On the Relationship between the Northern Limit of Southerly Wind and Summer Precipitation over East China

The relationship between the summer northernmost position of southerly wind and precipitation over East China is investigated. The northern limit of summer southerly wind index(INLSSW) over East China is defined as the latitude where the zonal-averaged(105–120°E)low-level meridional wind is equal to zero. Results show that there is a significant negative(positive) correlation between INLSSW and summer precipitation over the Yangtze River(North China) region. Thus, the proposed INLSSW may have implications for the prediction of summer precipitation anomalies in these regions. In positive INLSSW years, a cyclonic circulation anomaly is observed over the tropical western North Pacific and an anticyclonic circulation anomaly is seen over the subtropics of East China,accompanied by southerly anomalies over East China.This leads to above-normal moisture penetrating into the northern part of East China. In addition, significant upward(downward) motion anomalies can be found over the North China(Yangtze River) region. As a result, there are significant positive(negative) precipitation anomalies over the North China(Yangtze River) region. Further examination shows that sea surface temperature anomalies over the tropical eastern Pacific and Indian Ocean both contribute to the formation of INLSSW-related circulation anomalies over the tropical western North Pacific.

Oscillation of Surface PM2.5 Concentration Resulting from an Alternation of Easterly and Southerly Winds in Beijing： Mechanisms and Implications

We used simultaneous measurements of surface PM_（2.5） concentration and vertical profiles of aerosol concentration,temperature, and humidity, together with regional air quality model simulations, to study an episode of aerosol pollution in Beijing from 15 to 19 November 2016. The potential effects of easterly and southerly winds on the surface concentrations and vertical profiles of the PM_（2.5） pollution were investigated. Favorable easterly winds produced strong upward motion and were able to transport the PM_（2.5） pollution at the surface to the upper levels of the atmosphere. The amount of surface PM_（2.5） pollution transported by the easterly winds was determined by the strength and height of the upward motion produced by the easterly winds and the initial height of the upward wind. A greater amount of PM_（2.5） pollution was transported to upper levels of the atmosphere by upward winds with a lower initial height. The pollutants were diluted by easterly winds from clean ocean air masses. The inversion layer was destroyed by the easterly winds and the surface pollutants and warm air masses were then lifted to the upper levels of the atmosphere, where they re-established a multi-layer inversion. This region of inversion was strengthened by the southerly winds, increasing the severity of pollution. A vortex was produced by southerly winds that led to the convergence of air along the Taihang Mountains. Pollutants were transported from southern–central Hebei Province to Beijing in the boundary layer. Warm advection associated with the southerly winds intensified the inversion produced by the easterly winds and a more stable boundary layer was formed. The layer with high PM_（2.5） concentration became dee-per with persistent southerly winds of a certain depth. The polluted air masses then rose over the northern Taihang Mountains to the northern mountainous regions of Hebei Province.

Mesoscale Analysis of a Heavy Rainfall Event over Hong Kong During a Pre-rainy Season in South China

During the Heavy Rainfall Experiment in South China （HUAMEX） of 1998, a record heavy rainfall event occurred in the delta of the Pearl River during the 24 hours from 1200 UTC 8 June to 1200 UTC 9 June, 1998, and a 24-hour precipitation maximum of 574 mm was reported in Hong Kong. In this paper, some mesoscale characteristics of this heavy rainfall event are studied using data from satellites, Doppler radar, wind profilers, and automatic meteorological stations collected during HUAMEX. The following conclusions are drawn： （1） During this heavy rainfall event, there existed a favorable large-scale environment, that included a front with weak baroclinity in the heavy rain area and with an upward motion branch ahead of the front. （2） Unlike most extratropical or subtropical systems, the closed low in the geopotential height field does not exited. The obvious feature was that a southerly branch trough in the westerlies existed and Hong Kong was located ahead of the trough. （3） The rainfall areas were located in the warm sector ahead of the front, rather than in the frontal zone, which is one of the characteristics of heavy rainfalls during the pre-rainy season of South China. A southerly warm and moist current contributed to the heavy rainfall formation, including the transportation of rich water vapor and the creation of strong horizontal wind convergence. （4） The observations show that the heavy rainfall in Hong Kong was directly caused by a series of meso β systems rather than a mesoscale convective complex （MCC）. These meso β systems moved with the steering current in the lower-mid troposphere, their life cycles were 3-6 hours, and their horizontal sizes were 10-100 km. （5） The disturbances in the lower and mid troposphere, especially that in the planetary boundary layer （PBL） were very shallow. However, they are a possible trigger mechanism for the occurrence and development of the mesoscale convective systems and related heavy rainfalls. Finally, a conceptual model of the heavy rainfall in the warm sector ahead of the front in South China is proposed.

IMPROVED FORECASTING OF COLD AIR OUTBREAKS OVER SOUTHERN CHINA THROUGH OROGRAPHIC GRAVITY WAVE DRAG PARAMETERIZATION

The parameterization of gravity wave drag induced by sub-grid scale orography(GWDO), which has been used in the regional model based on the Global/Regional Assimilation and Prediction System for Tropical Mesoscale Model(GRAPES_TMM), is extended to include the effect of mountain flow blocking drag(MBD). The extended scheme is evaluated against non-GWDO parameterization, including a cold air outbreak over southern China and a monthly verification in February 2012. The experiment results show that the GWDO and MBD parameterization both improves the forecasting of the cold air outbreaks over southern China, as well as alleviations of system bias of GRAPES_TMM.(1) The extended scheme alleviates the strong southerly wind and high surface temperature simulation during the cold air outbreak, especially over northern Guangxi and Guangdong(NGG) province, where local high surface temperature simulation reduces nearly 5 degree.(2) The MBD parameterization improves southerly wind simulations over NGG, as well as surface temperature forecasts improvement over Guangxi, Guizhou province and southern Yunnan-Guizhou plateau(YUP), and low level southerly wind simulation improvement over intertidal zone over south China.(3) The formation of MBD is mainly in the mountain area(Wuyi, Daba mountain, east of YUP) and coastal area. The MBD over plateau, which is mainly formed at the west of 105°E, is stronger and thicker than that over Nanling mountain.(4) The improvement of GWDO and MBD parameterization is stable in model physics. MBD parameterization demonstrates more overall improvements in the forecasts than GWDO, and the larger of the model forecast error is, the greater improvements of MBD contribute to. Overall, the extended GWDO scheme successfully improves the simulations of meteorological elements forecasting during cold air outbreaks.

ApoA-I/C-Ⅲ RFLPs与动脉粥样硬化

应用 RFLPs 方法分析了21名冠心病心肌梗死患者及30名正常对照基因组 DNA。结果表明 ApoA-Ⅰ 基因 EcoRI RFLP 由13kb 和6.5kb 组成,其6.5kb 片段频率在正常人为0.03,而在心肌梗死患者中为0.17。两者存在显著性差异(P<0.01),提示此多态片段与心肌梗死相关。ApoC-Ⅲ基因 SacⅠRFLP 由5.7kb,4.2kb 和3.2kb 片段组成,其3.2kb 片段频率在正常人为0.22,在心肌梗死患者中为0.24,无明显差异、但其在正常人中频率可能存在群体或种族特异性。