This algorithm is intended to intercalibrate, merge, and interpolate “all” satellite microwave precipitation estimates, together with microwave-calibrated infrared (IR) satellite estimates, precipitation gauge analyses, and potentially other precipitation estimators at fine time and space scales for the TRMM and GPM eras over the entire globe. The system is run several times for each observation time, first giving a quick estimate and successively providing better estimates as more data arrive. The final step uses monthly gauge data to create research-level products.

Documentation:

• IMERG Technical Documentation
• IMERG Algorithm Theoretical Basis Document (ATBD)
• IMERG Day 1 Early Run Release Notes
• IMERG Day 1 Final Run Release Notes
• IMERG Day 1 Late Run Release Notes
• IMERG GIS TIFF + Wordfile Documentation
• Transitioning from TMPA (3B42x) to IMERG and Dataset Comparison

Resolution	Regions - Dates	Latency	Format	Source	DL
0.1° - 30 minute	Gridded, 60°N-60°S, March 2015 to present	6 hours (NRT / early run)	HDF5 NRT: FTP (PPS)* GIS TIFF + Wordfile NRT: FTP (PPS)* Giovanni Giovanni HDF5 OpenDAP HDF5 Mirador NETCDF Simple Subset Wizard
0.1° - 30 minute	Gridded, 60°N-60°S, March 2015 to present	18 hours (NRT / late run)	HDF5 NRT: FTP (PPS)* GIS TIFF + Wordfile NRT: FTP (PPS)* Giovanni Giovanni HDF5 OpenDAP HDF5 Mirador NETCDF Simple Subset Wizard
0.1° - 30 minute	Gridded, 60°N-60°S, March 2014 to present	4 months (Prod / final run)	HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/imerg/) GIS TIFF + Wordfile Prod: FTP (PPS)* (/YYYY/MM/DD/gis/) HDF5 Prod: STORM HDF5 Mirador Giovanni Giovanni NETCDF Simple Subset Wizard
0.1° - 3 Hours	Gridded, 60°N-60°S, April 2015 to present	6 hours (NRT / Early Run)	GIS TIFF + Wordfile NRT: FTP (PPS)*
0.1° - 3 Hours	Gridded, 60°N-60°S, April 2015 to present	18 hours (NRT / Late Run)	GIS TIFF + Wordfile NRT: FTP (PPS)*
0.1° - 1 Day	Gridded, 60°N-60°S, April 2015 to present	6 hours (NRT / early run)	GIS TIFF + Wordfile NRT: FTP (PPS)* GIS TIFF + Wordfile NRT: FTP (PPS)* NetCDF GES DISC
0.1° - 1 Day	Gridded, 60°N-60°S, April 2015 to present	18 hours (NRT / late run)	GIS TIFF + Wordfile NRT: FTP (PPS)* NetCDF GES DISC
0.1° - 1 Day	Gridded, 60°N-60°S, April 2015 to present	4 Months (research / final run)	NETCDF OpenDAP NetCDF GES DISC
0.1° - 3 Day	Gridded, 60°N-60°S, April 2015 to present	18 hours (NRT / late run)	GIS TIFF + Wordfile NRT: FTP (PPS)*
0.1° - 7 Day	Gridded, 60°N-60°S, April 2015 to present	18 hours (NRT / late run)	GIS TIFF + Wordfile NRT: FTP (PPS)*
0.1° - Monthly	Gridded, 60°N-60°S, March 2014 to present	4 months (Prod / final run)	HDF5 Prod: FTP (PPS)* (monthly data files are in the folder corresponding to the first day of each month) HDF5 Mirador Giovanni Giovanni NETCDF Simple Subset Wizard
IMERG Derived Imagery
			Video (mp4) Past 7 Days IMERG Late/Early Run Global Precip. Animation (SVS) In-browser 3D viewer Latest 0.5 hr, 24 hr, 7 day IMERG global precip. data.

3CMB, 'Combined precipitation', computes statistics of the Combined measurements at both a low horizontal resolution (G1, 5 degree x 5 degree latitude/longitude) and a high horizontal resolution (G2, 0.25 degree x 0.25 degree latitude/longitude). There will be both a monthly product and a daily product. Full Documentation

