Reference Radiosonde Soundings Contacts: Terry Hock hock@ucar.edu Junhong Wang junhong@ucar.edu Kate Beierle kbeierle@ucar.edu Mailing Address: NCAR/Atmospheric Technology Division P.O. Box 3000 1850 Table Mesa Drive Boulder, CO 80307; USA Phone: (303)-497-8833 Fax: (303)-497-8770 I. Reference Radiosonde Flights For the IHOP 2002 project Refence Radiosondes were launched 16 times along with either a Vaisala RS80 radiosonde from the Homestead site, or the National Weather Services (NWS) VIZ radiosonde out of Dodge City, KS. The chart below shows which sondes were launched simultaneously. Reference Radiosonde Vaisala RS80 at Homestead NWS VIZ at Dodge City Text Format (sse below) CLASS format (see below) CLASS format Z20020528_162645.hms y5281739.hom side by side launch Z20020530_172030.ddc DDC53018.cls Z20020601_170628.ddc DDC60118.cls Z20020603_172501.ddc DDC60318.cls Z20020607_182119.hms y6071856.hom Z20020609_104618.hms y6091135.hom Z20020610_171611.ddc DDC61018.cls Z20020612_165049.ddc Bad Data Z20020613_145507.hms y6131535.hom Z20020615_165517.ddc DDC61518.cls Z20020616_171109.hms y6161756.hom Z20020617_173142.hms y6171801.hom Z20020618_171723.hms y6181752.hom Z20020619_165359.ddc DDC61918.cls Z20020620_025610.hms y6200330.hom Z20020623_190357.hms y6232004.hom II. Reference Radiosonde a. File Format (Z-files) Column names Description Units Time Time sec Pres Pressure mb Alt Altitude above m ground level Temp Temperature degree C DPT Dewpoint temperture degree C RH1 Relative Humidity (with % respect to water) from SW RH2 RH from carbon hygristor % in reference sonde Wspd Wind speed m/s Wdir Wind direction degree Uwind U wind speed m/s Vwind V wind speed m/s Wwind ascension rate of balloon m/s Long Longitude degree Lati Latitude degree _______________ In the soundings files missing values are represented with "NA". b. Important Notes to Users!! Pressure errors: The Reference Sonde (RS) uses a hypsometer to measure pressure. This sensor is not reliable so we suggest not using the pressure data. However, the altitude data are good and can be used to calculate the correct pressures. Note, this only applies to the pressure data from the RS data. The pressure data from the VIZ or Vaisala radiosondes should be good. Time difference: There is a time difference between the launch time indicated in the RS sounding file, and the launch time in the the VIZ/Vaisala soundings. The reason for this difference is that the RS began recording data while still of the ground, while the other sondes began recording closer to, or at, the actual launch time. Therefore, you should always use the the launch time found in the Vaisala/VIZ soundings. Wind data: The RS wind data were not corrected for balloon pendulum swing because the effects of the balloon swing are large, they vary from sounding to sounding, and because the focus of of the reference radiosonde for IHOP was on humidity measurements. Therefore, the wind data should not be used without further evaluation. For further information visit: NCAR/ATD IHOP_2002 Reference Radiosonde Home Page: http://www.atd.ucar.edu/rtf/projects/ihop_2002/RefSonde/ Preliminary Results from IHOP Reference Radiosonde Data: http://www.atd.ucar.edu/homes/junhong/paper/spie02.pdf III. CLASS file format (y-files and DDC-files) a. Header Information The first five header lines contain information identifying the sounding, and have rigidly defined form. Line Label (fixed to 35 chars in length) Contents 1. Data Type: Description of type and resolution of data. 2. Project ID: ID of weather project. 3. Launch Site Type/Site ID: Description of launch site. 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. b. Data Records 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. Instrumentation The main components of the reference radiosonde are a Swiss SRS C34 radiosonde manufactured by Meteolabor AG, Switzerland to measure temperature, humidity and pressure, a Garmin GPS receiver to measure wind, a dropsonde 400 MHz telemetry transmitter to transmit data from multiple sensors to the ground, and a wood or plastic boom for carrying the reference radiosonde at one end and another radiosonde at the other end. The C34 consists of a Snow White (SW) chilled-mirror dew point hygrometer and a carbon hygristor manufactured by Sippican Inc. for humidity measurements, a small copper-constantan thermocouple (0.05 mm diameter) for temperature and a full range hypsometer for pressure. The SW hygrometer is used as the reference humidity sensor and is bassed on the physically well known chilled mirror principle, in which a layer of condensate on a mirror is maintained at a constant reflectivity by continuously adjusting the temperature of the mirror, so that condensate neither grows nor shrinks. The mirror temperature is equivalent to the dew point temperature of the air. The SW uses a 3mm x 3mm copper-constantan thermocouple mounted directly on the cold side of the Peltier cooler as a mirror and a temperature sensor at the same time. The accuracy of the mirror temperature measurement is <0.1K. The SW response time is negligible at +20degC, 10s at -30degC, and 80s at -60degC. The SW needs no individual calibration and can be used again without recalibration if recovered after flight.