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-1Rmtsat2-imager_hrit: For data from the Imager instrument on MTSAT-2ahi_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.
Compression
Gzip-compressed MTSAT files can be decompressed on the fly using
FSFile:
import fsspec
from satpy import Scene
from satpy.readers import FSFile
filename = "/data/HRIT_MTSAT1_20090101_0630_DK01IR1.gz"
open_file = fsspec.open(filename, compression="gzip")
fs_file = FSFile(open_file)
scn = Scene([fs_file], reader="jami_hrit")
scn.load(["IR1"])
- class satpy.readers.hrit_jma.HRITJMAFileHandler(filename, filename_info, filetype_info, use_acquisition_time_as_start_time=False)[source]
Bases:
HRITFileHandlerJMA 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.
- property end_time
Get end time of the scan.
- property start_time
Get start time of the scan.