环湖地区天然草地土壤水分变化分析及预报

通过对铁卜加牧业气象试验站1987～1996年土壤湿度资料的分析，对土壤湿度随深度、时间的变化及各时段土壤湿度与降水的关系有了初步结论，并研制了春季解冻时和解冻到5月下旬各层次土壤湿度的长期预报方法。     

农田土壤湿度的人工神经网络预测诊断系统

采用人工神经网络（ＡＮＮ）方法，研制了农田土壤湿度预测，诊断分析系统，该系统根据不同的土壤湿度特点和影响因子，可自动提供时间序列拓展的人工神经网络预测模型和人工神经网络的混合预测模型进行土壤湿度的动态预测。并提供不同降水量的土壤湿水分渗透深度诊断分析，系统采用中文菜单显示的人机对话方式操作，使具有准动力学特性，多种可调参数和网络结构的ＡＮＮ方法变得简便易于操作。实际使用表明，该系统对土壤湿度的预测     

关于贵州作物地段土壤湿度观测的几个问题

分析了贵州作物地段土壤湿度观测中存在的两个问题，其一为观测数据不完善，其二为观测数据代表性差，对如何有效地提高土壤湿度观测的代表性和实用性提出了一些建议。     

试用极轨气象卫星遥感监测土壤墒情

讨论了用极轨气象卫星资料监测表层土壤湿度的方法。在建立土壤湿度与卫星遥感资料的关系时，为了消除土壤条件的影响，把全省分为４个区域来研究。考虑了气候条件，植被状况不同的影响，并给出了简单的订正方法，同时也给出了卫星资料的重新地理校正，资料的输出及存储方法等。     

用NOAA卫星资料监测土壤湿度方法的探讨

本文提出一种利用ＮＯＡＡ气象卫星资料结合数字化地形资料进行土壤湿度监测的方法，其思想是以冠层温度随植被指数的变化率作为监测土壤湿度的因子。     

土壤湿度——一个跨季度降水预测中的重要因子及其应用探讨

阐述了土壤湿度对短期气候变化的重要作用,结合我国的业务现状提出亟需将这一因子应用于跨季度降水预测。通过将一个土壤湿度反演模型引入IAP跨季度气候预测系统,探讨了土壤湿度应用于季节降水预测的可行性及其效果。初步的个例分析表明:前期土壤湿度的异常分布对降水变化有较显著的影响,继续改进土壤湿度反演模型可望获得更好的降水预测效果。同时,提出的基于常规气象观测进行反演以获得大范围土壤湿度分布的办法在当前业务预测中具有很强的可操作性。     

四维变分同化和集合平方根滤波联合反演土壤湿度廓线的研究

提出将集合平方根滤波（EnSRF）估计的预报误差协方差用于四维变分（4DVAR）的同化方案（文中称混合四维变分同化方法,简称混合方法）来反演土壤湿度廓线,该方法由两个同化时段构成: 第一时段为EnSRF,第二时段为4DVAR,此种组合可以充分发挥每一同化方法的优势。通过同化表层土壤湿度观测反演土壤湿度廓线这一理想试验来验证方法的可行性,并与EnSRF和4DVAR的反演结果进行比较,结果表明, 混合方法反演的分析时刻土壤湿度廓线都优于EnSRF和4DVAR的结果。与此同时,为了克服小样本在估算背景场误差协方差矩阵时出现的虚假相关对反演的干扰, 提出在原有协方差矩阵中加入具有高斯指数函数成分来降低其影响;与修正前结果相比,反演的中下层（地下34～100 cm） 土壤湿度的均方根误差从0.036 cm3/cm3降到0.016 cm3/cm3, 降幅为55.6%, 更重要的是大大降低了部分深度处反演土壤湿度的误差, 如地下90 cm处误差从0.085 cm3/cm3降到0.024 cm3/cm3, 降幅达71.8%。     

西南喀斯特地区中层土壤湿度时空变化特征

本文利用中国西南喀斯特区域内该区域内全部31个农业气候站点1991～2013年50cm层土壤湿度(体积含水量)旬资料，应用线性趋势分析、EOF空间分解方法，详细分析其时空演变特征，进一步认识中国西南喀斯特地区土壤湿度的时空演变特征，结果表明:(1)西南喀斯特地区中层土壤湿度多年平均的空间大小及分布具有明显的区域性差异。(2)1991～2013年季节平均中，中层秋季的土壤湿度整体最高，夏季土壤湿度的低值区范围最大，反映了西南喀斯特地区土壤的独特性。(3)中层土壤湿度年际变化有明显的“南升北降”空间分布特征，相应线性趋势分析和EOF的结果也同样印证了这一主要特征。(4)50cm的年际变化较稳定且波动趋势较小；整体的土壤湿度以夏、秋季最高，春、冬季较低。      

卫星被动微波遥感土壤湿度研究进展

土壤湿度是控制陆地和大气间水分和能量交换过程的重要变量,而被动微波遥感是众多监测土壤湿度技术中最有效的手段之一。文中概述了被动微波反演土壤湿度的物理原理,重点介绍了被动微波反演土壤湿度的主要模型。在对不同模型进行比较分析后,基于不同传感器类型分别列举了当今发展较完善的3个典型算法：①Njoku和Li基于AMSR的多通道同时反演土壤湿度、土壤温度、植被含水量的方法;②Owe等基于SMMR利用极化差异指数同时反演土壤湿度和植被光学厚度2个参数的方法;③Wen等基于SSM／I同时反演土壤湿度和土壤温度的方法。对被动微波遥感土壤湿度研究中目前所存在的问题和发展前景进行了一些探讨。     

用NOAA卫星可见光和红外资料估算甘肃省东部农田区土壤湿度

应用NOAA卫星AVHRR通道1、2计算的植被指数和通道4的亮温、农业气象试验站观测的土壤湿度，并结合气象卫星完成的土地覆盖分类等资料，建立了由植被指数和亮温估算甘肃省东部农田区土壤湿度的方程。结果表明，农田土壤湿度与植被指数和亮温间均存在一定相关关系；用植被指数和亮温可以估计土壤湿度情况，并对干旱进行监测。     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

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.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

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.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

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.     

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

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.     

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正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.SUBMISSIONAll submitted     

A Brief Introduction to Marine Meteorological Science Experiment Base at Bohe Town,Maoming City,Guangdong Province

<正>With the support of specialized funds for national science institutions,the Guangzhou Institute of Tropical and Marine Meteorology,China Meteorological Administration set up in October 2008 an experiment base for marine meteorology and a number of observation systems for the coastal boundary layer,air-sea flux,marine environmental elements,and basic meteorological elements at Bohe town,Maoming city,Guangdong province,in the northern part of the South China Sea.     

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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.     

Information for Authors

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.     

Information for Authors

正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences