Hydrological assessment of TRMM rainfall data over Yangtze River Basin

High-quality rainfall information is critical for accurate simulation of runoff and water cycle processes on the land surface. In situ monitoring of rainfall has a very limited utility at the regional and global scale because of the high temporal and spatial variability of rainfall. As a step toward overcoming this problem, microwave remote sensing observations can be used to retrieve the temporal and spatial rainfall coverage because of their global availability and frequency of measurement. This paper addresses the question of whether remote sensing rainfall estimates over a catchment can be used for water balance computations in the distributed hydrological model. The TRMM 3B42V6 rainfall product was introduced into the hydrological cycle simulation of the Yangtze River Basin in South China. A tool was developed to interpolate the rain gauge observations at the same temporal and spatial resolution as the TRMM data and then evaluate the precision of TRMM 3B42V6 data from 1998 to 2006. It shows that the TRMM 3B42V6 rainfall product was reliable and had good precision in application to the Yangtze River Basin. The TRMM 3B42V6 data slightly overestimated rainfall during the wet season and underestimated rainfall during the dry season in the Yangtze River Basin. Results suggest that the TRMM 3B42V6 rainfall product can be used as an alternative data source for large-scale distributed hydrological models.     

TRMM3B43降水产品在西藏地区的精度检验和应用

以西藏地区38个国家基准站和基本站的实测降水资料,利用双线性插值、相关系数、散点斜率和相对误差等指标,对热带降水测量卫星(TRMM)的3B43降水产品的精度进行检验和分析。结果表明:月尺度上,整体而言TRMM3B43降水产品与实测降水量具有较好的一致性,其中西藏西部和东部喜马拉雅山脉东段北麓地区相关性相对较差,平均相对误差较大。年尺度上TRMM3B43降水产品的相关性不如月尺度好,平均相对误差随统计数值的增大而减小。在应用TRMM3B43降水产品进行流域面雨量估算时,采用气象站点实测降水资料校准TRMM3B43降水产品的T-G联合法,对TRMM3B43降水产品进行订正。     

TRMM卫星降水数据在老哈河流域的精度评估

采用地面雨量站点观测降水作为基准数据,评估热带降雨观测计划(TRMM)最新一代降水产品3B42V7在高纬度半干旱的老哈河流域的精度。结果显示:TRMM 3B42V7在老哈河流域较基准降水系统偏大,平均偏差为17.46%,相关系数为0.73,平均意义上日卫星降水精度相对较高;但TRMM 3B42V7绝对值偏差达到81.26%,在绝对值意义上日卫星降水精度较低;经过GPCC地面月降水量偏差校准,TRMM 3B42V7精度在月尺度上有较大提高,绝对偏差为21.95%,相关系数达到0.98;TRMM 3B42V7精度同纬度和高程存在明显的相关关系;TRMM3B42V7能较好反映老哈河流域日降水事件并展现降水的空间分布特征。因此,TRMM 3B42V7可用于老哈河流域月尺度的水文过程模拟、水资源评价与规划等相关研究。     

乌苏里江流域TRMM降水数据精度评价与修正

将地面站点观测的降水数据作为基准降水数据,评估汛期热带降雨观测计划(TRMM)降水产品3B42研究型数据(V7)与实时降水数据(RT)的日以及月尺度数据在黑龙江省乌苏里江流域的时空精度。结果表明:在时间尺度上,TRMM 3B42V7与3B42RT的日降水数据与站点降水数据相比,均系统性偏小,且相关性不是很好;相对而言,3B42RT与站点数据的偏差程度较小,相关性较好;月尺度数据与日尺度数据相比,月数据精度均有很大提高,且2种产品数据精度相差不大;在空间尺度上,TRMM 3B42V7和3B42RT都能较好地展现乌苏里江流域降水的空间分布特征。针对评估结果,使用加法和乘法模型对TRMM 3B42V7和3B42RT的月降水数据进行修正。修正后,2种TRMM卫星降水产品的月降水数据精度均有提高,并且加法模型修正效果更好。因此,可选取加法模型修正后的3B42RT月尺度降水数据用于汛期乌苏里江流域的相关水文研究。     

