IMERG Early Run

Near real-time low-latency gridded global multi-satellite precipitation estimates
Description

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 (IMERG Early Run) and successively providing better estimates as more data arrive (IMERG Late Run). The final step uses monthly gauge data to create research-level products (IMERG Final Run).

The main difference between the IMERG Early and Late Run is that Early only has forward propagation (which basically amounts to extrapolation) due to the short latency, while the Late has both forward and backward propagation (allowing interpolation).

Notes:

  • The PPS has completed reprocessing GPM IMERG data for IMERG V06B. The IMERG dataset now includes TRMM-era data going back to June 2000.
  • As of IMERG V05B, full coverage is provided for the latitudes of 60°N-60°S, while the remaining upper and lower latitudes extending to 90° are considered "partial coverage". 

 

Processing Level
3
Current Algorithm Version
V07B
Dates Covered
June 2000 - Present
Minimum Latency
4 hours
Spatial Resolution
10km / 0.1 Degree
Date Last Updated
July 13th, 2023
Document Description

The Integrated Multi-satelliE Retrievals for GPM (*IMERG*) is the unified U.S. algorithm that provides the multi-satellite precipitation product for the U.S. GPM team.

Date Last Updated
July 11th, 2023
Document Description

(document coming soon)

Date Last Updated
July 12th, 2023
Document Description

This document describes the algorithm and processing sequence for the Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement (GPM) mission (IMERG). 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 Tropical Rainfall Measuring Mission (TRMM) and GPM eras over the entire globe.

Date Last Updated
February 21st, 2024
Document Description

The algorithm for the Integrated Multi-satellitE Retrievals for GPM (IMERG) has now been upgraded to Version 07.  IMERG V07 involves a wide range of changes to all aspects of the algorithm, many of which are implemented in response to feedback on V06, which was the first time the IMERG record spanned the TRMM-GPM eras.  IMERG V07 is being reprocessed for the entire TRMM-GPM record and thus supersedes all prior IMERG versions, as well as superseding the prior TRMM-based TMPA products (3B42, 3B43).

Date Last Updated
October 6th, 2020
Document Description

The algorithm for the Integrated Multi-satellitE Retrievals for GPM (IMERG) has now been upgraded to Version 06. The transition to V05 for the IMERG Final Run began 13 March 2019 at PPS and the new data started flowing down to the GES DISC as well. However, on 15 March 2019 an error was discovered in processing the initial batches of V06 IMERG Final Run months. A design choice in the code ended up retaining microwave precipitation estimates in the latitude band 60°N-S when there is snow/ice on the surface, rather than masking out the estimates due to low performance in such cases.

Date Last Updated
March 15th, 2019
Document Description

Users have requested a “simple” quality index (QI) to give some guidance on when they should most trust the Integrated Multi-satellitE Retrievals for GPM (IMERG). While the goal is reasonable, there is no agreement about how this quantity should be defined. After some discussion within the team, two distinctly different quality indices were chosen for the half-hourly and monthly data fields (QIh and QIm, respectively) for implementation in Version 05 and continued in V06.

File Downloads
Date Last Updated
June 27th, 2023
Document Description

NASA produces a GIS translation of IMERG for various accumulation periods. The GIS translation maintains the 0.1-degree spatial resolution of the original HDF5 data product. In July 2023, Version 7 IMERG was released in both HDF5 and GIS formats. In April 2019, Version 6 of IMERG had been released, covering June 2000 to 2019. The long- duration archive for all versions starting with Version 6 is a boon to scientific research and provides a training set for near real-time applications such as disaster monitoring.

Date Last Updated
October 6th, 2020
Document Description

The Integrated Multi-satelliE Retrievals for GPM (*IMERG*) is the unified U.S. algorithm that provides the multi-satellite precipitation product for the U.S. GPM team.  The precipitation estimates from the various precipitation-relevant satellite passive microwave (PMW) sensors comprising the GPM constellation are computed using the 2017 version of the Goddard Profiling Algorithm (GPROF2017), then gridded, intercalibrated to the GPM Combined Radar Radiometer Analysis product (with GPCP climatological calibration), and combined into half-hourly 0.1°x0.1° fields.

File Downloads
Date Last Updated
January 3rd, 2020
Document Description

This document describes the algorithm and processing sequence for the Integrated Multi-satellitE Retrievals for GPM (IMERG).  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.

File Downloads