Frequently Asked Questions (FAQs)

Due to the system constraints, only those observed during 00 to 09 minutes per hour are shown for images that has passed over 3 months from the observations, and others are removed from the web server.

Note that all the physical products can be obtained from the ftp site (including those data taken during 10-59 minutes). Note that geophysical products of all past periods are available via FTP in NetCDF format.

We provide you the geostationary satellite Himawari Standard Data provided by the Japan Meteorological Agency (JMA) as well as the geophysical parameter data produced by JAXA using the Himawari Standard Data via our FTP site. Request your account from here.

No major web browser accept you to access FTP sites. Use FTP client software, such as FileZilla or WinSCP.

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• Himawari Standard Data (HSD)
• Himawari L1 Gridded data
• Geophysical Parameters
• Model Products

Our FTP server limits the number of simultaneous connections. You can simultaneously download data up to 30 connections from a host or 100 hosts. Also, the connection time is limited to 12 hours, so please do not download more than the time limit.

When a server trouble occurs, we will announce in What's New. Network traffic might be temporarily very busy. Try to access later. If data down load delays to long time, contact us.

Currently, P-Tree's FTP site can be accessed via the following protocols (port numbers in parentheses) except FTP.

• FTPS（990）
• SFTP（2051）

The Himawari Standard Data(HSD) is the most closest data to raw data and is the data with the largest amount of information among the Himawari observation data provided from the Japan Meterology Agency (JMA). JAXA disseminates the HSD data to users for non-profit purposes such as research and education based on cooperative agreement with JMA. For details on the HSD data, please refer to the following URLs.

• Himawari Standard Data (Meteorological Satellite Center of JMA)
• Himawari Standard Data User's Guide

Due to system constraints, those data that has passed over 30 days has been deleted from the P-Tree FTP server. The other services distributing the Himawari Original Data are listed below. Please contact the administrator of each sites for further details.

• World Science Data Bank by NICT
• Data Integration and Analysis System (DIAS) by the University of Tokyo

It is placed under /jma/hsd/ same as Himawari-8. The file name has changed to H09 because of the switch to Himawari-9. Please refer to README (README_HimawariHSD_en.txt) for details.

Please refer to the Himawari Calibration Portal by JMA.
https://www.data.jma.go.jp/mscweb/en/oper/calibration/calibration_portal.html
You can get spectral response function of the sensor from below. https://www.data.jma.go.jp/mscweb/en/himawari89/space_segment/spsg_ahi.html#srf
For details, we recommend that you ask to JMA/MSC.

NetCDF is a self-describing, machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. The detail of the NetCDF can be found in the following URL:
https://www.unidata.ucar.edu/software/netcdf/

Use the programming languages (C, FORTRAN, C++, Java, etc.) with including the NetCDF libraries, which are freely distributed from the NetCDF official website. As a GUI-based software, the 'hdfview' is also useful to access There are also some other commercial software that support the NetCDF.

ATBD has not been published for JAXA Himawari products. See our User’s guide as well as documents and references.

The observation time contained in the file name's time is in UTC. Please convert to your local time.

The level 3 hourly products are created from the Level 2 product on the hour to 50 minutes past the hour. The time in the file name indicates the beginning of the period.

The level 3 daily products are created from the Level 2 product at 00:00 to 23:50 UTC.

The geographic coordinates represent the center of the pixel for the full-disk Himawari L1 gridded data.

No. We distribute top of atmosphere (TOA) reflectance without atmospheric correction. We define albedo as reflectance*cos(SOZ), where SOZ is solar zenith angle, for JAXA Himawari product.

No. The Himawari L1 Gridded data is projected onto the WGS84 ellipsoid without orthorectification. Therefor ground elevation and cloud height are not corrected.

The solar azimuth angle ranges from -180 to 180 degree. When you want them ranging from 0 to 360 degree, follow as following. From 0 to 180 degree, you can use the azimuth angle without any correction. From -180 to 0 degree, just add 360 degree to convert them into the range of 180 to 360 degree.

The full-disk Himawari L1 Gridded Data covers 60S-60N, 80E-160W in 0.02 degree resolution. You can convert x, y (both start from zero) in the image to longitude and latitude as

• longitude = 80 + x * 0.02
• latitude = 60 - y * 0.02

Or, you can retrieve latitude and longitude table from the netCDF file by using software to treat netCDF format.

Use the scale factor and add offset stored in NetCDF file to obtain the physical quantity.

For bands 1 to 6, the scale factor and add offset are 0.0001 and 0.0. For bands 7 to 16, the scale factor and add offset are 0.01 and 273.15.

See the document of Meteorological Satellite Center.

You can obtain reflectance*cos(SOZ) by the following equation,

(DN * scale_factor + add_offset) * correction factor + correction offset

In addition, correction_update_MJD is the date when the correction factor was calculated.

Himawari L1 Gridded Data contains all TIR bands (band 7-16), and band 14 is used in the Himawari TIR images of the JAXA Himawari Monitor.

About Imaging bands, please refer to following url.
https://www.data.jma.go.jp/mscweb/en/himawari89/space_segment/spsg_ahi.html

Please refer the following websites and references.

