Lake-ICE National Weather Service High-Resolution Upper-Air Data Set 1.0 General Description This data set includes high resolution sounding data from 67 NWS sites over the lower 48 states of the United States (see section 4.0 for a list of sites. These soundings were typically released at 00 12 UTC. The final dataset consists of 6-sec vertical resolution files. 2.0 Detailed Data Description 2.0.1 National Weather Service High-Resolution Sounding Algorithms The detailed description of NWS sounding collection and instrumentation is located in NWS (1991). 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 next 3 lines in the Lake-ICE NWS soundings contain the ascension number, radiosonde serial number, and radiosonde manufacturer. The following 3 header lines are used for auxiliary information and comments about the sounding, and these are empty for the Lake-ICE NWS soundings. The next heder line contains the nominal release time. 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 five 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 Launch Site Type/Site ID: Description of launch site. 4 Launch Location (lon,lat,alt): Position of launch site, in format described below. 5 GMT Launch 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 ESOP 1996 NWS High- Resolution Upper-Air data 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: NWS Project ID: LAKE ICE NWS 6-second class format sounding Launch Site Type/Site ID: EYW Key West, FL Launch Location (lon,lat,alt): 081 48.00'W, 24 30.00'N, -81.80, 24.50, 2.0 GMT Launch Time (y,m,d,h,m,s): 1997, 12, 29, 23:02:00 Ascension No: 1679 Radiosonde Serial Number: 84726586.CSN Radiosonde Manufacturer: VIZ B2 / / / Nominal Launch Time (y,m,d,h,m,s): 1997, 12, 30, 00:00:00 Time Press Temp Dewpt RH Uwind Vwind Wspd Dir dZ Lon Lat Rng Ang Alt Qp Qt Qh Qu Qv Qdz sec mb C C % m/s m/s m/s deg m/s deg deg km deg m code code code code code code ------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- ------- ----- ----- ------- ---- ---- ---- ---- ---- ---- 0.0 1011.8 20.0 12.0 60.0 9.7 -3.5 10.3 290.0 999.0 -81.800 24.500 999.0 999.0 2.0 99.0 99.0 99.0 99.0 99.0 9.0 6.0 1010.3 20.1 11.2 56.6 9999.0 9999.0 999.0 999.0 2.2 9999.000 999.000 999.0 999.0 15.0 2.0 99.0 99.0 9.0 9.0 99.0 12.0 1006.1 19.9 11.0 56.6 9999.0 9999.0 999.0 999.0 6.0 9999.000 999.000 999.0 999.0 51.0 2.0 99.0 99.0 9.0 9.0 99.0 2.2 Data Remarks The NWS soundings during Lake-ICE utilized either the VIZ Inc. 2B (or sometimes the old VIZ radiosondes were used as the sites used up old supplies) or the Vaisala RS-80 radiosonde. See section 4.0 for the list of sites and the radiosondes they used. The use of the raw 6-sec resolution elevation and azimuth angle data to derive the winds sometimes led to large oscillations in wind speed, due to the presence of oscillations in the elevation angle data, particularly at low elevation angles. The general approach to correct this problem was to remove the outlier radiosonde position data before computing the wind components (Williams et al. 1993). For both the azimuth and elevation angles from 360 sec to the end of the sounding, a ninth order polynomial was fit to the curve. The residuals were calculated and compared to the observed values. The outliers of the residuals were then removed. Then to help correct the more extensive problems at low elevation angles within 10 degrees of the limiting angles (LA) some additional smoothing was applied. If the elevation angle was between (LA + 7.5) and (LA + 10), the new elevation angle was computed with a 2 min linear fit. If the elevation angle was between (LA + 5) and (LA + 7.5), the new elevation angle was computed with a 3 min linear fit. If the elevation angle was less than (LA + 5), the new elevation angle was computed with a 4 min linear fit. If the number of observations with low elevation angles was greater than 20% of the total number of observations for the sounding no frequency smoothing occurred. Then, for the elevation angle only, a finite Fourier analysis was performed on the residuals. Periods from 90-190 sec were removed and those below 30 sec were flattened. Finally, a 2 min second order polynomial was then fit to the position to derive the u and v wind components, except for the beginning and end minute (or 1.5 minutes if over 50 mb) which used a 3 min fit. If there were less than 15% of the total number of points, not counting the beginning or end of the flight, on one side of the point for which the wind value was being computed, a linear fit was used. For further information on this methodology and its changes since Williams et al. (1993) please see Williams, et al. (1998). 