云南快速更新循环数值预报系统及其12小时降水预报检验与改进

以中尺度WRF模式为基础,参照北京地区高分辨率快速更新循环同化系统,建立了云南快速更新循环数值预报系统(WRF-RUC)。为了充分了解该系统在云南省的预报性能,对预报结果进行个例和2016年6~7月检验。结果表明:快速更新循环同化数值预报系统能进行强降水过程预报,但与业务化“区域WRF数值预报系统”预报结果相比,12h降水预报评分较低。通过个例数值试验表明WRF-RUC系统进行本地化参数方案试验,挑选适合云南省的物理方案,是系统预报效果改进的有效途径。     

中国西北地区夏季降水分区客观预报

本文在降水分区的基础上,对西北地区夏季降水进行预报。利用2007—2010年的6—8月T639资料和相应时段的实况资料,通过概率回归降水等级方案进行建模,对2011年6—8月进行了试报。结果表明:与单站建模预报相比,分区建模降水预报TS评分在各时效、各量级上均有提高,并且在空报和漏报上有较大减少,特别是中雨预报改善明显。分区建模比单站建模所选因子更丰富,利用了模式产品的有用信息,因此预报效果更好。分区建模降水预报与模式直接输出降水预报的对比分析表明:分区建模的降水预报效果优于模式直接输出降水预报,尤其小雨预报效果显著,中雨和大雨36 h和60 h预报的空报现象明显减少。     

High-resolution mean sea surface computed with altimeter data of Ers-1 (geodetic mission) and topex-poseidon

The remote-sensing satellite ERS-1, launched in 1991 to study the Earth's environment, was placed on a geodetic (168-day repeat) orbit between 1994 April and 1995 March to map, through altimetric measurements, the gravity field over the whole oceanic domain with a resolution of 8 km at the equator in both along-track and cross-track directions. We have analysed the precise altimeter data of the geodetic mission, and, by also using one year of Topex-Poseidon altimeter data, we have computed a global high-resolution mean sea surface. The various steps involved in pre-processing the ERS-1 data consisted of correcting the data for environmental factors, editing, and reducing, through crossover analyses, the radial orbit error, which directly affects sea-surface height measurements. For this purpose, we adjusted sinusoids at 1 and 2 cycle rev⁻¹ along the ERS-1 profiles in order to minimize crossover differences between ERS-1 and yearly averaged Topex-Poseidon profiles. In effect, the orbit of Topex-Poseidon is very accurately determined (within 2–3 cm for the radial component), so Topex-Poseidon altimeter profiles can serve as a reference to reduce the ERS-1 radial orbit error. The ERS-1 residual orbit error was further reduced through a second crossover analysis between all ascending and descending profiles of the geodetic mission. The along-track ERS-1 and Topex-Poseidon data were then interpolated over the whole oceanic domain on a regular grid of 1/16°× 1/16° size. The mapping of the gridded sea-surface heights reveals the very fine structure of the marine geoid, up until now unknown at a global scale. This new data set will be most useful for marine geophysical and tectonic investigations.     

中国高分辨率温度和降水模拟数据的验证

PRISM模型是一种基于地理特征和回归统计方法生成气候图的模型。基于中国及其周边国家地区2450多个气象台站观测数据,以PRISM模型模拟生成了中国2.5′×2.5′(≈4～5km)逐月温度和降水数据。利用独立于模拟数据的中国生态系统研究网络18个野外观测站的长年气候观测数据,检验了PRISM模型的模拟结果,表明PRISM模型较好地模拟了我国温度和降水的空间分布及季节变化,除了在高山和亚热带地区由于地表覆盖和局部地形的差异影响模拟结果,其模拟值与实测值之间的趋势线同1∶1线基本一致,具有显著相关关系,其中降水效果略差     

可可西里地区库赛湖变化及湖水外溢成因

以库赛湖研究区地形图、Landsat TM/ETM+和中国环境与灾害监测预报卫星HJ1A/BCCD影像为基础,结合五道梁气象站气温降水资料,利用地理信息技术和数理统计方法,对2011 年9 月可可西里地区库赛湖湖水外溢成因进行分析。结果表明,库赛湖湖水外溢发生在2011 年9 月20 日至30 日期间,卓乃湖湖水进入库赛湖是后者发生变化的直接原因,而库赛湖规模近20 年来的持续增长,尤其是2006 年之后湖泊面积快速增加是其湖水外溢的基础。卓乃湖湖水外泄的主要诱因是区域持续降水,其中8 月17 日和21 日强降水使卓乃湖于8 月22 日出现漫顶溢流,8 月31 日至9 月5 日、9 月16 日至17 日期间两次持续降水导致卓乃湖水量剧增,并在9 月14 日至21 日期间形成洪水。由于水量外泄,卓乃湖面积骤降,截至11 月29 日,湖泊面积168.07 km²,仅为8 月22 日湖泊面积的62%,共减少104.88 km²。库赛湖外溢湖水流入海丁诺尔后又进入盐湖,其中海丁诺尔湖水进入盐湖时间介于10 月6 日至20 日期间。外来湖水大量进入导致海丁诺尔和盐湖在10-11月份快速扩大。     

