Evaluation of IMERG, TMPA, ERA5, and CPC precipitation products over China's Mainland: Spatiotemporal patterns and extremes

A comprehensive assessment of representative satellite-retrieved(Integrated Multi-satellite Retrievals for Global Precipitation Measurement(IMERG)and Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis(TMPA)),reanalysis-based(fifth generation of atmospheric reanalysis by the European Centre for Medium Range Weather Forecasts(ERA5)),and gauge-estimated(Climate Prediction Center(CPC))precipitation products was conducted using the data from 807 meteorological stations across China's Mainland from 2001 to 2017.Error statistical metrics,precipitation distribution functions,and extreme precipitation indices were used to evaluate the quality of the four precipitation products in terms of multi-timescale accuracy and extreme precipitation estimation.When the timescale increased from daily to seasonal scales,the accuracy of the four precipitation products first increased and then decreased,and all products performed best on the monthly timescale.Their accuracy ranking in descending order was CPC,IMERG,TMPA,and ERA5 on the daily timescale and IMERG,CPC,TMPA,and ERA5 on the monthly and seasonal timescales.IMERG was generally superior to its predecessor TMPA on the three timescales.ERA5 exhibited large statistical errors.CPC provided stable estimated values.For extreme precipitation estimation,the quality of IMERG was relatively consistent with that of TMPA in terms of precipitation distribution and extreme metrics,and IMERG exhibited a significant advantage in estimating moderate and heavy precipitation.In contrast,ERA5 and CPC exhibited poor performance with large systematic underestimation biases.The findings of this study provide insight into the performance of the latest IMERG product compared with the widely used TMPA,ERA5,and CPC datasets,and points to possible directions for improvement of multi-source precipitation data fusion algorithms in order to better serve hydrological applications.

TMPA卫星降水数据质量评估及水文过程模拟

卫星降水资料在测站分布稀疏的复杂地形区域具有较大的优越性,但卫星与测站获取降水原理不同,需对卫星资料的可用性进行评估。以赣江上游为例,根据雨量站实测降水数据评估热带降雨观测计划(TRMM)多卫星分析降水数据资料(TMPA)的精度,并将该降水数据作为陆面水文模式Noah-LSM的输入,以评估TMPA降水数据在流域水文过程模拟的适用性。结果表明,TMPA日降水数据精度虽偏低,但在我国南方降水资料匮乏地区的水文过程模拟研究中具有一定的应用前景,TMPA月降水数据精度较高,可为无资料地区水资源计算和规划提供数据支持。

TMPA卫星遥感降水数据产品在中国大陆的干旱效用评估

为评估基于卫星遥感的高时空分辨率降水数据产品在干旱研究中的应用能力,该研究以标准化降水指数(standardized precipitation index,SPI)和标准化降水蒸散指数(standardized precipitation evapotranspiration index,SPEI)为例,以站点实测降水数据产品作为参考,评估了热带降水测量计划——多卫星降水分析(tropical rainfall measurement mission(TRMM)multi-satellite precipitation analysis,TMPA)3B42V7产品在中国大陆范围内1998-2015年间的干旱效用。结果表明:1)基于3B42V7计算的干旱指数总体上具有较高的精度,在中国东部大部分地区与基于降水实测数据的干旱指数相关系数均在0.8以上;2)基于西南和华北2个典型干旱发生地区的干旱时空变异评估结果表明,3B42V7能较为准确地反映干旱事件的发展过程和强度并能较好地捕捉干旱事件的空间模式,并且在大多数情况下单纯基于3B42V7数据计算的SPI指数即可满足干旱监测的要求;3)干旱事件识别能力评估结果表明,3B42V7产品能够较准确地识别和定位1998年以来的大范围干旱。TMPA产品能从时间和空间上刻画出中国大陆干旱的演变规律,适用于大尺度气象干旱的监测与评估。

三峡区间TMPA和IMERG卫星降水产品精度评估

为了验证卫星降水产品对地面站点降水观测数据的可替代性,研究利用地面站点观测数据,采用统计分析方法,对三峡区间流域TMPA3B43V7、GPMIMERG卫星降水产品进行月尺度下的精度评估。结果表明:2种卫星降水产品表现出较好的一致性;在流域上游地势平坦区域纬度较低,卫星降水产品精度相对较差;在流域下游高山峡谷地形纬度较高,卫星降水产品精度较好;卫星降水产品具有替代地面站点降水观测数据的潜力,在三峡区间流域具有一定的适用性。研究成果可为应用卫星降水产品进行三峡区间流域水文模拟、降水趋势分析等奠定基础。