3.0 Quality Control Processing This dataset underwent a two-stage QC process. First, the dataset underwent internal consistency checks. This included two types of checks, gross limit checks on all parameters and rate-of-change checks on temperature, pressure and ascension rate. Second, each sounding was visually examined to verify those parameters that are too variable for automatic checks (wind speed, wind direction and moisture). This stage of the QC process also allows for a verification of the QC flags generated by the automatic checks. Some further information on the QC processing conducted by JOSS can be found in Loehrer et al. (1996) and Loehrer et al. (1998). 3.1 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 1996 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 > 35000 m P, T, RH Q Temperature < -80C or > 45C T Q Dew Point < -99.9C or > 30C 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 > 100 m/s U Q > 150 m/s U B V Wind Component < 0 m/s or > 100 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 _________________________________________________________________ 3.2 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 6-sec data points (except at pressures less than 100 mb where 30-sec average values were used. 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 > 5 C/km (not applied at p , 150mb) P, T, RH Q < 30 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 _____________________________________________________________________ 3.3 Data Quality Issues 3.3.1 Near Surface Winds A common problem in near surface wind speed values calculated from the 6-second position data is that the first radiosonde wind speed is much higher than the independently measured surface value. The calculated radiosonde winds then decrease rapidly so that within about 60 s (20-30 mb) after release the wind speeds are more realistic. The cause of this appears to be the acceptance of radiosonde position data prior to a "good lock" being achieved on the radiosonde by the tracking system. Thus there appear to be rapid positional shifts of the radiosonde while the tracking system "searches" for the radiosonde. 3.3.2 Wind Oscillations Despite the extensive efforts to remove oscillations in wind speeds caused by oscillations in elevation angles (see Section 2.2) there are occasional cases with remaining oscillations. Most of the remaining oscillations have periods just slightly longer than the 190 s maximum point of our notch filter. 3.3.3 General Low Level Humidity Problem Another frequent occurrence in NWS soundings is what appears to be a very dry surface relative to the radiosonde values. An example is shown below from Albuquerque, NM at 00 UTC 25 April 1996. Time Press Temperature Dew Relative Point Humidity ------ ------ --------------- ----- ----------- 0.0 834.4 28.9 -14.5 5.0 6.0 830.9 28.1 -8.7 8.4 12.0 827.4 27.7 -9.7 7.9 18.0 823.9 27.3 -10.0 7.9 24.0 820.5 26.8 -10.4 7.9 The independently measured surface RH is about 4% less than the first radiosonde value. Then the remainder of the radiosonde values appear to be consistent with the first radiosonde value and not the surface value. It has been suggested (Wade 1995) that when this problem occurs, the entire sounding RH may be to moist. 