Resolution	Regions - Dates	Latency	Format	Source	DL
0.25°, daily	Gridded, 70°N-70°S, March 2014 to present	Daily (Prod)	HDF5 Prod: FTP (PPS) * Gridded ASCII Prod: FTP (PPS)* (/YYYY/MM/DD/textgrid) HDF5 Prod: STORM HDF5 Mirador
5°, daily	Gridded, 70°N-70°S, March 2014 to present	Daily (Prod)	HDF5 Prod: FTP (PPS) * HDF5 Prod: STORM HDF5 Mirador
.25°, monthly	Gridded, 70°N-70°S, March 2014 to present	Monthly (Prod)	HDF5 Prod: FTP (PPS) * HDF5 Prod: STORM HDF5 Mirador
5°, monthly	Gridded, 70°N-70°S, March 2014 to present	Monthly (Prod)	HDF5 Prod: FTP (PPS) * HDF5 Prod: STORM HDF5 Mirador

3DPR, 'DPR Full Product', computes statistics of the DPR measurements at both a low horizontal resolution (G1, 5 degree x 5 degree latitude/longitude) and a high horizontal resolution (G2, 0.25 degree x 0.25 degree latitude/longitude). The product can be monthly or daily. Full Documentation

Resolution	Regions - Dates	Latency	Format	Source	DL
0.25°, daily	Gridded, 67°N-67°S, March 2014 to present	Daily (Prod)	HDF5 Prod: FTP (PPS)*
5°, daily	Gridded, 70°N-70°S, March 2014 to present	Daily (Prod)	HDF5+PNG Prod: STORM
0.25°, monthly	Gridded, 67°N-67°S, March 2014 to present	Monthly (Prod)	HDF5 Mirador Giovanni Giovanni TOVAS NetCDF Simple Subset Wizard   OPeNDAP OPeNDAP   GDS GrADS Data Server (GDS)
5°, daily	Gridded, 70°N-70°S, March 2014 to present	Monthly (Prod)	HDF5 Prod: FTP (GES DISC)

3GPROF, 'GPROF Profiling', produces global 0.25 degree x 0.25 degree gridded means using Level 2 Gprof data. Vertical hydrometeor profiles and surface rainfall means are computed. Various pixel counts are also reported. The PI is Joyce Chou. The product can be monthly or daily.

Documentation:

• 3GPROF File Specification
• GPROF Caveats

Resolution	Regions - Dates	Latency	Format	Source	DL
0.25°, daily	Gridded, 90°N-90°S, March 2014 to present	daily (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/GPROF) Gridded ASCII Prod: FTP (PPS)* (/YYYY/MM/DD/textgrid) HDF5 Mirador Giovanni Giovanni TOVAS NetCDF Simple Subset Wizard   OPeNDAP OPeNDAP   GDS GrADS Data Server (GDS)
0.25°, monthly	Gridded, 90°N-90°S, March 2014 to present	Monthly (Prod)	HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/3A-MO.*.HDF5) HDF5 Prod: STORM

The GPM Combined Radar-Radiometer Algorithm performs two basic functions: first, it provides, in principle, the most accurate, high resolution estimates of surface rainfall rate and precipitation vertical distributions that can be achieved from a spaceborne platform, and it is therefore valuable for applications where information regarding instantaneous storm structure are vital. Second, a global, representative collection of combined algorithm estimates will yield a single common reference dataset that can be used to “cross-calibrate” rain rate estimates from all of the passive microwave radiometers in the GPM constellation. The cross-calibration of radiometer estimates is crucial for developing a consistent, high time-resolution precipitation record for climate science and prediction model validation applications.

Documentation:

• GPM Combined Radar-Radiometer Precipitation Algorithm Theoretical Basis Document
• CMB Level 2 Caveats

Resolution	Region - Dates	Latency	Format	Source	DL
5km	orbital, Past 2 weeks (NRT)	3 hours (RT); 40 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The objective of the level 2 DPR algorithms is to generate from the level 1 DPR products radar-only derived meteorological quantities on an instantaneous FOV (field of view) basis. A subset of the results will be used by the level 2 combined radar-radiometer algorithm and the level 3 combined and radar-only products. The general idea behind the algorithms is to determine general characteristics of the precipitation, correct for attenuation and estimate profiles of the precipitation water content, rainfall rate and, when dual-wavelength data are available, information on the particle size distributions in rain and snow. It is particularly important that dual-wavelength data will provide better estimates of rainfall and snowfall rates than the TRMM PR data by using the particle size information and the capability of estimating, even in convective storms, the height at which the precipitation transitions from solid to liquid. 

