Figure 1. Visualisation of the cloud top altitude variable from the CTTH product for 2020-01-01 03:00 UTC.
Abstract
The cloud top temperature and height (CTTH), developed within the NWC SAF context, aims to
support nowcasting applications. This product contributes to the analysis and early warning of
thunderstorm development. Other applications include the cloud top height assignment for aviation
forecast activities. The product may also serve as input to mesoscale models.The CTTH product contains information on the cloud top temperature and height for all pixels
identified as cloudy in the satellite scene.Cloud top pressure or height are derived from their IR brightness temperatures by comparison to
simulated IR brightness temperatures computed from temperature and humidity vertical profiles
forecast by NWP using a IR radiative transfer model (RTTOV). Exact retrieval method depends on
cloud type as semi-transparency correction using window and sounding IR channels may be needed.For further information please view the following documents:
Format
NetCDF4
Basepath, Filename Template and Data Access
On NCI (requires an NCI account and membership of the rv74 data collection)
Base path: /g/data/rv74/satellite-products/arc/der/himawari-ahi/cloud/ctth/latest/<year>/<month>/<day>/
Filename Template: S_NWC_CTTH_<satellite>_HIMA-N-NR_<year><month><day>T<hour><minute>00Z.nc
<satellite>: HIMA08 or HIMA09
On THREDDS (publicly available, no NCI account required)
Bureau of Meteorology - Satellite Derived Products (rv74) THREDDS
Base Path: satellite-products/arc/der/himawari-ahi/cloud/ctth/latest/<year>/<month>/<day>/
Filename Template: S_NWC_CTTH_<satellite>_HIMA-N-NR_<year><month><day>T<hour><minute>00Z.nc
<satellite>: HIMA08 or HIMA09
Version
Version 2.0: Initial release. Processed using EUMETSAT NWCSAF GEO software, version v2021.1. Input data includes Himawari-AHI data, NOAA's GFS 0.5 degree 6 and 12 hour forecasts and Bureau of Meteorology GAMSSA Sea Surface Temperature.
License
Update Frequency
Monthly with 3 month data latency
Temporal extents (YYYY/MM/DD)
2015/07/07 - present (with 3 month data latency)
Spatial Extents
81N ~ 81S, 59E ~ 222E
Owner
Bureau of Meteorology
Contact
Satellite Science Team, Research, Bureau of Meteorology
Credit
Many thanks to the Japan Meteorological Agency (JMA) for providing Himawari-AHI data and NOAA for providing GFS data.
Cloud Top Height and Temperature data derived from satellite imagery processed by the Bureau of Meteorology from Himawari-AHI data provided by the Japan Meteorological Agency using software provided by EUMETSAT NWCSAF.
Metadata Example
netcdf S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z {
dimensions:
ny = 5500 ;
nx = 5500 ;
pal02_colors = 256 ;
pal_RGB = 3 ;
pal04_colors = 256 ;
pal01_colors = 256 ;
pal03_colors = 256 ;
variables:
ushort ctth_alti(ny, nx) ;
ctth_alti:standard_name = "cloud_top_altitude" ;
ctth_alti:long_name = "NWC GEO CTTH Cloud Top Altitude" ;
ctth_alti:scale_factor = 1.f ;
ctth_alti:add_offset = -2000.f ;
ctth_alti:units = "m" ;
ctth_alti:valid_range = 0US, 27000US ;
ctth_alti:_FillValue = 65535US ;
ctth_alti:ancillary_variables = "ctth_status_flag ctth_conditions ctth_quality ctth_alti_pal" ;
ctth_alti:coordinates = "lon lat" ;
ctth_alti:grid_mapping = "geostationary" ;
ubyte ctth_alti_pal(pal02_colors, pal_RGB) ;
ctth_alti_pal:long_name = "RGB palette for ctth_alti" ;
ctth_alti_pal:valid_range = 0UB, 255UB ;
ctth_alti_pal:colormodel = "RGB" ;
ctth_alti_pal:comment = "Palette applicable to field ctth_alti" ;
