Estimating actual rainfall from satellite rainfall products

The lack of uncertainty measures in operational satellite rainfall (SR) products leads to a situation where users of the SR products know that there are significant errors in the products, but they have no quantitative information about the distribution of these errors. The authors propose a semiparametric model to characterize the conditional distribution of actual rainfall (AR) given measures from SR products. The model consists of two components: a conditional gamma density given each SR, and a smooth functional relationship between the gamma parameters and SR. The model is developed for monthly rainfall, estimated from a satellite with sampling frequency once a day, averaged over an area of 512 × 512 km² in the Mississippi River basin. The conditional distribution results are more informative than deterministic SR products since the whole conditional distribution enables users to take appropriate actions according to their own risk assessments and cost/benefit analyses.     

自动雨量与人工雨量的差值对比分析

应用青海省班玛县国家基本气象站2011年6月1日—9月30日的降水资料,进行自动站与人工观测降水量记录统计、对比分析,发现自动站观测雨量与人工观测雨量存在一些偏差。分析表明,导致误差产生的主要原因是仪器测量原理与观测方法不同、人为影响、观测时间不一致、降水强度等其他原因。     

大暴雨过程中短时强降水机制分析

利用雷达径向速度、风暴相对径向速度和风廓线产品以及数值预报产品和雨量资料,分析了临沂2008年汛期中最大也是最后一场大暴雨过程中短时强降水发生机制。结果发现:在有利的大尺度环流背景形势下,中小尺度系统的生成是短时强降水产生的原因。分析还表明:低空西南气流的稳定维持利于降水过程持续,而高空气流的短波波动则造成降水强度的强弱波动变化;当高空气流由偏西风转为西南风,中低空西南气流和中高空西南气流同向叠加时,对流层中层西南急流建立并且向超低空传递,高空冷空气的加入和低层西南气流加强促使中小尺度系统生成,导致短时强降水。     

流域面雨量的计算方法

经对面雨量的几种计算方法对比分析，确定了以等雨量线法为计算流域面雨量的方法，同时对于计算方法进行了部分优化，并应用于业务中。     

流域面雨量的计算方法

经对面雨量的几种计算方法对比分析,确定了以等雨量线法为计算流域面雨量的方法,同时对于计算方法进行了部分优化,并应用于业务中.     

Extreme rainfall intensities

Theoretical and Applied Climatology - Statistics of the total time, in minutes, that extreme rainfall rates are exceeded were computed from weighing raingage records at stations in several rainfall...     

The impacts of the Indian summer rainfall on North China summer rainfall

Previous studies have indicated a connection between interannual variations of the Indian and North China summer rainfall. An atmospheric circulation wave pattern over the mid-latitude Asia plays an important role in the connection. The present study compares the influence of the above-normal and below-normal Indian summer rainfall on the North China summer rainfall variations. Composite analysis shows that the mid-latitude Asian atmospheric circulation and the North China rainfall anomalies during summer tend to be anti-symmetric in above-normal and below-normal Indian rainfall years. Analysis indicates that the Indian-North China summer rainfall relation tends to be stronger when larger Indian rainfall anomaly occurs during a higher mean rainfall period. The observed long-term change in the Indian-North China summer rainfall relationship cannot be explained by the impact of the El Niño-Southern Oscillation (ENSO). The present study evaluates the Indian-North China summer rainfall relationship in climate models. Analysis shows that the Indian-North China summer rainfall relationship differs largely among different climate models and among different simulations of a specific model. The relationship also displays obvious temporal variations in both individual and ensemble mean model simulations. This suggests an important role of the atmospheric internal variability in the change of the Indian-North China summer rainfall relationship.     

降水云团移动速度对风云四号A星降水反演误差的影响

针对FY-4A卫星降水反演产品GPM-SCaMPR中的误差,提出台风区域降水云团移动速度的计算方法并用于误差改进,以全球降水观测计划(Global Precipitation Mission,GPM)的IMERG(the Integrated Multi-satellite Retrievals for GPM)降水产品为参照、以台风"罗莎"、"利奇马"和"白鹿"降水反演为例进行误差影响研究。结果表明,其误差随降水云团移动速度的增大而增大,降水率均方根误差(Root Mean Square Error,RMSE)在台风成熟阶段比其他阶段大20%左右,在衰亡阶段最小。采用GPM/IMERG降水产品作校准数据,对3个台风初期、成熟和衰亡阶段的降水反演结果进行误差订正,台风"罗莎"初期、成熟及衰亡阶段订正后的降水率RMSE由5.81、7.07、5.51 mm·h^-1减小到5.54、6.16、5.27 mm·h^-1(分别减小0.27、0.91、0.24 mm·h^-1)。     

