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1.
Temporal and spatial distribution characteristics of sea surface wind in Guangdong''s coastal areas were analyzed with data from four offshore observational stations between 2012 and 2015. The results are shown as follows: (1) The probability distribution of wind speed was basically consistent with Gaussian distribution characteristics; winds of Beaufort force 6 or higher were observed mainly in far offshore stations from October to March. (2) The probability distribution of wind direction was represented well by Weibull distribution. The deviation of wind direction of far station was relatively small for it was mainly controlled by monsoon over the South China Sea, while the near offshore station had a relatively large diurnal variation because of the influence of local synoptic systems such as sea-land breeze. (3) There were significant seasonal differences in wind speed and direction observed by different offshore observational stations. In strong wind seasons, the deviation of wind direction was relatively small while the deviation of wind speed was relatively large, and vice versa. In contrast with Class I station, the other three stations exhibited approximately normal distribution of wind direction and wind speed deviations. (4) Wind direction diurnal variation was moderate in windy periods, while it was obvious in relatively lower speed conditions. The deviation of wind speed in windy periods was generally greater because it was influenced by mesoscale weather systems for 10-20 h, and the influence was complicated, resulting in greater local differences in wind speed. 相似文献
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Carbonate-hosted Zn-Pb (± barite, fluorite) occurrences in the Franklinian Basin of North Greenland were studied using the Rb-Sr method, applied to sphalerite, and combined Sr and Pb isotope analysis of ore and gangue minerals, to place constraints on their age and genesis. The occurrences are located in the easternmost part of the basin in Peary Land and Kronprins Christian Land, and are hosted by Upper Ordovician to lowermost Silurian dolostones of the Turesø Formation.Sphalerite samples from the Zn-Pb occurrence at Børglum, in Peary Land, reflect undisturbed Rb-Sr systems and return an isochron age of 388 ± 4 Ma (MSWD = 1.6, 87Sr/86Sri = 0.70930 ± 1). Sphalerites and their fluid inclusion fractions from an adjacent Zn-Pb occurrence, at Tvilum, exhibit various degrees of isotopic disturbance caused by secondary fluid overprint. They yield no age, however, reconstructive modelling of their Rb-Sr and Pb-Pb signatures indicates original isotope systematics consistent with the Børglum data. Likewise, due to a lack of suitable samples, no Rb-Sr age could be determined for a third occurrence in southeastern Peary Land at Løgum, however, the time-integrated Pb isotopic evolution of fluorite and calcite from this mineralization over c. 390 Ma is compatible with modelled initial signatures for Tvilum and Børglum ores. Consequently, a contemporaneous formation at c. 390 Ma can be assumed for all studied locations in Peary Land. For the Zn-Pb occurrence in Kronprins Christian Land farther east, a Rb-Sr sphalerite age of c. 360–365 Ma has been obtained through a combined isochron and paleomixing line approach.The absolute ages obtained at the studied occurrences, corresponding to Middle to Upper Devonian ages, are in no conflict with the age of the host dolostones of the Turesø Formation, which placed a maximum age limit for the mineralization. Actually, the fact that mineralization was emplaced at least 50 Ma after deposition of the host rocks, which would have been completely lithified by then, warrants the classification of the studied occurrences as epigenetic Mississippi Valley-Type, rather than diagenetic Irish-type. Furthermore, the obtained ages are contemporaneous to the Middle or Upper Devonian to the Lower Carboniferous Ellesmerian Orogeny, indicating that the mineralization likely formed from basinal brines expelled by tectonism and/or hydraulic head caused by Ellesmerian orogenic uplift, as previously suggested for the Polaris carbonate-hosted Zn-Pb deposit (Cornwallis Island, Canada).Pb isotope systematics of base metal mineralization in the Franklinian Basin point to principal metal sources located in the crystalline basement and in basement-derived clastic sediments. These two reservoirs define radiogenic and unradiogenic end components from which lead was mobilized and mixed in different proportions during discrete periods of hydrothermal activity. Distinct thorogenic Pb isotope signatures indicate that specific local sources (lower crustal basement, carbonate rocks and possibly organic-rich shales) were also involved in mineralization. 相似文献
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利用RHtest软件结合台站元数据对广州1908—2019年平均气温进行非均一性检验和订正,结果显示在1912、1928、1942、1988、1995、2004和2010年有7个显著的非均一间断点,订正后升温速率为1.39℃/(100 a),较订正前显著增加,具有准50 a和准3 a的显著周期。运用DB16正交小波分析其多时间尺度变化特征,结果显示方差贡献最大的是趋势分量,其次是准3 a和准6 a周期分量。趋势分量从20世纪40年代开始呈现持续的升温趋势;20世纪80年代中期至20世纪末的快速增暖是准50 a和准20 a周期分量的上升期叠加于趋势分量的结果;1998—2014年增暖停滞特征是准50 a、准20 a和准10 a这3个年代际周期分量的降温位相叠加在趋势分量上引起的。 相似文献
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Based on the observations of a squall line on 11 May 2020 and stratiform precipitation on 6 June 2020 from two X-band dual-polarization phased array weather radars (DP-PAWRs) and an S-band dual-polarization Doppler weather radar (CINRAD/SA-D), the data reliability of DP-PAWR and its ability to detect the fine structures of mesoscale weather systems were assessed. After location matching, the observations of DP-PAWR and CINRAD / SA-D were compared in terms of reflectivity (ZH), radial velocity (V), differential reflectivity (ZDR), and specific differential phase (KDP). The results showed that: (1) DP-PAWR has better ability to detect mesoscale weather systems than CINRAD/SA-D; the multi-elevation-angles scanning of the RHI mode enables DP-PAWR to obtain a wider detection range in the vertical direction. (2) DP-PAWR’s ZH and V structures are acceptable, while its sensitivity is worse than that of CINRAD/SA-D. The ZH suffers from attenuation and the ZH area distribution is distorted around strong rainfall regions. (3) DP-PAWR’s ZDR is close to a normal distribution but slightly smaller than that of CINRAD/SA-D. The KDP products of DP-PAWR have much higher sensitivity, showing a better indication of precipitation. (4) DP-PAWR is capable of revealing a detailed and complete structure of the evolution of the whole storm and the characteristics of particle phase variations during the process of triggering and enhancement of a small cell in the front of a squall line, as well as the merging of the cell with the squall line, which cannot be observed by CINRAD/SA-D. With its fast volume scan feature and dual-polarization detection capability, DP-PAWR shows great potential in further understanding the development and evolution mechanisms of meso-γ-scale and microscale weather systems. 相似文献
5.