TRMM卫星降雨数据在湖南省的精度和可靠性评定

卫星降雨数据的高时空分辨率使其在洪涝灾害监测、流域水文模型模拟等方面得以广泛应用,而对卫星降雨数据的精度评定和可靠性分析仍然是当前重要的研究课题。采用中低纬度旱涝灾害频发的湖南省23个国家基准气象站的降雨数据作为地面验证数据,对最新一代TRMM卫星降雨产品(3B42V7)的精度和误差特征进行了全面评估。从日、月、年和季节的不同时间尺度以及空间分布和高程等不同的空间要素方面对比分析了1999-2012年该卫星降雨产品在湖南地区的适应情况。研究表明:TRMM卫星反演降雨数据在日尺度上与地面气象站数据的匹配情况较差,相关系数仅为0.31;而在月尺度上有显著提高,相关系数为0.88。在干旱季节(11、12、1、2月)的表现要优于湿润季节(5、6、7、8月)。3B42卫星反演降雨数据存在比较明显的空间变异性,空间要素如高程、位置分布等对卫星降雨数据可靠性的影响强于降雨量的影响。     

基于TRMM卫星产品的长江流域降水精度评估

卫星降水产品在降水空间格局分析中扮演着重要角色。为分析卫星降水产品在长江流域的应用精度,利用2003~2010年长江流域175个雨量站实测降水资料检验了同期TRMM(Tropical Rainfall Measurement Mission)降水产品3B42 RTV7及V7的精度。结果显示:(1)长江流域年平均降水总量从东南向西北呈现明显的梯度变化,年降水量从2 000 mm/a减少到400 mm/a,降水空间差异极大,时间分布也不均。(2)RTV7和V7降水产品能够捕捉到长江流域降水空间分布格局,尤其是V7在长江流域有较高的精度,对59.85%流域面积的估算偏差在-10%~10%之间;实时产品RTV7在长江上游存在明显的高估现象,偏差大于50%的流域面积高达33.51%。(3)长江中下游RTV7和V7日降水数据与对应的实测数据相关系数都大于长江上游地区,偏差更小。(4)RTV7和V7降水产品在丰水期的估算精度整体优于枯水期。     

多源降水信息在秦淮河流域洪水模拟中的应用

目前天气雷达测雨与卫星遥感降水具有高时空分辨率与大面积的覆盖范围等特点,为洪水模拟预报提供了新的数据支持,但此类降水产品的预报能力差别较大,因此需对其进行精度评估。结合地面雨量站观测数据,在中纬度秦淮河下游流域定量评估S波段雷达测雨和全球高分辨率卫星CMORPH,Era-Interim,GPM和TRMM(3B42V7)降水数据的精度,并采用三水源新安江模型对选定的3场洪水过程进行了模拟。结果表明:在洪水过程径流模拟中,S波段雷达测雨数据与4种卫星降水产品均具有较好的径流模拟适用性;除雨量站外,精确度最高为S波段雷达和GPM,是当前评估中最好的降水产品,径流模拟精度达到0.92以上,且两种降水产品的趋势一致,其次是TRMM(3B42V7),Era-Interim,CMORPH卫星降水数据。研究成果可为天气雷达与常用卫星遥感降水数据在流域洪水模拟的水文预报应用提供参考与借鉴。     

Capability of TMPA products to simulate streamflow in upper Yellow and Yangtze River basins on Tibetan Plateau

