Dataset

ALOS-2 Typhoon/Hurricane Sea Surface Wind Products (test release)

1. Overview

Based on the joint research with Meteorological Research Institute, Japan Meteorological Agency, JAXA aims to estimate high-resolution sea surface wind of typhoons/hurricanes, contributing to forecast accuracy improvements. This page provides experimental products of wind speed of past typhoons/hurricanes derived from ALOS-2 data. This product is under development and is experimentally released to improve its accuracy through users’ feedback and to expand its utilization.

2. About the data

This product is under development and validation and is not yet intended for operational use. The wind speed may include various errors due to sensor characteristics, ionospheric effects, and radio interference. The accuracy of this product was validated by comparing the maximum wind speed from the Japan Meteorological Agency (JMA) and the Joint Typhoon Warning Center (JTWC) [1][2] (derived from the interpolation of the best-track data at the time of ALOS-2 observation) with the maximum wind speed of this product (the maximum value from the wind speed profiles calculated at 15-degrees intervals radially from the eye of the typhoon). As a result, the root mean square error (RMSE) is found to be 7 to 10 meters (see the figures below). This validation used 11 observation cases from 2022 to 2024. Only the data observed under ALOS-2 observation conditions suitable for sea wind estimation (beam W2 and W3, with low ionospheric effects) are available, and not all typhoons/hurricanes are covered. Updates and additions to the dataset may be made irregularly.


Figure: the accuracy evaluation of this product by comparing with best-track data.
Left: comparison with the best-track data by JTWC (1-minute average wind speed)
right: comparison with the best-track data by JMA (10-minute average wind speed).

3. Download

2024 2023 2022

2024

2403 GAEMI
PALSAR-2 HV 2024-7-22 04:10 UTC PALSAR-2 HV 2024-7-23 04:30 UTC
NetCDF NetCDF
2405 MARIA
PALSAR-2 HV 2024-8-10 04:10 UTC
NetCDF
2406 SON-TINH
PALSAR-2 HV 2024-8-13 02:00 UTC
NetCDF
2407 AMPIL
PALSAR-2 HV 2024-8-14 02:24 UTC PALSAR-2 HV 2024-8-14 14:48 UTC PALSAR-2 HV 2024-8-15 13:34 UTC
NetCDF NetCDF NetCDF
2410 SHANSHAN
PALSAR-2 HV 2024-8-23 02:19 UTC PALSAR-2 HV 2024-8-23 14:39 UTC
NetCDF NetCDF

2023

2307 LAN
PALSAR-2 HV 2023-8-11 14:41 UTC PALSAR-2 HV 2023-8-13 13:48 UTC
NetCDF NetCDF

2022

2211 HINNAMNOR
PALSAR-2 HV 2022-8-31 4:02 UTC
NetCDF

4. Detaset description

(1) Overview of the dataset

Dataset name SAR ocean surface wind field
Content ・Normalized radar cross section (HH and HV polarization)
・Ocean wind speed
・Incidence angle
・Faraday rotation angle calculated from the Global Ionospheric Map (GIM)[3] and the International Geomagnetic Reference Field (IGRF)[4]
・Other parameters (see "NetCDF parameters" below)
Satellite data source ALOS-2 ScanSAR mode typhoons/hurricanes observation data that meet following conditions.
・Incidence angle: Beam W2 and W3 (26–60 degrees)
・Period: 2022-
・The data that are assessed to have low ionospheric effects.
Data format NetCDF
Processing algorithm The method for estimating ocean surface wind from ALOS-2 cross-polarization (HV) data[5], ionospheric effects. Ionospheric effects[6] is reduced as much as possible.

(2) NetCDF parameters

Parameter Description
LONGITUDE Longitude at wind cell center
LATITUDE Latitude at wind cell center
WIND SPEED Ocean 10m wind speed from HV polarization
FARADAY_ROTATION_ANGLE Faraday rotation angle from TEC, magnetic field, and SAR beam angles
INCIDENCE_ANGLE Incidence angle at wind cell center
SENSOR_AZIMUTH_ANGLE Azimuth angle from the north
SIGMA_NAUGHT_HH Normalized radar cross section of HH polarization
SIGMA_NAUGHT_HV Normalized radar cross section of HV polarization
MASK Mask of data
ERA5_WIND_SPEED ERA5 10m wind speed
ERA5_WIND_DIRECTION ERA5 10m wind direction (meteorological conversion)
ACQUISITION_TIME Seconds since 1970-01-01 00:00:00
TITLE "SAR ocean surface wind field"
SENSORID Sensor ID

5. Teams of Use

This dataset is available to use with no charge under the "Terms of Use of Research Data".
To publish images using the dataset as it is, please display "©JAXA" in the image.

6. Contact

ALOS-2/ALOS Science Project

Earth Observation Research Center (EORC)

Japan Aerospace Exploration Agency (JAXA)

E-mail: aprojectjaxa.jp

Please refer to FAQ before sending an email.
Please contact us in English or Japanese.

* References

  1. Knapp, K. R., M. C. Kruk, D. H. Levinson, H. J. Diamond, and C. J. Neumann, "The International Best Track Archive for Climate Stewardship (IBTrACS): Unifying tropical cyclone best track data,", Bulletin of the American Meteorological Society, 91, 363-376, 2010. doi.org/10.1175/2009BAMS2755.1
  2. Gahtan, J., K. R. Knapp, C. J. Schreck, H. J. Diamond, J. P. Kossin, and M. C. Kruk, "International Best Track Archive for Climate Stewardship (IBTrACS) Project, Version 4.01,", NOAA National Centers for Environmental Information. doi.org/10.25921/82ty-9e16
  3. CODE final product series for the IGS. Published by Astronomical Institute, University of Bern.
    http://www.aiub.unibe.ch/download/CODE
    10.7892/boris.75876.4
  4. Alken, P., E. Thébault, C.D. Beggan, et al. "International Geomagnetic Reference Field: the thirteenth generation,", Earth Planets Space, 73 (49), 2021. doi.org/10.1186/s40623-020-01288-x
  5. Isoguchi, O., T. Tadono, M. Ohki, U. Shimada, M. Yamaguchi, and M. Hayashi, "Hurricane Ocean Surface Wind Retrieval from ALOS-2 PALSAR-2 Cross-Polarized Measurements," IGARSS2021, 7291–7294, Brussels, Belgium, 2021. doi.org/10.1109/IGARSS47720.2021.9554411
  6. Isoguchi, O., K. Ishizuka, T. Tadono, T. Motohka, and M. Shimada, "Effect of Faraday Rotation on L-Band Ocean Normalized Radar Cross Section and Wind Speed Detection,", IEEE JSTARS, 12(7), 2477–2485, 2019. doi.org/10.1109/JSTARS.2019.2894814