微波辐射计可获取高时间分辨率的大气层结信息,为探索其在短时强降水预报方面的应用潜力,利用微波辐射计仪器获得对流参数特征,提取对短时强降水敏感的对流参数作为预报因子,并利用叠套法建立短时强降水潜势预报。结果表明:液态水路径LWP、SI、LI、CAPE、KOI这5种参数可作为预报因子建立潜势预报,经验证后得出短时强降水的POD、CSI、FAR分别为53.85%、50.01%、12.49%;另外,研究利用LWP的标准偏差在短时强降水发生前明显增大的特征改进预报,POD和CSI分别提升至73.08%、63.33%,FAR虽然增加至17.39%,但增量仅有4.9%。改进后的短时强降水预报效果提升明显,这说明水汽参数LWP在短时强降水预报中有较强的指示意义。 相似文献
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为评估用于超大城市综合气象观测试验的测风激光雷达,从最大有效探测高度和数据获取率两方面对测风激光雷达的探测能力进行分析,同时使用测风激光雷达与深圳气象梯度观测塔的测风资料从不同观测高度、不同观测值等方面进行对比分析,结果表明:测风激光雷达与深圳气象梯度观测塔的风速、风向一致性较好,相关系数分别为0.96、0.99,平均绝对误差分别为0.54 m/s、9.95 °,且不同高度层的测风结果也较为一致,但雨天和雾天条件对测风激光雷达的最大有效探测高度和数据获取率影响较大,设备探测能力受到一定的限制。 相似文献
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针对高分辨率数值天气预报的时空不确定性, 利用邻域最优概率方法对华南区域GRAPES快速更新循环同化预报系统的24 h预报进行逐时降水订正和检验评估。结果表明: (1)邻域法能改善模式降水预报的空间不确定性, 最优邻域半径随降水等级增加而减小, 强降水的最优邻域半径约为60 km; (2)通过引入时间滞后因子, 可进一步改善模式不同时间起报的不确定性, 结合Brier评分确定了时间滞后窗为4 h; (3)提出基于邻域最优概率阈值的降雨进行分级订正方法, 有效提升了降水客观预报能力, 晴雨预报较模式全部为正技巧, TS评分达到0.89以上, 总体提升幅度约5.3%;强降水预报同样均为正技巧, TS评分呈先降后升趋势, 在12 h时效前后预报效果最优, 进一步提升了GRAPES快速更新循环同化预报系统的业务预报水平。 相似文献
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台风艾云尼（1804号）第2次登陆广东过程中降水表现出显著的非对称分布,强降水主要位于其路径前进方向的右侧（简称台风右侧）。利用欧洲中期天气预报中心ERA5再分析资料、广东风廓线雷达观测资料以及降水观测资料,对造成非对称降水的环流背景和动力、热力结构演变特征进行了分析。结果表明:艾云尼左右两侧水汽输送及动力、热力条件差异是造成降水非对称的主要原因。加强的低空急流以及台风马力斯（1805号）水汽的输送为台风右侧强降水的产生提供了更好的水汽背景,而低空急流的加强配合高空强的辐散抽吸使得右侧垂直上升运动也明显大于左侧。边界层内强盛的低空急流以及珠江三角洲地区下垫面强摩擦辐合作用导致艾云尼右前侧径向入流强度更强、强入流层厚度更厚、边界层高度更高,且由于距离台风眼墙越近风速越大,上述现象越明显,为强降水的产生提供的动力和水汽条件越好。强降水期间艾云尼右侧低层大气维持不稳定状态,分析表明强低空急流携带的θse平流及其随高度的减弱弥补了强降水造成的能量损耗,是不稳定能量维持的重要原因。 相似文献
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利用Himawari-8高时空分辨率红外亮温资料和ERA-Interim再分析资料,对比冷锋型和暖区型飑线个例("4·13"和"5·6")亮温特征与雷暴大风、地面强降水的关系,结果表明:(1)两次过程的云顶最低亮温、冷云区平均亮温差异小,但两次过程初生阶段云型不同,"4·13"与"5·6"相比,冷云顶面积较小、持续时间较短、移动速度较快;(2)"4·13"("5·6")的亮温梯度大值区主要位于冷云区东南侧(西南侧),与云团移动方向平行(垂直);两次过程雷暴大风与亮温梯度均具有较好的空间对应关系,亮温梯度增大超前于雷暴大风增强,可作为提前预警指标;(3)"4·13"地面强降水集中分布在低亮温区西侧,原因为风暴顶前移导致强降水与冷云区具有空间位置差异;"5·6"地面强降水则与云顶低亮温具有较好的对应关系。 相似文献
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