GSMaP¶

Global Satellite Mapping of Precipitation (GSMaP), algorithm version 8

Available

At a glance¶

Note on period: v8 standard (MVK, Gauge) and near-real-time (NRT, Gauge_NRT) records run from 1998-01-01 thanks to the July 2023 reprocessing (1998-01 to 2000-01 uses GridSat-B1 IR only; 2000-02 blends GridSat-B1 and CPC 4-km IR). Operational production started on 2021-12-01, and real-time GSMaP_NOW v8 on 2021-12-06. The older reanalysis GSMaP_RNL (v6) covers 2000-03 to 2014-02.

Overview¶

GSMaP is JAXA's multi-satellite precipitation map. It combines passive microwave (PMW) radiometer estimates from the GPM Core Observatory and many low-Earth-orbit satellites, propagated with cloud motion vectors from geostationary IR imagery and a Kalman filter, into global hourly 0.1° precipitation. There is a real-time product (NOW) available right after observation, a near-real-time product (NRT) about 4 hours later and a standard product (MVK) about 3 days later, each paired with a Gauge version adjusted to the NOAA CPC daily gauge analysis. Its rapid updates over Asia and the Pacific, using Himawari data, make it widely used for flood and disaster monitoring.

What changes with the successor¶

GSMaP v7 (product version V04) → GSMaP v8 (product version V05)¶

Transition: 2021-12

Distribution of algorithm v8 began on 1 December 2021, and the July 2023 reprocessing produced a record from 1998. Microwave retrievals were extended to the poles, and the input sensors, database, orographic-rain detection and gauge adjustment all changed. Updates to v7 ended in 2026.

Sources: GSMaP version05 / Algorithm version8 summary (JAXA) · GSMaP V05/v8 Release Note (2023-11-10) · GSMaP reprocessing note (2023-07) · JAXA EORC GPM news (end of v7 updates, 2026-06-16 and 07-29)

GSMaP product version V05 (algorithm v8) → GSMaP product version V06 Planned¶

Transition: 2026-10

JAXA announced that a new version V06 of the GSMaP hourly and monthly products will be released on G-Portal on 19 October 2026. The format changes from HDF5 to NetCDF4, V06 will be offered only on the new G-Portal system, and V05 will continue to be provided. When checked on 2026-10-13, details of the algorithm changes and of any change on the FTP (Global Rainfall Watch) side had not yet been published.

Sources: Plan for the GSMaP product version up (V06) (G-Portal, 2026-10-09) · Notice Regarding G-Portal System Renewal

Available variables¶

Variable names from the G-Portal HDF files (product format specification V5). FTP binary files carry no names: they are 4-byte little-endian float arrays (gzip-compressed), with the satellite information, observation time and reliability flags in separate files. Negative values mean missing or no retrieval (-4 sea ice, -8 low temperature, -99 no IR or microwave observation; -999.9 in daily and monthly binaries).

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Hourly (GSMaP_MVK and Gauge, NRT and Gauge_NRT, NOW)¶

Monthly (G-Portal HDF)¶

Daily (FTP binary, 0.1° and 0.25°)¶

The full variable list is in the official documentation.

How to get the data¶

• JAXA Global Rainfall Watch (FTP; binary, text and NetCDF) — FTP (username and password issued after registration), web maps and CSV subsetting
  • FTP connection details are emailed after registration. Standard products are under /standard/v8/ (hourly, hourly_G, daily, monthly, netcdf), near-real-time products under /realtime_ver/v8/ (the latest 24 hours in latest/). HDF files from January 2024 onward are under /HDF/. Web browsers cannot open the FTP site, so JAXA recommends an FTP client such as FileZilla or WinSCP. The web map lets you download hourly CSV for points or areas for up to six months at a time.
• JAXA G-Portal (HDF5; NetCDF4 from V06) — Web search and download, SFTP (sftp.gportal.jaxa.jp, public-key authentication), CSW
  • The new system opened on 1 October 2026 and the old system (gportal.jaxa.jp/gpr) is planned to close at the end of October. A new account is required and SFTP accepts public-key authentication only. GSMaP Hourly and Monthly V05 are available; V06 will be offered only on the new system.
• Google Earth Engine — Cloud analysis (JAXA/GPM_L3/GSMaP/v8/operational)
  • Near-real-time images are later replaced by standard ones; the image property status (provisional/permanent) tells them apart.
• JAXA Climate Rainfall Watch (GSMaP_CLM) — Web maps and statistics
  • Daily, 3-day, pentad, weekly, 10-day and monthly means, normals and a drought index (SPI) based on Gauge_NRT.

Example code¶

Reads one standard hourly binary file (gzip) from the FTP site with numpy and clips the Korean Peninsula. As the format description states, it is a 3600×1200 grid of 4-byte little-endian floats, stored from the north (59.95°N) southward and from 0.05°E eastward. Replace the version string (vP.RSKI.J) in the file name with the one in your files.

import gzip
import numpy as np

fname = "gsmap_mvk.20230715.0300.v8.0000.1.dat.gz"   # replace with your file name
with gzip.open(fname, "rb") as f:
    rain = np.frombuffer(f.read(), dtype="<f4").reshape(1200, 3600)   # (lat, lon), mm/hr

lat = 59.95 - 0.1 * np.arange(1200)
lon = 0.05 + 0.1 * np.arange(3600)
rain = np.where(rain < 0, np.nan, rain)   # -4 sea ice, -8 low temperature, -99 no observation

jj = (lat >= 33) & (lat <= 39)
ii = (lon >= 124) & (lon <= 132)
korea = rain[np.ix_(jj, ii)]
print("Area-mean rate 03-04 UTC (mm/hr):", np.nanmean(korea))