4.0 Radiosonde Stations Included within Data Set Net Id Name St lat lon elev total files sonde type ********************************************************************************** NWSS Caribou ME 46.90 -68.00 191 121 VIZ B2 NWSS Quillayute WA 48.00 -124.60 56 115 VIZ B2 NWSS Little Rock AR 34.80 -92.30 172 115 VIZ B2 NWSS Rapid City SD 44.10 -103.20 1029 117 VIZ B2 NWSS Reno NV 39.60 -119.80 1516 125 VIZ B2 NWSS Glasgow MT 48.20 -106.60 693 122 VIZ B2 NWSS Fort Worth TX 32.80 -97.30 198 124 VIZ B2 NWSS Chatham MA 41.70 -70.00 16 124 VIZ B2 NWSS Gray ME 43.90 -70.30 125 116 Vaisala NWSS Shreveport LA 32.50 -93.80 83 116 VIZ B2 NWSS Aberdeen SD 45.50 -98.40 397 123 VIZ B2 NWSS Springfield MO 37.20 -93.40 390 124 VIZ B2 NWSS Topeka KS 39.10 -95.60 270 122 VIZ B2 NWSS Bismarck ND 46.80 -100.70 505 87 VIZ B2 NWSS Desert Rock NV 36.60 -116.00 1007 122 VIZ B2 NWSS Boise ID 43.60 -116.20 871 124 Vaisala NWSS Tucson AZ 32.10 -110.90 787 121 Vaisala NWSS Amarillo TX 35.20 -101.70 1094 115 Vaisala NWSS Greensboro NC 36.10 -79.90 277 127 VIZ B2 NWSS Wilmington OH 39.40 -83.70 323 125 VIZ B2 NWSS Buffalo NY 42.90 -78.70 218 127 VIZ B2 NWSS Charleston SC 32.90 -80.00 15 120 VIZ B2 NWSS Brownsville TX 25.90 -97.40 7 114 VIZ B2 NWSS Tallahassee FL 30.40 -84.30 18 124 VIZ B2 NWSS Jacksonville FL 30.50 -81.70 9 121 VIZ B2 NWSS Green Bay WI 44.50 -88.10 214 115 VIZ B2 NWSS Newport NC 34.80 -76.90 11 117 VIZ B2 NWSS Great Falls MT 47.50 -111.40 1132 124 VIZ B2 NWSS Albuquerque NM 35.00 -106.60 1615 125 VIZ B2 NWSS Elko NV 40.90 -115.70 1592 122 VIZ B2 NWSS Spokane WA 47.70 -117.60 728 1 VIZ B2 NWSS North Platte NE 41.10 -100.70 849 123 VIZ B2 NWSS Riverton WY 43.10 -108.50 1700 123 Vaisala NWSS Medford OR 42.40 -122.90 397 124 VIZ B2 NWSS Tampa Bay Area FL 27.70 -82.40 13 124 VIZ B2 NWSS Corpus Christi TX 27.80 -97.50 14 117 VIZ B2 NWSS Slidell LA 30.40 -89.80 10 122 VIZ B2 NWSS Lake Charles LA 30.10 -93.20 5 119 VIZ B2 NWSS Miami FL 25.80 -80.40 5 117 VIZ B2 NWSS Brookhaven NY 40.90 -72.90 20 115 VIZ B2 NWSS Peachtree City GA 33.40 -84.60 246 122 VIZ B2 NWSS Pittsburgh PA 40.50 -80.20 360 121 VIZ B2 NWSS Sterling VA 39.00 -77.50 85 120 Vaisala NWSS Nashville TN 36.20 -86.60 180 124 VIZ B2 NWSS Valley NE 41.30 -96.40 350 124 VIZ B2 NWSS Davenport IA 41.60 -90.60 229 122 VIZ B2 NWSS Chanhassen MN 44.80 -93.60 288 124 VIZ B2 NWSS Del Rio TX 29.40 -100.90 314 124 VIZ B2 NWSS Santa Teresa NM 31.90 -106.70 1257 119 Vaisala NWSS Midland TX 32.00 -102.20 873 115 Vaisala NWSS Flagstaff AZ 35.20 -111.80 2180 124 VIZ B2 NWSS Denver INT APT CO 39.80 -104.90 1611 119 Vaisala NWSS Salem OR 44.90 -123.00 61 124 VIZ B2 NWSS White Lake MI 42.70 -83.50 329 120 VIZ B2 NWSS Jackson MS 32.30 -90.10 91 122 VIZ B2 NWSS Key West FL 24.50 -81.80 2 121 VIZ B2 NWSS Grand Junction CO 39.10 -108.50 1475 122 VIZ B2 NWSS Central Illinoi IL 40.20 -89.30 178 120 VIZ B2 NWSS Shelby County AL 33.20 -86.80 178 123 VIZ B2 NWSS Gaylord MI 44.90 -84.70 447 120 VIZ B2 NWSS International F MN 48.50 -93.40 361 121 Vaisala NWSS Norman OK 35.20 -97.40 357 123 VIZ B2 NWSS Dodge City KS 37.80 -100.00 788 123 VIZ B2 NWSS Blacksburg VA 37.20 -80.40 640 125 VIZ B2 NWSS Oakland CA 37.70 -122.20 6 123 VIZ B2 NWSS San Diego CA 32.80 -117.10 134 107 VIZ B2 NOTE: High resolution soundings from Albany, NY and Wallops Island, VA are not yet available from NCDC. Due to problems with format conversions at NCDC no high resolution data are available from Salt Lake City, UT and only the one sounding is available from Spokane, WA. 5.0 References Loehrer, S. M., T. A. Edmands, and J. A. Moore, 1996: TOGA COARE upper-air sounding data archive: development and quality control procedures. Bull. Amer. Meteor. Soc., 77, 2651-2671. Loehrer, S. M., S. F. Williams, and J. A. Moore, 1998: Results from UCAR/JOSS quality control of atmospheric soundings from field projects. Preprints, Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, AZ, Amer. Meteor. Soc., 1-6. NWS, 1991: Micro-ART Observation and Rework Programs Technical Document, National Weather Service, National Oceanic and Atmospheric Administration, Washington, D.C., March 1991. Wade, C. G., 1995: Calibration and data reduction problems affecting National Weather Service radiosonde humidity measurements. Preprints, Ninth Symposium on Meteorological Observations and Instrumentation, Charlotte, NC, Amer. Meteor. Soc., 37-42. Williams, S. F., C. G. Wade, and C. Morel, 1993: A comparison of high resolution radiosonde winds: 6-second Micro-ART winds versus 10-second CLASS LORAN winds. Preprints, Eighth Symposium on Meteorological Observations and Instrumentation, Anaheim, California, Amer. Meteor. Soc., 60-65. Williams, S. F., S. M. Loehrer, and D. R. Gallant, 1998: Computation of high-resolution National Weather Service rawinsonde winds. Preprints, Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, AZ, Amer. Meteor. Soc., 387-391.