东北平原西部沙地近10年的沙质荒漠化

东北平原西部沙地位于欧亚大陆中纬度巨型沙带的东部边缘，为我国沙质荒漠化土地的东缘，是我国自然环境最好的沙区，随着经济的发展，生态环境遭到严重破坏，沙质荒漠化景观日益明显，尤其是南部的科尔沁沙地，沙质荒漠化已十分严重，已经超过与其相邻的西部环境条件更差的沙区，利用RS和GIS，根据NOAA/AVHRR数据建立的沙质荒漠化监测指标，对东北平原西部沙地沙质荒膜化现代过程进行了动态监测，在此基础上利用TM数据对沙质荒漠化的发展方式与成因进行了深入的探讨，并有针对性地提出了区域沙质荒漠化的防治对策。     

A 60-year record of rainfall from the sediments of Jinheung Pond,Jeongeup, Korea

This paper describes mean grain-size data from the ¹³⁷Cs- and ²¹⁰Pb-dated sediment core BS-3 (33-cm long) recovered from Jinheung Pond, located in the southwestern part of the Korean Peninsula. Grain-size analysis of the Jinheung Pond sediments shows a clear signal for changes in annual precipitation over the past 60 years. Instrumental records of annual precipitation (AP) and the annual summation of the precipitation of >50 mm per day (AP50), which reflects the energy available for sediment transport, correlate well with the mean grain-size distributions measured in the core. The most plausible mechanism for this response in mean grain size is variations in the annual amount and intensity of precipitation. Heavy precipitation enhances soil erosion over the catchment area and increases the transport capacity of streams and rivers. Thus, coarser mean grain size should reflect higher precipitation, and smaller mean grain size should reflect lower rainfall. In the data from core BS-3, however, grain-size peaks attributed to increased annual precipitation are not prominent. This is because a dam prevents removal of fine particles from the pond via the outflow. Therefore, the mean grain-size value represents somewhat larger sediments together with fine clays. The results of this study show that sediments of dammed lakes and ponds are well suited for high-resolution environmental investigations, especially for records of changes in precipitation over time.     

Machine learning predictions of passive microwave brightness temperature over snow-covered land using the special sensor microwave imager (SSM/I)

Abstract

Two different forms of machine learning – an artificial neural network (ANN) and a support vector machine (SVM) – are used to estimate passive microwave (PMW) brightness temperatures (Tb) as observed by the special sensor microwave imager (SSM/I) satellite sensor over snow- covered land in North America. Both techniques reasonably reproduce unbiased estimates of SSM/I observations at 19.35 and 37.0 GHz for both vertically- and horizontally-polarized channels. When compared against SSM/I observations not used during training, domain-averaged statistics from 1 September 1987 to 1 September 2002 yielded a root mean squared error (RMSE) of less than 9 K for all frequency and polarization combinations examined in this study. Even though both ML techniques reasonably reproduced SSM/I Tb observations, the SVM outperformed the ANN because the SVM: (1) better captured the high-frequency (i.e. day-to-day) temporal characteristics in the Tb observations across the majority of the study domain, (2) better reproduced the spatial variability as a function of snow classification, and (3) yielded greater sensitivity to snow-related input variables during the estimation of PMW Tb. These findings reinforce previous research of SVM-based estimation of PMW Tb employing observations from the advanced microwave scanning radiometer.     