Documentation:

• DPR Level-2 Algorithm Theoretical Basis Document
• Caveats for the DPR Level 1 and Level 2 Products

Resolution	Region - Dates	Latency	Format	Source	DL
5.2km x 125m - 16 orbits per day	Latitudes 70°N-S, Past 2 Weeks (NRT); March 2014 - present (Prod)	20 - 120 minutes (NRT); 24 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The objective of the level 2 DPR algorithms is to generate from the level 1 DPR products radar-only derived meteorological quantities on an instantaneous FOV (field of view) basis. A subset of the results will be used by the level 2 combined radar-radiometer algorithm and the level 3 combined and radar-only products. The general idea behind the algorithms is to determine general characteristics of the precipitation, correct for attenuation and estimate profiles of the precipitation water content, rainfall rate and, when dual-wavelength data are available, information on the particle size distributions in rain and snow. It is particularly important that dual-wavelength data will provide better estimates of rainfall and snowfall rates than the TRMM PR data by using the particle size information and the capability of estimating, even in convective storms, the height at which the precipitation transitions from solid to liquid. 

Documentation:

• DPR Level-2 Algorithm Theoretical Basis Document
• Caveats for the DPR Level 1 and Level 2 Products

Resolution	Region - Dates	Latency	Format	Source	DL
5.2km x 125m - 16 orbits per day	Latitudes 70°N-S, Past 2 Weeks (NRT), March 2014 - present (Prod)	20 - 120 minutes (NRT); 24 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The objective of the level 2 DPR algorithms is to generate from the level 1 DPR products radar-only derived meteorological quantities on an instantaneous FOV (field of view) basis. A subset of the results will be used by the level 2 combined radar-radiometer algorithm and the level 3 combined and radar-only products. The general idea behind the algorithms is to determine general characteristics of the precipitation, correct for attenuation and estimate profiles of the precipitation water content, rainfall rate and, when dual-wavelength data are available, information on the particle size distributions in rain and snow. It is particularly important that dual-wavelength data will provide better estimates of rainfall and snowfall rates than the TRMM PR data by using the particle size information and the capability of estimating, even in convective storms, the height at which the precipitation transitions from solid to liquid.

Documentation:

• DPR Level-2 Algorithm Theoretical Basis Document
• Caveats for the DPR Level 1 and Level 2 Products

Resolution	Region - Dates	Latency	Format	Source	DL
5.2km x 125m - 16 orbits per day	Latitudes 70°N-S; Past 2 Weeks (NRT), March 2014 - present (Prod)	20 - 120 minutes (NRT); 24 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

This ATBD describes the Global Precipitation Measurement (GPM) passive microwave rainfall algorithm, which is a parametric algorithm used to serve all GPM radiometers. The output parameters of the algorithm are enumerated in Table 1. It is based upon the concept that the GPM core satellite, with its Dual Frequency Radar (DPR) and GPM Microwave Imager (GMI), will be used to build a consistent a-priori database of cloud and precipitation profiles to help constrain possible solutions from the GMI radiometer beyond the swath of the radar as well as the constellation radiometers.

Documentation:

• GPROF Caveats

Resolution	Region - Dates	Latency	Format	Source	DL
Varies by satellite	orbital, varies by satellite - past week (RT)	Varies by satellite (NRT)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The 2AGPROF (also known as, GPM GPROF (Level 2)) algorithm retrieves consistent precipitation and related science fields from the following GMI and partner passive microwave sensors: GMI, SSMI (DMSP F15), SSMIS (DMSP F16, F17, F18) AMSR2 (GCOM-W1), TMI MHS (NOAA 18&19, METOP A&B), ATMS (NPP), SAPHIR (MT1) This provides the bulk of the 3-hour coverage achieved by GPM. For each sensor, there are near-realtime (NRT) products, standard products, and climate products. These differ only in the amount of data that are available within 3 hours, 48 hours, and 3 months of collection, as well as the ancillary data used. 

Documentation:

• 2AGPROFGMI File Specification
• GPROF Caveats

Resolution	Region - Dates	Latency	Format	Source	DL
4km x 4km, 16 orbits per day	Latitudes 90°N-S, Past 2 weeks (NRT); March 2014 - present (Prod)	2 hours (NRT); 40 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

1AGMI contains unpacked packet data from GMI science data from the GMI passive microwave instrument flown on the GPM satellite. Swath S1 has 9 channels which are similar to TRMM TMI (10V 10H 19V 19H 23V 37V 37H 89V 89H). Swath S2 has 4 channels similar to AMSU-B (166V 166H 183+/-3V 183+/-8V). Data for both swaths is observed in the same revolution of the instrument. Swath S3 has ScienceDataHeader. Swath S4 has full rotation for low freq channels (S1). Swath S5 has full rotation for high freq channels (S2). Full Documentation

Resolution	Region - Dates	Latency	Format	Source	DL
4km x 4km - 16 orbits per day	Latitudes 70°N-S, March 2014 - present	40 hours (Prod)	HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/1A) HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP   HDF5 Prod: FTP (GES DISC)*

