ERA5 Reanalysis Model Level Data in the RDA
Dec. 2, 2022
Posted by:
Dave Stepaniak
Note: This page was originally sourced from our Blogger page: http://ncarrda.blogspot.com/2022/12/era5-reanalysis-model-level-data-in-rda.html
NCAR/CISL/DECS personnel are in the process of downloading ECMWF Meteorological Archival and Retrieval System (MARS) ERA5 GRIB 2 and GRIB 1 model level T639 spherical harmonic and N320 reduced Gaussian data, and synthesizing or interpolating this to a 1280 longitude x 640 Gaussian latitude 0.28125° gridded dataset with 137 levels. In addition, the final gridded product is being converted to CF-compliant compressed netCDF4/HDF5 format. The period of coverage is 1979 to the present time. Please see ds633.6,
ERA5 Reanalysis Model Level Data
for processing and archiving status. Data is made available in netCDF4/HDF5 format only, via the RDA website and NCAR/CISL GLADE storage. A snapshot of the metadata content of a typical file is presented below.
netcdf e5.oper.an.ml.0_5_0_0_0_t.regn320sc.1999050100_1999050105 {
dimensions:
time = UNLIMITED ; // (6 currently)
level = 137 ;
latitude = 640 ;
longitude = 1280 ;
half_level = 138 ;
variables:
float T(time, level, latitude, longitude) ;
T:long_name = "Temperature" ;
T:standard_name = "air_temperature" ;
T:short_name = "t" ;
T:units = "K" ;
T:original_format = "WMO GRIB 2" ;
T:wmo_discipline = 0 ;
T:wmo_master_table = 5 ;
T:wmo_local_table = 0 ;
T:wmo_center = 98 ;
T:wmo_parameter_category = 0 ;
T:wmo_parameter_number = 0 ;
T:_FillValue = 9.999e+20f ;
T:missing_value = 9.999e+20f ;
T:minimum_value = 175.1045f ;
T:maximum_value = 314.6406f ;
T:grid_specification = "0.28125° x ~0.28125° from 0E to 359.71875E and 89.78488N to 89.78488S (1280 x 640 Longitude/Gaussian Latitude), ~31km at Equator" ;
T:original_data_representation = "T639 spherical harmonics, ECMWF Meteorological Archival and Retrieval System (MARS)" ;
T:rda_dataset = "ds633.6" ;
T:rda_dataset_url = "https:/rda.ucar.edu/datasets/ds633.6/" ;
T:rda_dataset_doi = "DOI: 10.5065/XV5R-5344" ;
T:rda_dataset_group = "ERA5 atmospheric model level analysis [netCDF4]" ;
T:QuantizeGranularBitGroomNumberOfSignificantDigits = 7 ;
double a_half(half_level) ;
a_half:long_name = "half level a coefficient" ;
a_half:alternate_name = "interface a coefficient" ;
a_half:short_name = "a_half" ;
a_half:units = "Pa" ;
a_half:source = "https://confluence.ecmwf.int/display/UDOC/L137+model+level+definitions, column 2" ;
double a_model(level) ;
a_model:long_name = "model level a coefficient" ;
a_model:short_name = "a_model" ;
a_model:units = "Pa" ;
a_model:source = "https://www.ecmwf.int/en/elibrary/9203-ifs-documentation-cy40r1-part-iii-dynamics-and-numerical-procedures, pdf download, page 7, in Section 2.2.1 Vertical Discretization, model level a coefficients are found by average of adjacent half levels (interfaces)" ;
a_model:for_an_alternative_derivation_see = "Simmons, A. J., and D. M. Burridge, 1981: An energy and angular-momentum conserving finite-difference scheme and hybrid vertical coordinates. Mon. Wea. Rev., 109, 758-766.; Trenberth, K. E., J. C. Berry, and L. E. Buja, 1993: Vertical interpolation and truncation of model-coordinate data. NCAR Technical Note NCAR/TN-396+STR, 54 pp." ;
double b_half(half_level) ;
b_half:long_name = "half level b coefficient" ;
b_half:alternate_name = "interface b coefficient" ;
b_half:short_name = "b_half" ;
b_half:units = "1" ;
b_half:source = "https://confluence.ecmwf.int/display/UDOC/L137+model+level+definitions, column 3" ;
double b_model(level) ;
b_model:long_name = "model level b coefficient" ;
b_model:short_name = "b_model" ;
b_model:units = "1" ;
b_model:source = "https://www.ecmwf.int/en/elibrary/9203-ifs-documentation-cy40r1-part-iii-dynamics-and-numerical-procedures, pdf download, page 7, in Section 2.2.1 Vertical Discretization, model level b coefficients are found by average of adjacent half levels (interfaces)" ;
