Sierra Rotors 2004 Mobile GLASS Data Set Contents: I. Project Information and File Names II. Header Information III. Data Records IV. Data File Specifics V. Data Quality Control Contacts: Kate Young kbeierle@ucar.edu Phone: (303)-497-8743 Tim Lim tdlim@ucar.edu Junhong Wang junhong@ucar.edu Mailing Address: NCAR/Atmospheric Technology Division P.O Box 3000 1850 Table Mesa Drive Boulder, CO 80307; USA Fax: (303)-497-8770 I. File Naming Conventions The Sierra Rotors Mobile GLASS sounding dataset contains 52 quality controlled soundings launched from various locations in and around Fresno, CA between March 3 and April 29, 2004. The data files are typically one-second data files with appropriate corrections and and quality control measures applied. The naming convention for most of these files is the same - "D", followed by "yyyymmddhhmmQC.cls" where yyyy = year, mm = month, hh = hour of the day GMT, mm = minute of the hour, and "QC.cls" refers to the NCAR CLASS format. II. Header Information The header records contain data type, project ID, site ID, site location, actual release time, sonde ID, and possibly other specialized information. The first five header lines contain information identifying the sounding, and have rigidly defined form. The following 6 header lines contain auxiliary information and commments about the sounding, and they can vary from data set to data set. 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) signifying the end of the header. The six standard header lines are as follows: Line Label (fixed to 35 chars in length) Contents 1. Data Type: Description of data type 2. Project ID: ID of weather project. 3. Launch Site Type/Site ID: Description of sounding system and sonde used. 4. Launch Location (lon,lat,alt): Position of launch 5. GMT Launch: 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 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 six non-standard header lines may contain any label and contents. The label is fixed to 35 characters to match the standard header lines. III. Data Records The data records each contain time from release, pressure, temperature, dew point, relative humidity, U and V wind components, wind speed and direction, ascent rate, balloon position data, altitude, and quality control flags. Field Parameter Units Missing Value No. ------------------------------------------------------------------------------------------ 1 Time Seconds 9999.0 2 Pressure Millibars 9999.0 3 Dry-bulb Temp Degrees C 999.0 4 Dew Point Temp Degrees C 999.0 5 Relative Humidity Percent 999.0 6 U Wind Component Meters/Second 999.0 7 V Wind Component Meters/Second 999.0 8 Wind Speed Meters/Second 999.0 9 Wind Direction Degrees 999.0 10 Ascension Rate Meters/Second 999.0 11 Longitude Degrees 999.0 12 Latitude Degrees 999.0 13 Range Kilometers 999.0 14 Angle Degrees 999.0 15 Altitude Meters 99999.0 16 QC flag for Pressure 99.0 17 QC flag for Temp 99.0 18 QC flag for Humidity 99.0 19 QC flag for U Component 99.0 20 QC flag for V Component 99.0 21 QC flag for Horizontal Wind 99.0 IV. Data File Specifics The files contain data calculated at one-second intervals . The variables pressure, temperature, and relative humidity are calibrated values from measurements made by the sonde. The dew point is calculated from the relative humidity. The altitude value is calculated from the hydostatic equation using pressure, temperature, and dew point. The rate of ascent is obtained from the altitude difference between two successive time steps. The position (lat, lon), angle and range come from the GPS and altitude data. This data is interpolated to one second in order to match the wind data. All wind data are computed from GPS navigation signals received from the sonde. The raw wind values are calculatd at a one half second data rate by a commercial processing card. These raw values are subjected to a digital filter to remove low frequency oscillations due to the sonde pendulum motion beneath the balloon. The resolution of the data is reduced to one second. This time record is used in the interpolation of the pressure, temperature, and humidity data. V. Data Quality Control The raw soundings are first run through the Atmospheric Sounding Processing ENvironment (ASPEN), which analyzes the data, performs smoothing, and removes suspect data points. The soundings are then visually evaluated for outliers, or any other obvious problems. Scatter plots of the data are created to check the range in values of pressure, temp and RH. Lastly, we create profiles of temperature and RH, in order to check for any major inconsistencies.