IHOP 2002 Soundings Dropsonde Lear and Falcon Profiles [NCAR/ATD]

	1.0 General Description

		This is one of the upper air data sets developed for the 
	International H2O Project 2002 (IHOP 2002). This data set contains 
	high resolution dropsonde data from the Lear and Falcon 
	aircraft. Dropsondes were released during Intensive Observing Periods
        (IOPs). The Lear made drops on May 14th,15th,16th, the 22nd, and 24th 
	and on June 3rd,8th thru 12th,15th thru 20th, the 22nd, and 24th thru 
	25th 2002. The Falcon dropped sondes on May 17th,19th,21st, 25th, 
	29th, and 31st,	and on June 3rd,8th, and 9th 2002. The dropsonde data 
	was provided by the National Center for Atmospheric Research 
	Atmospheric Technology Divison (NCAR/ATD). An important note for users:
	ATD reprocessed Lear and Dropsonde profiles and released new versions of this
	data May 1st, 2003. The reprocessed IHOP 2002 Soundings Dropsonde Lear and Falcon 
	Profiles were made available May 13th, 2003. See section 3.0 and ATD Reprocessing
	for more details.

	Also in September 2008 the IHOP_2002 Falcon and Lear dropsonde data sets 
	were updated to include latitude and longitude data that were not in
	the earlier version. The PTH and wind data are unchanged.
	1.1 ATD Contacts and Mailing Address

	Contacts:               Terry Hock

			        Junhong Wang
			        Kate Beierle

	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

	2.0  Detailed Data Description

	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
     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 launch site.
            4   Release Location (lon,lat,alt):   Position of launch site,
                                                    in format described below.
            5   UTC Release 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. The following are non-standard header lines contained in 
     the header record. 

          Line  Label (padded to 35 char)              Contents

            6   Sonde Type/ID/Sensor ID/Tx Freq:  Vaisala RD93 GPS Dropsonde Serial Number 
	                                          YYWWDSSSS, where YY last two digits 
                                                  of year, WW - week number (1-52),
						  D - day of the week (1-7,Monday=1), and
						  SSSS is the sequence number

            7   System Operator/Comments:	  Comments recorded by operator during
	                                          flight. This line is often blank.          

	    8   Input File:                       Original file from ATD.

     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  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 are sample records for the IHOP 2002 Soundings
     Dropsonde Lear and Falcon Profiles data set 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 
Data Type:                         Sounding  
Project ID:                        IHOP 2002 Class Format Dropsonde Sounding 
from Lear
Release Site Type/Site ID:         FI Lear 36-016, N12FN              
Release Location (lon,lat,alt):    100 36.12'W, 36 33.00'N, -100.60,  36.55,
UTC Release Time (y,m,d,h,m,s):    2002, 05, 15, 23:30:00
Sonde Type/ID/Sensor ID/Tx Freq:   992435097
System Operator/Comments:          ,
Input File:                        D20020515_233000QC.cls
Nominal Release Time (y,m,d,h,m,s):2002, 05, 15, 23:30:00
 Time  Press  Temp  Dewpt  RH    Uwind  Vwind  Wspd  Dir   dZ      Lon   
  Lat   Elev  Azim    Alt    Qp   Qt   Qh   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
------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- 
------- ----- ----- ------- ---- ---- ---- ---- ---- ----
 783.2  909.7  27.7   8.2  28.8 9999.0 9999.0 999.0 999.0 999.0 9999.000 
999.000 999.0 999.0  1035.3 99.0 99.0 99.0  9.0  9.0  9.0
 782.7  909.3  27.7   8.2  28.8 9999.0 9999.0 999.0 999.0  -8.8 9999.000 
999.000 999.0 999.0  1039.7 99.0 99.0 99.0  9.0  9.0 99.0
 782.2  908.8  27.7   8.2  28.8 9999.0 9999.0 999.0 999.0  -8.6 9999.000 
999.000 999.0 999.0  1044.0 99.0 99.0 99.0  9.0  9.0 99.0
 781.7 9999.0 999.0 999.0 999.0 9999.0 9999.0 999.0 999.0 999.0 9999.000 
999.000 999.0 999.0 99999.0  9.0  9.0  9.0  9.0  9.0  9.0
 781.2  908.0  27.6   8.2  28.9 9999.0 9999.0 999.0 999.0 999.0 9999.000 
999.000 999.0 999.0  1052.1 99.0 99.0 99.0  9.0  9.0  9.0

