基于PLS的面雨量统计学降尺度     

王靖宇  邱新法 《南京气象学院学报》2013,5(5):439-448

基于GIS的面雨量估算方法和基于模式输出的雨量产品都无法解决分辨率过低的问题,并且都不同程度地忽略了中小尺度地形对降水的影响.回顾了各种统计学降尺度方法,使用NCEP/NCAR提供的2011年4—9月的6 h一次的再分析资料,以及江苏省气象台提供的全省20多个常规站降水实况观测资料,结合高分辨率DEM数据,利用偏最小二乘法(PLS)设计了一套考虑地形因子动力作用的面雨量降尺度方案.通过合理选择和构造大尺度预报因子,地形因子动力作用参数化,回归分析与空间插值相结合的面雨量降尺度方案,成功还原了研究区域内代表站的实况降水序列,并绘制出研究区域内高分辨率的面雨量空间分布图.  相似文献   

Downscaling of Precipitation over Vancouver Island using a Synoptic Typing Approach     

Stephen R. Sobie  Andrew J. Weaver 《大气与海洋》2013,51(2):176-196

A statistical downscaling technique is employed to link atmospheric circulation produced by an ensemble of global climate model (GCM) simulations over the twenty-first century to precipitation recorded at weather stations on Vancouver Island. Relationships between the different spatial scales are established with synoptic typing, coupled with non-homogeneous Markov models to simulate precipitation intensity and occurrence. Types are generated from daily precipitation observations spanning 1971 to 2000. Atmospheric predictors used to influence the Markov models are derived from two versions of GCM output: averages of GCM grid cells selected by correlation maps of circulation and precipitation data and an approach involving common Empirical Orthogonal Functions (EOFs) calculated from GCM output over the northeast Pacific Ocean. Projections for 2081 to 2100 made using averaged grid cells find that winter (November–February) precipitation anomalies produce modestly positive values, with gains of 7.5% in average precipitation, typical increases of 9.0% rising to 20% in the case of high-intensity precipitation, and little spatial dependence. In contrast, average and high-intensity summer precipitation (June–September) decline negligibly at most island weather stations with the exception of those in the southwestern sections, which experience reductions of 15% relative to 1971 to 2000. Projections made using common EOFs display a strong spatial dependence. Future winter precipitation is expected to increase only on the west coast of the island by 11%, on average, while the southeastern coast will experience decreases of 5% to 10%. The same pattern repeats in summer, though with negligible increases on the west coast and declines of 12% to 16% on the southeastern coast. The reliability of this novel EOF method remains to be confirmed definitively, however. In both seasons precipitation occurrence decreases slightly at all stations with declines in the total days with measurable precipitation ranging from 2% to 8%.

RÉSUMÉ [Traduit par la rédaction] Nous employons une technique statistique de réduction d’échelle pour lier la circulation atmosphérique produite par un ensemble de simulations du GCM (Global Climate Model) durant le XXI^e siècle aux précipitations enregistrées à des stations météorologiques sur l’île de Vancouver. Les relations entre les différentes échelles spatiales sont établies au moyen d'un typage synoptique couplé avec des modèles markoviens non homogènes pour simuler l'intensité et la fréquence des précipitations. Les types sont générés à partir des observations quotidiennes de précipitations au cours de la période 1971–2000. Les prédicteurs atmosphériques utilisés pour influencer les modèles markoviens sont dérivés de deux versions de sorties du GCM : les moyennes de mailles du GCM sélectionnées par tables de corrélation des données de circulation et de précipitations et une approche fondée sur les fonctions orthogonales empiriques (EOF) communes calculées d'après la sortie du GCM pour le nord-est du Pacifique. Les projections pour la période 2081–2100 basées sur des moyennes de mailles montrent que les anomalies de précipitations hivernales (novembre–février) produisent de faibles valeurs positives, avec des gains de 7.5% dans les précipitations moyennes, des accroissements caractéristiques de 9.0% augmentant à 20% dans le cas des précipitations de forte intensité, et peu de dépendance spatiale. En revanche, les précipitations estivales (juin–septembre) moyennes et de forte intensité diminuent de façon négligeable à la plupart des stations météorologiques de l’île, à l'exception de celles situées dans secteur sud-ouest qui subissent une réduction de 15% par rapport à 1971–2000. Les projections faites à l'aide des fonctions orthogonales empiriques communes exhibent une forte dépendance spatiale. Les précipitations hivernales futures devraient augmenter seulement sur la côte ouest de l’île de 11% en moyenne alors que la côte sud-est connaîtra des diminutions de 5 à 10%. La même configuration se répète en été, bien qu'avec des accroissements négligeables sur la côte ouest et des diminutions de 12 à 16% sur la côte sud-est. La fiabilité de cette nouvelle méthode EOF reste toutefois à établir. Dans les deux saisons, la fréquence des précipitations diminue légèrement à toutes les stations, les diminutions du nombre total de jours avec précipitations mesurables variant entre 2 et 8%.  相似文献   

A Hybrid Statistical-Dynamical Downscaling of Air Temperature over Scandinavia Using the WRF Model     

Jianfeng WANG  Ricardo M. FONSECA  Kendall RUTLEDGE  Javier MARTíN-TORRES  Jun YU 《大气科学进展》2020,37(1):57-74

An accurate simulation of air temperature at local scales is crucial for the vast majority of weather and climate applications.In this work,a hybrid statistical–dynamical downscaling method and a high-resolution dynamical-only downscaling method are applied to daily mean,minimum and maximum air temperatures to investigate the quality of localscale estimates produced by downscaling.These two downscaling approaches are evaluated using station observation data obtained from the Finnish Meteorological Institute over a near-coastal region of western Finland.The dynamical downscaling is performed with the Weather Research and Forecasting(WRF)model,and the statistical downscaling method implemented is the Cumulative Distribution Function-transform(CDF-t).The CDF-t is trained using 20 years of WRF-downscaled Climate Forecast System Reanalysis data over the region at a 3-km spatial resolution for the central month of each season.The performance of the two methods is assessed qualitatively,by inspection of quantile-quantile plots,and quantitatively,through the Cramer-von Mises,mean absolute error,and root-mean-square error diagnostics.The hybrid approach is found to provide significantly more skillful forecasts of the observed daily mean and maximum air temperatures than those of the dynamical-only downscaling(for all seasons).The hybrid method proves to be less computationally expensive,and also to give more skillful temperature forecasts(at least for the Finnish near-coastal region).  相似文献   

气候变化下水文极端事件变化预测研究进展   总被引：7，自引：1，他引：6       下载免费PDF全文

杨涛  陆桂华  李会会  何海  王晓燕 《水科学进展》2011,22(2):279-286

全球气候变化对洪水、干旱等极端水文事件的影响已成为一个亟待解决的科学问题.针对国内外在气候变化下采用统计降尺度和降雨径流模型对水文极端事件进行预测的研究进展进行了系统分析,在分类阐述的基础上,总结了国内外最新的研究进展及在预估过程中存在的问题和解决方案,试图凝练出一些气候变化背景下水文极端事件预估的新思路.结果表明:为有效降低极端水文事件预估的不确定性,各种集合模拟技术、数据同化方法、强化观测技术及水文模型的尺度转换理论将是有效的解决途径.  相似文献   

基于GCM模式预报的江西汛期降水降尺度预测模型          下载免费PDF全文

张超美  宋进波  章毅之  蔡娟  马锋敏 《气象与减灾研究》2017,40(3):171-177

基于1951—2013年江西省87个台站逐日降水数据和NCEP/NCAR再分析资料,利用偏相关统计方法选取影响江西省汛期降水的强迫因子,并进行归因分析,最终基于GCM模式预报结果建立江西省汛期降水的降尺度预测模型。结果表明:对江西省汛期降水产生主要影响的两个强迫因子分别是蒙古500 hPa位势高度和前期1—3月黑潮延伸区海表温度,前者反映中高纬的冷空气活动,后者能影响西太平洋副热带高压的位置和强度,两者都将影响江西省汛期降水。利用这两个强迫因子建立降尺度模型能够准确拟合江西省汛期降水,可较好地把握汛期降水的主要趋势,因而可用于江西省汛期降水预测。  相似文献   

Validation of hydrological models for climate scenario simulation: the case of Saguenay watershed in Quebec     

Yonas B. Dibike  Paulin Coulibaly 《水文研究》2007,21(23):3123-3135

This paper presents the results of an investigation into the problems associated with using downscaled meteorological data for hydrological simulations of climate scenarios. The influence of both the hydrological models and the meteorological inputs driving these models on climate scenario simulation studies are investigated. A regression‐based statistical tool (SDSM) is used to downscale the daily precipitation and temperature data based on climate predictors derived from the Canadian global climate model (CGCM1), and two types of hydrological model, namely the physically based watershed model WatFlood and the lumped‐conceptual modelling system HBV‐96, are used to simulate the flow regimes in the major rivers of the Saguenay watershed in Quebec. The models are validated with meteorological inputs from both the historical records and the statistically downscaled outputs. Although the two hydrological models demonstrated satisfactory performances in simulating stream flows in most of the rivers when provided with historic precipitation and temperature records, both performed less well and responded differently when provided with downscaled precipitation and temperature data. By demonstrating the problems in accurately simulating river flows based on downscaled data for the current climate, we discuss the difficulties associated with downscaling and hydrological models used in estimating the possible hydrological impact of climate change scenarios. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Development of a Downscaling Method in China Regional Summer Precipitation Prediction   总被引：1，自引：0，他引：1       下载免费PDF全文

GU Weizong  CHEN Lijuan  LI Weijing  CHEN Deliang 《Acta Meteorologica Sinica》2011,25(3):303-315

A downscaling method taking into account of precipitation regionalization is developed and used in the regional summer precipitation prediction (RSPP) in China. The downscaling is realized by utilizing the optimal subset regression based on the hindcast data of the Coupled Ocean-Atmosphere General Climate Model of National Climate Center (CGCM/NCC), the historical reanalysis data, and the observations. The data are detrended in order to remove the influence of the interannual variations on the selection of predictors for the RSPP. Optimal predictors are selected through calculation of anomaly correlation coe±cients (ACCs) twice to ensure that the high-skill areas of the CGCM/NCC are also those of observations, with the ACC value reaching the 0.05 significant level. One-year out cross-validation and independent sample tests indicate that the downscaling method is applicable in the prediction of summer precipitation anomaly across most of China with high and stable accuracy, and is much better than the direct CGCM/NCC prediction. The predictors used in the downscaling method for the RSPP are independent and have strong physical meanings, thus leading to the improvements in the prediction of regional precipitation anomalies.  相似文献   

Projection of Extreme Temperatures in Hong Kong in the 21st Century          下载免费PDF全文

LEE Tsz-cheung  CHAN Kin-yu  GINN Wing-lui 《Acta Meteorologica Sinica》2011,25(1):1-20

The possible changes in the frequency of extreme temperature events in Hong Kong in the 21st century were investigated by statistically downscaling 26 sets of the daily global climate model projections (a combination of 11 models and 3 greenhouse gas emission scenarios, namely A2, A1B, and B1) of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. The models’ performance in simulating the past climate during 1971–2000 has also been verified and discussed. The verification revealed that the models in general have an acceptable skill in reproducing past statistics of extreme temperature events. Moreover, the models are more skillful in simulating the past climate of the hot nights and cold days than that of the very hot days. The projection results suggested that, in the 21st century, the frequency of occurrence of extremely high temperature events in Hong Kong would increase significantly while that of the extremely low temperature events is expected to drop significantly. Based on the multi-model scenario ensemble mean, the average annual numbers of very hot days and hot nights in Hong Kong are expected to increase significantly from 9 days and 16 nights in 1980–1999 to 89 days and 137 nights respectively in 2090–2099. On the other hand, the average annual number of cold days will drop from 17 days in 1980–1999 to about 1 day in 2090–2099. About 65 percent of the model-scenario combinations indicate that there will be on average less than one cold day in 2090–2099. While all the model-emission scenarios in general have projected consistent trends in the change of temperature extremes in the 21st century, there is a large divergence in the projections between difierent model/emission scenarios. This reflects that there are still large uncertainties in the model simulation of the future climate of extreme temperature events.  相似文献   

A comparison of three methods for downscaling daily precipitation in the Punjab region   总被引：1，自引：0，他引：1  

Deepashree Raje  P. P. Mujumdar 《水文研究》2011,25(23):3575-3589

Many downscaling techniques have been developed in the past few years for projection of station‐scale hydrological variables from large‐scale atmospheric variables simulated by general circulation models (GCMs) to assess the hydrological impacts of climate change. This article compares the performances of three downscaling methods, viz. conditional random field (CRF), K‐nearest neighbour (KNN) and support vector machine (SVM) methods in downscaling precipitation in the Punjab region of India, belonging to the monsoon regime. The CRF model is a recently developed method for downscaling hydrological variables in a probabilistic framework, while the SVM model is a popular machine learning tool useful in terms of its ability to generalize and capture nonlinear relationships between predictors and predictand. The KNN model is an analogue‐type method that queries days similar to a given feature vector from the training data and classifies future days by random sampling from a weighted set of K closest training examples. The models are applied for downscaling monsoon (June to September) daily precipitation at six locations in Punjab. Model performances with respect to reproduction of various statistics such as dry and wet spell length distributions, daily rainfall distribution, and intersite correlations are examined. It is found that the CRF and KNN models perform slightly better than the SVM model in reproducing most daily rainfall statistics. These models are then used to project future precipitation at the six locations. Output from the Canadian global climate model (CGCM3) GCM for three scenarios, viz. A1B, A2, and B1 is used for projection of future precipitation. The projections show a change in probability density functions of daily rainfall amount and changes in the wet and dry spell distributions of daily precipitation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Statistical Downscaling Prediction of Summer Precipitation in Southeastern China   总被引：2，自引：0，他引：2       下载免费PDF全文

LIU Ying  FAN Ke  WANG Hui-Jun 《大气和海洋科学快报》2011,4(3):173-180

A statistical downscaling approach based on multiple-linear-regression (MLR) for the prediction of summer precipitation anomaly in southeastern China was established, which was based on the outputs of seven operational dynamical models of Development of a European Multi-model Ensemble System for Seasonal to Interannual Prediction (DEMETER) and observed data. It was found that the anomaly correlation coefficients (ACCs) spatial pattern of June-July-August (JJA) precipitation over southeastern China between the seven models and the observation were increased significantly; especially in the central and the northeastern areas, the ACCs were all larger than 0.42 (above 95% level) and 0.53 (above 99% level). Meanwhile, the root-mean-square errors (RMSE) were reduced in each model along with the multi-model ensemble (MME) for some of the stations in the northeastern area; additionally, the value of RMSE difference between before and after downscaling at some stations were larger than 1 mm d-1. Regionally averaged JJA rainfall anomaly temporal series of the downscaling scheme can capture the main characteristics of observation, while the correlation coefficients (CCs) between the temporal variations of the observation and downscaling results varied from 0.52 to 0.69 with corresponding variations from -0.27 to 0.22 for CCs between the observation and outputs of the models.  相似文献