颠覆列车强风数值模式参数敏感性对比分析

新疆的三十里风区是著名的风口,兰新线和南疆铁路线横穿此地,时有列车被强风颠覆,对铁路运输影响很大,急需大风精细预报。数值模式中有许多参数,如何确定改进预报最显著的参数是个问题。采用MM5V3模式做模拟实验,设计3重嵌套,最小格距3km,用30″数字高程数据生成模式地形。分析表明,3km格距模式分辨率对地形有较为精确的表达。无论东西剖面还是南北剖面,3km所预报的风场更为详细,风速预报更准确;不仅可以预报出强的下坡风,亦可以预报出地形波列。对强风预报而言,模式水平分辨率是一个敏感因子。     

2005—2017 年拉萨小时降水变化特征

利用拉萨站 2005—2017 年汛期（5～9 月）逐时地面观测资料,分析了拉萨逐年小时降水（降 水量、降水频次和降水强度）的变化特征,结合谐波分析方法讨论了小时降水的日循环信号,最后 对比了不同时长和等级的小时降水出现频次及其对总降水的贡献。结果表明：（1）拉萨逐年汛期 小时降水以“单峰型”结构为主,峰值出现在夜间。（2）拉萨汛期小时降水变化为全日周期,其中盛 夏（7～8 月）期间的日循环信号最强。（3）拉萨汛期降水按持续时间可分为：短历时（1～3 h）、中历 时（4～6 h）和长历时（＞6 h）3 种类型,其中短（长）历时降水出现频次最多（少）,但其贡献率最小 （大）,短历时降水的日峰值出现在下午到前半夜,而中历时和长历时降水的日峰值出现在后半 夜。（4）各等级小时降水中小雨（3＞r≥1）和中雨（r≥3）对降水总量的贡献率明显大于微雨（1＞r≥ 0.1）,随着降水等级的上升,夜雨概率增大。     

Time dependent IRM acquisition as a tool to quantify the abundance of ultrafine superparamagnetic magnetite in loessic soils

The time dependence of Isothermal Remanent Magnetization acquisition (tIRM) is a rapid, sensitive and inexpensive way to quantify the presence of ultrafine ferrimagnetic grains straddling the superparamagnetic–single domain grain size boundary, well suited for use in small rock magnetic laboratories. The technique is very selective to the presence of grains with a diameter of approximately 25 nm, and tIRM results correlate well with measurements of frequency dependent susceptibility without the need of correcting for the presence of paramagnetic minerals. A simple IRM acquisition model can be used to obtain quantitative abundance estimates for these ultrafine magnetic grains. Application of tIRM measurements to eleven soil profiles from the Midwestern United States shows that the abundance of ultrafine particles increases with precipitation, as long as the mean annual precipitation is below 850 mm a⁻¹. Sites that developed under more humid conditions show a decrease in tIRM and likely SP abundance, probably caused by increased iron reduction and translocation during more common periods of reducing conditions.     

辽宁省大雨以上降水日数分布与趋势分析

大雨以上降水日数反映了降水的非平均状况,对于气候异常变化和预报预测都有非常重要的意义。以辽宁省作为研究区域,根据1957-2013年辽宁省内23个和省外4个雨量站点的逐日降水数据,利用趋势系数法计算大雨以上降水日数的变化趋势,通过Mann-Kendall检验法检测突变。采用Morlet小波技术分析年际与各季节的变化周期;借助ArcGIS软件工具的Kriging插值和IDW插值模块对研究区进行空间分析。结果表明：辽宁省大雨以上降水日数的空间变化表现为由东南向西北递减;年际以及春、夏两季的周期大约为38年,秋季周期约为15年;大雨以上降水日数的年际变化呈现微弱的减少趋势,不同季节略有差异。57年来,辽宁省大雨以上降水日数变化总体呈现下降趋势,辽中地区下降趋势略有滞后,辽西地区变化情况较其他区域相对复杂。     

天山北侧成灾雹云移动路径及预警指标的研究

利用2005-2014年5～8月天山北侧气象台站观测记录、人工防雹作业点记录、灾害调查等资料,克拉玛依探空站08：00探空资料和克拉玛依、奎屯、石河子、五家渠四部雷达探测资料及其基数据反演产品,对冰雹的年分布、月分布及日变化特征进行了分析,归纳出成灾雹云的雷达回波特征及移动路径,依据百分位数方法确定了成灾雹云的预报及雷达特征预警指标,并利用2015-2016年降雹及相应的雷达探测资料对预报预警指标进行了检验分析。     

Winter stemflow nutrient inputs into a southern New England broadleaved deciduous forest