IMERG及TMPA降水卫星产品在红河流域的适用性评估

为明确最新的IMERG降水数据产品性能与上一代的TMPA系列降水数据产品性能的优劣,基于红河流域12个气象站点,考虑降水探测能力(P_(POD)、F_(FAR)、C_(CSI))、相关性(C_(CC))、误差情况(R_(NMSE)、R_(RB)),对IMERG及TMPA降水卫星产品进行适用性评估。结果表明,在进行评估时放大时空尺度,会平滑卫星数据和地面数据之间的误差,从而得到更好的相关性;IMERG与TMPA在探测微弱降水(0.1~1.0 mm/d)方面的精度较差,与地面观测降水偏差程度大;IMERG与TMPA在雨季(6~10月)的性能表现要好于旱季(11月~次年5月);地面站点的校正提高了卫星降水产品探测的识别率和成功率,但同时也增加了误报的几率;三种IMERG产品的评估中,IMERG-F的性能表现最佳;在IMERG V06与TMPA 3B42的评估中,IMERG V06的性能优于TMPA 3B42。

气候校正算法对TMPA 3B42 V7产品精度的影响分析

遥感降水数据是区域降水研究的重要数据源,尤其在无实测资料区域,可改善对降水格局的认识。然而,广泛使用的TMPA 3B42数据受校正数据空间范围的限制,其最新的气候校正算法在中高纬度地区无法有效实施,造成较大的不确定与误差存在于该区域的TMPA数据中。选取两个气候和地形条件相似的区域,分别位于TRMM卫星观测范围(南北纬38°)内外区域。基于1998-2012年期间多个气象站点的实测降水数据,采用四个统计指标,对比两个区域的数据精度差异与相似性,进而揭示气候校正算法对TMPA降水数据的影响。结果表明年、月、日尺度的TMPA数据在两个地区都高估降水量,尤其对0~10 mm的降水高估较为严重。气候校正算法虽无法消除此高估,但一定程度上削弱了高估程度,辽宁地区的高估程度显著高于山东(2.79%),达到8.87%。从降水变化过程看,TMPA可重现区域的年月降水过程,与实测降水的变化趋势一致。但值得注意的是,冬季期间TMPA数据精度在两个地区都不理想且年变化波动较大。气候校正算法在山东地区的应用,使得该区域两种降水数据集的相关性有所改善,也减弱了TMPA对降水量的高估程度。

IMERG和TMPA降水产品在夏季中国中东部的检验

基于500个国家站雨量计的观测,从时空分布、不同地形条件、不同等级的降水强度及日变化角度,对比评估了2014-2016年夏季多星集成降水产品TMPA和IMERG在中国中东部的适用性。研究结果表明,与雨量计相比.TMPA和IMERG降水产品能较好地反映夏季中国中东部逐日降水量的变化规律,IMERG的平均误差更小。IMERG降水产品的日平均降水量与雨量计的相关性更高,相关系数超过0.9,而TMPA仅为0.8。在中国中东部的平原和山区,IMERG降水产品对弱降水(<4 mm·d-1)强度和弱降水频次的表征能力,较TMPA降水产品有明显的改善;但IMERG降水产品对山区的强降水频次的探测较TMPA降水产品改进有限。从日变化来看,TMPA降水产品明显低估早晨的降水强度和降水频次,且高估了午后的降水强度和降水频次。IMERG降水产品作为高时空分辨率的准全球降水资料,在中国中东部有较高的精度,未来可应用于气象和水文模式中。

三峡区间流域TMPA 3B43V7卫星降水产品多时空尺度精度评估

卫星降水产品属于间接估测降水,需要进行精度评估、适用性分析才能使用。利用地面站点观测数据评估了三峡区间流域TMPA 3B43V7卫星降水产品的年、月时间尺度及格点、流域空间尺度下的精度。结果表明,TMPA 3B43V7降水产品在月尺度上精度较高,在年尺度上数据精度稍差,但具有应用在降水变化特征分析、流域水文过程模拟等领域的潜力。

中国大陆TMPA降水产品气候态的评估

利用逐日全国降水分析产品,对2012年12月下旬发布的最新版本的TRMM等多源卫星降水估算产品(TMPA)进行评估,评估时间从2008年9月到2012年8月。从评估结果来看,研究产品3B42V7产品与CPAP产品具有高的相关性,两者的相关系数达到了0.94,相对误差在—0.11%左右,标准偏差约为0.53 mm·d^(-1)。实时产品3B42RT产品与CPAP产品的相关性相对较差,相关系数为0.75,相对误差也上升到了39.3%,标准偏差为1.25 mm·d^(-1)。3B42RT产品在我国西部高估了降水,全年的相对误差为116.60%(春夏秋冬四季分别为104.52%、105.73%、117.64%和326.60%);3B42V7产品的相对误差仅为0.82%(春夏秋冬四季分别为2.25%、1.24%、—5.27%和—24.64%)。

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.

