SALLJEX: Upper Air Santa Cruz Sounding Data (NCAR/ATD) 

I. File Naming Conventions
II. Header Information
III. Data Records
IV. Data File Specifics
V. Data Quality Control
VI. Important Note to Users
VII. Contacts

I. File Naming Conventions

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  "yyyymmddhhmm.cls" where yyyy = year, mm = month, 
hh = hour of the day GMT, mm = minute of the hour, and ".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, 
nominal release time, 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 type and resolution of 
2. Project ID:					   ID of weather project.
3. Release Site Type/Site ID:			   Description of launch site.
4. Release Location (lon,lat,alt):		   Position of launch 
5. UTC Release Time:                               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 
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

 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           9999.0
 7			V Wind Component  	     Meters/Second           9999.0
 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.  Histograms of the data are created
to check the range, and number of occurances, in values of pressure, temp, RH,
wind speed and direction, and are derived from data at all levels for all soundings.
Lastly, we created profiles and scatter plots of temperature and RH,
in order to check for any major inconsistencies.

VI. Important Note to Users.

While visually analyzing the skew-t diagrams it became apparent that there were problems 
near the surface. It seems that the surface met relative humidity sensor
recorded measurements more moist than those recorded from the radiosonde. The mean
RH(sonde-sfc) was -5.35%, with differences as great as -35%. From talking with 
one of the operators who was at the project, we learned that rather than transporting
surface sensors from NCAR to the site, the investigators chose to use sensors
already located at the site.  It is our belief that this sensors  
accuracy is questionable, and therefore neither the humidity (RH or dewpoint) nor the 
temperature data at the surface collected by the surface sensors (first line in the data 
at -1 second) should be used. We suggest the user use the prelaunch data collected by the 
radiosonde sensor (second line in the data at 0 second) as the surface value.

VII. Contacts:
			Kate Beierle

                        Tim Lim

			Junhong Wang

	Mailing Address:        NCAR/Atmospheric Technology Division
        			P.O Box 3000
				1850 Table Mesa Drive
				Boulder, CO 80307; USA

				Phone: (303)-497-8743 
				Fax:   (303)-497-8770