Due to the high elevation, complex terrain, severe weather, and inaccessibility, direct meteorological observations do not exist over large portions of the Tibetan Plateau, especially the western part of it. Satellite rainfall estimates have been very important sources for precipitation information, particularly in rain gauge-sparse regions. In this study, Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） products 3B42, RTV5V6, and RTV7 were evaluated for their applicability to the upper Yellow and Yangtze River basins on the Tibetan Plateau. Moreover, the capability of the TMPA products to simulate streamflow was also investigated using the Variable Infiltration Capacity （VIC） semi-distributed hydrological model. Results show that 3B42 performs better than RTVSV6 and RTV7, based on verification of the China Meteorological Administration （CMA） observational precipitation data. RTVSV6 can roughly capture the spatial precipitation pattern but overestimation exists throughout the entire study region. The anticipated improvements of RTV7 relative to RTVSV6 have not been realized in this study. Our results suggest that RTV7 significantly overestimates the precipitation over the two river basins, though it can capture the seasonal cycle features of precipitation. 3B42 shows the best performance in streamflow simulation of the abovementioned satellite products. Although involved in gauge adjustment at a monthly scale, 3B42 is capable of daily streamflow simulation. RTV5V6 and RTV7 have no capability to simulate streamflow in the upper Yellow and Yangtze River basins.     

TRMM/ GPM卫星降水产品在淮河上游逐日和小时尺度的精度评估

基于淮河流域上游区(洪河口以上) 2014年4月-2015年12月的实测逐日和小时降水数据,采用综合评价指标评估了TRMM 3B42 v7和GPM IMERG卫星产品在逐日和小时尺度上的监测精度。结果表明:逐日尺度上,对于流域面平均降水和网格降水,GPM产品与实测降水的相关性略优于TRMM,相关系数为0. 87,误差略大于TRMM,但均控制在0. 8 mm/d以内;降水探测能力方面,GPM与实测降水的一致性较高,尤其表现在小雨和中雨降水事件上,可用于日尺度的水文模拟和水资源评价等研究。小时尺度上,TRMM对6场极端降水的监测能力比较稳定,略有低估(BIAS均值为-6%),GPM对不同的极端降水事件监测能力不一,可靠性相对较低,相对于TRMM卫星降水产品,GPM在对极端降水的监测能力方面还有待提高。     

Evaluation of latest TMPA and CMORPH satellite precipitation products over Yellow River Basin

The main objective of this study was to evaluate four latest global high-resolution satellite precipitation products(TMPA 3B42 RT, CMORPH,TMPA 3B42V7, and CMORPH_adj) against gauge observations of the Yellow River Basin from March 2000 to December 2012. The assessment was conducted with several commonly used statistical indices at daily and monthly scales. Results indicate that 3B42V7 and CMORPH_adj perform better than the near real-time products(3B42RT and CMORPH), particularly the 3B42V7 product. The adjustment by gauge data significantly reduces the systematic biases in the research products. Regarding the near real-time datasets, 3B42 RT overestimates rainfall over the whole basin, while CMORPH presents a mixed pattern with negative and positive values of relative bias in low- and high-latitude regions,respectively, and CMORPH performs better than 3B42 RT on the whole. According to the spatial distribution of statistical indices, these values are optimized in the southeast and decrease toward the northwest, and the trend is similar for the spatial distribution of the mean annual precipitation during the period from 2000 to 2012. This study also reveals that all the four products can effectively detect rainfall events. This study provides useful information about four mainstream satellite products in the Yellow River Basin, and the findings can facilitate the use of global precipitation measurement(GPM) data in the future.     

TRMM降雨数据在喀斯特地区的适用性分析——以贵州省为例

为验证TRMM(Tropical Rainfall Measurement Mission)降雨数据在喀斯特地区的适用性,以贵州省为研究区,利用贵州省19个气象台站1998-2015年的降水数据,在年尺度和月尺度上验证了TRMM卫星降水数据的精度,并在此基础上基于TRMM月降水数据分析了贵州省的降水时空分布特征。结果表明TRMM降水数据基本能反映降水的空间分布及演变过程,年尺度上TRMM降水数据与站点实测降水量相关系数R=0.817,斜率K=0.751,数据精度较高,数值上比站点实测降水量略高。月尺度上TRMM降水数据与站点实测降水量相关系数最高,达到0.927,斜率为0.9127,数值略高于站点实测降水量。分析表明:坡度对TRMM降水数据精度的影响大于高程和坡向,坡度小于10°的精度较高。总体而言,TRMM降水数据在喀斯特地区具有一定精度,但是降水量少或地形起伏大的地区精度相对较低。     

