PACS Upper Air Sounding Data from GTS (mandatory/significant levels) 1. General Description This data set contains all land- and ship-based upper air sounding data available from the Global Telecommunication System (GTS) over the region from 30 N to 30 S latitude and 60 to 180 W longitude as collected by NCAR/SCD for the period starting 1 July 1997 through 31 March 2006. The data came to UCAR/JOSS in NCEP Office Note format. JOSS converted the data to University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) Cross Chain LORAN Atmospheric Sounding System (CLASS) Format (JCF) format (see Section 2). JOSS conducted no quality control on these data. New versions of this data set were released on 29 April 2004 and 27 January 2005 to correct problems (see section 1.1). 1.1 29 April 2004 Data Set Corrections 1) The winds included in the previous version of the data set were knots rather than meters/second. The winds in the data set are now in m/s. 2) There was a problem where the surface data point was not being included in the data set. The surface data points are now being included in the data set. 1.2 27 January 2005 Data Set Corrections 1) In the Nov 2002 to April 2003 time period soundings with the same month, day, and hour of release from Nov 2001 to April 2002 and Nov 2002 to April 2003 were combined into a single sounding for the later year (e.g. if there were soundings from station 72202 taken at 00 UTC on 21 Nov in both 2001 and 2002 then all of the data from the 2001 sounding was included with the 2002 sounding). 2) In the Nov 2001 to April 2002 time period there were soundings that should have been included but were not due to the error mentioned above (from the example above, there would not have been a sounding file created for the 2001 sounding). 3) Another issue that was more minor in terms of number of soundings impacted, but covers the entire time period of the data set was that missing temperature values were utilized in the derivation of heights. 4) This one impacts a very small number of soundings from a limited set of locations (those with WMO id's in the 90000 range) but again may have occurred throughout the entire time period of the data set. The problem was that stations with short id's (four characters) and starting with a letter were not being recognized. The data from these stations was being combined into a single sounding with the last numerical id (often 91958). As a reminder, there are still a number of data errors included in this data set. These errors were typically due to GTS coding errors at the stations. These errors have sometimes significant impacts on the derived heights. UCAR/JOSS is now conducting and automated QC on these data. Data values are not changed, but problem data points are being flagged. 2.0 Detailed Data Description 2.0.1 Conversion from NCEP Office Note Format to JCF JOSS developed software coverting soundings in NCEP Office Note Format to University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) Cross Chain LORAN Atmospheric Sounding System (CLASS) Format (JCF). The resulting sounding files contain only mandatory and significant level data. JOSS used the following procedure to merge the mandatory and significant level data. The surface mandatory level was found and assigned the surface altitude obtained from the NCEP Office Note file. Altitudes from significant PTH and Wind levels, and mandatory pressure levels were used to place data in altitude increasing (pressure decreasing) order. In cases where the altitude was missing, the missing altitude was calculated using the temperature, pressure and previous significant or mandatory pressure level's pressure, temperature, and altitude (humidities were used when available). No altitude calculations were needed for significant wind level data. There are cases in the final data set where the alitude decreases with decreasing pressure. This is primarily due to two causes, first there are cases of slight variations that are due to things such as GTS rounding to the nearest 10 m and probable cases of surface elevations being slightly in error. The other cases are due to coding errors in the original GTS messages (e.g. height at 500 hPa given as 540 m rather than 5400 m. These errors can be perpetuated in the data set as they are used to derive the heights for the next data point. Such errors are given data quality flags. 