青藏高原夏季旱涝与大尺度环流的关系

利用欧洲中心ERA-40再分析数据和降水观测数据,分析了大尺度大气环流和海表温度对青藏高原夏季极端干旱与湿润的影响。研究指出,该地区的极端干旱和湿润事件与北大西洋/欧洲地区的环流异常以及横跨欧亚大陆的波列有关。西藏地区夏季发生干旱时,在北欧的斯堪的纳维亚上空会产生由北大西洋西南—东北向的风暴轴支配的强高压异常现象,产生沿"大圆路径"跨越欧亚向南传播至亚洲东南部的波列,并通过反气旋—气旋偶极子调整高原北部和东部流场,进而抑制孟加拉湾水汽向高原地区的输送。西藏地区夏季异常多雨时,纬向横跨大西洋的风暴轴引起欧洲中部低压异常,与之相关联的副热带西风急流和热带东风急流向北移动;与此同时,在北大西洋形成了沿着朝赤道方向路径传播的波列,使其更有利于到达副热带急流入口区(而不是进一步向南传播)。然后,当波列穿越地中海和阿拉伯海到达印度时被再次加强,并与(印度)季风的偏西风分支相互作用,为西藏地区带来充足的水汽。海表温度对于由厄尔尼诺(拉尼娜)/南方涛动和印度洋偶极子引发的青藏高原极端和严重干旱(湿润)事件具有指示意义。当热带北大西洋海表温度明显偏冷时,青藏高原同时或者滞后出现干旱。

Variability in upper-ocean salinity stratification in the tropical Pacific Ocean

Using a gridded array for real-time geostrophic oceanography(Argo)program float dataset,the features of upperocean salinity stratification in the tropical Pacific Ocean are studied.The salinity component of the squared Brunt-V?is?l?frequency N2(NS2)is used to represent salinity stratification.Layer-max NS2(LMN),defined as the NS2 maximum over the upper 300 m depth,and halocline depth(HD),defined as the depth where the NS2 maximum is located,are used to specifically describe the intensity of salinity stratification.Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability.Over the western and eastern equatorial Pacific,the LMN has a large magnitude with a shallow HD,and both have completely opposite distributions outside of the equatorial region.An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations,followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline,significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event.When an El Ni?o event occurs,the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward,together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool.The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves.

Simultaneous monitoring of PCB profiles in the urban air of Dalian,China with active and passive samplings

The concentration of polychlorinated biphenyls （PCBs） in the urban air of Dalian, China was monitored from November 2009 to October 2010 with active high-volume sampler and semipermeable membrane device （SPMD） passive sampler. The concentration of PCBs （particle ＋ gas） （∑PCBs） ranged from 18.6 to 91.0 pg/m3, with an average of 50.9 pg/m3, and the most abundant dioxin-like PCB （DL-PCBs） was PCB118. The WHO-TEQ values of DL-PCBs were 3.6--22.1 fg/m3, with an average of 8.5 fg/m3, and PCB126 was the maximum contributor to ZTEQ. There was a much larger amount of PCBs in the gas phase than in the particulate phase. The dominant PCB components were lower and middle molecular weight PCBs. With increasing chlorination level, the concentration of the PCB congeners in the air decreased. The gas-particulate partitioning of PCBs was different for the four seasons. The gas- particulate partitioning coefficients （logKp） vs. subcooled liquid vapor pressures （logPL~） of PCBs had reasonable correlations for different sampling sites and seasons. The absorption mechanism contributed more to the gas-particulate partitioning process than adsorption. Correlation analysis of meteorological parameters with the concentration of PCBs was conducted using SPSS packages. The ambient temperature and atmospheric pressure were important factors influencing the concentration of PCBs in the air. The distribution pattern of the congeners of PCBs and the dominant contributors to DL-PCBs and TEQ in active samples and SPMDs passive samples were similar. SPMD mainly sequestrated gas phase PCBs.

Monitoring gas-and particulate-phase short-chain polychlorinated paraffins in the urban air of Dalian by a self-developed passive sampler

The concentration of short-chain polychlorinated paraffins(SCCPs) in the urban air of Dalian,China was monitored from September 2016 to August 2017 with a self-developed passive sampler(PAS1) and an active high-volume sampler, simultaneously. PAS1 successfully collected the entire target SCCPs in the ambient air. Air SCCPs sampled by PAS1 were found be in the linear uptake stage during 181 days of sampling. Passive and active samples showed comparable congener profiles, and the dominant contributors of SCCPs in the two kinds of samples were similar. A significant linear correlation was observed between the total concentration of SCCPs sampled by PAS1 and active sampler in the four seasons. The passive sampling rates of the PAS1 for the gas and particulate phases of SCCPs were measured. The quantitative structure–property relationship of the sampling rate of PAS1(Rair) for gas-phase SCCPs was studied. From the molecular point of view, Rairwas mainly affected by the molecular weight and sub-cooled liquid vapor pressure of SCCPs. In general, SCCPs in the urban air of Dalian mainly existed in gas phase,lower molecular weight SCCPs primarily occurred in the gas phase, whereas higher molecular weight SCCPs were predominately adsorbed or absorbed on airborne particles. The air concentration of SCCPs in the four seasons were different, the correlation of the concentration of SCCPs in the air with the meteorology parameters was conducted. The exposure risk by intake air SCCPs of the residents around the sampling sites was evaluated according to the European risk assessment standards.

Monitoring of organochlorine pesticides in the urban air of Dalian, China with semipermeable membrane devices

The concentrations of 28 organochlorine pesticides(OCPs)in the urban air of Dalian,China were measured using semipermeable membrane devices(SPMDs)for the first time.Alpha-hexachlorocyclohexane(a-HCH),b-HCH,pentachlorobenzene(PentCB),hexachlorobenzene(HexCB),4,40-dichlorodiphenyltrichloroethane(4,40-DDT),4,40-dichlorodiphenyldichloroethene,endosulfan-I and endosulfan-II were the predominant OCPs in the urban air of Dalian.The concentration of OCPs sequestrated by SPMDs(CSPMD)ranged from undetected to 56,772 pg SPMD-1and had a linear correlation with the reciprocal of the average ambient atmospheric temperature(1/T).The CSPMDof PentCB and HexCB had negative correlations with T,whereas the other detected OCPs had a positive correlation.The source of HCHs,DDTs,HexCB,PentCB,chlordane,and endosulfan in the air were also evaluated.The OCPs in the urban air of Dalian could be attributed to the seasonal usage of pesticides,combustion,volatilization of aged OCPs from soil,water,plants,and long-range atmospheric transport.