======================================================================= Rev. 31 May 2023 ======================================================================= The gdas0p5 archive may be accessed by a ftp client or by a web browser: 1) If you want to use a ftp client, Windows PC users may use WinSCP, FileZilla, etc. that support passive mode. MacOS and Linux users may use the ftp command. Connect your ftp client to ftp.arl.noaa.gov using anonymous and your email address for the username and password, respectively and change directory to /archives/gdas0p5. Note if you are using multiple ftp connections, limit the number of concurrent connections equal to or less than two. Otherwise, your access to our ftp server may be blocked off. 2) If you are using a web browser, point it to https://www.ready.noaa.gov/data/archives/gdas0p5. It may take a few minutes or longer for the webpage to display. ======================================================================= Rev. 25 July 2017 ======================================================================= Coinciding with NCEP's upgrade to the global forecast model (GFS), effective beginning with the file 20170719_gdas0p5, (1) there is no vertical velocity, and (2) the data are short-term GFS forecasts instead of GDAS because NCEP is no longer outputting vertical velocity to the files which are used to create the hybrid-level global files in ARL/HYSPLIT- format and because ARL is no longer processing NCEP GDAS files. For these *_gdas0p5 files, HYSPLIT will automatically compute vertical velocity from the divergence when the vertical motion is set to "data" (0), and the following message will be in standard output and the WARNING file: *WARNING*: metini - vertical velocity missing, switching to divergence ======================================================================= Rev. 10 November 2015 ======================================================================= Clarified description of A.B for hybrid levels. ======================================================================= Rev. 29 January 2015 ======================================================================= Note that with the old method (pre July 29, 2013) there are more missings. Also that mid-2009 and earlier, there is an error in the precipitation rate and the u-momentum flux. See the 'missing' file ftp://ftp.arl.noaa.gov/archives/gdas0p5/readme_gdas0p5_missings.txt *********************************************************************** ======================================================================= Rev. 29 July 2013 ======================================================================= Implemented new method of creating these half-degree files. The description below remains, however added vertical velocity and pressure to the hybrid levels, and changed some of the surface fields. ----------------------------------------------------------------------- Data fields, 4-character identifier, units ----------------------------------------------------------------------- Surface or single level: PRSS hPa surface pressure MSLE hPa mean sea level pressure UMOF N/m2 u-component of momentum flux VMOF N/m2 v-component of momentum flux TPP6 m precipitation, 6-hourly accumulation SHTF W/m2 sensible heat net flux DSWF W/m2 downward short wave radiation flux SPH2 kg/kg specific humidity at 2 meters AGL U10M m/s u wind component at 2 meters AGL V10M m/s v wind conponent at 2 meters AGL T02M K temperature at 2 meters AGL TCLD % total cloud cover PBLH m planetary boundary layer height LHTF W/m2 latent heat net flux USTR m/s friction velocity RGHS m surface roughness PTRO hPa pressure at the tropopause 3-dimensional: TEMP K temperature UWND m/s u wind component VWND m/s v wind component WWND hPa/h w wind component SPHU kg/kg specific humidity PRES hPa pressure *********************************************************************** July 9 - 28, 2013 There is an overlap of the below and the above files. For this period, the new (above) files are named with ".new" appended to the filename. *********************************************************************** ======================================================================= readme_gdas0p5_info.txt 28 November 2012 ======================================================================= These daily archive files contain global 3-dimensional gridded meteorological model output. The files contain 3-hourly data, at a half-degree latitude by half-degree longitude resolution, on hybrid sigma-pressure surfaces. ----------------------------------------------------------------------- Filenames such as for November 28, 2012: ----------------------------------------------------------------------- 20121128_gdas0p5 ----------------------------------------------------------------------- File creation ----------------------------------------------------------------------- NOAA NWS NCEP runs numerical weather prediction (NWP) models. This archive contains output from the NCEP Global Data Assimilation System (GDAS) model (http://www.emc.ncep.noaa.gov/index.php?branch=GFS). NOAA OAR ARL processes the NCEP output into the HYSPLIT-compatible format. Since NCEP runs the GDAS 4 times a day, at 00, 06, 12, and 18 UTC, each day's file is a concatenation of successive 0-hour initialization and 3-hour forecasts from the 4 daily runs. In addition 6-hour forecast fields are written to the 0-hour valid times (00, 06, 12, 18 UTC) because they are not output by NCEP at the the 0-hour initialation time. ----------------------------------------------------------------------- These files are not created in a 24x7 operational environment. ----------------------------------------------------------------------- A missing file can result when ARL's processing job fails. Failures can be caused by computer outages, file transfer failures, or other reasons. If files are missing please use the GDAS1 (GDAS). See http://ready.arl.noaa.gov/archives.php ----------------------------------------------------------------------- Data fields, 4-character identifier, units ----------------------------------------------------------------------- Surface or single level: PRSS hPa surface pressure PRT6 m/minute precipitation rate, 6-hourly accumulation UMOF N/m2 u-component of momentum flux VMOM N/m2 v-component of momentum flux SHTF W/m2 sensible heat net flux DSWF W/m2 downward short wave radiation flux SH2M kg/kg specific humidity at 2 meters AGL U10M m/s u wind component at 2 meters AGL V10M m/s v wind conponent at 2 meters AGL T02M K temperature at 2 meters AGL TCLD % total cloud cover SHGT m surface height PBLH m planetary boundary layer height SOLM fraction soil moisture LHTF W/m2 latent heat net flux 3-dimensional: TEMP K temperature SPHU kg/kg specific humidity UWND m/s u wind component VWND m/s v wind component ----------------------------------------------------------------------- 55 hybrid sigma-pressure Levels ----------------------------------------------------------------------- 0.9999, 0.9947, 0.9886, 0.9817, 0.9739, 1.9648, 1.9544, 2.9425, 4.9288, 6.9132, 8.8954, 11.875, 16.853, 21.827, 26.799, 33.769, 41.735, 49.699, 59.660, 69.619, 80.576, 91.531, 102.49, 113.44, 123.39, 133.35, 143.30, 151.26, 157.22, 162.18, 165.15, 166.12, 165.09, 162.07, 157.05, 150.04, 142.02, 132.01, 122.01, 111.00, 99.002, 88.000, 78.000, 68.000, 59.000, 52.000, 45.000, 39.000, 34.000, 29.000, 25.000, 21.000, 18.000, 15.000, 13.000 The pressure level is defined as: P = A + .B*PRSS, where PRSS is the surface pressure and A.B is defined as the level (ie., 16.853 = 869 hPa when the surface pressure is 1000 hPa [P=16+0.853*1000]) ----------------------------------------------------------------------- half-degree horizontal grid ----------------------------------------------------------------------- 720 x 361 gridpoints ----------------------------------------------------------------------- Acronyms - Web sites ----------------------------------------------------------------------- ARL - Air Resources Laboratory - http://www.arl.noaa.gov/ NCEP - National Centers for Environmental Prediction - http://www.ncep.noaa.gov/ NOAA - National Oceanic and Atmospheric Administration - http://www.noaa.gov/ NWS - National Weather Service - http://www.weather.gov/ OAR - Office of Oceanic and Atmospheric Administration - http://www.oar.noaa.gov/