2.1 Detailed Format Description All upper air soundings were converted to University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) Cross Chain LORAN Atmospheric Sounding System (CLASS) Format (JCF). JCF is a version of the National Center for Atmospheric Research (NCAR) CLASS format and is an ASCII format consisting of 15 header records for each sounding followed by the data records with associated QC information. Header Records The header records (15 total records) contain data type, project ID, site ID, site location, release time, sonde type, meteorological and wind data processors, and the operator's name and comments. The first five header lines contain information identifying the sounding, and have a rigidly defined form. The following 7 header lines are used for auxiliary information and comments about the sounding, and may vary from dataset to dataset. The last 3 header records contain header information for the data columns. Line 13 holds the field names, line 14 the field units, and line 15 contains dashes ('-' characters) delineating the extent of the field. The standard header lines are as follows: Line Label (padded to 35 char) Contents 1 Data Type: Description of type and resolution of data. 2 Project ID: ID of weather project. 3 Release Site Type/Site ID: Description of launch site. 4 Release Location (lon,lat,alt): Position of launch site, in format described below. 5 UTC Release Time (y,m,d,h,m,s): Time of release, in format: yyyy, mm, dd, hh:mm:ss The release location is given as: lon (deg min), lat (deg min), lon (dec. deg), lat (dec. deg), alt (m) Longitude in deg min is in the format: ddd mm.mm'W where ddd is the number of degrees from True North (with leading zeros if necessary), mm.mm is the decimal number of minutes, and W represents W or E for west or east longitude, respectively. Latitude has the same format as longitude, except there are only two digits for degrees and N or S for north/south latitude. The decimal equivalent of longitude and latitude and station elevation follow. The seven non-standard header lines may contain any label and contents. The label is padded to 35 characters to match the standard header lines. Data Records The data records each contain time from release, pressure, temperature, dewpoint, relative humidity, U and V wind components, wind speed and direction, ascent rate, balloon position data, altitude, and quality control flags (see the QC code description). Each data line contains 21 fields, separated by spaces, with a total width of 130 characters. The data are right-justified within the fields. All fields have one decimal place of precision, with the exception of latitude and longitude, which have three decimal places of precision. The contents and sizes of the 21 fields that appear in each data record are as follows: Field Format No. Width Parameter Units Missing Value ------------------------------------------------------------------------ 1 6 F6.1 Time Seconds 9999.0 2 6 F6.1 Pressure Millibars 9999.0 3 5 F5.1 Dry-bulb Temperature Degrees C 999.0 4 5 F5.1 Dew Point Temperature Degrees C 999.0 5 5 F5.1 Relative Humidity Percent 999.0 6 6 F6.1 U Wind Component Meters / Second 9999.0 7 6 F6.1 V Wind Component Meters / Second 9999.0 8 5 F5.1 Wind Speed Meters / Second 999.0 9 5 F5.1 Wind Direction Degrees 999.0 10 5 F5.1 Ascension Rate Meters / Second 999.0 11 8 F8.3 Longitude Degrees 9999.0 12 7 F7.3 Latitude Degrees 999.0 13 5 F5.1 Range Kilometers 999.0 14 5 F5.1 Azimuth Degrees 999.0 15 7 F7.1 Altitude Meters 99999.0 16 4 F4.1 QC for Pressure Code (see below) 99.0 17 4 F4.1 QC for Temperature Code (see below) 99.0 18 4 F4.1 QC for Humidity Code (see below) 99.0 19 4 F4.1 QC for U Component Code (see below) 99.0 20 4 F4.1 QC for V Component Code (see below) 99.0 21 4 F4.1 QC for Ascension Rate Code (see below) 99.0 Fields 16 through 21 contain the Quality Control information derived at the UCAR Joint Office for Science Support (UCAR/JOSS). Any QC information from the original sounding is replaced by the following JOSS codes: Code Description 99.0 Unchecked (QC information is "missing.") ("UNCHECKED") 1.0 Checked, datum seems physically reasonable. ("GOOD") 2.0 Checked, datum seems questionable on physical basis.