CCN)及云滴数浓度观测资料,分析研究了气溶胶的垂直分布、谱分布、来源特征及其与云凝结核、云滴数浓度的转化关系。研究结果表明,大气边界层逆温层结对气溶胶、CCN垂直分布有重要影响,不同天气条件下气溶胶谱型在低层差异较大而高层基本一致;垂直方向上CCN数浓度与气溶胶数浓度有较好的相关性,过饱和度0.3%条件下CCN比率(云凝结核/凝结核)与气溶胶有效直径呈线性关系;积云云下气溶胶与云滴的线性拟合方程为y=1.3x-616.3,拟合相关系数为0.96,气溶胶转化为云滴的比率可达到47%。在过饱和度0.3%条件下,云下CCN与云滴的线性拟合方程为y=1.6x-473.8,拟合相关系数也为0.96,CCN转化为云滴的比率可达到69%。

The Microphysical Characteristics of Wintertime Cold Clouds in North China

The microphysical characteristics of wintertime cold clouds in North China were investigated from 22 aircraft observation flights from 2014 to 2017,2020,and 2021.The clouds were generated by mesoscale weather systems with little orographic component.Over the mixed-phase temperature range(–40℃to 0℃),the average fraction of liquid,mixedphase,and ice cloud was 4.9%,23.3%,and 71.8%,respectively,and the probability distribution of ice mass fraction was a half-U-shape,suggesting that ice cloud was the primary cloud type.The wintertime mixed-phase clouds in North China were characterized by large cloud droplet number concentration,small liquid water content(LWC),and small effective diameter of cloud droplets.The main reason for larger cloud droplet number concentration and smaller effective diameter of cloud droplets was the heavy pollution in winter in North China,while for smaller LWC was the lower temperature during flights and the difference in air mass type.With the temperature increasing,cloud droplet number concentration,LWC,and the size of ice particles increased,but ice number concentration and effective diameter of cloud droplets decreased,similar to other mid-latitude regions,indicating the similarity in the temperature dependence of cloud properties of mixed-phase clouds.The variation of the cloud properties and ice habit at different temperatures indicated the operation of the aggregation and riming processes,which were commonly present in the wintertime mixed-phase clouds.This study fills a gap in the aircraft observation of wintertime cold clouds in North China.

Microphysical characteristics of precipitating cumulus cloud based on airborne Ka-band cloud radar and droplet measurements

Based on cloud-probe data and airborne Ka-band cloud radar data collected in Baoding on 5 August 2018,the microphysical structural characteristics of cumulus(Cu)cloud at the precipitation stage were investigated.The cloud droplets in the Cu cloud were found to be significantly larger than those in stratiform(STF)cloud.In the Cu cloud,most cloud particles were between 7 and 10μm in diameter,while in the STF cloud the majority of cloud particles grew no larger than 2μm.The sensitivity of cloud properties to aerosols varied with height.The cloud droplet effective radius showed a negative relationship with the aerosol number concentration(Na)in the cloud planetary boundary layer(PBL)and upper layer above the PBL.However,the cloud droplet concentration(Nc)varied little with decreased Na in the high liquid water content region above 1500 m.High Na values of between 300 and 1853 cm-3 were found in the PBL,and the maximum Na was sampled near the surface in August in the Hebei region,which was lower than that in autumn and winter.High radar reflectivity corresponded to large FCDP(fast cloud droplet probe)particle concentrations and small aerosol particle concentrations,and vice versa for low radar reflectivity.Strong updrafts in the Cu cloud increased the peak radius and Nc,and broadened cloud droplet spectrum;lower air temperature was favorable for particle condensational growth and produced larger droplets.

