STorm-scale Operational and Research Meteorology Weather-data Assimilation and Verification Experiment (STORM-WAVE) Interpolated 5 hPa Vertical Resolution Composite Dataset 1.0 General Description This is one of the upper air sounding datasets developed for the STorm-scale Operational and Research Meteorology Weather-data Assimilation and Verification Experiment (STORM-WAVE). STORM-WAVE was conducted from 1 April through 30 June 1995 and was conducted by the United States Weather Research Program (USWRP) in the central United States. This dataset includes interpolated 5-hPa vertical resolution versions of all soundings from 34 National Weather Service upper-air sites within the STORM-WAVE domain. The STORM-WAVE domain extends from 85W to 109W degrees longitude and 30N to 45N degrees latitude. The dataset includes soundings from the regular 12-hourly intervals at 0000 and 1200 UTC as well as additional special ascensions. The National Weather Service sites included within this dataset are: Id Station Name State Latitude Longitude Elev(m) Record Length *********************************************************************** ABR Aberdeen SD 45.50 -98.40 397 950401-950630 ABQ Albuquerque NM 35.00 -106.60 1615 950401-950630 AMA Amarillo TX 35.20 -101.70 1094 950401-950630 BMX Birmingham AL 33.20 -86.80 178 950401-950630 BNA Nashville TN 36.20 -86.60 180 950329-950630 BIS Bismarck ND 46.80 -100.70 505 950401-950630 CRP Corpus Christi TX 27.80 -97.50 14 950401-950630 DAY Dayton OH 39.90 -84.10 298 950401-950630 DDC Dodge City KS 37.80 -100.00 790 950401-950630 DNR Denver CO 39.80 -104.90 1611 950401-950630 DRT Del Rio TX 29.40 -100.90 314 950401-950630 DTX White Lake MI 42.70 -83.50 329 950401-950630 DVN Davenport IA 41.60 -90.60 229 950401-950630 ELP El Paso TX 31.80 -106.40 1199 950401-950630 FWD FT WORTH TX 32.80 -97.30 198 950401-950630 GJT Grand Junction CO 39.10 -108.50 1475 950401-950630 GRB Green Bay WI 44.50 -88.10 214 950401-950630 ILX Central Illinois IL 40.20 -89.30 178 950401-950630 JAN Jackson MS 32.30 -90.10 91 950401-950630 LBF North Platte NE 41.10 -100.70 849 950401-950630 LCH Lake Charles LA 30.10 -93.20 5 950401-950630 LND Lander WY 42.80 -108.70 1695 950401-950630 LIT North Little Rock AR 34.80 -92.30 172 950401-950630 MAF Midland TX 32.00 -102.20 873 950401-950630 MPX Minneapolis MN 44.80 -93.60 288 950602-950627 OAX Omaha NE 41.30 -96.40 350 950330-950630 OUN Norman OK 35.20 -97.40 357 950401-950630 RAP Rapid City SD 44.00 -103.10 966 950401-950630 SGF Springfield MO 37.20 -93.40 390 950519-950630 SHV Shreveport LA 32.50 -93.80 83 950401-950630 SIL Slidell LA 30.40 -89.80 10 950331-950630 STC St Cloud MN 45.50 -94.10 315 950401-950531 TOP Topeka KS 39.10 -95.60 270 950401-950630 UMN Monett MO 36.90 -93.90 438 950401-950517 *********************************************************************** On 17 May 1995 Monett (UMN) moved to Springfield (SGF). On 1 June 1995 St Cloud (STC) moved to Minneapolis (MPX). 2.0 Detailed Dataset Description 2.1 Detailed Format Description (ASCII format only) All upper air soundings were originally converted to UCAR/Joint Office for Science Support (JOSS) Class Format(JCF). JCF is an ASCII format where a sounding file consists of 15 header records followed by that sounding's data records containing quality control (QC) information. Header Records -------------- The Header records (15 total records) contain data type, project ID, site ID, site location, release time, and comments. The first five header lines hold information identifying the sounding, and have a rigidly defined form. The ensuing 6 header lines are used for auxiliary information and comments about the sounding, and may vary from data set to data set. The next line (line 12) contains the Nominal date and time of the launch. The last 3 header lines contain headers for the data columns, enhancing readability. Line 13 holds the field names, line 14 the field units, and line 15 dashes ('-' characters) delineating the field's extent. The six 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 launch, in format: yyyy, mm, dd, hh:mm:ss 12 GMT Nominal Launch Time (y,m,d,h,m,s): Nominal launch time. The launch 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'X where ddd is the number of degrees (with leading zeros if need be), mm.mm is decimal minutes, and X represents W or E for west or east longitude respectively. Latitude has the same format, except there are only two digits for degrees and X represents N or S for north/south latitude. An example of line 4 would thus be: Launch Location (lon,lat,alt): 096 06.60'W, 39 49.80'N, -96.11, 39.83, 384 The seven non-standard header lines may contain any label and contents. As mentioned above line 12 has been used in the sounding composite for the nominal launch date and time. Data Records ------------ The data records (1 record per 5-hPa interval including surface) 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 (see QC description below). 