b_model:for_an_alternative_derivation_see = "Simmons, A. J., and D. M. Burridge, 1981: An energy and angular-momentum conserving finite-difference scheme and hybrid vertical coordinates. Mon. Wea. Rev., 109, 758-766.; Trenberth, K. E., J. C. Berry, and L. E. Buja, 1993: Vertical interpolation and truncation of model-coordinate data. NCAR Technical Note NCAR/TN-396+STR, 54 pp." ;
int half_level(half_level) ;
half_level:long_name = "half level" ;
half_level:alternate_name = "interface" ;
half_level:short_name = "hlev" ;
half_level:formula = "p = a + b*ps" ;
half_level:order = "top of atmosphere to surface" ;
half_level:units = "1" ;
double latitude(latitude) ;
latitude:long_name = "gaussian latitude" ;
latitude:standard_name = "latitude" ;
latitude:short_name = "lat" ;
latitude:units = "degrees_north" ;
int level(level) ;
level:long_name = "model level" ;
level:standard_name = "atmosphere_hybrid_sigma_pressure_coordinate" ;
level:short_name = "lev" ;
level:formula = "p = a + b*ps" ;
level:order = "near top of atmosphere to near surface" ;
level:units = "1" ;
double longitude(longitude) ;
longitude:long_name = "longitude" ;
longitude:standard_name = "longitude" ;
longitude:short_name = "lon" ;
longitude:units = "degrees_east" ;
int time(time) ;
time:long_name = "time" ;
time:standard_name = "time" ;
time:units = "hours since 1900-01-01 00:00:00" ;
time:calendar = "gregorian" ;
int utc_date(time) ;
utc_date:long_name = "UTC date yyyy-mm-dd hh:00:00 as yyyymmddhh" ;
utc_date:units = "Gregorian_year month day hour" ;
double weight(latitude) ;
weight:long_name = "gaussian weight" ;
weight:short_name = "weight" ;
weight:units = "1" ;
double zero(latitude) ;
zero:long_name = "gaussian zero" ;
zero:short_name = "zero" ;
zero:units = "1" ;
// global attributes:
:RDA_DATASET = "ds633.6" ;
:RDA_DATASET_URL = "https:/rda.ucar.edu/datasets/ds633.6/" ;
:RDA_DATASET_DOI = "DOI: 10.5065/XV5R-5344" ;
:RDA_DATASET_GROUP = "ERA5 atmospheric model level analysis [netCDF4]" ;
:DATA_SOURCE = "Downloaded by NCAR/CISL/DECS from ECMWF\"s Meteorological Archival and Retrieval System (MARS): ERA5 GRIB 2 data (T639 Spherical harmonics and N320 reduced Gaussian data)" ;
:DOWNLOAD_SPECIALIST = "Chi-Fan Shih, NCAR/CISL/DECS, chifan@ucar.edu" ;
:DATA_INTERPOLATION = "Computed by NCAR/CISL/DECS: ERA5 GRIB 2 T639/N320 data synthesized or interpolated to 1280 longitude x 640 Gaussian latitude GRIB 2 gridded data using emoslib-4.3.9 (compiled with cmake with grib_api-1.14.7 and fftw-3.3.8 support for gnu/gfortran-9.1.0). NOTE: u-component and v-component of horizontal wind derived from spectral vorticity and divergence." ;
:COMPUTATIONAL_PLATFORM = "cheyenne supercomputer, NCAR-Wyoming Supercomputing Center (NWSC), https://www2.cisl.ucar.edu/" ;
:COMPUTATIONAL_SPECIALIST = "Dave Stepaniak, NCAR/CISL/DECS, davestep@ucar.edu" ;
:NETCDF_CONVERSION = "Conversion by NCAR/CISL/DECS: Conversion from synthesized or interpolated 1280 longitude x 640 Gaussian latitude GRIB 2 gridded data to netCDF4/HDF5." ;
:NETCDF_VERSION = "4.8.1" ;
:Conventions = "CF-1.6" ;
:NETCDF_COMPRESSION = "Precision-preserving compression to netCDF4/HDF5 using NCO (see \"history\" and \"NCO\" global attributes below for specifics)." ;
:CONVERSION_AND_COMPRESSION_PLATFORM = "cheyenne node employed: Linux r14i0n16 4.12.14-95.51-default #1 SMP Fri Apr 17 08:14:12 UTC 2020 (c6bab98) x86_64 x86_64 x86_64 GNU/Linux" ;
:CONVERSION_AND_COMPRSSION_DATE = "Fri Dec 2 12:05:36 MST 2022" ;
:CONVERSION_AND_COMPRESSION_SPECIALIST = "Dave Stepaniak, NCAR/CISL/DECS, davestep@ucar.edu" ;
:history = "Fri Dec 2 12:05:50 2022: ncks -4 --ppc T=7 e5.oper.an.ml.0_5_0_0_0_t.regn320sc.1999050100_1999050105.unc.nc e5.oper.an.ml.0_5_0_0_0_t.regn320sc.1999050100_1999050105.nc" ;
:NCO = "netCDF Operators version 5.0.3 (Homepage = http://nco.sf.net, Code = http://github.com/nco/nco)" ;