("MAYBE") 3.0 Checked, datum seems to be in error. ("BAD") 4.0 Checked, datum is interpolated. ("ESTIMATED") 9.0 Checked, datum was missing in original file. ("MISSING") Sample Data The following is a sample record of PACS Upper Air from GTS in JOSS CLASS format. The data portion is much longer than 80 characters and, therefore, wraps around to a second line. See section 2.1 for an exact format specification Data Type: Sounding Project ID: PACS GTS Release Site Type/Site ID: 85469 ISLA DE PASCUA/EASTER , CI Release Location (lon,lat,alt): 109 25.80'W, 27 10.20'S, -109.43, -27.17, 41.0 UTC Release Time (y,m,d,h,m,s): 1997, 09, 01, 00:00:00 / / / / / / Nominal Release Time (y,m,d,h,m,s):1997, 09, 01, 00:00:00 Time Press Temp Dewpt RH Uwind Vwind Wspd Dir dZ Lon Lat Elev Azim Alt Qp Qt Qh Qu Qv Qdz sec mb C C % m/s m/s m/s deg m/s deg deg deg deg m code code code code code code ------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- ------- ----- ----- ------- ---- ---- ---- ---- ---- ---- 9999.0 1007.0 18.8 12.8 68.1 9999.0 9999.0 999.0 999.0 999.0 9999.000 999.000 999.0 999.0 41.0 99.0 99.0 99.0 9.0 9.0 9.0 9999.0 1000.0 18.3 8.3 52.1 0.0 11.0 11.0 180.0 999.0 9999.000 999.000 999.0 999.0 105.0 99.0 99.0 99.0 99.0 99.0 9.0 9999.0 999.0 18.0 8.0 52.0 9999.0 9999.0 999.0 999.0 999.0 9999.000 999.000 999.0 999.0 113.6 99.0 99.0 99.0 9.0 9.0 9.0 2.2 Data Remarks The time from release field is set to missing in all files. Some files are either wind only or contain just pressure, temperature, and dew point. 3.0 Quality Control Procedures This dataset underwent the JOSS QC process which consisted of internal consistency checks. The internal consistency checks included gross limit checks on all parameters and vertical consistency checks on temperature, pressure, and ascension rate. 5.1 Automated Quality Control Procedures 5.1.1 Gross Limit Checks These checks were conducted on each sounding and data were automatically flagged as appropriate. Only the data point under examination was flagged. JOSS conducted the following gross limit checks on the San Cristobal PACS sounding dataset. In the table P = pressure, T = temperature, RH = relative humidity, U = U wind component, V = V wind component, B = bad, and Q = questionable. ---------------------------------------------------------------- Parameter(s) Flag Parameter Gross Limit Check Flagged Applied ---------------------------------------------------------------- Pressure < 0 mb or > 1030 mb P B Altitude < 0 m or > 40000 m P, T, RH Q Temperature < -99.9C or > 40C T Q Dew Point < -99.9C or > 33C RH Q > Temperature T, RH Q Relative Humidity < 0% or > 100% RH B Wind Speed < 0 m/s or > 100 m/s U, V Q > 150 m/s U, V B U Wind Component < 0 m/s or > 70 m/s U Q > 150 m/s U B V Wind Component < 0 m/s or > 70 m/s V Q > 150 m/s V B Wind Direction < 0 deg or > 360 deg U, V B Ascent Rate < -10 m/s or > 10 m/s P, T, RH Q ---------------------------------------------------------------- 5.1.2 Vertical Consistency Checks These checks were conducted on each sounding and data were automatically flagged as appropriate. These checks were started at the lowest level of the sounding and compared neighboring values. In the case of checks ensuring that the values increased/decreased as expected, only the data point under examination was flagged. However, for the other checks, all of the data points used in the examination were flagged. All items within the table are as previously defined. ---------------------------------------------------------------- Vertical Consistency Parameter(s) Flag Parameter Check Flagged Applied ---------------------------------------------------------------- Time decreasing/equal None None Altitude decreasing/equal P, T, RH Q Pressure increasing/equal P, T, RH Q > 1 mb/s or < -1 mb/s P, T, RH Q > 2 mb/s or < -2 mb/s P, T, RH B Temperature < -15 C/km P, T, RH Q < -30 C/km P, T, RH B from surface to 150 mb: > 50 C/km (not applied at p < 150mb) P, T, RH Q > 100 C/km (not applied at p < 150mb) P, T, RH B for pressures < 150 mb: > 100 C/km (not applied at p > 150mb) P, T, RH Q > 200 C/km (not applied at p > 150mb) P, T, RH B Ascent Rate change of > 3 m/s or < -3 m/s P Q change of > 5 m/s or < -5 m/s P B ---------------------------------------------------------------- 6.0 References Loehrer, S. M., T. A. Edmands and J. A. Moore, 1996: "TOGA COARE upper-air sounding data archive: development and quality control procedures", BAMS, 77, 2651-2671.