Interdecadal modulation of Australian rainfall

Interdecadal variability is investigated in a 300 year run of the Parallel Climate Model, a global coupled atmosphere-land-ocean-sea ice model. The model simulates El Niño variability of realistic magnitude and is found to produce interdecadal characteristics similar to those observed, both in frequency, spatial patterns and amplitude. Modulation of Australian rainfall on interdecadal time scales is similar to observed and is found to have contributions from both the modulation of ENSO, changes in the position of the Walker circulation and variations in western Pacific SSTs. A slackening of the equatorial Pacific thermocline slope is associated with diminished ENSO variability during interdecadal periods of positive tropical Pacific SSTs. These interdecadal changes to ENSO and shifts in the position of the Walker circulation are physical mechanisms that contribute to the weakened correlations between the SOI and Australian climate during interdecadal periods of positive tropical Pacific SSTs. Warm anomalies in the western Pacific also contribute to a decrease in Australian rainfall in the model on interdecadal time scales.     

雨量站网的设计——江汉平原雨量站网合理分布

本文用江汉平原地区42个气象站1961—1985年的日降水量资料进行统计和分析,得出该区域的雨量站间距30km,为最佳距离。同时指出该方法也适用于平原地区基它类型气象站网的设计。     

Seasonal variability of rainfall extremes

Monthly rainfall extremes have been analyzed for three stations in Southern Ontario. The double exponential probability distribution was fitted to the extreme values for each month considered, each duration selected, and sets of annual extremes. A station‐year approach yielded monthly and annual extreme value distributions for the lumped region of Southern Ontario. The analysis has revealed a pronounced seasonal pattern in the rainfall extremes – the amount of rain expected with a selected probability of occurrence during the summer being considerably greater than the rainfall that might be expected to be exceeded at the same probability level during the spring or fall. The extent of the seasonal variability was found also to vary with duration. The implications of the variability are seen to be significant for the estimation of the magnitude and frequency of floods.     

Stochastic intervention analysis of rainfall

Summary Urbanization and industrialization are claimed to affect local climate and to increase precipitation in urban and surrounding rural areas. In the past, considerable meteorologic data have been collected in urban areas and the effects of urbanization on precipitation and other variables have been analyzed by using various techniques. In evaluating urban effects on precipitation, changes in precipitation due to urban effects must be distinguished from changes which are due to natural variability, noise effect, and sampling error. Stochastic intervention analysis is used in this study to establish the statistical significance of changes in monthly precipitation attributed to the effects of urbanization and industrialization and to investigate the nature of these changes. Intervention analysis is especially useful in the analysis of correlated and seasonal monthly rainfall data. Intervention analysis is used to determine whether changes have occurred in the overall mean value or in warm and cold seasons. Monthly rainfall data from Laporte and St. Louis areas are analyzed and the results are presented.

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Zusammenfassung Urbanisierung und Industrialisierung beeinflussen wahrscheinlich das Lokalklima und erhöhen dabei den Niederschlag in städtischen Gebieten sowie deren ländlicher Umgebung. In der Vergangenheit sind meteorologische Daten beträchtlichen Umfangs in städtischen Gebieten gesammelt worden und die Effekte der Urbanisierung auf den Niederschlag wurden mit Hilfe verschiedener Methoden untersucht. Bei der Abschätzung dieser Stadtklimaeffekte auf den Niederschlag müssen Varianten davon unterschieden werden, die natürlichen Ursprungs sind, einschließlich dem Rausch-Effekt und dem Probenahmefehler. In der vorliegenden Studie wird die stochastische Interventionsanalyse dazu benützt, die statistische Signifikanz der Änderungen des monatlichen Niederschlages herauszufinden, die der Urbanisierung und Industrialisierung zugeschrieben werden können und die Art dieser Änderungen zu untersuchen. Dié Interventionsanalyse ist insbesondere bei der Analyse korrelierter jahreszeitlich-monatlicher Niederschlagsdaten nützlich. Diese Interventionsanalyse wird nun dazu benützt, festzustellen, ob sich die Änderungen im Gesamtmittelwert oder aber in der warmen bzw. kalten Jahreszeit zeigen. Die monatlichen Niederschlagsdaten von Laporte und St. Louis (U.S.A.) werden analysiert und die Ergebnisse mitgeteilt.