Stemflow leaching from the above‐ground vegetative surfaces of broadleaved deciduous canopy trees has been well documented during the growing season. Winter stemflow leaching from the leafless crowns of deciduous trees is less well understood, especially in the context of global climate change. Boreal and northern temperate forests are forecast to have a lower incidence of snow events and an increased frequency of rain and mixed precipitation events. A change in the seasonal precipitation regime may be significant due to linkages among global change, stemflow leaching, and biogeochemical processes. The aim of this paper is to (1) demonstrate the extent of winter stemflow nutrient leaching from deciduous trees; (2) explore how winter stemflow leachate quantity may vary as a function of the type of precipitation event; and (3) quantify the extent to which an increase in the incidence of snow‐to‐rain events would enhance stemflow leaching. Measuring meteorological conditions, stemflow volumes, and stemflow chemistry over two successive winter seasons in New England demonstrated that winter stemflow drainage was significantly enriched compared to the incident bulk precipitation: 162 times greater for K+, 44 times greater for Ca2+, and 29 times greater for Mg2+. Snow‐to‐rain events leached considerably greater quantities of base cations from the deciduous trees than all other types of precipitation events. An increased frequency of snow‐to‐rain events from 13.8% to 25% of winter precipitation events would substantially increase mean stemflow nutrient inputs to the bases of forest trees during winter. Implications for significantly increased winter stemflow leachate inputs, corresponding to an increased incidence of snow‐to‐rain events, include a shift in the biogeographic range of species, delayed leaf emergence, and increased soil respiration.     

Comment on 'Systematic determination of earthquake rupture directivity and fault planes from analysis of long-period P-wave spectra' by L. M. Warren and P. M. Shearer

Warren and Shearer describe a method of estimating the duration of P pulses radiated by earthquakes, on the assumption that the source is a unilateral fracture. The estimates are made in the frequency domain. The estimates obtained by Warren and Shearer for seven of the earthquakes are compared to durations estimated here in the time domain; the time-domain measurements being made on broad-band seismograms (∼0.1–4.0 Hz) derived by filtering from short-period recordings. Overall, the time-domain method indicates that the pulse duration of the earthquakes studied here range from 2.0 to 7.6 s, whereas the estimates from the results of Warren and Shearer range from 7.1 to 9.8 s. This suggests that the method of Warren and Shearer cannot resolve pulse lengths less than about 7 s. The suggestion is supported by the estimates of the duration of rupture—fault length/speed of rupture—implied by the results of Warren and Shearer. For, although the estimated fault-length ranges from 0.8 km to over 40 km most rupture durations are around 8 s.     

新疆克里雅河源流区径流变化与气候因子关系的非线性分析

利用克里雅河源流区兰干站1957～2009年的年径流量、气温和降水量实测数据,借助小波分析和R/S分析等方法探讨了径流量、气温和降水量的变化趋势及多时间尺度相关性。结果表明:(1)年径流量与气温和降水量存在明显的正相关关系并皆呈增加趋势,结合R/S分析,这种增加趋势在未来的50a仍将可能持续。(2)研究区年径流量、气温和降水量均存在9年的年际变化周期,而在年代际上由于气温和降水量周期性不同致使径流量的周期为15年。另外,三者在未来的20年存在不同的周期性突变。(3)克里雅河源流区径流量与气温和降水量存在显著的非线性相关关系。年径流量的变化是气温和降水量综合作用的结果。     

Evaluation of Diverse Geometric and Geostatistical Estimation Methods Applied to Annual Precipitation in Asturias (NW Spain)

Several alternative estimation and interpolation methods for making annual precipitation maps of Asturias are analysed. The data series in this study corresponds to the year 2003. There exists an evident relationship between precipitation and altitude, with a high correlation coefficient of 0.70, that reflects the hillside effect; that is, the increase in the amount of precipitation in more mountainous areas. The direct spatial variability of precipitation and of altitude and the cross variability of precipitation–altitude are defined by two exponential variogram models: one with a short-range structure (15–30 km) that reflects the control exerted by the lesser, local mountain ranges over the amount of precipitation; and another with a long-range structure (80 km) that supposes the influence over precipitation of the major mountainous alignments of the inland areas of the Cantabrian Mountain Range (Cordillera Cantábrica) situated between 60 and 90 km from the coastline. These variogram models had to be validated for coregionalization by the Pardo-Igúzquiza and Dowd method so as to be able to make the cokriging map. The geometric estimation methods employed were triangulation and inverse distance. The geostatistical estimation methods developed were simple kriging, ordinary kriging, kriging with a trend model (universal kriging), lognormal kriging, and cokriging. In all of these methods, a 3 × 3 km² grid was selected with a total of 2580 points to estimate, a circular search window of 60 km, and a relatively small number of samples with the aim of highlighting the local features and variations on isohyet maps. The kriging methods were implemented using the WinGslib software, incorporating two specific programs, Prog2 and Fichsurf, so as to be able then to make isohyet maps using the Surfer software. All the methods employed, apart from triangulation, rendered realistic maps with good fits to the values of the original data (precipitation) of the sample maps. The problem with triangulation lies not in the reliability of the estimates but in the fact that it gives rise to contrived maps because of the tendency of isohyets to present abundant triangular facets. The reliability of the methods was based on cross-validation analysis and on evaluation of the different types of errors, both in their values and in their graphical representations. Substantial differences were not found in the values of the errors that might discriminate some methods from others in an evident way. Bearing the aforesaid in mind, should we have to make an evaluation of the different estimation methods in decreasing order of acceptance, this would be: kriging with a trend model, inverse distance, cokriging, lognormal kriging, ordinary kriging, simple kriging, and triangulation. The application of other estimation methods such as colocated cokriging, kriging with an external drift, and kriging of variable local means (residual kriging) is dependent on the availability of a digital model of the terrain with an altitude grid of the region.     