GPM 遥感降水产品在广东省的极端降水事件 适用性分析

在广东省研究新一代 GPM(Global?Precipitation?Measurement) 产品的精度及其探测极端降水事件的能力,探 讨其对地面站点观测数据的可替代性,可为 GPM 产品在中国南方湿润区的应用提供参考依据。以广东省的珠江 流域、韩江及粤东诸河流域、粤西沿海诸河流域为研究区,采用国家基准气象站观测的降水量为基准数据,使用 相关系数 R、平均绝对误差 EMA、均方根误差 ERMS、相对偏差 BIAS、探测率 POD、空报率 FAR和成功系数 CSI共 7 个 指标验证 GPM 遥感降水产品与?TRMM(Tropical?Rainfall?Measuring?Mission) 产品的精度;对 GPM 产品与 TRMM 产品在广东省的各个子流域的精度进行对比分析;使用 9 种广泛应用的极端降水指数来描述研究区域的极端降 水特征,对比分析 TRMM 产品与 GPM 产品探测极端降水事件的能力。研究结果表明：以地面实测降水为基准, GPM 与 TRMM 产品在广东省的平均 R 值分别为 0.57 与 0.49,BIAS值分别为 7.93% 与 9.13%,CSI值分别为 0.51 与 0.44,表明两种遥感降水产品均有一定的偏差;从整体上来看,相较 TRMM 而言,GPM 的精度更高;对比广东省的 不同子流域,GPM 产品与 TRMM 产品在珠江三角洲的 BIAS值分别仅为 2.28% 与 8.72%,表明两种遥感降水产品在 珠江三角洲流域的精度最高。在探测极端降水方面,GPM 产品对中雨、大雨和连续无雨日数都有更为准确的监 测。综合来看,GPM 新一代遥感降水产品精度较高、对极端降水探测能力强,更适用于广东省的洪水、旱情监测, 在广东省特别是珠江三角洲具有巨大的应用潜力。     

多卫星遥感降水产品在柬埔寨的应用比较分析

柬埔寨地区的水资源十分丰富,但由于气象、水文站点的稀缺以及水文气象数据的不连续等原因,导致流域基本水雨情及水资源特征数据不够完善、全面和准确,不利于该国水资源的科学管理和开发利用。一系列高时空分辨率的遥感降水产品的出现为降水数据的缺失和不连续提供了新的解决方法。选取了5种高精度的遥感降雨数据(CHIRPS、CMORPH_CRT、CMORRPH_BLD、MSWEP、TRMM)对柬埔寨地区2003~2015年降雨的时空分布差异、精度评价、极端降雨估计情况进行了对比分析。结果表明,5组遥感降雨产品总体均能较好地反映柬埔寨地区降雨的时间及空间变化规律。这对于柬埔寨及其它无资料地区的水资源研究及工程设计工作具有一定的指导作用。     

Evaluation of high-resolution satellite precipitation products with surface rain gauge observations from Laohahe Basin in northern China

Three high-resolution satellite precipitation products, the Tropical Rainfall Measuring Mission (TRMM) standard precipitation products 3B42V6 and 3B42RT and the Climate Precipitation Center's (CPC) morphing technique precipitation product (CMORPH), were evaluated against surface rain gauge observations from the Laohahe Basin in northern China. Widely used statistical validation indices and categorical statistics were adopted. The evaluations were performed at multiple time scales, ranging from daily to yearly, for the years from 2003 to 2008. The results show that all three satellite precipitation products perform very well in detecting the occurrence of precipitation events, but there are some different biases in the amount of precipitation. 3B42V6, which has a bias of 21%, fits best with the surface rain gauge observations at both daily and monthly scales, while the biases of 3B42RT and CMORPH, with values of 81% and 67%, respectively, are much higher than a normal receivable threshold. The quality of the satellite precipitation products also shows monthly and yearly variation: 3B42RT has a large positive bias in the cold season from September to April, while CMORPH has a large positive bias in the warm season from May to August, and they all attained their best values in 2006 (with 10%, 50%, and -5% biases for 3B42V6, 3B42RT, and CMORPH, respectively). Our evaluation shows that, for the Laohahe Basin, 3B42V6 has the best correspondence with the surface observations, and CMORPH performs much better than 3B42RT. The large errors of 3B42RT and CMORPH remind us of the need for new improvements to satellite precipitation retrieval algorithms or feasible bias adjusting methods.     