ushort ctth_conditions(ny, nx) ;
ctth_conditions:long_name = "Common geophysical and processing conditions" ;
ctth_conditions:valid_range = 1US, 65535US ;
ctth_conditions:_FillValue = 0US ;
ctth_conditions:flag_mask = 1US, 6US, 6US, 6US, 8US, 48US, 48US, 48US, 64US, 128US, 768US, 768US, 768US, 3072US, 3072US, 3072US, 12288US, 12288US, 12288US, 49152US, 49152US, 49152US ;
ctth_conditions:flag_values = 1US, 2US, 4US, 6US, 8US, 16US, 32US, 48US, 64US, 128US, 256US, 512US, 768US, 1024US, 2048US, 3072US, 4096US, 8192US, 12288US, 16384US, 32768US, 49152US ;
ctth_conditions:flag_meanings = "space night day twilight sunglint land sea coast not_used not_used all_satellite_channels_available useful_satellite_channels_missing mandatory_satellite_channels_missing all_NWP_fields_available useful_NWP_fields_missing mandatory_NWP_fields_missing all_product_data_available useful_product_data_missing mandatory_product_data_missing all_auxiliary_data_available useful_auxiliary_data_missing mandatory_auxiliary_data_missing" ;
ctth_conditions:comment = "Common geophysical and processing conditions" ;
ctth_conditions:grid_mapping = "geostationary" ;
ushort ctth_effectiv(ny, nx) ;
ctth_effectiv:standard_name = "cloud_area_fraction" ;
ctth_effectiv:long_name = "NWC GEO CTTH Effective Cloudiness" ;
ctth_effectiv:scale_factor = 0.01f ;
ctth_effectiv:add_offset = 0.f ;
ctth_effectiv:units = "1" ;
ctth_effectiv:valid_range = 0US, 100US ;
ctth_effectiv:_FillValue = 65535US ;
ctth_effectiv:ancillary_variables = "ctth_status_flag ctth_conditions ctth_quality ctth_effectiv_pal" ;
ctth_effectiv:coordinates = "lon lat" ;
ctth_effectiv:grid_mapping = "geostationary" ;
ubyte ctth_effectiv_pal(pal04_colors, pal_RGB) ;
ctth_effectiv_pal:long_name = "RGB palette for ctth_tempe" ;
ctth_effectiv_pal:valid_range = 0UB, 255UB ;
ctth_effectiv_pal:colormodel = "RGB" ;
ctth_effectiv_pal:comment = "Palette applicable to field ctth_effectiv" ;
ushort ctth_method(ny, nx) ;
ctth_method:standard_name = "status_flag" ;
ctth_method:long_name = "NWC GEO CTTH List of Methods" ;
ctth_method:valid_range = 0US, 16383US ;
ctth_method:_FillValue = 32768US ;
ctth_method:flag_mask = 1US, 2US, 4US, 8US, 16US, 32US, 64US, 128US, 256US, 512US, 1024US, 2048US, 4096US, 8192US ;
ctth_method:flag_values = 1US, 2US, 4US, 8US, 16US, 32US, 64US, 128US, 256US, 512US, 1024US, 2048US, 4096US, 8192US ;
ctth_method:flag_meanings = "Cloud-free No_reliable_method Opaque_cloud_RTTOV_not_available Opaque_cloud_using_RTTOV Opaque_cloud_using_RTTOV_in_case_thermal_inversion Intercept_method_108um_134um Intercept_method_108um_62um Intercept_method_108um_70um Intercept_method_108um_73um Radiance_ratioing_method_108um_134um Radiance_ratioing_method_108um_62um Radiance_ratioing_method_108um_70um Radiance_ratioing_method_108um_73um Spatial_smoothing" ;
ctth_method:coordinates = "lon lat" ;
ctth_method:grid_mapping = "geostationary" ;
ushort ctth_pres(ny, nx) ;
ctth_pres:standard_name = "air_pressure_at_cloud_top" ;
ctth_pres:long_name = "NWC GEO CTTH Cloud Top Pressure" ;
ctth_pres:scale_factor = 10.f ;
ctth_pres:add_offset = 0.f ;
ctth_pres:units = "Pa" ;
ctth_pres:valid_range = 0US, 11000US ;
ctth_pres:_FillValue = 65535US ;
ctth_pres:ancillary_variables = "ctth_status_flag ctth_conditions ctth_quality ctth_pres_pal" ;
ctth_pres:coordinates = "lon lat" ;
ctth_pres:grid_mapping = "geostationary" ;
ubyte ctth_pres_pal(pal01_colors, pal_RGB) ;
ctth_pres_pal:long_name = "RGB palette for ctth_pres" ;