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 place precision. The contents and sizes of the fields are detailed below. The 21 fields that appear in each data line are as follows: Field Format No. Width Parameter Unit Missing Flag 1 6 F6.1 Time Seconds 9999.0 2 6 F6.1 Pressure Millibar 9999.0 3 5 F5.1 Dry-bulb Temperature Degrees C 999.0 4 5 F5.1 Dew Point 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 (dZ) Meters/Second 999.0 11 8 F8.3 Longitude Degrees 9999.0 12 7 F7.3 Latitude Degrees 999.0 13 5 F5.1 Variable (see below) 999.0 14 5 F5.1 Variable (see below) 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 where Format is the FORTRAN format that could be used to write the field, and Missing Flag is the missing data flag for that field. Note that the missing data flag consists of just enough 9s to fill the field. Note also that there is a space (FORTRAN format 1X) between each field. A FORTRAN 77 FORMAT statement that conforms to the above would be: 100 format(2(2(F6.1,1X),3(F5.1,1X)),F8.3,1X,F7.3,2(1X,F5.1),1X, + F7.1,6(1X,F4.1)) Fields 13 and 14 are "variable" because true CLASS soundings use these fields for range in km and angle in degrees, respectively, which is information unavailable for NWS soundings. NWS soundings do, however, have elevation in degrees and azimuth in degrees, which are used to fill these fields. Processing programs should simply copy the contents of these fields. Fields 16 through 21 contain the JOSS derived Quality Control information. Currently, field 21 will always be missing. The codes used are as follows: Code Meaning 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") 2.2 Data Remarks 2.2.1 National Weather Service Rawinsonde Types The National Weather Service was using two types of rawinsondes during the STORM-WAVE time period. The Amarillo, Texas and El Paso, Texas sites used Space Data rawinsondes from the beginning of STORM-WAVE until 31 May 1995. All other sites, as well as Amarillo and El Paso after 1 June 1995, used VIZ rawinsondes. 2.2.2 Interpolation Methodology The `native' resolution data for every sounding were interpolated to 5 hPa vertical reslution files. The surface data point was kept as the initial level in each sounding. The first interpolated data point was at the next lowest pressure evenly divisible by 5 and then every 5 hPa pressure level beyond that point to either 50 hPa or the lowest pressure level reached by the radiosonde, whichever came first. The first 15 lines of each file (the header information) were kept without change. For the interpolation, the routines searched for two data points around the desired pressure level. The search was conducted by looking for two valid (i.e. non-missing) data points around the desired pressure level, while also paying attention to the time difference between the two data points as well as their quality control flags. There was a search for the two best possible data points to use in the interpolation. If the desired pressure level was within the original dataset, that data point was used without interpolation. There was first a search for values flagged as good within some time range (50 sec for temperature, humidity, and wind and 100 sec for pressure; hereafter termed the ARANGE) and the interpolated data point was flagged as good. Failing that, it searched for values flagged as estimated within the same time range and the interpolated data point was flagged as estimated. Then the search went for good values within a wider time range (100 sec for temperature, humidity, and wind and 200 sec for pressure; hereafter termed the BRANGE) the flag for the interpolated data point here was then degraded (even though two `good' data points were used there was a significant time difference between them) to questionable. Then, in turn, estimated values within the BRANGE were used (flag set to questionable), questionable values within the BRANGE (flag set to bad), good values greater than the BRANGE apart (flag set to bad), estimated values greater than BRANGE apart (flag set to bad), questionable values greater than BRANGE apart (flag set to bad), finally any bad values (flag set to bad). This search was conducted separately for each interpolated variable (pressure, temperature, relative humidity, and the u and v wind components). Thus for each interpolated data point, the quality control flag was set to the worst case among the data points used in the interpolation, except, for each time range apart, the