satpy.readers.hrit_jma module

HRIT format reader for JMA data.

Introduction

The JMA HRIT format is described in the JMA HRIT - Mission Specific Implementation. There are three readers for this format in Satpy:

  • jami_hrit: For data from the JAMI instrument on MTSAT-1R

  • mtsat2-imager_hrit: For data from the Imager instrument on MTSAT-2

  • ahi_hrit: For data from the AHI instrument on Himawari-8/9

Although the data format is identical, the instruments have different characteristics, which is why there is a dedicated reader for each of them. Sample data is available here:

Example

Here is an example how to read Himwari-8 HRIT data with Satpy:

from satpy import Scene
import glob

filenames = glob.glob('data/IMG_DK01B14_2018011109*')
scn = Scene(filenames=filenames, reader='ahi_hrit')
scn.load(['B14'])
print(scn['B14'])

Output:

<xarray.DataArray (y: 5500, x: 5500)>
dask.array<concatenate, shape=(5500, 5500), dtype=float64, chunksize=(550, 4096), ...
Coordinates:
    acq_time  (y) datetime64[ns] 2018-01-11T09:00:20.995200 ... 2018-01-11T09:09:40.348800
    crs       object +proj=geos +lon_0=140.7 +h=35785831 +x_0=0 +y_0=0 +a=6378169 ...
  * y         (y) float64 5.5e+06 5.498e+06 5.496e+06 ... -5.496e+06 -5.498e+06
  * x         (x) float64 -5.498e+06 -5.496e+06 -5.494e+06 ... 5.498e+06 5.5e+06
Attributes:
    orbital_parameters:   {'projection_longitude': 140.7, 'projection_latitud...
    standard_name:        toa_brightness_temperature
    level:                None
    wavelength:           (11.0, 11.2, 11.4)
    units:                K
    calibration:          brightness_temperature
    file_type:            ['hrit_b14_seg', 'hrit_b14_fd']
    modifiers:            ()
    polarization:         None
    sensor:               ahi
    name:                 B14
    platform_name:        Himawari-8
    resolution:           4000
    start_time:           2018-01-11 09:00:20.995200
    end_time:             2018-01-11 09:09:40.348800
    area:                 Area ID: FLDK, Description: Full Disk, Projection I...
    ancillary_variables:  []

JMA HRIT data contain the scanline acquisition time for only a subset of scanlines. Timestamps of the remaining scanlines are computed using linear interpolation. This is what you’ll find in the acq_time coordinate of the dataset.

class satpy.readers.hrit_jma.HRITJMAFileHandler(filename, filename_info, filetype_info, use_acquisition_time_as_start_time=False)[source]

Bases: HRITFileHandler

JMA HRIT format reader.

By default, the reader uses the start time parsed from the filename. To use exact time, computed from the metadata, the user can define a keyword argument:

scene = Scene(filenames=filenames,
              reader='ahi_hrit',
              reader_kwargs={'use_acquisition_time_as_start_time': True})

As this time is different for every channel, time-dependent calculations like SZA correction can be pretty slow when multiple channels are used.

The exact scanline times are always available as coordinates of an individual channels:

scene.load(["B03"])
print(scene["B03].coords["acq_time"].data)

would print something similar to:

array(['2021-12-08T06:00:20.131200000', '2021-12-08T06:00:20.191948000',
       '2021-12-08T06:00:20.252695000', ...,
       '2021-12-08T06:09:39.449390000', '2021-12-08T06:09:39.510295000',
       '2021-12-08T06:09:39.571200000'], dtype='datetime64[ns]')

The first value represents the exact start time, and the last one the exact end time of the data acquisition.

Initialize the reader.

calibrate(data, calibration)[source]

Calibrate the data.

property end_time

Get end time of the scan.

get_area_def(dsid)[source]

Get the area definition of the band.

get_dataset(key, info)[source]

Get the dataset designated by key.

property start_time

Get start time of the scan.

satpy.readers.hrit_jma.mjd2datetime64(mjd)[source]

Convert Modified Julian Day (MJD) to datetime64.