National Weather Service (NWS) High Resolution Rawinsonde (6-sec vertical levels) Data

1.0  General Description

     This is one of the upper air data sets developed for the Terrain-
induced Rotor Experiment (T-REX) project.  This data set includes 457 high 
vertical resolution (6-second) soundings from 4 National Weather Service 
(NWS) rawinsonde stations in the T-REX region (Oakland and San Diego, CA
and Desert Rock and Reno, NV) for the period 01 March 2005 to 30 April 2005.  
The soundings were typically released twice per day (0000 and 1200 UTC).

The Desert Rock, NV station typically did not do releases on Saturdays or 

1.1  Data Set Contact

Steve Williams

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 the National Center for
Atmospheric Research/Earth Observing Laboratory (NCAR/EOL) Sounding
Composite Format (ESC).  ESC 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

     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   Release Site Type/Site ID:        Description of release site.
       4   Release Location (lon,lat,alt):   Position of release 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'W where ddd
is the number of degrees from True North (with leading zeros if
necessary), 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 labels are padded to 35 characters to match the standard
header lines. Records for this dataset include the following three
non-standard header lines.

     Line  Label (padded to 35 char)              Contents

       6   Ascension No:                      1299
       7   Radiosonde Serial Number:          152551614
       8   Radiosonde Manufacturer:           Vaisala

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 (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
  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  Elevation Angle             Degrees              999.0
 14     5  F5.1  Azimuth Angle               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 NCAR Earth Observing Laboratory (NCAR/EOL).
Any QC information from the original sounding is replaced by the
following EOL 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 T-REX Sounding Rawinsonde NWS
upper air data in EOL ESC 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:                         National Weather Service Sounding.
Project ID:                        0
Release Site Type/Site ID:         OAK Oakland, CA
Release Location (lon,lat,alt):    122 12.00'W, 37 42.00'N, -122.2,  37.7, 2.0
UTC Release Time (y,m,d,h,m,s):    2006, 03, 01, 11:00:00
Ascension No:                      1153
Radiosonde Serial Number:          84966633.CSN
Radiosonde Manufacturer:           VIZ B2
Nominal Release Time (y,m,d,h,m,s):2006, 03, 01, 12:00:00
 Time  Press  Temp  Dewpt  RH    Ucmp   Vcmp   spd   dir   Wcmp     Lon     Lat   Ele   Azi    Alt    Qp   Qt   Qrh  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
------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- ------- ----- ----- ------- ---- ---- ---- ---- ---- ----
   0.0 1021.2   7.7   6.2  90.0   -1.0    0.4   1.1 111.8 999.0 -122.200  37.700 999.0 999.0     2.0  2.0  2.0  2.0 99.0 99.0  9.0
   6.0 1011.8   8.8   6.9  88.0   -1.1    0.7   1.3 122.5  12.7 9999.000 999.000 999.0 999.0    78.0  3.0  2.0  2.0  4.0  4.0 99.0
  12.0 1007.1   9.3   7.4  87.8   -1.2    1.0   1.6 129.8   6.5 9999.000 999.000 999.0 999.0   117.0  3.0 99.0 99.0  4.0  4.0 99.0
  18.0 1003.2   9.2   7.4  88.2   -1.4    1.3   1.9 132.9   5.3 -122.200  37.700  74.1 115.0   149.0 99.0 99.0 99.0  4.0  4.0 99.0
  24.0  999.2   8.9   7.3  89.5   -1.5    1.6   2.2 136.8   5.5 -122.200  37.700  88.6  83.9   182.0 99.0 99.0 99.0  4.0  4.0 99.0
  30.0  995.1   8.6   7.2  91.2   -1.5    1.8   2.3 140.2   5.7 -122.200  37.700  79.2 125.5   216.0 99.0 99.0 99.0  4.0  4.0 99.0

2.2  Data Remarks

     NWS soundings during RAINEX utilized the VIZ type radiosonde
produced by Sippican Inc. (

     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 out-lier 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).

2.3  Station List

DRA Desert Rock        NV     US     -116.0    36.6   1007.0       VIZ B2
NKX San Diego          CA     US     -117.1    32.8    134.0       VIZ B2
OAK Oakland            CA     US     -122.2    37.7      2.0       VIZ B2
REV Reno               NV     US     -119.8    39.6   1516.0      Vaisala

3.0  Quality Control Processing

        This dataset underwent an automated QC process.  The dataset
underwent internal consistency checks which included two types of checks,
gross limit checks on all parameters and rate-of-change checks on
temperature, pressure and ascension rate. Some further information on the
QC processing conducted by EOL 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.  EOL conducted the following gross limit
checks on the T-REX NWS 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 > 1050 mb         P             B

     Altitude           < 0 m  or > 40000 m      P, T, RH         Q

     Temperature        < -90C or > 45C             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 > 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
                        >  50 C/km (not applied
                            at p < 250mb)           P, T, RH          Q
                        > 100 C/km (not applied
                            at p < 250mb)           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

4.0  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.