Using the ECMWF Research Data Set for ASTEX Christopher Bretherton Atmospheric Science Department University of Washington May 19, 1993 A special set of analysis products for the ASTEX region during June 1-28, 1992 was prepared by Ernst Klinker and Tony Hollingsworth of ECMWF. These analyses, or more correctly initializations and very short range forecasts using the ECMWF T213L30 operational model, incorporate routine observations from the global network and special soundings from ASTEX that were sent to ECMWF during ASTEX via the GTS telecommunication system. About 650 special soundings were incorporated, including nearly all soundings from Santa Maria, Porto Santo, and the French ship Le Suroit, most of the soundings taken on the Valdivia and Malcolm Baldridge, and almost none of the soundings from the Oceanus. Surface reports from the research ships were also incorporated into the analyses after the first week of the experiment. Aircraft soundings were not included in the analyses. ECMWF has requested that anyone making use of this dataset acknowledge them, and that those investigators publishing research that makes more than casual use of this dataset contact Ernst Klinker and Tony Hollingsworth about possible coauthorship (and perhaps acknowledge the effort I have put into making this dataset convenient to use). This dataset was sent as 3 IBM3480 cartridge tapes, totalling about 250 MBytes, in a packed (GRIB) format to me, and I have decoded the data into ASCII files, one for each horizontal field at a given level and base time. All data has the same horizontal resolution of 1.25 degrees in lat and lon and corresponds to base (initialization) times of 00,06,12, or 18Z. Different fields have different lat/lon ranges and sets of available vertical levels, as tabulated below. Also, some fields are instantaneous (I) while others are accumulated (A) over the first 6 hours of a forecast initialized at the base time. This is tabulated in the 'time range' column below. Instantaneous fields are best compared with data at the base time, while accumulated fields are best compared with data three hours after the base time. The ASCII files have been combined into tar files, repacked using the unix compress utility, and are available via anonymous ftp from kiwi.atmos.colostate.edu (129.82.107.43) in the directory pub/astex. Each tar file contains all the ASCII files corresponding to one of six groups of fields at all pressure levels on one day. Stored in this way, the entire dataset is about 340 MBytes. Copies of the original tapes can be obtained through Lola Olsen at NSSDC. The table below summarizes the data in the pub/astex subdirectories. Subdir Name ECMWF ECMWF Time Field Units field ID# range abbrev. ----------- ------ ----- ----- ----- ----- basic_fields (lat/lon range 85W to 10E, 70N to 15 N) (7.7 MB/file) (levels 1010,1000,975,950,925,900,875,850,825,800,775,750,700 650,600,550,500,400,300,200,100 HPa) Z 129 I Geopotential m^2/s^2 T 130 I Temperature K Q 133 I Specific humidity kg/kg U 131 I U[ eastward]-velocity m/s V 132 I V[northward]-velocity m/s W 135 I Vertical velocity Pa/s meanw (same lat/lon and levels as above) (1.2 MB/file) MVV 232 A Mean vertical velocity Pa/s surface (lat/lon range 85W to 10E, 70N to 15 N; at surface pressure) (0.1 MB/file) SP 134 I Surface pressure Pa ST 139 I [Sea] surface temperature K diagnostic (lat/lon range 35W to 05W, 20N to 45 N) (2.2 MB/file) (levels 1010,1000,975,950,925,900,875,850,825,800,775,750,700) DHR 214 A Diabatic heating by radiation K/s DHVD 215 A Diab. heat. by vert. diffusion K/s DHCC 216 A Diab. heat. by cu. convection K/s DHLC 217 A Diab. heat. by lg-scale