Seasonal prediction of June rainfall over South China: Model assessment and statistical downscaling

The performances of various dynamical models from the Asia-Pacific Economic Cooperation(APEC) Climate Center(APCC) multi-model ensemble(MME) in predicting station-scale rainfall in South China(SC) in June were evaluated.It was found that the MME mean of model hindcasts can skillfully predict the June rainfall anomaly averaged over the SC domain.This could be related to the MME's ability in capturing the observed linkages between SC rainfall and atmospheric large-scale circulation anomalies in the Indo-Pacific region.Further assessment of station-scale June rainfall prediction based on direct model output(DMO) over 97 stations in SC revealed that the MME mean outperforms each individual model.However,poor prediction abilities in some in-land and southeastern SC stations are apparent in the MME mean and in a number of models.In order to improve the performance at those stations with poor DMO prediction skill,a station-based statistical downscaling scheme was constructed and applied to the individual and MME mean hindcast runs.For several models,this scheme can outperform DMO at more than 30 stations,because it can tap into the abilities of the models in capturing the anomalous Indo-Paciric circulation to which SC rainfall is considerably sensitive.Therefore,enhanced rainfall prediction abilities in these models should make them more useful for disaster preparedness and mitigation purposes.     

深圳华侨城湿地物种多样性及其保护研究

深圳华侨城湿地位于珠江口深圳湾北岸,通过箱涵与深圳湾海水相通,总面积69万m2,水域面积约50万m2,是深圳湾湿地生态系统的重要组成部分。对华侨城湿地植被、鸟类、底栖生物、浮游生物的多样性进行了调查,结果表明:华侨城湿地共有植物60科162种,其中真红树植物5科6属7种,半红树植物3科4属5种,外来入侵植物27种;鸟类共有12目36科101种,约占深圳湾鸟类总种数的50%,其中国家Ⅱ级重点保护野生鸟类6种;共鉴定出藻类5门11属14种;浮游动物25种。华侨城湿地面临严重的生态危机,主要包括入侵植物大面积分布、物种单一,鸟类、底栖生物类等生物多样性与福田红树林保护区及凤塘河口相比较低,并据此提出了相应的保护建议。     

THE CLIMATIC CHARACTERISTICS OF SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA I.40-YEAR AVERAGE

By using 40-year NCEP reanalysis daily data (1958-1997), we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105°E ~ 120°E, 5°N ~ 20°N, to be simplified as SCS in the text followed) pentad by pentad (5 days). According to our new definition, in the monsoon area of the SCS two of the following conditions should be satisfied: 1) At 850hPa, the southwest winds should be greater than 2m/s. 2) At 850 hPa, θ_se should be greater than 335°K. The new definition means that the summer monsoon is the southwest winds with high temperature and high moisture. The onset of the SCS summer monsoon is defined to start when one half of the SCS area (105°E ~ 120°E,5°N ~ 20°N) is controlled by the summer monsoon. The analyzed results revealed the following: 1) The summer monsoon in the SCS starts to build up abruptly in the 4th pentad in May. 2) The summer monsoon onset in the SCS is resulted from the development and intensification of southwesterly monsoon in the Bay of Bengal. 3) The onset of the summer monsoon and establishment of the summer monsoon rainfall season in the SCS occur simultaneously. 4) During the summer monsoon onset in the SCS, troughs deepen and widen quickly in the lower troposphere of the India; the subtropical high in the Western Pacific moves eastward off the SCS in the middle troposphere; the easterly advances northward over the SCS in the upper troposphere.     

基于互补源的紧凑型圆极化倾斜波束天线

本文提出一种结构紧凑且固有倾斜辐射波束的圆极化天线.通过使用一对正交的互补源,将在俯仰面的倾角方向上产生圆极化波.为了验证方法的可行性,该天线主要由扇形的单极子、短路钉和L型的接地板组成.短路钉一端连接单极子天线,另一端连接接地板的水平部分,从而形成一个环路辐射单元.研究结果表明：该天线的最大辐射增益在θ=60°,φ=90°的方向上,具有6.2%左右的3 dB轴比工作带宽.同时,相较于现有的倾斜波束圆极化天线,它的结构更加紧凑,适用于小型化的设计需求.     

