README FILE for Version 2.0 of the IGRA-Derived Sounding Parameters -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- I. DOWNLOAD QUICK START Start by downloading "derived-stations.txt", which has metadata for all stations in the dataset. You can find this file in the same location where this README file resides, i.e., by going to directory pub/data/igra/derived-v2 at ftp.ncdc.noaa.gov or pointing your browser to http://www1.ncdc.noaa.gov/pub/data/igra/derived-v2 . Then, to find and download the data for a specific station, proceed as follows: - Find the station's name in "derived-stations.txt" and note its station identification code (e.g., Key West is "72201"); - From the subdirectory "data-por", download the GZIP-compressed data file (i.e., ".dat.gz" file) that corresponds to this code (e.g., "72201.dat.gz" has the data for Key West ); and - Uncompress the downloaded file using an uncompressing software (e.g., 7-Zip, winzip under Windows or the "gunzip" command under Linux). -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- II. CONTENTS OF ftp://ftp.ncdc.noaa.gov/pub/data/igra/derived-v2 data-por: Directory with all ".dat.gz" files derived-countries.txt: List of country codes and names derived-stations.txt: List of stations and their metadata readme.txt: This file status.txt: Notes on the current status of the IGRA-derived data -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- III. FORMAT OF DATA FILES (".dat.gz" FILES) Each ".dat.gz" file contains data for one station. The name of the file corresponds to a station's World Meteorological Organization (WMO) identification number (e.g., "72201.dat.gz" contains the data for the station with the identification number 72201). Each file contains a series of multiline sounding records, each of which consists of a header record followed by one line of data for each pressure level in the sounding. The variables in each header record include the following: --------------------------------- Variable Columns Type --------------------------------- HEADREC 1- 1 Character ID 2- 6 Integer YEAR 7- 10 Integer MONTH 11- 12 Integer DAY 13- 14 Integer HOUR 15- 16 Integer RELTIME 17- 20 Integer NUMLEV 21- 24 Integer PW 25- 30 Integer INVPRESS 31- 36 Integer INVHGT 37- 42 Integer INVTEMPDIF 43- 48 Integer MIXPRESS 49- 54 Integer MIXHGT 55- 60 Integer FRZPRESS 61- 66 Integer FRZHGT 67- 72 Integer LCLPRESS 73- 78 Integer LCLHGT 79- 84 Integer LFCPRESS 85- 90 Integer LFCHGT 91- 96 Integer LNBPRESS 97-102 Integer LNBHGT 103-108 Integer LI 109-114 Integer SI 115-120 Integer KI 121-126 Integer TTI 127-132 Integer CAPE 133-138 Integer CIN 139-144 Integer --------------------------------- These variables have the following definitions: HEADREC is the header record indicator (always set to "#"). ID is the station identification code. Please see "derived-stations.txt" for a complete list of stations and their metadata. YEAR is the year of the sounding. MONTH is the month of the sounding. DAY is the day of the sounding. HOUR is the hour of the sounding. RELTIME is the release time of the sounding (format HHMM, missing=9999). NUMLEV is the number of levels in the sounding (i.e., the number of data records that follow). PW is the precipitable water (mm*100) between the surface and 500 hPa. INVPRESS is the pressure (in Pa or mb*100) at the level of the warmest temperature in the sounding. Only provided if the warmest temperature is above the surface. INVHGT is the height (in meters above the surface) of the warmest temperature in the sounding. Only provided when the warmest temperature is above the surface. INVTEMPDIF is the difference between the warmest temperature in the sounding and the surface temperature (K * 10). Only provided if the warmest temperature is above the surface. MIXPRESS is the pressure (in Pa or mb * 100) at the top of the mixed layer as determined using the parcel method. MIXHGT is the height (in meters above the surface) of the top of the mixed layer As determined using the parcel method. FRZPRESS is the pressure (in Pa or mb * 100) where the temperature first reaches the freezing point when moving upward from the surface. Determined by interpolating linearly with respect to the logarithm of pressure between adjacent reported levels. Not provided if the surface temperature is below freezing. FRZHGT is the height (in meters above the surface) where the temperature first reaches the freezing point when moving upward from the surface. Determined analogously to FRZPRESS. Not provided if the surface temperature is below freezing. LCLPRESS is the pressure (in Pa or mb * 100) of the lifting condensation level. LCLHGT is the height (in meters above the surface) of the lifting condensation level. LFCPRESS is the pressure (in Pa or mb * 100) of the level of free convection. LFCHGT is the height (in meters above the surface) of the level of free convection. LNBPRESS is the pressure (in Pa or mb * 100) of the level of neutral buoyancy (or equilibrium level). LNBHGT is the height (in meters above the surface) of the level of neutral buoyancy (or equilibrium level). LI is the lifted index (in degrees C). SI is the Showalter index (in degrees C). KI is the K index (in degrees C). TTI is the total totals index (in degrees C). CAPE is the convective