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.

用TMPA88系列实现YUV信号的简易方案

利用TOSHIBA公司的电视解码芯片TMPA88系列实现YUV信号的设计原理,并用于将隔行扫描变为逐行扫描等数字处理。给出了设计的输入输出测试波形。

Drought monitoring and reliability evaluation of the latest TMPA precipitation data in the Weihe River Basin, Northwest China

The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing the latest Version-7 TRMM Multi-satellite Precipitation Analysis （TMPA 3B42V7） data for drought condition monitoring in the Weihe River Basin （0.135×10^6 km2）. The accuracy of the monthly TMPA 3B42V7 satellite precipitation data was firstly evaluated against the ground rain gauge observations. The statistical characteristics between a short period data series （1998-2013） and a long period data series （1961-2013） were then compared. The TMPA 3B42V7-based SPI （Standardized Precipitation Index） sequences were finally validated and analyzed at various temporal scales for assessing the drought conditions. The results indicate that the monthly TMPA 3B42V7 precipitation is in a high agreement with the rain gauge observations and can accurately capture the temporal and spatial characteristics of rainfall within the Weihe River Basin. The short period data can present the characteristics of long period record, and it is thus acceptable to use the short period data series to estimate the cumulative probability function in the SPI calculation. The TMPA 3B42V7-based SPI matches well with that based on the rain gauge observations at multiple time scales （i.e., 1-, 3-, 6-, 9-, and 12-month） and can give an acceptable temporal distribution of drought conditions. It suggests that the TMPA 3B42V7 precipitation data can be used for monitoring the occurrence of drought in the Weihe River Basin.

COMPARISON OF PERSIANN AND TMPA DAILY PRECIPITATION ESTIMATES OVER HUNAN PROVINCE OF CHINA

This study presented a detailed comparison of daily precipitation estimates from Precipitation Estimation from Remote Sensing Information using Artificial Neural Network(PERSIANN) and Tropical Rainfall Measuring Mission(TRMM) Multi-satellite Precipitation Analysis(TMPA) over Hunan province of China from 1998 to 2014. The ground gauge observations are taken as the reference. It is found that overall TMPA clearly outperforms PERSIANN, indicating by better statistical metrics(including correlation coefficient, root mean square error and relative bias). For the geospatial pattern, although both products are able to capture the major precipitation features(e.g., precipitation geospatial homogeneity) in Hunan, yet PERSIANN largely underestimates the precipitation intensity throughout all seasons. In contrast, there is no clear bias tendency from TMPA estimates. Precipitation intensity analysis showed that both the occurrence and amount histograms from TMPA are closer to the gauge observations from spring to autumn.However, in the winter season PERSIANN is closer to gauge observation, which is likely due to the ground contamination from the passive microwave sensors used by TMPA.

长虹(TMPA88XX)超级单片彩电原理与维修(三)

(接第上期) 由色带通滤波器所提取的色度信号在I2C总线控制下完成色度放大、自动彩色制式识别后,色度信号一路送入R-Y、B-Y同步解调器,在彩色副载波(FSC)的配合下,解调出R-Y、B-Y色差信号,另一路则送入色同步选通电路,在选通脉冲的控制下分离出色同步信号.

长虹TMPA88XX超级单片彩电原理与维修（1）

继长虹飞利浦超级单片彩电推出之后，长虹公司又引进日本东芝公司开发的TMPA88XX系列电视芯片，如TMPA8801、TMPA8803、TMPA8823、TMPA8827、TMPA8829(其中，TMPA8827具有SECAM解调功能)等，开发出新一代超级单片机心，该机心被长虹公司命名为CN-18机心。为了适应长虹品牌需要，经对TMPA88XX芯片作掩膜处理后，便派生出了CH08T06XX系列芯片，包括CH08T0601、CH08T0602、CH08T0604、CH08T0605、CH08T0608等，

长虹TMPA88XX超级单片彩电原理与维修（2）

微控制系统 一、微控制系统电路分析 SF2170E彩电微控制系统由N201①～⑩、54～64脚内外部电路组成，如图2所示。该控制系统各主要引脚功能如下：①②脚：高频头频段切换控制端。全自动搜索过程中由①②脚输出组合电平，加到高频头U101的VL、VH端，实现L、H、U段供电的切换。其逻辑切换表见表2。