• JAXA Himawari Monitor Aerosol Products
• References
  (L2 Aerosol Algorithm)
  Yoshida, M, M. Kikuchi, T. M. Nagao, H. Murakami, T. Nomaki, and A. Higurashi, 2018: Common retrieval of aerosol properties for imaging satellite sensors, J. Meteor. Soc. Japan, doi:10.2151/jmsj.2018-039. https://www.jstage.jst.go.jp/article/jmsj/advpub/0/advpub_2018-039/_article/-char/en.
  
  (L3 Hourly Aerosol Algorithm)
  Kikuchi, M., H. Murakami, K. Suzuki, T. M. Nagao, and A. Higurashi, Improved Hourly Estimates of Aerosol Optical Thickness using Spatiotemporal Variability Derived from Himawari-8 Geostationary Satellite, IEEE Transactions on Geoscience and Remote Sensing, accepted.

The release timing of the Level 3 aerosol product is generally 2 and half hours to 6 hours from the observation.

The algorithm to generate the Level 2 aerosol product sacrificed processing time to improve the accuracy.

Usually it takes 2 to 5 hours from the observation to process the Level 2 aerosol product.

Then the Level 3 aerosol products are generally created 2 and half hours to 6 hours from the observation because the Level 3 products are created based on the Level 2 products during one hour.

The parameter "AOT_Merged_uncertainty" is a unitless and you can write the uncertainty as the following: "AOT_Merged" ± "AOT_Merged_uncertainty"

We only retrieve the data whose solar zenith angle less than 70, because we assume the plane-parallel atmosphere in radiative transfer calclulations. Therefore, there are no retrieved data in time transition periods between day and night.

The aerosol is retrieved from Himawari based on the theory of the scattering and absorbing of the sun-light. Therefore, the aerosol can not be retrieved at night time.

The cloud property retrieval relies on a lookup table of cloud optical thickness and effective particle radius calculated by radiative transfer simulation.

The cloud retrieval algorithm flag would be 011=Failed when the retrieval algorithm could not find optimal solution which occurs when cloud is extremely thin or thick, land surface was coverd by ice/snow, or the pixel was corresponding to sunglint.

When the flag was 011=Failed, check an additional flag, namely, (4,3) Cloud Mask Confidence Level Flag: 00=Clear, 01=Probably Clear, 10=Probably Cloudy, 11=Cloudy; If the ""011=Failed"" occurred over the pixels with very thick cloud (perhaps, the Cloud Mask Confidence Level Flag=11), you should treat the pixel as cloud.

However, when the ""011=Failed"" occurred on the edge of cloud or thick aerosol, the Cloud Mask Confidence Level Flag is usually 10=Probably Cloudy. In such case, the pixel is ambiguous to be cloudy or not."

No. CLP cannot be calculated without solar radiance.

JAXA's Himawri-8 cloud property product is generated based on the different algorithm. The cloud types were classified from the retrieved cloud optical thickness and cloud top pressure based on International Satellite Cloud Climatology Project (ISCCP) definition of cloud types.

The references are listed below:

Kawamoto, K., T. Nakajima, and T. Y. Nakajima, 2001: A Global Determination of Cloud Microphysics with AVHRR Remote Sensing, J. Clim., 14(9), 2054-2068, doi:10.1175/1520-0442(2001)014<2054:AGDOCM>2.0.CO;2.

Nakajima, T. Y., and T. Nakajima, 1995: Wide-Area Determination of Cloud Microphysical Properties from NOAA AVHRR Measurements for FIRE and ASTEX Regions, J. Atmos. Sci., 52(23), 4043-4059, doi:10.1175/1520-0469(1995)052<4043:WADOCM>2.0.CO;2.

ISCCP (International Satellite Cloud Climatology Project) cloud type:
https://isccp.giss.nasa.gov/cloudtypes.html

The format of SST product conforms to Group for High Resolution Sea Surface Temperature (GHRSST) format instead of other JAXA Himawari products.

The artifact on the Chlorophyll a data is attributed to the pixel to pixel sensitivity variation of the scan unit of the AHI sensor, which is calibrated within the sensor spec.

The slight difference between the pixel sensitivity can be emphasized after the atmospheric correction.

This stripe noise is noticeable over daily and monthly products because temporal averaging reduce the other noises but the difference between the pixel sensitivity remains.

The Chlorophyll-a concentrations represents the depth of about 0 to few m depending on the transmittance of the water, which generally increases from coastal to open ocean. Subsurface chlorophyll-a is not detected over subtropical stratified ocean.

We provide files in csv format.
CSV is text data where each item is separated by commas (,).
Please refer to the User's Guide and README (Level 2 and Level 3) for details on the data.

Aerosol model product is NetCDF format data in Gaussian grids.
On the web, it is projected by Web Mercator projection.

There are cases where Best Estimate data is not available due to system maintenance or other reasons.

The images on the web page are created using Near Real-Time data (Forecast (FCST) and Analysis (ANAL)). For periods when Best Estimate data is not available, please refer to the Near Real-Time data.

The layer information is stored in grid.nc, which is separate from the product.

Use of the data provided from the system is limited to non-profit purposes such as research and education based on the policy of the JMA. For profit or business purposes, please contact the Japan Meteorological Business Support Center.

When you publish a thesis, a report, and so on by using research products or images supplied by the Service, please clearly state that you are using JAXA's data in accordance with the User Guide "3. Reporting Results".
If you are writing a document (including papers and thesis), please refer to the algorithm papers of the product you are using, which is listed in the User Guide "7. References".