# NASA Global Satellite and Model Data Products and Services for Tropical Meteorology and Climatology
## 2 Satellite Missions, Projects and Data
### Datasets for Tropical Meteorology and Climatology  
NASA Earth science datasets are categorized into four levels [39]: (1) Level-0 datasets are reconstructed, unprocessed instrument and payload data at full resolution, with the removal of any and all communications artifacts, e.g., synchronization frames, communications headers, and duplicate data; Level-1 datasets are reconstructed, unprocessed instrument data at full resolution, time-referenced, and annotated with ancillary information; (2) Level-2 datasets are derived geophysical variables at the same resolution and location as Level-1 source data; (3) Level-3 datasets consist of variables mapped on uniform space-time grid scales, usually with some completeness and consistency; and (4) Level-4 are the model output or results from the analyses of lower-level data (e.g., variables derived from multiple measurements). Datasets addressed in this article mainly consist of Levels 2-4. Table 3 lists the datasets from major satellite missions and projects described above for tropical meteorology. First, Level-2 orbital precipitation datasets from TRMM and GPM missions are listed, including instantaneous surface and profile precipitation from the radars (TRMM PR and GPM DPR) and passive microwave imagers (TMI and GMI) as well as their combined datasets (PR and TMI, DPR and GMI). These datasets offer the sensor's spatial resolutions and are suitable for case studies, ground validation activity, and more. The merged precipitation suite, IMERG, that is the successor of TMPA, is popular in many areas of research and applications. The NCEP CPC merged IR dataset (Table 3) is normally used for tracking system movement and development due to its high spatial and temporal resolutions. Others important datasets include 2D and 3D winds, sea surface temperature, sea-level pressure, air temperature and humidity from MERRA-2 and AIRS. The North American Land Data Assimilation System (NLDAS) and MERRA-2 provide soil moisture and surface runoff datasets over land. Aerosols, ozone and other trace gases are from OMI, SeaWiFS, and MERRA-2 (Table 3). Climatological datasets can be derived from these datasets as well and examples are given in the next section, but cautions are needed in data processing for the use of climatology for several reasons. First, for some satellite missions, their life spans are short, in terms of the World Meteorological Organization (WMO) 30 year definition for climatology [40]. A dataset collection may contain several missions such as TMPA, IMERG. Evaluation and corrections are typically needed for ensuring satellite sensor consistency in the same mission and/or the follow-up missions. For multi-satellite datasets, cross-satellite and cross-sensor calibrations are needed to minimize the systematic differences from different satellites and sensors. Furthermore, bias correction with ground truth or observations is a common practice in precipitation algorithms which produce products such as TMPA and IMERG. Beginning with TRMM Version 8, the GPM algorithms are used in reprocessing. As a result, TRMM and its constellation data have become part of the GPM dataset family. Major changes include the TRMM data format and the file naming conventions, both of which are now consistent with those of GPM. The datasets format is HDF5. The datasets described above are primarily archived and distributed at GES DISC with emphasis on water and energy cycles. Satellite, airborne and in situ datasets are also available at other NASA Earth Science data centers or universities for tropical meteorology and climatology. The NASA A-Train program consists of a set of eight coordinated satellites (Aqua, Aura, PARASOL, CLIPSO, CloudSat, GCOM-W1, OCO-2 and Glory) [41]. The NASA Physical Oceanography Distributed Active Archive Center (PODAAC) archives ocean winds, salinity, ocean temperature and more [42].