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991.
广西近50年暴雨日数变化的小波分析 总被引:15,自引:0,他引:15
利用1951—2005年广西降水资料,使用Morlet小波分析方法分析了暴雨和大暴雨日数的年际变化,结果表明均具有明显的周期变化规律特征,都存在着2、4、8、14年周期振荡信号,其中2年周期振荡信号最强,其次为4,8,14年,各周期信号分布的时间区域略有差异。广西暴雨日数变化总趋势为逐渐增多,在1990年代进入高峰期。影响广西暴雨发生的主要天气系统为热带气旋、西南低涡、低空急流、高空槽,其中热带气旋、西南低涡是广西特大暴雨发生的主要原因。 相似文献
992.
Satellite-derived SSTs are validated in the northern South China Sea (NSCS) using in situ SSTs from the drifting buoys and well-calibrated sensors installed on Research/Vessel(R/V) Shiyan 3. The satellite SSTs are Advanced Very High Resolution Radiometer (AVHRR) daytime SST, AVHRR nighttime SST, Tropical rainfall Measuring Mission Microwave Imager (TMI) daytime SST and TMI nighttime SST. Availability of satellite SST, which is the ratio that the number of available satellite SST to the total ocean pixels in NSCS is calculated; annual average SST availabilities of AVHRR daytime SST, AVHRR nighttime SST, TMI daytime SST and TMI nighttime SST are 68.42%, 69.99%, 56.57% and 52.80%, respectively. Though the TMI SST availability is nearly constant throughout the year, the variations of the AVHRR SST availability are much larger because of seasonal variations of cloud cover in NSCS. Validation of the satellite-derived SSTs shows that bias±standard deviation (STD) of AVHRR SST is −0.43±0.76 and −0.33±0.79 °C for daytime and nighttime, respectively, and bias±STD of TMI SSTs is 0.07±1.11 and 0.00±0.97 °C for daytime and nighttime, respectively. It is clear that AVHRR SSTs have significant regional biases of about −0.4 °C against the drifting buoy SSTs. Differences between satellite-derived−in situ SSTs are investigated in terms of the diurnal SST cycle. When satellite-derived wind speeds decrease down below 6 m/s, the satellite SSTs become higher than the corresponding in situ SSTs, which means that the SST difference (satellite SST−Buoy SST) is positive. This wind-speed dependence of the SST difference is consistent with the previous results, which have mentioned that low wind speed coupled with clear sky conditions (high surface solar radiation) enhance the diurnal SST amplitude and the bulk-skin temperature difference. 相似文献
993.
994.
辽宁凌源柏杖子金矿区花岗岩SHRIMP锆石U-Pb年龄 总被引:6,自引:0,他引:6
采用SHRIMP测年方法测得柏杖子金矿区含矿花岗岩的锆石U-Pb年龄为(222±3)Ma,与区内都山花岗岩基和三家子金矿区花岗斑岩的年龄一致,属中生代印支期后碰撞花岗岩.该年龄限定了金矿化年龄的下限,即金矿化不可能早于印支期,但并不能确定金矿化的精确年龄.根据金矿脉与后期岩脉伴生的特征,矿化可能发生在中生代燕山期. 相似文献
995.
996.
利用2015~2017年淮河流域汛期ECMWF(空间分辨率0.125~ox0.125~o)、JMA(空间分辨率0.5~ox0.5~o)、WRF(空间分辨率0.1~ox0.1~o)6h、12h、24h时间分辨率的降水预报产品计算淮河流域面雨量预报,对比评估各预报时效的绝对误差、相对误差、晴雨正确率及各量级面雨量预报的TS评分。结论如下:(1)0~72h预报时效,EC的绝对误差最小、WRF居中,JMA最大。(2)三个模式的晴雨正确率随着时效的增加缓慢下降,但都维持较高水平。(3)EC和JMA的面雨量预报存在系统性高估。(4)WRF在对短历时强降水的预报性能优于其他两个模式。(5)各模式的面雨量预报性能存在日变化,且随着降水强度的增大,日变化特征更加显著,对午后到傍晚的暴雨预报准确率明显低于其他时间段。 相似文献
997.
998.
~(210) Po and ~(210) Pb are increasingly used to constrain particle dynamics in the open oceans, however they are less used in coastal waters. Here, distributions and partitions of ~(210) Po and ~(210) Pb were examined in the Taiwan Strait, as well as their application to quantify particle sinking. Activity concentrations of dissolved ~(210) Po and ~(210) Pb(0.6 μm)ranged from 1.21 to 7.63 dpm/(100 L) and from 1.07 to 6.33 dpm/(100 L), respectively. Activity concentrations of particulate ~(210) Po and ~(210) Pb varied from 1.96 to 36.74 dpm/(100 L) and from 3.11 to 38.06 dpm/(100 L). Overall,particulate ~(210) Po and ~(210) Pb accounted for the majority of the bulk ~(210) Po and ~(210) Pb. 210 Po either in dissolved or particulate phases showed similar spatial patterns to 210 Pb, indicating similar mechanisms for controlling the distributions of ~(210) Po and ~(210) Pb in the Taiwan Strait. The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC) inclined to absorb 210 Po prior to 210 Pb while they showed an opposite effect in the Taiwan Warm Current(TWC). Based on the disequilibria between ~(210) Po and ~(210) Pb, the sinking fluxes of total particulate matter(TPM) were estimated to range from –0.22 to 3.84 g/(m2·d), showing an overall comparable spatial distribution to previous reported sediment accumulation rates. However, our sinking fluxes were lower than the sedimentation rates, indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea. 相似文献
999.
Earth fissures in Jiangsu Province,China and geological investigation of Hetang earth fissure 总被引:1,自引:0,他引:1
Earth fissures are a geohazard in Jiangsu Province, China. They can be caused by earthquakes and active faults, underground
mining, groundwater extraction and landslides. In order to establish a provincial rehabilitation plan in Jiangsu, a range
of monitoring programs, surveys, geological investigations and modeling have been implemented or planned. One of the focuses
of the project is the land subsidence and earth fissures caused by excessive groundwater withdrawal in Suzhou, Wuxi and Changzhou
(Su-Xi-Chang) area, southern Jiangsu Province. Hetang earth fissure within the Su-Xi-Chang area was first reported in 1995
and a series of investigation has been conducted since then. The site investigations and geophysical survey in 1997 have recognized
the causative factor as the excessive groundwater drawdown coupled by the underlying bedrock ridge. An open trench excavation
in 2007 and a plane strain analysis suggest that Hetang earth fissures may have cracked from the bedrock ridge to ground surface.
Geological drilling in 2007 has further confirmed the existence and configuration of the ridge and extracted soil samples
for laboratory tests to obtain soil parameters for numerical analyses and modeling of land subsidence and earth fissures in
the Su-Xi-Chang area, Jiangsu, China. The laboratory tests are currently in progress and the result of numerical analyses
and modeling is expected to be presented in the near future. 相似文献
1000.