quality control flag was degraded one level (i.e. good to questionable, etc). The quality control flags should be carefully heeded in these files. While some of the data may look good, it may have been interpolated over large pressure intervals, and thus be suspect. For each interpolated data point the dew point was calculated from the temperature and relative humidity (Bolton 1980) and the total wind speed and direction were calculated from the interpolated u and v component values. Also, the altitude and time were interpolated using the same data points used for the pressure interpolation. The ascension rate was recalculated based on the time and altitude values from the two data points used to interpolate the 5 hPa data point. Thus the ascension rate values do not reflect the values based on the interpolated data. The latitude and longitude values were interpolated using the same data points used in the wind component interpolation. 2.2.3 Space Data Relative Humidity Correction This section describes the correction applied to the 6-second vertical resolution relative humidity in the Space Data rawinsondes. JOSS applied a correction to the Space Data radiosonde relative humidity RH) calculations. In the resistance and RH calculations, the NWS Micro-ART sounding system used, instead of the observed temperature, the observed temperature divided by 100. The JOSS applied a correction re-deriving the resistance ratio, using the observed temperature divided by 100 and the observed RH, iterating the so termed "1A" and "1B" coefficients. Now using the new calculated resistance ratio, the observed temperature and the "1A" coefficients only, the new RH was determined. 2.2.4 VIZ Relative Humidity Correction This section describes the correction applied to the 6-second vertical resolution relative humidity in the VIZ rawinsondes. Also, JOSS implemented a correction to the VIZ radiosonde RH calculations. Using the observed temperature and RH and iterating both the "1A" and "1B" coefficients the resistance ratio was re-derived. Using the calculated resistance ratio, the observed temperature and only the "1A" coefficients , the new RH was computed. 2.2.5 Wind Component Derivation This section describes the processing conducted to derive the 6-second vertical resolution wind components. In both radiosonde types, deriving winds using raw 6-sec resolution elevation and azimuth angle data containing elevation angle oscillations occasionally led to large oscillations in wind velocity, specifically at low elevation angles. The general approach correcting this problem was removing outlier radiosonde position data before computing the wind components. This process required fitting a ninth order polynomial to the azimuth and elevation angle data from 360 seconds to the end of the sounding, then comparing the calculated residuals and observed values, and finally removing the outliers when detected. Applying some additional smoothing helped rectify the more extensive problem occurring when low elevation angles were within 10 degrees of the limiting angles (LA). When the elevation angle was between (LA + 7.5) and (LA + 10), the new elevation angle was computed using a 2 min linear fit. When the elevation angle was between (LA + 5) and (LA + 7.5), the new elevation angle was computed using a 3 min linear fit. When the elevation angle was less than (LA + 5), the new elevation angle was computed employing a four minute linear fit. No frequency smoothing occurred when the number of low elevation angle observations was greater than 20% of the total number of observations. A Finite Fourier Series analysis performed using the elevation angle's residuals allowed the removal of 90-190 second periods and smoothing periods below 30 seconds. Obtaining the u and v wind components entailed fitting a 2 min second order polynomial to the position except for the beginning and end minute (or 1.5 minutes if over 50 mb) which used a 3 min fit. A linear fit was employed when there were less than 15% of the total number of points, not including the beginning or end of the flight, on one side of the point undergoing the wind value calculation. 3.0 Quality Control Procedures No additional quality control was applied to this dataset. The quality control procedures were conducted on the high resolution dataset and the results were applied during the interpolation (see above). 4.0 Reference Bolton, D., 1980: The Computation of Equivalent Potential Temperature. Mon. Wea. Rev., 108, 171-180. Micro-ART Observation and Rework Programs Technical Document, National Weather Service, National Oceanic and Atmospheric Administration, Washington, D.C., March 1991. 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.