三工河流域山地—绿洲—荒漠系统降水空间变异性研究

山地—绿洲—沙漠系统（MODS）是中国内陆干旱区最基本、也最典型的地理景观格局,以天山北麓中段、准噶尔盆地南缘的三工河流域为典型区,设置降雨量监测网,获取2007-2014年5-8月份降雨量数据,利用（旋转）经验正交函数分解（REOF/EOF）、分形理论及克里金法（Kriging）等方法探讨流域尺度干旱内陆区MODS多地貌单元复合情况下降水的空间结构型及异质性特征,为深入了解MODS生态系统植被演变规律及其恢复提供借鉴。主要结论为：依据第一特征向量（对总体方差贡献82.4%）0~30 km、30~70 km及70~150 km的3个荷载区段,将研究区划分为山地区、绿洲区及沙漠区;其夏季降水场以“整体一致”型为主,表现为降水一致全流域整体增加,且增幅自山地—绿洲—荒漠依次减小。山地区半变异函数曲线符合高斯模型,绿洲区符合球状模型变程为15.3 km,荒漠区5月、6月及其它时段分别符合高斯模型、指数模型及球状模型,变程58.6 km比山地和绿洲大。随机因素引起的空间异质性占0.01%~9.57%;绿洲区降水空间变异性最大,山地次之沙漠区最小;6月份降水空间异质性最显著,8月最小;在南北方向（0°）和东南—西北方向（135°）变异性最强。     

珠江流域多尺度极端降水时空特征及影响因子研究

基于珠江流域74个气象站点1952~2013年逐日降水和气温数据,采用POT抽样、Mann-Kendall（MK）趋势检验、泊松回归等方法,从降水量级、降水频率及发生时间等方面系统分析了珠江流域年、雨季及旱季3个时间尺度上的极端降水特征,并从降水对温度变化响应及ENSO影响等角度,探讨了极端降水变化特征的机理。研究表明：① 珠江流域极端降水年内分布不均,多发于4~9月,其中6月份发生频率最高;② 珠江流域极端降水频率在雨季及年际间分布较为均匀。但在旱季,珠三角地区极端降水在不同年份差异性较大;③ 在雨季及年际尺度上,极端降水年序列趋势性并不显著;而相对干旱季节,极端降雨量级、发生频次均随年份增加呈显著上升趋势,且发生时间提前。珠江流域农业以水稻(Oryzasativa)种植为主,旱季极端降水增加易导致冬汛及其引起的作物倒伏与农田渍涝等灾害,同时对秋冬防洪提出新的挑战,需要引起人们的关注;④ 温度升高和ENSO事件对珠江流域极端降水过程有显著影响。从ENSO影响的角度讲,在厄尔尼诺年,珠江流域西部极端降水量级和频率增加,而流域东部沿海区域极端降水量级减少,时间延后。     

基于GWR模型的陕西秦巴山区TRMM降水数据降尺度研究

应用TRMM降水数据,进行国内典型区域降尺度相关研究,可弥补应用气象站点数据研究带来的局限。以陕西秦巴山区为研究区,基于TRMM降水数据和NDVI数据,应用GWR模型和比例指数,获得GWR年、月降尺度数据并进行检验,最后分析地形对降尺度结果的影响。结果表明：获得的1 km分辨率的GWR降尺度降水数据,具有较强的细节表现能力;降尺度数据与实测降水数据年尺度上相关系数为0.88,月为0.93,相关性较好;与TRMM原始数据对比,降尺度结果降水值略小,整体低估降水;区内秦岭山地GWR降尺度结果精度变化幅度最小,相似地形条件下,海拔越高,GWR降尺度结果表现越好;采用GWR模型进行秦巴山区TRMM降水数据的降尺度研究,具有较强的适用性。