Reducing False Flood Warnings of TRMM Rain Rates Thresholds over Riyadh City,Saudi Arabia by Utilizing AMSR-E Soil Moisture Information

Rainfall rates and soil moisture content have been recognized as the most critical parameters in flood forecasts; the former known as forcing and the latter as the state variable. The main objective of this article is the incorporation of antecedent soil moisture information to reduce false flood warnings over Riyadh City, Saudi Arabia. The forcing variable was obtained from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) Real Time (RT) data (3B42RT). Soil moisture (SM) information was obtained from Advanced Microwave Scanning Radiometer (AMSR-E) as the state variable. Long time series SM information (2002–2011) provided Cumulative Distribution Function (CDF) of SM. CDF with 90% was taken as the SM threshold value. Flooding is indicated for rainy dates exceeding the rain thresholds with the previous satellite overpass SM being greater than 90% CDF of the respective month. The methodology removed the false flood warnings substantially when compared to the flood warnings where SM information was absent. The method is robust and simple, and it can be applied on TRMM and AMSR-E follow on missions; like Global Precipitation Measurement (GPM) and Soil Moisture Active Passive (SMAP).     

TRMM数据在京津冀地区干旱监测适用性研究

基于气象站点实测降水数据和热带降雨卫星(Tropical Rainfall Measurement Mission,TRMM)3B43 Version7(V7)降水产品,计算了京津冀地区1998-2017年多时间尺度标准化降水指数(standardized precipitation index,SPI)(SPI-1、SPI-3、SPI-6和SPI-12)。结果表明:TRMM 3B43数据与站点观测月和年降水数据在时空上具有良好的一致性;从时间变化趋势来看,基于TRMM 3B43数据和站点降水数据计算的不同时间尺度的SPI值存在高度一致性;从空间变化趋势来看,基于两种数据计算的京津冀地区25个站点多时间尺度SPI的相关系数均大于0.7,POD值大于0.6,80%以上的FAR值小于0.3,70%以上站点的FBI值在0.9~1.1之间;两种数据计算的干旱的面积百分比基本一致,1、3、6和12个月的干旱面积的CC值分别为0.93、0.95、0.96和0.96。     

The Falling Lake Victoria Water Level: GRACE,TRIMM and CHAMP Satellite Analysis of the Lake Basin

In the last 5 years, Lake Victoria water level has seen a dramatic fall that has caused alarm to water resource managers. Since the lake basin contributes about 20% of the lakes water in form of discharge, with 80% coming from direct rainfall, this study undertook a satellite analysis of the entire lake basin in an attempt to establish the cause of the decline. Gravity Recovery And Climate Experiment (GRACE), Tropical Rainfall Measuring Mission (TRMM) and CHAllenging Minisatellite Payload (CHAMP) satellites were employed in the analysis. Using 45 months of data spanning a period of 4 years (2002–2006), GRACE satellite data are used to analyse the variation of the geoid (equipotential surface approximating the mean sea level) triggered by variation in the stored waters within the lake basin. TRMM Level 3 monthly data for the same period of time are used to compute mean rainfall for a spatial coverage of .25°×.25° (25×25 km) and the rainfall trend over the same period analyzed. To assess the effect of evaporation, 59 CHAMP satellite’s occultation for the period 2001 to 2006 are analyzed for tropopause warming. GRACE results indicate an annual fall in the geoid by 1.574 mm/year during the study period 2002–2006. This fall clearly demonstrates the basin losing water over these period. TRMM results on the other hand indicate the rainfall over the basin (and directly over the lake) to have been stable during this period. The CHAMP satellite results indicate the tropopause temperature to have fallen in 2002 by about 3.9 K and increased by 2.2 K in 2003 and remained above the 189.5 K value of 2002. The tropopause heights have shown a steady increase from a height of 16.72 m in 2001 and has remained above this value reaching a maximum of 17.59 km in 2005, an increase in height by 0.87 m. Though the basin discharge contributes only 20%, its decline has contributed to the fall in the lake waters. Since rainfall over the period remained stable, and temperatures did not increase drastically to cause massive evaporation, the remaining major contributor is the discharge from the expanded Owen Falls dam.     

