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第Ⅰ部分研究结果 (徐枝芳等, 2007) 表明模式与实际观测站地形高度差异对地面观测资料同化效果有较大影响.此文在MM5_3DVAR同化系统中利用近地层相似理论将地面观测资料进行直接三维变分同化分析, 考虑模式与实际观测站地形高度差异对同化效果的影响, 提出在地面观测误差中增加地形代表性误差来解决这个问题.研究结果表明: 地面资料同化分析时, 在其观测误差中加入一项新的误差--地形代表性误差, 能较好地解决地面资料同化分析中模式与观测站地形高度差异问题; 地面资料参与同化分析, 在观测误差中加入与模式和实际观测站地形高度差异大小相关的地形代表性误差时, 地面观测值对分析值的影响随着地形高度差异代表性误差的加入而减小, 同时又部分地将地面观测信息通过变分分析融进分析场, 使得低层分析更接近真实场, 且地面资料利用率更高, 24小时降水数值预报 (模拟) 的效果较好. 相似文献
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介绍了一种基于单片机的上下肢训练机器人.首先介绍了它的机械设计和控制系统设计.上下肢康复训练机器人由SSU7301单片机控制直流电机系统,由C8051F320单片机负责与上位机的USB通信部分,两部分之间通过串口通信.它可在一台康复训练机器人上实现上、下肢的康复训练,并有被动模式和主动模式2种训练方式,主、被动模式能实现自动切换.最后给出了上下肢训练机器人产品实例和实验结果,经过试验验证,该机器人设计合理,性能稳定,实现了上下肢的康复训练. 相似文献
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第I部分研究结果(徐枝芳等,2007)表明模式与实际观测站地形高度差异对地面观测资料同化效果有较大影响。此文在MM5_3DVAR同化系统中利用近地层相似理论将地面观测资料进行直接三维变分同化分析,考虑模式与实际观测站地形高度差异对同化效果的影响,提出在地面观测误差中增加地形代表性误差来解决这个问题。研究结果表明:地面资料同化分析时,在其观测误差中加入一项新的误差——地形代表性误差,能较好地解决地面资料同化分析中模式与观测站地形高度差异问题;地面资料参与同化分析,在观测误差中加入与模式和实际观测站地形高度差异大小相关的地形代表性误差时,地面观测值对分析值的影响随着地形高度差异代表性误差的加入而减小,同时又部分地将地面观测信息通过变分分析融进分析场,使得低层分析更接近真实场,且地面资料利用率更高,24小时降水数值预报(模拟)的效果较好。 相似文献
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地球静止卫星云图象点定位方法之比较 总被引：1，自引：0，他引：1
在假定ＧＭＳ－４地球静止卫星所发定位网格数据的精度满足要求的基础上，通过数学原理分析、改变二维插值顺序、比较插值结果与实际分布等手段，对比分析了利用线性和非线性插值方法给每一个象点定位的结果，发现非线性插值所得结果明显优于线性插值，更加符合实际情况。线性插值的误差在经度方向上较小。可以忽略，但是在纬度方向的误差，即经度误差极为明显。在星下点的左上部，误差由东南向西北迅速增大，有相当一部分地区内经度 相似文献
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基于粒子群优化(PSO)算法和遗传算法(GA)对支持向量机(SVM)的核函数及主要参数进行训练优化,分别建立PSO算法、GA的支持向量机模型(PSO_SVM、GA_SVM)。选用ECMWF及T639数值预报产品资料和乌东德水电站降水资料,普查最优预报因子,构建包含各种类型降水过程的训练样本和测试样本。比较分析SVM模型RBF和Sigmoid核函数优劣。尝试先分段寻找局部最优,再选择全局最优的参数优化方法。通过增大训练样本集、降低交叉验证准确率、迭代次数截断和控制惩罚系数范围的方法,提高模型的稳定性和泛化能力,防止过拟合和收敛缓慢现象。利用测试样本对SVM、PSO_SVM和GA_SVM三种方案进行对比检验,优化的GA_SVM预报效果较好且稳定。经2018年试报表明,GA_SVM逐3 h累计降水量预报TS评分在50%以上,漏报率在15%以下,与ECMWF和T639比较,该模型TS评分提高1. 4%。 相似文献
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柏建 《高原山地气象研究》2006,26(3)
建立台站经度、纬度、高度资料与气象资料的回归模型,再用栅格DEM资料代入展开来推估气象要素的空间分布,目前已得到了较为广泛的应用.但是,由于DEM空间分辨率及复杂地形的影响,DEM在表征地形高度时存在明显误差.误差的大小和空间分布,往往直接影响到模型的精度.本文利用四川省1:25万DEM资料和全省157个气象站高度实测资料,分析了的DEM高度的误差特点和空间分布状况,对正确应用空间分布模型、准确评估区域生态条件具有十分重要的意义. 相似文献
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在中尺度WRF-EnSRF系统中最新引入的采样误差订正局地化方法不仅考虑了回归系数偏差,而且计算量较小。该方法基于状态变量和对应观测值的相关系数的分布关系,根据离线蒙特卡洛技术制作的关于集合数和样本相关系数的查找表格确定局地化系数因子,进而订正由集合数选取有限造成的背景误差协方差被低估引起的采样误差。本文利用风暴过程的雷达观测资料做了一系列风暴尺度的资料同化理想试验,探讨了采样误差订正局地化方法在风暴尺度集合卡尔曼滤波同化中的技术特点和同化效果。结果表明:相比于经验局地化方法,采样误差订正局地化方法能够有效地改善集合同化的效果,对距离的敏感度更低,尤其在天气系统发展变化较快的阶段,新方法优势更大。并且,对不同观测变量以及在风暴发展的不同阶段使用不同的局地化方法,所得的结果都存在一定的差异,因此需要根据同化对象合理地选择局地化方法。 相似文献
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The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics. 相似文献
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Yuepeng PAN Mengna GU Yuexin HE Dianming WU Chunyan LIU Linlin SONG Shili TIAN Xuemei Lü Yang SUN Tao SONG Wendell W. WALTERS Xuejun LIU Nicholas A. MARTIN Qianqian ZHANG Yunting FANG Valerio FERRACCI Yuesi WANG 《大气科学进展》2020,37(9):933-938
正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on 相似文献
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Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d. 相似文献
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Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region. 相似文献
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Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms. 相似文献
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《大气和海洋科学快报》2013,(4):227
正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. 相似文献
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《大气和海洋科学快报》2014,7(6):F0003-F0003
AIMS AND SCOPE
Atmospheric and Oceanic Science Letters （AOSL） publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome. 相似文献
Atmospheric and Oceanic Science Letters （AOSL） publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome. 相似文献
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《大气和海洋科学快报》2014,(5):F0003-F0003
AIMS AND SCOPE Atmospheric and Oceanic Science Letters （AOSL） pub- lishes short research letters on all disciplines of the atmos- phere sciences and physical oceanography. Contributions from all over the world are welcome. 相似文献
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《大气科学进展》2014,(6)
正Aims Scope Advances in Atmospheric Sciences(AAS)is an international journal on the dynamics,physics,and chemistry of the atmosphere and ocean with papers across the full range of the atmospheric sciences,co-published bimonthly by Science Press and Springer.The journal includes Articles,Note and Correspondence,and Letters.Contributions from all over the world are welcome. 相似文献