# NASA Global Satellite and Model Data Products and Services for Tropical Meteorology and Climatology
## 2 Satellite Missions, Projects and Data
### Gpm  
As the TRMM follow-on mission, the GPM mission [15; 16; 17; 18] was launched in February 2014, extending the spatial coverage of TRMM measurements from 40\({}^{\circ}\) N-S to 70\({}^{\circ}\) N-S. In addition to the aforementioned scientific goals in TRMM, the GPM mission is designed to improve measurements of both light rain and falling snow which have been the existing challenges in satellite-based precipitation estimates. A new frequency (Ka-band) band is added to the Dual-frequency Precipitation Radar (DPR) to improve light rain measurement in addition to the Ku-band radar (Table 2) that existed on TRMM. The frequency channels in the GPM Microwave Imager (GMI) have been expanded to include several high frequencies for improving falling snow estimates in high latitudes. GPM also serves as a core observatory satellite in the GPM satellite constellation for inter-satellite sensor calibration (e.g., the inter-calibrated passive microwave (PMW) brightness temperatures), which is crucial for developing integrated multi-satellite retrieval products such as the Integrated Multi-satellite Retrievals for GPM (IMERG) [28; 29]. The GPM launch schedule was made to ensure there would be an overlapping period, especially with TRMM for inter-satellite calibration and consistency in datasets, which is imperative for validating and deriving climatological datasets. The IMERG precipitation product suite consists of datasets in three categories, the Early Run (latency: \(\sim\)4 h), the Late Run (latency: \(\sim\)12-14 h), and the Final Run (latency: \(\sim\)3.5 months). Compared to TMPA, both spatial and temporal resolutions of IMERG have been significantly improved from 0.25 deg. \(\times\) 0.25 deg. to 0.1 deg. \(\times\) 0.1 deg. and from 3-hourly to half-hourly, respectively. The Early Run can be used in supporting near-real-time operations or research such as flood forecast. The Late Run, with more observations available for improving precipitation estimates, can be used in applications such as monitoring crop conditions. The Final Run, which is research-grade with improvements in quality control such as incorporating rain gauge data at the Global Precipitation Climatology Centre (GPCC) [30] for bias correction, is suitable for research. IMERG also provides over two decades of global precipitation data for various studies including the development of baseline precipitation products, seasonal to inter-annual studies, and more. The production of TMPA ended in December 2019, but data are still available at GES DISC for various purposes, but users are encouraged to use the much-improved TMPA successor product suite, IMERG. NOAA National Center for Environmental Prediction (NCEP))/Climate Prediction Center (CPC) Merged IR Project  
The 4 km, pixel-resolution, half-hourly global (60\({}^{\circ}\) N-S) IR brightness temperature dataset is generated by NOAA NCEP CPC [31]. Data from several domestic and international geostationary satellites (NOAA GOES-8/10, EUMETSAT Meteosat-8/5 and JMA-JAXA GMS) are merged into this dataset. The dataset is used to derive global IR-based precipitation estimates which are used in NOAA operations [32]. Since the TRMM era, the merged IR dataset has been a part of the multi-satellite precipitation estimates. In the GPM era, the IR-based precipitation estimates continue to be merged into the IMERG product suite [28; 29]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Description** & \\ \cline{2-4}
**Instrument Name** & **Band** & & \\  & **Frequencies/Wavelengths** & & \\ \hline GPM Microwave Imager (GMI) & 13 frequencies (10–183 GHz) & 5.1 km at 85.5 GHz & 885 km \\ \hline Dual-frequency Precipitation & 13.8 GHz (KuPR), 33.5 GHz & 5 km. Vertical: 250 m & 245 km (KuPR), \\ Radar (DPR) & (KaPR) & (KuPR); 250 m/500 m (KaPR) & 120 km (KaPR) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Global Precipitation Measurement (GPM) instruments. The IR dataset can be used in weather studies and model development including constraint and verification.