# Daily files (...daily.00Z-23Z...) hold mean rates (mm/hr) on the same grid, so multiply by 24 for daily totals

Practical tips¶

• Daily and monthly binary files hold mean rates in mm/hr. Multiply daily values by 24, and get monthly totals from the first layer (mean rate) × the second layer (valid-pixel count) of the monthly file.
• NOW, NRT, MVK and their Gauge versions are different datasets. Use the standard products (MVK, Gauge) for long-term work, and if you appended recent days from NRT, say so in your paper.
• Do not mix versions. v7 stopped updating in 2026, and v8 is a separate record rebuilt from 1998. On G-Portal, 'product version V05' is algorithm v8, and values for the whole period may change once V06 is out.
• 1998-01 to 2000-02 is built from GridSat-B1 IR data, which JAXA says has not been fully evaluated, so use it with caution. Be careful too with the 1997/98 El Niño period, when TRMM PR and TMI disagreed strongly.
• JAXA's usage guidelines note low accuracy in areas of orographic heavy rain and that snowfall estimation is still under development, with poorer performance along the Sea of Japan coast in the cold season. Take particular care with mountain and winter precipitation over Korea.
• JAXA advises caution when the reliability flag (reliabilityFlag) is below 4. Real-time products can underestimate rain when the interval between microwave overpasses is long.
• Changes in input satellites change the character of the data; for example, NOAA-19 AMSU-A/MHS has not been used since 2025-06-17. Check the satellite information flag together with the official list of input changes.
• FTP binary files start at 59.95°N and run southward, so plotting them as is flips the map. NetCDF and HDF files use a 90°N–90°S grid with different array sizes.

Notices and change history¶

References for your paper¶

Dataset citation¶

GSMaP(Hourly) — JAXA dataset DOI — DOI 10.57746/EO.01gs73bkt358gfpy92y2qns5e9

@misc{jaxa_gsmap_hourly,
  author    = {{Japan Aerospace Exploration Agency}},
  title     = {{GSMaP(Hourly)}},
  year      = {1998},
  publisher = {Japan Aerospace Exploration Agency (JAXA)},
  doi       = {10.57746/EO.01gs73bkt358gfpy92y2qns5e9}
}

Reference papers¶

GSMaP products in the GPM era (chapter in Satellite Precipitation Measurement) — DOI 10.1007/978-3-030-24568-9_20

@incollection{kubota2020gsmap,
  author    = {Kubota, Takuji and Aonashi, Kazumasa and Ushio, Tomoo and Shige, Shoichi and Takayabu, Yukari N. and Kachi, Misako and Arai, Yoriko and Tashima, Tomoko and Masaki, Takeshi and Kawamoto, Nozomi and Mega, Tomoaki and Yamamoto, Munehisa K. and Hamada, Atsushi and Yamaji, Moeka and Liu, Guosheng and Oki, Riko},
  title     = {Global Satellite Mapping of Precipitation ({GSMaP}) Products in the {GPM} Era},
  booktitle = {Satellite Precipitation Measurement},
  series    = {Advances in Global Change Research},
  volume    = {67},
  publisher = {Springer International Publishing},
  address   = {Cham},
  pages     = {355--373},
  year      = {2020},
  doi       = {10.1007/978-3-030-24568-9_20}
}

GSMaP production and validation (Kubota et al., 2007) — DOI 10.1109/TGRS.2007.895337

@article{kubota2007gsmap,
  author  = {Kubota, Takuji and Shige, Shoichi and Hashizume, Hiroshi and Aonashi, Kazumasa and Takahashi, Nobuhiro and Seto, Shinta and Hirose, Masafumi and Takayabu, Yukari N. and Ushio, Tomoo and Nakagawa, Katsuhiro and Iwanami, Koyuru and Kachi, Misako and Okamoto, Ken'ichi},
  title   = {Global Precipitation Map Using Satellite-Borne Microwave Radiometers by the {GSMaP} Project: Production and Validation},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  volume  = {45},
  number  = {7},
  pages   = {2259--2275},
  year    = {2007},
  doi     = {10.1109/TGRS.2007.895337}
}

Gauge-adjusted GSMaP (Mega et al., 2019) — DOI 10.1109/TGRS.2018.2870199

@article{mega2019gauge,
  author  = {Mega, Tomoaki and Ushio, Tomoo and Takahiro, Matsuda and Kubota, Takuji and Kachi, Misako and Oki, Riko},
  title   = {Gauge-Adjusted Global Satellite Mapping of Precipitation},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  volume  = {57},
  number  = {4},
  pages   = {1928--1935},
  year    = {2019},
  doi     = {10.1109/TGRS.2018.2870199}
}

Acknowledgements¶

JAXA asks users to credit the data, e.g. "GSMaP data by Japan Aerospace Exploration Agency (JAXA)", and to cite the major GSMaP papers. If you used a Gauge product, also cite Mega et al. (2019), and state the product (NOW, NRT or MVK; with or without gauge adjustment) and the algorithm version (v8) in the text. JAXA's usage guidelines also ask that publications using GSMaP be reported to JAXA.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• JAXA Global Rainfall Watch user guide (products and input satellite changes)
• GSMaP FAQ list (product differences Q6, format documents Q18)
• GSMaP_MVK and Gauge v8 Data Format Description
• GSMaP_NRT and Gauge_NRT v8 Data Format Description
• G-Portal GSMaP product format specification V5 (HDF)
• GSMaP Guidelines, second edition (2026-02)
• JAXA EORC GSMaP documents page
• User registration (Global Rainfall Watch)
• NASA IMERG in the same satellite precipitation tab (for comparison)