Impact of Long-Term Observation on the Sampling Characteristics of TRMM PR Precipitation

Abstract

Observations of the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR) over 16 yr yielded hundreds of large precipitation systems (≥100 km) for each 0.1° grid over major rainy regions. More than 90% of the rainfall was attributed to large systems over certain midlatitude regions such as La Plata basin and the East China Sea. The accumulation of high-impact snapshots reduced the significant spatial fluctuation of the rain fraction arising from large systems and allowed the obtaining of sharp images of the geographic rainfall pattern. Widespread systems were undetected over low-rainfall areas such as regions off Peru. Conversely, infrequent large systems brought a significant percentage of rainfall over semiarid tropics such as the Sahel. This demonstrated an increased need for regional sampling of extreme phenomena. Differences in data collected over a period of 16 yr were used to examine sampling adequacy. The results indicated that more than 10% of the 0.1°-scale sampling error accounted for half of the TRMM domain even for a 10-yr data accumulation period. Rainfall at the 0.1° scale was negatively biased in the first few years for over more than half of the areas because of a lack of high-impact samples. The areal fraction of the 0.1°-scale climatology with a 50% accuracy exceeded 95% in the ninth year and in the fifth year for those areas with rainfall >2 mm day−1. A monotonic increase in the degree of similarity of finescale rainfall to the best estimate with an accuracy of 10% illustrated the need for further sampling.

Vertical gradient of stratiform radar reflectivity below the bright band from the Tropics to the extratropical latitudes seen by GPM

“…Finally, one limitation of this study is that we used only the two and a half years of data from the GPM Ku radar. To obtain the regional characteristics more clearly, the long-term mean at high resolution is necessary, as shown by Hirose et al (2008;2017a;2017b) for precipitation climatologies generated from the TRMM PR. Another limitation is that we examine only those profiles where a bright band is detected and that are classified as stratiform, excluding stratiform precipitation profiles without a bright band under cold environments.…”

Large-Scale Environmental Conditions Related to Midsummer Extreme Rainfall Events around Japan in the TRMM Region

“…Figure 1 shows the locations of extreme events determined in this study. Note that the numbers of extreme events have latitudinal dependence due to the orbital characteristics of TRMM PR, where the number of PR footprints has a sharp peak at around 348N and 348S (Hirose et al 2017, their Fig. 1).…”

A 0.01° Resolving TRMM PR Precipitation Climatology

“…Unlike other sensors, the Precipitation Radar (PR) on the Tropical Rainfall Measuring Mission (TRMM) satellite directly observed precipitation echoes in various regions over a period of more than 16 yr (Hirose et al 2017b). The long-term operation of the PR was realized using an orbit boost, maintaining the orbital altitude using fuel intended for a controlled reentry, and switching between primary and redundant systems (NASA 2007).…”

“…Several studies have utilized a 0.18 grid spacing to ensure sampling sufficiency. Hirose et al (2017b) demonstrated that TRMM PR has advantages in the detection of orographic and coastal rainfall at the 0.18 scale. Even though these footprintscale gridded data provide the highest-resolution rainfall information of global estimates, comparative studies with regional observations highlight the need for even finerscale datasets to better understand local phenomena and improve the nonuniformity of the data (e.g., Zhang et al 2004;Kirstetter et al 2013;Heymsfield et al 2000).…”