Evolution of planetary boundary layer under different weather conditions,and its impact on aerosol concentrations

A field experiment was conducted in Tianjin, China from September 9-30, 2010, focused on the evolution of Planetary Boundary Layer （PBL） and its impact on surface air pollutants. The experiment used three remote sensing instruments, wind profile radar （WPR）, microwave radiometer （MWR） and micro-pulse lidar （MPL）, to detect the vertical profiles of winds, temperature, and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants （aerosol, CO, SO2, NOx）, and also collected sonic anemometers data from a 255-m meteorological tower. Based on these measurements, the evolution of the PBL was estimated. The averaged PBL height was about 1000-1300 m during noon/afternoon-time, and 200-300 m during night-time. The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions. The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m＆3 under haze and clear sky conditions, respectively, The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower. The heat flux was found significantly decreased by haze （heavy pollution） or cloud, which tended to depress the development of PBL, while the repressed structure of PBL further weakened the diffusion of pollutants, leading to heavy pollution. This possible positive feedback cycle （more aerosols→lower PBL height → more aerosols） would induce an acceleration process for heavy ground pollution in megacities.

Ground-high altitude joint detection of ozone and nitrogen oxides in urban areas of Beijing

Based on observational data of ozone （O3） and nitrogen oxide （NOx） mixing ratios on the ground and at high altitude in urban areas of Beijing during a period of six days in November 2011, the temporal and spatial characteristics of mixing ratios were analyzed. The major findings include： urban O3 mixing ratios are low and NOx mixing ratios are always high near the road in November. Vertical variations of the gases are significantly different in and above the planetary boundary layer. The mixing ratio of O3 is negatively correlated with that of NOx and they are positively correlated with air temperature, which is the main factor directly causing vertical variation of O3 and NOx mixing ratios at 600-2100 m altitude. The NOx mixing ratios elevated during the heating period, while the O3 mixing ratios decreased： these phenomena are more significant at high altitudes compared to lower altitudes. During November, air masses in the urban areas of Beijing are brought by northwesterly winds, which transport O3 and NOx at low mixing ratios. Due to Beijing＇s natural geographical location, northwest air currents arc beneficial to the dilution and dispersion of pollutants, which can result in lower O3 and NOx background values in the Beijing urban area.

Hypoxia activates the hypoxia-inducible factor-1α/vascular endothelial growth factor pathway in a prostatic stromal cell line:A mechanism for the pathogenesis of benign prostatic hyperplasia

Background The development of benign prostatic hyperplasia(BPH)is closely related to hypoxia in the prostatic stroma,and the hypoxia-inducible factor-1α/vascular endothelial growth factor(HIF-1α/VEGF)pathway has been shown to significantly activate in response to hypoxia.The underlying mechanism for activation of this pathway in the pathogenesis of BPH remains unclear.Materials and methods We constructed HIF-1αoverexpression and knockdown BPH stromal(WPMY-1)and epithelial(BPH-1)cell lines,which were cultured under different oxygen conditions(hypoxia,normoxia,and hypoxia+HIF-1αinhibitor).Quantitative real-time polymerase chain reaction(qPCR)and Western blotting were applied to detect the expression of the HIF-1α/VEGF pathway.Cell proliferation and apoptosis were analyzed by Cell Counting Kit-8 and flow cytometry.We used the miRWalk 2.0 database and Western blotting to predict the potential miRNA that selectively targets the HIF-1α/VEGF pathway,and verified the prediction by qPCR and dual-luciferase assays.Results In a BPH stromal cell line(WPMY-1),the expression of VEGF was in accordance with HIF-1αlevels,elevated in the overexpression cells and decreased in the knockdown cells.Hypoxia-induced HIF-1αoverexpression,which could be reversed by a HIF-1αinhibitor.Moreover,the HIF-1αinhibitor significantly depressed cellular proliferation and promoted apoptosis in hypoxic conditions,assessed by Cell Counting Kit-8 and flow cytometry.However,in the BPH epithelial cell line(BPH-1),the expression level of HIF-1αdid not influence the expression of VEGF.Finally,a potential miRNA,miR-17-5p,regulating the HIF-1α/VEGF pathway was predicted from the miRWalk 2.0 database and Western blotting,and verified by qPCR and dual-luciferase assay.Conclusions In hypoxia,activation of the HIF-1α/VEGF pathway plays a crucial role in regulating cell proliferation in a BPH stromal cell line.Regulation by miR-17-5p may be the potential mechanism for the activation of this pathway.Regulation of this pathway may be involved in the pathogenesis of BPH.