condens.K/s VDZW 218 A Vert. diffusion of zonal wind m^2/s^3 VDMW 219 A Vert. diffusion of meri. wind m^2/s^3 EWGD 220 A E-W gravity wave drag m^2/s^3 NSGD 221 A N-S gravity wave drag m^2/s^3 CTZW 222 A Convective tend. of zonal wind m^2/s^3 CTMW 223 A Convective tend. of meri. wind m^2/s^3 VDH 224 A Vertical diffusion of humidity kg/(kg s) HTCC 225 A Humid. tend. by cu. convection kg/(kg s) HTLC 226 A Humid. tend. by lg-scale cond. kg/(kg s) ATT 228 A Adiabatic tend. of temperature K/s ATH 229 A Adiabatic tend. of humidity kg/(kg s) ATZW 230 A Adiabatic tend. of zonal wind m/s^2 ATMW 231 cloud (lat/lon range 35W to 05W, 20N to 45 N) (0.5 MB/file) (levels 1010,1000,975,950,925,900,875,850,825,800,775,750,700 650,600,550,500,400,300,200,100 HPa) CLW 212 I Cloud liquid water kg/kg CF 213 I Cloud fraction 0-1 surface_diag (lat/lon range 35W to 05W, 20N to 45 N; at surface pressure) (0.2 MB/file) LSP 142 A Large scale precipitation m/(6 hr) CP 143 A Convective precipitation m/(6 hr) BLD 145 A Boundary layer dissipation W/m^2 SSHF 146 A Surface sensible heat flux W/m^2 SLHF 147 A Surface latent heat flux W/m^2 TCC 164 I Total cloud cover 0-1 10U 165 I 10 meter u m/s 10V 166 I 10 meter v m/s 2T 167 I 2 meter temperature K 2D 168 I 2 meter dewpoint temperature K SSR 176 A Surface solar radiation W/m^2 STR 177 A Surface thermal radiation W/m^2 TSR 178 A Top solar radiation W/m^2 TTR 179 A Top thermal radiation W/m^2 EWSS 180 A U-stress N/m^2 NSSS 181 A V-stress N/m^2 E 182 A Evaporation m (H2O) CCC 185 I Convective cloud cover 0-1 LCC 186 I Low cloud cover 0-1 MCC 187 I Medium cloud cover 0-1 HCC 188 I High cloud cover 0-1 TSRU 208 I Top solar radiation upward W/m^2 TTRU 209 I Top thermal radiation upward W/m^2 TSUC 210 I Top solar radiation upward clear sky The ECMWF field abbreviation, ID#, field description and units are taken directly from ECMWF Code Table 2, in case you ever need to consult with ECMWF about this dataset. Within each subdirectory of ecmwfdata, the tar files are named mmdd.tar.Z, where mm=06, dd is the day of June, and tar.Z reminds you that this is a unix-compressed tar file. Uncompressing any of these tar files will increase its size by about a factor of four. To uncompress and untar the data on any unix machine, type zcat mmdd.tar.Z | tar -xvf - This will create for you a subdirectory ecmwfdata in your current directory with the ASCII files in it for the fields in astex/subdir. If an ecmwfdata subdirectory already exists, the files will be added to it. If you want to move all the files in ecmwfdata to another directory (e.g. ecmwfdata2) which you can create by typing mkdir ecmwfdata2, type mv ecmwfdata/* ecmwfdata2 If you want to organize your fields in several directories, this can be done in a similar manner. Each file has a unique name mmddhh.fff.llll where mmddhh is the month, day and base hour (UTC), fff is the three digit ECMWF field ID, and llll is the pressure level, padded with zeroes in front to make it four digits. Surface fields have llll=0000. Since all fields have different names they can be organized into subdirectories as you find convenient. Each file has a three line header of the form ASTEX 1992 6 13 0 ECMWF field 232 Level 850 loni lonf dlon nlon lati latf dlat nlat -85.00 15.00 1.25 81 70.00 10.00 1.25 49 The first line gives the mm dd and hh of the analysis, the ECMWD field id and the pressure level, while the two other lines give lat-lon info. Following this are the field values in 6e13.6 format (which unfortunately does not always leave a blank between numbers, so watch out with unformatted reads). Good luck and email me at breth@amath.washington.edu if you have further questions.