ctth_pres_pal:valid_range = 0UB, 255UB ;
ctth_pres_pal:colormodel = "RGB" ;
ctth_pres_pal:comment = "Palette applicable to field ctth_pres" ;
ushort ctth_quality(ny, nx) ;
ctth_quality:long_name = "Common Quality Indicators" ;
ctth_quality:valid_range = 1US, 56US ;
ctth_quality:_FillValue = 0US ;
ctth_quality:flag_mask = 1US, 2US, 4US, 56US, 56US, 56US, 56US ;
ctth_quality:flag_values = 1US, 2US, 4US, 8US, 16US, 24US, 32US ;
ctth_quality:flag_meanings = "nodata internal_consistency temporal_consistency good questionable bad interpolated" ;
ctth_quality:comment = "Common Quality Indicators" ;
ctth_quality:grid_mapping = "geostationary" ;
ushort ctth_status_flag(ny, nx) ;
ctth_status_flag:standard_name = "status_flag" ;
ctth_status_flag:long_name = "Information on specific NWC GEO CTTH processing" ;
ctth_status_flag:valid_range = 0US, 63US ;
ctth_status_flag:_FillValue = 32768US ;
ctth_status_flag:flag_mask = 1US, 2US, 4US, 8US, 16US, 32US ;
ctth_status_flag:flag_values = 1US, 2US, 4US, 8US, 16US, 32US ;
ctth_status_flag:flag_meanings = "Cloud-free Low_level_thermal_inversion_in_NWP_field Opaque_cloud Fractional_clouds_no_reliable_method Too_thin_clouds_no_reliable_method Multilayer_cloud_suspected" ;
ctth_status_flag:coordinates = "lon lat" ;
ctth_status_flag:grid_mapping = "geostationary" ;
ushort ctth_tempe(ny, nx) ;
ctth_tempe:standard_name = "air_temperature_at_cloud_top" ;
ctth_tempe:long_name = "NWC GEO CTTH Cloud Top Temperature" ;
ctth_tempe:scale_factor = 0.01f ;
ctth_tempe:add_offset = 130.f ;
ctth_tempe:units = "K" ;
ctth_tempe:valid_range = 0US, 22000US ;
ctth_tempe:_FillValue = 65535US ;
ctth_tempe:ancillary_variables = "ctth_status_flag ctth_conditions ctth_quality ctth_tempe_pal" ;
ctth_tempe:coordinates = "lon lat" ;
ctth_tempe:grid_mapping = "geostationary" ;
ubyte ctth_tempe_pal(pal03_colors, pal_RGB) ;
ctth_tempe_pal:long_name = "RGB palette for ctth_tempe" ;
ctth_tempe_pal:valid_range = 0UB, 255UB ;
ctth_tempe_pal:colormodel = "RGB" ;
ctth_tempe_pal:comment = "Palette applicable to field ctth_tempe" ;
float nx(nx) ;
nx:standard_name = "projection_x_coordinate" ;
nx:long_name = "X Georeferenced Coordinate for each pixel count" ;
nx:units = "m" ;
float ny(ny) ;
ny:standard_name = "projection_y_coordinate" ;
ny:long_name = "Y Georeferenced Coordinate for each pixel count" ;
ny:units = "m" ;
float geostationary ;
geostationary:proj_name = "GEOS141" ;
geostationary:sweep_angle_axis = "y" ;
geostationary:false_northing = 0LL ;
geostationary:grid_mapping_name = "geostationary" ;
geostationary:false_easting = 0LL ;
geostationary:satellite_height = 35785863. ;
geostationary:semi_major_axis = 6378137. ;
geostationary:semi_minor_axis = 6356752.3 ;
geostationary:perspective_point_height = 35785863. ;
geostationary:GeoTransform = -5500000., 2000., 0., 5500000., 0., -2000. ;
geostationary:longitude_of_projection_origin = 140.7 ;
geostationary:proj4 = "+proj=geos +lon_0=140.7 +h=35785863 +x_0=0 +y_0=0 +a=6378137 +b=6356752.3 +units=m +no_defs" ;
geostationary:spatial_ref = "PROJCS[\"unnamed\",GEOGCS[\"unnamed ellipse\",DATUM[\"unknown\",SPHEROID[\"unnamed\",6378137,298.2570248822731]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433]],PROJECTION[\"Geostationary_Satellite\"],PARAMETER[\"central_meridian\",140.7],PARAMETER[\"satellite_height\",35785863],PARAMETER[\"false_easting\",0],PARAMETER[\"false_northing\",0],UNIT[\"Meter\",1]]" ;
// global attributes:
:Conventions = "CF-1.6" ;
:title = "NWC GEO Cloud Top Temperature and Height Product" ;
