Retrieval of water vapor profiles with radio occultation measurements using an artificial neural network

A new method applying an artificial neural network （ANN） to retrieve water vapor profiles in the troposphere is presented. In this paper, a fully-connected, three-layer network based on the backpropagation algorithm is constructed. Month, latitude, altitude and bending angle are chosen as the input vectors and water vapor pressure as the output vector. There are 130 groups of occultation measurements from June to November 2002 in the dataset. Seventy pairs of bending angles and water vapor pressure profiles are used to train the ANN, and the sixty remaining pairs of profiles are applied to the validation of the retrieval. By comparing the retrieved profiles with the corresponding ones from the Information System and Data Center of the Challenging Mini-Satellite Payload for Geoscientific Research and Application （CHAMP-ISDC）, it can be concluded that the ANN is relatively convenient and accurate. Its results can be provided as the first guess for the iterative methods or the non-linear optimal estimation inverse method.     

热带气旋登陆维持和迅速消亡的诊断研究

采用动态合成方法, 对登陆后长久维持热带气旋(LTC)和迅速衰亡热带气旋(STC)的涡度、动能、热量和水汽的收支平衡进行计算和对比分析.结果表明: (1)LTC在陆上长久维持过程中, 其低层正涡度衰减缓慢并保持一定强度.STC登陆后正涡度减弱较快.(2)热带气旋登陆后涡度的收支主要取决于水平散度项、平流项和剩余项.散度项使LTC低层正涡度增加, 高层减少, 平流项和剩余项则使其低层涡度减弱, 高层涡度增加.总体而言, LTC自高层获得正涡度的补充, STC则没有获得环境正涡度.(3)低层, 摩擦耗散使LTC动能减少, 但动能通量辐合可补充部分动能而减缓衰减.中高层, LTC登陆后36～60 h动能收大于支, 动能的增加一部分来自于斜压动能制造, 一部分来自于次网格尺度.STC有类似的动能耗散, 却无动能补充.(4)LTC登陆后保持一定强度, 并从外界获得热量和水汽补充来支持积云对流发展, 而积云对流对LTC的维持具有正反馈作用.STC登陆后没有这一过程.     

热带对流层顶层结构的变化特征和趋势

利用1989～2008年欧洲中期天气预报中心高时空分辨率的再分析资料以及1980～2019年的大气化学—气候模式模拟资料分析了热带对流层顶层(Tropical Tropopause Layer,T TL)结构的变化特征,并且预测了其未来变化趋势.结果表明,TTL结构存在明显的季节和空间变化.其厚度在北半球的春、秋两季比...     

亚洲通量观测网建立的回顾与展望

1IntroductionTheelucidationofthebudgetsofcarbon,waterandothermassesatvariouslandecosystemshasbecomeanimportantsubjectintheglobalwarmingissue.Forthisstudy,thedatafrompreciseandlong-termobservationsofcarbondioxide,watervapor,andheatfluxtakeninvariouslandsur…     

Guest editorial

The Jason-1 satellite was launched on 7 December 2001 with the primary objective of continuing the high accuracy time series of altimeter measurements that began with the TOPEX/Poseidon mission in 1992. To achieve this goal, it is necessary to validate the performance of the Jason-1 measurement system, and to verify that its error budget is at least at the same level as that of the TOPEX/Poseidon mission. The article reviews the main components of the Jason-1 altimetric error budget from instrument characterization to the geophysical use of the data. Using the Interim Geophysical Data Records (16DR) that were distributed to the Jason-1 Science Working Team during the verification phase of the mission, it is shown that the Jason-1 mission is performing well enough to continue studies of the large-scale features of the ocean, and especially to continue time series of mean sea-level variations with an accuracy comparable to TOPEX/Poseidon.     