Hydrogeological Characteristics of a Karst Mountainous Catchment in the Northwest of Vietnam

This paper presents a preliminary assessment of the hydrogeological characteristics of a karst mountainous catchment, the Suoi Muoi River catchment, in the northwest of Vietnam. The catchment is located at 600 -700 m a.s.l. and covers an area of 284 km. Exposed limestone occupies 32% of the total catchment area. Various types of assessments have been carried out, including geological and hydrogeological field surveys, cave surveys, dye-tracer tests, meteorological and surface water monitoring. Geological studies and cave surveys have identified the most important active cave/conduit systems within the catchment. Although these data are essential, they are insufficient to make a comprehensive appraisal of the hydrologic nature of the catchment under interest. An attempt was made to calculate a global water balance of the catchment, based on short-term (15 months) meteorological and streamflow records. The results show that, despite the existence of a number of substantial cavem conduit systems, the groun     

VEGETATION ANALYSIS OF A TYPICAL MANGROVE SWAMP──LAI CHI WO COAST OF HONG KONG

INTRODUCTIONThemangroveswamPisaInaoransySteInwherespedallyadaptalplantSgrowintheintertidalbetattheinterfacebetweenlandandaninthetropiesandsub-tropies.ThernangrovefonstplaySrnanyrolessuchascoastalstabilizer,disperseroftheeneryofst0me,tida1boresandwinds,baniert0invasionofinlandarmbysaltwatCr,produoerofnutrientSandfoastresounasuchasfuel,chaimal,fodder,tirnberandsomeirnPor-tantanbeIsoferenoAncvalue.TheongoingintheiveandextenSivedestruCtion0frnangrovesbymankindseVereydarnagestemetrialandn…     

营养盐亏缺与恢复对威氏海链藻(Thalassiosira weissflogii)生长和生化组成的影响

通过室内纯培养,研究了营养盐亏缺以及解除亏缺对威氏海链藻 ( Thalassiosira weissflogii ) 的细胞形态、细胞增殖、胞内蛋白质、可溶性糖含量变化的影响,考察了藻细胞生长和生化组成的恢复情况.结果表明,在多种营养盐亏缺 ( N 亏缺、P 亏缺、Si 亏缺、N + P 亏缺、贫营养 ) 的条件下,威氏海链藻生长受到不同程度的抑制,全部受试细胞形态均出现不同程度变异,细胞增殖显著低于正常营养供给.恢复营养,细胞形态的损伤能得以有效恢复,细胞增殖能力得以一定程度的有限恢复,其中氮、磷亏缺的恢复效应最为明显.营养盐亏缺,各处理组细胞生化组成显著低于正常培养状态.恢复营养,氮、磷亏缺组藻细胞生化组成仍显著低于正常营养供给,生化组成的恢复效应不明显,生理活性无法恢复,而硅盐亏缺的藻细胞生长和生化组成均能恢复到正常水平.实验证明,微藻细胞的生化组成比形态变化与增殖更能反映营养盐亏缺,可作为微藻受氮、磷营养盐限制的指标.     

Projected changes in the characteristics of the East Asian summer monsoonal front and their impacts on the regional precipitation

Summer monsoonal rainfall over East Asia is dominated by precipitation associated with the East Asian summer monsoonal front (EASMF). A Community Atmospheric Model (CAM5.1) with a high horizontal resolution of 50 km is employed in this study to investigate the interannual variability as well as projected future trends in the EASMF under the Representative Concentration Pathway 8.5 scenario. Seasonal march of the EASMF is reproduced reasonably well in the model’s present-day simulation despite a northward shift of the simulated front from its observed position. Based upon a suite of objectively-defined daily indices of the EASMF, we show that the EASMF in the late twenty-first century will be more intense and displaced eastward and southward from its present-day mean location. Moreover, EASMF events will exhibit a wider meridional expansion and a longer duration. Monsoonal precipitation over East Asia is particularly sensitive to the meridional displacements of EASMF. In conjunction with the projected southward shift of EASMF, an enhanced rain band is seen to extend northeastward from southern China to the northwestern Pacific south of Japan. This precipitation feature is associated with strengthened and southward-shifted westerly jet streams at 250 and 700 hPa, which are respectively linked to tropical warming in the upper troposphere and warming over the South China Sea in the lower troposphere during the twenty-first century. Within the latitudinal “gap” south of the upper-level jet and north of the lower-level jet, the local vorticity tendencies are maintained by upper-level divergence and lower-level convergence, thus accompanied by enhanced upward motion and precipitation. The site at which this “jet stream-precipitation” relationship prevails is notably modulated by long-term trends in the temperature and circulation patterns associated with climate change.