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With 3 Figures     

On the relations of the rainfall variability and distribution with the mean rainfall over India

Summary Along with averages, rainfall variability and distribution are important climatological information. In this study, using 114 years (1871–1984) data of 306 stations, it is demonstrated that the variability and spatial distribution of annual, summer monsoon and monthly rainfall are highly dependent upon the respective period mean rainfall variation over India. The magnitude of three selected absolute measures of variability, e.g. standard deviation, absolute mean deviation and mean absolute interannual variability is found to increase linearly with mean rainfall.In order to describe the relation between the rainfall frequency distribution and the mean rainfall, a linear regression between the rainfall amount expected with a specified exceedance/non-exceedance probability and the mean rainfall amount is presented. Highly significant linear curves for a large number of probabilities specified in an average probability diagram clearly demonstrate the dependence of the rainfall frequency distribution on mean rainfall over India.With 8 Figures     

Mesoscale predictability of mei-yu heavy rainfall

Recently reported results indicate that small amplitude and small scale initial errors grow rapidly and subsequently contaminate short-term deterministic mesoscale forecasts. This rapid error growth is dependent on not only moist convection but also the flow regime. In this study, the mesoscale predictability and error growth of mei-yu heavy rainfall is investigated by simulating a particular precipitation event along the mei-yu front on 4-6 July 2003 in eastern China. Due to the multi-scale character of th...     

Volatility modeling of rainfall time series

Networks of rain gauges can provide a better insight into the spatial and temporal variability of rainfall, but they tend to be too widely spaced for accurate estimates. A way to estimate the spatial variability of rainfall between gauge points is to interpolate between them. This paper evaluates the spatial autocorrelation of rainfall data in some locations in Peninsular Malaysia using geostatistical technique. The results give an insight on the spatial variability of rainfall in the area, as such, two rain gauges were selected for an in-depth study of the temporal dependence of the rainfall data-generating process. It could be shown that rainfall data are affected by nonlinear characteristics of the variance often referred to as variance clustering or volatility, where large changes tend to follow large changes and small changes tend to follow small changes. The autocorrelation structure of the residuals and the squared residuals derived from autoregressive integrated moving average (ARIMA) models were inspected, the residuals are uncorrelated but the squared residuals show autocorrelation, and the Ljung–Box test confirmed the results. A test based on the Lagrange multiplier principle was applied to the squared residuals from the ARIMA models. The results of this auxiliary test show a clear evidence to reject the null hypothesis of no autoregressive conditional heteroskedasticity (ARCH) effect. Hence, it indicates that generalized ARCH (GARCH) modeling is necessary. An ARIMA error model is proposed to capture the mean behavior and a GARCH model for modeling heteroskedasticity (variance behavior) of the residuals from the ARIMA model. Therefore, the composite ARIMA–GARCH model captures the dynamics of daily rainfall in the study area. On the other hand, seasonal ARIMA model became a suitable model for the monthly average rainfall series of the same locations treated.     

安顺地区暴雨日数年际变化的气候特征

利用1979—2009年31 a安顺地区（安顺、平坝、普定、镇宁、关岭和紫云）6站的降水资料,统计分析6站暴雨日数和暴雨量的变化特征,提取代表安顺地区的代表站,对其进行统计分析,得到安顺地区暴雨日数年际变化的气候特征。安顺地区暴雨日数的在20世纪80年代末—90年代末期间具有明显的3～5a的年际震荡,并在90年代初达到峰值。安顺地区暴雨偏多年在高低空环流、风场和能量场配置的主要特征为：700hPa和500hPa高低空位势高度配置一致,位势高度在中高纬度出现＂东高西低＂的走势,安顺地区位于异常低涡的东南部,西太平洋副热带高压的西部,这样来自异常低涡东南侧的冷空气与来自海洋北上的暖湿气流在此交汇,利于底层切变线和准静止锋的建立;安顺地区位于高空偏西急流的右前方的出口处,低空西南急流右前方的出口处和低空东南急流左前方的出口处,这种高低空急流的配置非常有利于暴雨区垂直上升运动的产生;安顺地区及其附近区域对流不稳定较强,利于对流不稳定能量的积累,从而使对流不稳定区域易出现强对流系统,对安顺地区的不稳定能量的储存和释放十分有利。     

Analysis of Hawaiian diurnal rainfall patterns

Summary We analyzed hourly precipitation data over the period 1965–1998 for 133 stations located throughout the Hawaiian Islands and found distinctive diurnal cycles in the amount and frequency of the rainfall. The diurnal signals were generally strongest on the island of Hawaii and more pronounced in the summer than in the winter. Windward sides of the islands generally showed the time of maximum for frequency or amount to be before sunrise while the leeward sides generally revealed the primary maximum in the afternoon. We conducted the analyses for El Niño years and La Niña years and found the diurnal patterns in rainfall to be unaffected by this Pacific-area oscillation. The results are consistent with others who have argued, based on work on the island of Hawaii, that anabatic and katabatic wind flows are responsible for the observed diurnal rainfall patterns. A semi-diurnal cycle with two maxima and two minima appears to be important in the summer season in the leeward locations. Our results show that processes and patterns described for the island of Hawaii are found throughout the larger islands of the Hawaii chain.