:institution = "Bureau of Meteorology" ;
:source = "NWC/GEO version v2021.1" ;
:comment = "Copyright 2022, EUMETSAT, All Rights Reserved" ;
:references = "http://nwc-saf.eumetsat.int" ;
:contact = "safnwchd@aemet.es" ;
:summary = "Cloud Top Temperature and Height Product of the NWC/GEO. Information on cloud vertical extension and on cloud top temperature." ;
:keywords = "Cloud Height, Cloud Top Pressure, Cloud Top Temperature, Cloud Emissivity" ;
:keywords_vocabulary = "GCMD Science Keywords" ;
:id = "S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc" ;
:naming_authority = "Bureau of Meteorology" ;
:cdm_data_type = "Image" ;
:date_created = "2022-12-27T08:56:01Z" ;
:creator_name = "Bureau of Meteorology" ;
:creator_url = "www.bom.gov.au" ;
:creator_email = "SI-Research-SS@bom.gov.au" ;
:project = "NWC/GEO" ;
:processing_level = "Level 2" ;
:time_coverage_start = "2022-01-01T03:00:20Z" ;
:time_coverage_end = "2022-01-01T03:09:40Z" ;
:license = "EUMETSAT user policy" ;
:saf = "NWC/GEO" ;
:product_name = "CTTH" ;
:product_algorithm_version = "4.1" ;
:satellite_identifier = "HIMA08" ;
:sub-satellite_longitude = 140.7f ;
:centre_projection_longitude = 140.7f ;
:nominal_product_time = "2022-01-01T03:00:00Z" ;
:region_id = "HIMA-N" ;
:region_name = "HIMA-N; CENTRE=0N 140.7E; SIZE=5500x5500pix" ;
:spatial_resolution = 2.f ;
:cgms_projection = "+proj=geos +coff=2750.500000 +cfac=20466275.000000 +loff=2750.500000 +lfac=20466275.000000 +spp=140.699997 +r_eq=6378.137000 +r_pol=6356.752300 +h=42164.000000" ;
:gdal_projection = "+proj=geos +a=6378137.000000 +b=6356752.300000 +lon_0=140.699997 +h=35785863.000000 +sweep=y" ;
:gdal_geotransform_table = -5499996.f, 1999.998f, 0.f, 5499996.f, 0.f, -1999.998f ;
:gdal_xgeo_up_left = -5499996.f ;
:gdal_ygeo_up_left = 5499996.f ;
:gdal_xgeo_low_right = 5499996.f ;
:gdal_ygeo_low_right = -5499996.f ;
:product_quality = 54.49218f ;
:product_completeness = 84.37789f ;
:geospatial_lat_max = 81.04704f ;
:geospatial_lat_min = -81.04704f ;
:geospatial_lon_max = 180.f ;
:geospatial_lon_min = -180.f ;
:product_version = "2.0" ;
:history = "Fri Jan 20 06:20:55 2023: ncatted -O -a product_version,global,c,c,2.0 /scratch/er8/vov548/output/nwcsaf_2021.1_h8_reprocessing/ctth//S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc\nFri Jan 20 06:19:10 2023: ncks -O -L 9 --cnk_dmn x,5500 --cnk_dmn y,20 /scratch/er8/vov548/output/nwcsaf_2021.1_h8_compressed/ctth/S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc /scratch/er8/vov548/output/nwcsaf_2021.1_h8_reprocessing/ctth//S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc\nWed Dec 28 23:49:04 2022: ncatted -O -a product_version,global,c,c,2.0 /scratch/er8/vov548/output/nwcsaf_2021.1_h8//S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc\nWed Dec 28 23:47:18 2022: ncks -O -L 9 --cnk_dmn x,5500 --cnk_dmn y,20 /scratch/er8/vov548/output/nwcsaf_2021.1_h8/S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc /scratch/er8/vov548/output/nwcsaf_2021.1_h8//S_NWC_CTTH_HIMA08_HIMA-N-NR_20220101T030000Z.nc\n2022-12-27T08:56:01Z (null) Product Created by NWC/GEO v2021.1\n2022-12-27T08:56:01Z (null) GEO-CTTH.exe 2022-01-01T03:00:00Z /scratch/er8/vov548/ws/nwcsaf_2021.1_h8/install/tmp66z3dl8b/config/safnwc_HIMAN./scratch/er8/vov548/ws/nwcsaf_2021.1_h8/install/tmp66z3dl8b/config/safnwc_CTTH.c4.1 /scratch/er8/vov548/ws/nwcsaf_2021.1_h8/install/tmp66z3dl8b/config/safnwc_CTTH.c4.1" ;
:NCO = "netCDF Operators version 4.7.7 (Homepage = http://nco.sf.net, Code = http://github.com/nco/nco)" ;
}