## 1 Introduction  
Typhoon Morakot in Taiwan in August 2009 [1; 2; 3], severe floods in Pakistan in 2010 [4] and in Beijing in July 2012 [5; 6], and Hurricane Sandy [7] in northeast U.S. in October 2012 have shown that the precipitation system tends to develop into heavier storms with a longer dry period between two precipitation events [8]. On 21 July 2012, a 60-year return period extreme storm hit Beijing and adjacent regions, triggering flash floods in the urban area and landslides in the mountainous region. The storm led to 79 deaths and direct damages worth US $1.86 billion. The storm-triggered flood affected areas of 16,000 km\({}^{2}\) and concerned more than 1.6 million people, inundated many infrastructures like roads with trapped cars and buses, bridges, and collapsed buildings in the deep water [9; 10]. This extreme event was attributed to a frontal system and mid-tropospheric disturbance [6], and it was generated by a linear-shaped mesoscale convective system (MCS) [9]. [PERSON] and [PERSON] [5] pointed out that the topographic effect and the natural climate factors in a changing climate system could also be responsible for the intensive precipitation in the storm. In addition, a low standard had been applied to control the mountain torrents for small and medium rivers in the flooding region. This was another factor for the occurrence of the flooding disaster [5]. Satellite-based precipitation estimation has witnessed significant developments in recent years. High resolution satellite rainfall products emerged in succession, e.g., hourly 0.04\({}^{\circ}\) spatial resolution infrared (IR)-dominated Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks [11] and later PERSIANN-Cloud Classification System (PERSIANN-CSS) [12], passive-microwave (PWM)-dominated 30-min 8 km National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center (CPC) morphing technique (CMORPH) [13], 3-hourly 0.25\({}^{\circ}\) Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) based on the incorporation of IR- and PWM-based techniques [14]. The latest V7 TMPA products were released in May 2012. The new version of a gauge-adjusted post-real-time TRMM product (covering the period of 1998-present), 3B42V7, became available in late July 2012. The real time product 3B42 RT of V7 (covering the period of 1998-present) was also available in October 2012. The accurate measurement of precipitation would greatly benefit the detection and warning of severe storms, flash flooding and landslides [1, 15]. Therefore, it is a key task for NASA's missions to improve the satellite's performance in measuring precipitation in order to advance our understanding of Earth's water and energy cycle and improve the forecast of extreme events that cause natural hazards and disasters [16, 17, 18]. The comprehensive evaluation of satellite-based precipitation products is much desired by the satellite community. As for the latest TMPA products, related studies are still few, especially during extreme events. [PERSON], _et al_. [19] conducted a systematic study on the spatial error distribution of the V6 and V7 TMPA products over Continental United States (CONUS). In addition, [PERSON], _et al_. [20] conducted a systematic study on the similarity and difference of the two successive V6 and V7 TMPA products over China. Since TMPA provides rainfall estimation in a quasi-global coverage, it is helpful for NASA's algorithm developers to know TMPA's performance in other places of the world. Particularly, to the best of our knowledge, few efforts have been reported in evaluating V7 TMPA products for any extreme precipitation event. The primary objective of this study is to evaluate the latest TMPA products with a relatively dense rain gauge network in Beijing and adjacent regions for the extreme precipitation event on 21 July 2012 (from 00:00 UTC 21 July 2012 to 00:00 UTC 22 July 2012).