available potential energy (in J/kg). CIN is the convective inhibition (in J/kg). In the subsequent data records, the first record always represents the surface level. The variables in each data record include the following: ------------------------------- Variable Columns Type ------------------------------- PRESS 1- 7 Integer OBSGPH 9- 15 Integer CALCGPH 17- 23 Integer TEMP 25- 31 Integer TEMPGRAD 33- 39 Integer PTEMP 41- 47 Integer PTEMPGRAD 49- 55 Integer VTEMP 57- 63 Integer VTEMPGRAD 65- 71 Integer VAPPRESS 73- 79 Integer SATVAP 81- 87 Integer RH 89- 95 Integer RHGRAD 97-103 Integer UWND 105-111 Integer UWDGRAD 113-119 Integer VWND 121-127 Integer VWNDGRAD 129-135 Integer N 137-143 Integer ------------------------------- All missing values are coded as -99999. The variables have the following definitions: PRESS is the observed pressure (Pa or mb * 100). OBSGPH is the observed geopotential height (meters). This value is often not available at significant levels. CALCGPH is the calculated geopotential height (meters). The geopotential height has been estimated by applying the hydrostatic balance to the atmospheric layer between the next lower level with an observed geopotential height and the current level. TEMP is the observed temperature (K * 10). TEMPGRAD is the temperature gradient between the current level and the next higher level with a temperature (K/km * 10, positive if temperature increases with height). PTEMP is the potential temperature (K * 10). PTEMPGRAD is the potential temperature gradient between the current level and the next higher level with a potential temperature (K/km * 10, positive if potential temperature increases with height). VPTEMP is the virtual temperature (K * 10). VTEMPGRAD is the virtual temperature gradient between the current level and the next higher level with a virtual temperature (K/km * 10, positive if virtual temperature increases with height). VAPPRESS is the vapor pressure (mb * 1000) as computed from temperature, pressure, and dewpoint depression at the same level. SATVAP is the saturation vapor pressure (mb * 1000) as computed from pressure and temperature at the same level. RH is the relative humidity (Percent * 10) as calculated from vapor pressure, saturation vapor pressure, and pressure at the same level. RHGRAD is the relative humidity gradient between the current level and the next higher level with temperature and dewpoint depression (%/km * 10, positive if relative humidity increases with height). UWND is the zonal wind component (m/s * 10) as computed from the observed wind speed and direction. UWDGRAD is the vertical gradient of the zonal wind between the current level and the next higher level with a wind observation [(m/s per km) * 10, positive if zonal wind becomes more positive with height]. VWND is the meridional wind component (m/s * 10) as computed from the observed wind speed and direction. VWNDGRAD is the vertical gradient of the meridional wind component between the current level and the next higher level with a wind observation [(m/s per km) * 10, positive if the meridional wind becomes more positive with height]. N is the refractive index (unitless). -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- IV. FORMAT OF "derived-stations.txt" ------------------------------ Variable Columns Type ------------------------------ FIPS 1- 2 Character ID 5- 9 Integer NAME 12-46 Character LATITUDE 48-53 Real LONGITUDE 55-61 Real ELEVATION 63-66 Integer GUANFLAG 68-68 Character LKSFLAG 69-69 Character COMPFLag 70-70 Character FSTYEAR 73-76 Integer LSTYEAR 78-81 Integer ---------------------------------- These variables have the following definitions: FIPS is the FIPS country code. Please see "derived-countries.txt" for a complete list of country codes. ID is the WMO station identification number. NAME is the name of the station. LATITUDE is the latitude of the station (in decimal degrees). LONGITUDE is the longitude of the station (in decimal degrees). ELEVATION is the elevation of the station (in meters). GUANFLAG is a flag that indicates whether the station is part of the GCOS Upper Air Network (GUAN). There are three possible values: Blank = non-GUAN station F = Former GUAN station G = GUAN station LKSFLAG is a flag that indicates whether the station is part of the Lanzante-Klein-Seidel (LKS) station network. There are two possible values: Blank = non-LKS station L = LKS station COMPFLAG is a flag that indicates whether a station's record is a composite of two or more original station records. There are two possible values: Blank = Composite station C = Composite station FSTYEAR is the first year of record at the station in the IGRA-derived data. LSTYEAR is the last year of record at the station in the IGRA-derived data. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- V. FORMAT OF "derived-countries.txt" ------------------------------ Variable Columns Type ------------------------------ FIPS 1-2 Character NAME 5-44 Character ------------------------------ These variables have the following definitions: FIPS is the FIPS country code. NAME is the name of the country. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- For additional information, please send an e-mail to imke.durre@noaa.gov or xungang.yin@noaa.gov.