多卫星遥感降水数据在塔里木河流域的适用性分析

资料缺乏地区由于其复杂的地形,站点布设困难,实测资料匮乏,遥感降水产品是实测资料的有益补充及替代。以塔里木河流域的子流域开都-孔雀河流域为研究区,采用国家基准气象站观测的降水量为基准数据,评估了TRMM 3B42RT、TRMM 3B42V7、CMORPH RAW、CMORPH CRT等四种遥感降水产品的精度。同时,在塔里木河的子流域玉龙喀什河流域,基于SRM模型,评估了以上几种遥感降水产品模拟径流的适用性。结果表明,TRMM 3B42V7的精度最高,TRMM 3B42RT的精度较低,CMORPH在山区的精度也较高,而CMORPH在平原地区高估了降水量;在四种遥感降水产品中,TRMM 3B42V7最适于模拟径流,可以基本表征日径流变化过程。     

Spatial Pattern Characterization and Multivariate Hydrological Frequency Analysis of Extreme Precipitation in the Pearl River Basin, China

Consecutive extreme rainfall events, especially those having unfavourable spatio-temporal patterns, always trigger large floods. This paper aims to examine, through the multivariate hydrological frequency analysis, the probability of the synchronous occurrence of rainfall extremes in the Pearl River basin. The copula method together with the stationarity and independence tests, which are crucial to the valid use of statistical methods in regional frequency analyses, were applied in the study. The obtained results indicate that: (1) major precipitation events of the annual maximum 1-, 3-, 5- and 7-day rainfall recorded at 42 stations are the flat looking series and variables are independent, (2) the marginal distribution of all extreme rainfall variables in four homogeneous hydrologic regions fits the log-normal probability distribution and most of their joint distribution fits the Gumbel-Hougaard distribution, (3) on that basis the contour maps of the joint distribution of annual maximum 1-, 3-, 5- and 7-day rainfall between different regions are drawn and the probability of the synchronous occurrence of the extreme rainfalls in different regions are estimated. These findings have great practical value for the regional water resources and flood risk management and are important in exploration of the spatial patterns of rainfall extremes in the Pearl River basin in order to reveal the underlying linkages between precipitation and floods from a broader geographical perspective.     

A Robust Method to Update Local River Inundation Maps Using Global Climate Model Output and Weather Typing Based Statistical Downscaling

Global warming is changing the magnitude and frequency of extreme precipitation events. This requires updating local rainfall intensity-duration-frequency (IDF) curves and flood hazard maps according to the future climate scenarios. This is, however, far from straightforward, given our limited ability to model the effects of climate change on the temporal and spatial variability of rainfall at small scales. In this study, we develop a robust method to update local IDF relations for sub-daily rainfall extremes using Global Climate Model (GCM) data, and we apply it to a coastal town in NW Spain. First, the relationship between large-scale atmospheric circulation, described by means of Lamb Circulation Type classification (LCT), and rainfall events with potential for flood generation is analyzed. A broad ensemble set of GCM runs is used to identify frequency changes in LCTs, and to assess the occurrence of flood generating events in the future. In a parallel way, we use this Weather Type (WT) classification and climate-flood linkages to downscale rainfall from GCMs, and to determine the IDF curves for the future climate scenarios. A hydrological-hydraulic modeling chain is then used to quantify the changes in flood maps induced by the IDF changes. The results point to a future increase in rainfall intensity for all rainfall durations, which consequently results in an increased flood hazard in the urban area. While acknowledging the uncertainty in the GCM projections, the results show the need to update IDF standards and flood hazard maps to reflect potential changes in future extreme rainfall intensities.