The Level 1B algorithm and software transform Level 0 counts into geolocated and calibrated antenna temperatures (Ta) and brightness temperatures (Tb). Ta is obtained by utilizing the sensor radiometric calibration as well as various corrections based on after launch analyses. Tb is derived from Ta after antenna pattern correction (APC) and along scan corrections. Figure 1.16 describes the relationship between algorithm components and products (or output). Full Documentation

Resolution	Region - Dates	Latency	Format	Source	DL
Varies by Channel - 16 orbits per day	Latitudes 70°N-S, Past 2 Weeks (NRT)	20 minutes (NRT); 6 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/1B) HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The Level 1C algorithms transform equivalent Level 1B radiance data into Level 1C products. The input source data are geolocated and radiometric calibrated antenna temperature (Ta) or brightness temperature (Tb). The output Level 1C products are common intercalibrated brightness temperature (Tc) products using the GPM Microwave Imager (GMI) as the reference standard. The Level 1C algorithms contain the following major components:

• Orbitization.
• Satellite intercalibration.
• Quality control.
• Ancillary data calculations.

The detail of L1C algorithms and implementation depends on the details of each sensor. In this document, the Level 1C algorithms are described in a general sense. Individual sensor-specific details are provided separately in Appendices A through G: A) GMI, B) LIC-R GMI, C) Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), D) Special Sensor Microwave Imager/Sounder (SSMI/S), E) Advanced Microwave Scanning Radiometer 2 (AMSR2), F) Advanced Technology Microwave Sounder (ATMS), G) Sondeur Atmospherique du Profil d'Humidite Intertropicale par Radiometrie (SAPHIR), and H) Microwave Humidity Sounder (MHS). Full Documentation

Resolution	Region - Dates	Latency	Format	Source	DL
Varies by Channel - 16 orbits per day	orbital, Past 2 Weeks (NRT)	20 minutes (NRT); 6 hours (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/1C) HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)

The Level 1C algorithms transform equivalent Level 1B radiance data into Level 1C products. The input source data are geolocated and radiometric calibrated antenna temperature (Ta) or brightness temperature (Tb). The output Level 1C products are common intercalibrated brightness temperature (Tc) products using the GPM Microwave Imager (GMI) as the reference standard. The Level 1C algorithms contain the following major components:

• Orbitization.
• Satellite intercalibration.
• Quality control.
• Ancillary data calculations.

The detail of L1C algorithms and implementation depends on the details of each sensor. In this document, the Level 1C algorithms are described in a general sense. Individual sensor-specific details are provided separately in Appendices A through G: A) GMI, B) LIC-R GMI, C) Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), D) Special Sensor Microwave Imager/Sounder (SSMI/S), E) Advanced Microwave Scanning Radiometer 2 (AMSR2), F) Advanced Technology Microwave Sounder (ATMS), G) Sondeur Atmospherique du Profil d'Humidite Intertropicale par Radiometrie (SAPHIR), and H) Microwave Humidity Sounder (MHS). Full Documentation

Resolution	Region - Dates	Latency	Format	Source	DL
Varies by Channel, 16 orbits per day	Latitudes 90°N-S - Past 2 Weeks (NRT)	20 minutes (NRT)	HDF5 NRT: FTP (PPS)* HDF5 Mirador

The Level 1C algorithms transform equivalent Level 1B radiance data into Level 1C products. The input source data are geolocated and radiometric calibrated antenna temperature (Ta) or brightness temperature (Tb). The output Level 1C products are common intercalibrated brightness temperature (Tc) products using the GPM Microwave Imager (GMI) as the reference standard. The Level 1C algorithms contain the following major components:

• Orbitization.
• Satellite intercalibration.
• Quality control.
• Ancillary data calculations.

The detail of L1C algorithms and implementation depends on the details of each sensor. In this document, the Level 1C algorithms are described in a general sense. Individual sensor-specific details are provided separately in Appendices A through G: A) GMI, B) LIC-R GMI, C) Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), D) Special Sensor Microwave Imager/Sounder (SSMI/S), E) Advanced Microwave Scanning Radiometer 2 (AMSR2), F) Advanced Technology Microwave Sounder (ATMS), G) Sondeur Atmospherique du Profil d'Humidite Intertropicale par Radiometrie (SAPHIR), and H) Microwave Humidity Sounder (MHS). Full Documentation

Resolution	Region - Dates	Latency	Format	Source	DL
Varies by satellite	orbital, varies by satellite	varies by satellite (NRT); 2 days (Prod)	HDF5 NRT: FTP (PPS)* HDF5 Prod: FTP (PPS)* (/YYYY/MM/DD/1C) HDF5 Prod: STORM HDF5 Mirador OPeNDAP OPeNDAP    HDF5 Prod: FTP (GES DISC)