A hard-knock life: the foraging ecology of Cape cormorants amidst shifting prey resources and industrial fishing pressure

Once one of the most numerous seabirds of the Benguela upwelling system, the population of Cape cormorants Phalacrocorax capensis has decreased by 60% in the past three decades and the species is listed as Near Threatened. Declines in prey availability and/or abundance brought about by recent changes in the distribution of pelagic fish stocks and industrial purse-seine fishing are hypothesised to be a key driver of seabird population decreases in the southern Benguela. We investigated the foraging behaviour of breeding Cape cormorants by deploying GPS and temperature–depth recorders on 24 breeding adults from three islands off the coast of South Africa, two of them to the north of Cape Point and a third farther south on the western Agulhas Bank. This provided the first measures of foraging dispersal by a cormorant in the Benguela system, and enabled a comparison of foraging behaviour between birds from these islands. Foraging trips of Cape cormorants lasted between 17 min and >7 h, at a maximum distance of between 2 and 58 km away from their colony. Foraging effort was significantly greater for birds from farther north off the West Coast in terms of trip duration, distance travelled, number of dives and time spent flying compared to those from the southernmost island (Dyer), which is probably a response to low prey availability in the north. Coastal reserves that exclude pelagic fishing from inshore feeding grounds around Cape cormorant breeding colonies may result in increased local prey availability, which would benefit Cape cormorant populations.     

黄河源鄂陵湖地区辐射收支和地表能量平衡特征研究

利用2010年6-7月鄂陵湖野外试验的近地层观测数据,分析了在不同天气条件下黄河源鄂陵湖地区辐射分量、地表能量分量、土壤温度和反照率的变化特征. 结果表明：不同天气条件下,辐射和地表能量各分量日变化差异较大,晴天、阴天和雨天的地表反照率依次递减,平均反照率约为0.21;观测期内,平均辐射贡献从大到小依次为向上长波、向下长波、向下短波、向上短波,日积分值分别为31.4 MJ·m^-2、25.6 MJ·m^-2、22.4 MJ·m^-2、4.2 MJ·m^-2,净辐射(12.5 MJ·m^-2)占向下短波辐射的55.7%;平均地表能量和土壤温度的变化幅度较晴天小,感热、潜热、0 cm土壤热通量的平均日积分值分别占净辐射的21.2%、43.1%、8.2%;平均土壤温度变化幅度随深度增加逐渐减小,浅层土壤温度峰值较晴天低2 ℃,深层土壤温度相差不大. 云和降水的扰动削弱了向下短波辐射,导致平均感热通量和0 cm土壤热通量的峰值比晴天小,而平均潜热通量的峰值大于晴天. 由于湖泊水体巨大的热容量和水分供应,鄂陵湖地区的气温日较差较小,地表温度变化幅度变小,附近地表温度升高缓慢. 鄂陵湖区的地表能量平衡中,潜热通量占主导,感热和地表土壤热通量次之. 研究结果有助于理解气候变化背景下黄河源区湖泊的能量水分循环过程,为促进该地区光热资源的合理利用和畜牧业的可持续发展提供数据支持.     

GPS气象预报的可行性分析

基于中国区域5个IGS跟踪站的实测GPS数据,利用Bernese 4.2软件反演了部分典型测站上空的可降水量,并分析了该降水量变化与降雨之间的关系,探讨了将GPS应用于气象预报的可行性.     

蒙古野驴(Equus hemionus)昼间行为时间分配初探

于2007 年和2010 年采用焦点动物取样法研究了新疆卡拉麦里山有蹄类野生动物保护区蒙古野驴昼间行为时间分配和活动节律,共采集行为数据460 h,观察蒙古野驴2 760 头次,将蒙古野驴昼间行为分为采食、移动、警戒、休息和“其他”5 类。采用卡方检验分析不同季节各种行为时间分配,结果表明：季节因素对蒙古野驴行为时间分配存在极显著影响（χ2=79.06,df=12,P<0.01）。采用ANOVA分析同季节不同行为间差异,结果表明,春季：移动、警戒、“其他”两两间无显著差异（[WTBX]P＞0.05）,其余两两间差异显著（P＜0.05）;夏季：仅移动与“其他”间无显著差异（P＞0.05）;秋冬季：仅警戒与“其他”间无显著差异（P＞0.05）。对蒙古野驴昼间活动节律研究结果表明,蒙古野驴采食时间比例在春季各时段均较高（＞45%）,仅中午（14:00～15:00）有1个低谷（27.62%）,夏秋季则为晨昏采食模式,冬季采食峰值（87.85%）在中午时段（13:00～14:00）。休息和采食高峰在各季节交叉出现,呈现此消彼长的趋势。各季节移动主要发生在晨昏时段。蒙古野驴以特定的行为时间分配模式和活动节律适应环境条件季节性变化,如气候条件、食物资源、人为干扰、生理期、昼间长度、捕食风险等。