Data Type:                         Sounding  
Project ID:                        IHOP 2002 Class Format Dropsonde Sounding 
from Falcon
Release Site Type/Site ID:         Falcon 20, D-CMET                  
Release Location (lon,lat,alt):    100 49.86'W, 36 33.84'N, -100.83,  36.56,
UTC Release Time (y,m,d,h,m,s):    2002, 06, 09, 12:57:35
Sonde Type/ID/Sensor ID/Tx Freq:   020215430
System Operator/Comments:          ,
Input File:                        D20020609_125735QC.cls
Nominal Release Time (y,m,d,h,m,s):2002, 06, 09, 12:57:35
 Time  Press  Temp  Dewpt  RH    Uwind  Vwind  Wspd  Dir   dZ      Lon   
  Lat   Elev  Azim    Alt    Qp   Qt   Qh   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
------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- 
------- ----- ----- ------- ---- ---- ---- ---- ---- ----
 502.9  908.9  20.9  16.4  75.4   -2.9   11.7  12.1 166.0 999.0 -100.786 
 36.613 999.0 999.0  1029.2  3.0  3.0  3.0 99.0 99.0  9.0
 502.4  908.5  20.7  16.2  75.1 9999.0 9999.0 999.0 999.0  -6.4 -100.786 
 36.613 999.0 999.0  1032.4  3.0  3.0  3.0  9.0  9.0 99.0
 501.9  908.2  20.6  16.1  74.9   -2.6   12.2  12.5 168.0  -7.2 -100.786 
 36.613 999.0 999.0  1036.0 99.0 99.0 99.0 99.0 99.0 99.0
 501.4  907.8  20.5  16.0  74.9   -2.4   12.5  12.7 169.0  -7.6 -100.786 
 36.613 999.0 999.0  1039.8 99.0 99.0 99.0 99.0 99.0 99.0
 500.9  907.3  20.4  15.9  74.9   -2.2   12.7  12.9 170.0  -7.8 -100.786 
 36.613 999.0 999.0  1043.7 99.0 99.0 99.0 99.0 99.0 99.0
 500.4  906.9  20.4  15.9  74.9   -1.8   12.9  13.0 172.0  -8.2 -100.786 
 36.612 999.0 999.0  1047.8 99.0 99.0 99.0 99.0 99.0 99.0
 499.9  906.5  20.3  15.8  74.9   -1.6   13.0  13.1 173.0  -8.0 -100.786 
 36.612 999.0 999.0  1051.8 99.0 99.0 99.0 99.0 99.0 99.0

	2.2. Data File Specifics from ATD 

	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 hydrostatic 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 

	All wind data are computed from GPS navigation signals received from 
	the sonde.  The	raw wind values are calculated 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.

	3.0 Quality Control  

	3.1 ATD 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. For 
	many IHOP Dropsonde soundings the sondes continued to transmit data 
	(mostly bad) after hitting the ground. It was necessary to write a 
	script to solve this problem, and some additional manual corrections 
	were also necessary.  Histograms of the data are then created to check
	the range, and number of occurrences, in values of pressure, temp, RH, 
	wind speed and direction, and are derived from data at all levels for 
	all soundings. Finally, time series plots of temperature, relative 
	humidity, and wind speed and direction are created.  They are used to 
	both examine the consistency of soundings launched from the same 
	flight, and to show the variability of soundings from different missions. 

	Important Note to Users!!!


	In the previous version, the IHOP dropsonde geopotential height values were 
	calculated integrating from flight level down, using the hydrostatic equation, 
	because unlike with dropsondes launched over the ocean the surface altitude of 
	the land is unknown. We recommended not using geopotential altitude data in files 
	from either the IHOP Falcon or	the Lear jet for two reasons.  First, there are 
	uncertainties in the the flight level heights which are used as a reference by 
	ASPEN to integrate geopotential altitudes.  Second, there are no flight level PTU 
	data for any of the Lear jet soundings because there were no PTU sensors on board, 
	and for the Falcon soundings there is no flight level pressure data for 37 of the 
        88 soundings. For the Falcon soundings with flight level PTU data, the data were 
	manually entered and therefore its accuracy is unknown. 

	It was brought to our attention that there was a systematic ~200-300 m height
	difference found between co-located dropsondes and radiosondes. In order to correct 
	this error we obtained 1-km elevation data from NOAA's National Geophysical Data 
	Center, found the elevation of the dropsonde locations from the dataset, integrated 
	geopotential height from the surface to the flight level and inserted the new 
	geopotential height values into the data. After corrections, the new data reduced 
	the difference between co-located dropsonde and radiosonde geopotential heights to 
	less than 30m, however 27 of the dropsondes had missing data before reaching the 
	surface and for these, integrating from the surface upward produced incorrect 
	geopotential heights.  For these soundings, the geopotential heights were calculated
	integrating downward from flight level by incorporating "close to" flight-level PTU 
	data from both the raw file and the QCed file. For pressure we used the first 
	availbale measurement after launch, from the raw file, and for temperature and 
	humidity we manually entered the first available data after launch, found in the QC 
	CLASS file, which was most often recorded at 20 seconds.  This new D-file was then 
	re-run through ASPEN to produce the new corrected QCed data.
	(Note: the assumption of a constant temperature for the first 20 seconds has minor 
	impacts on the geopotential height calculation).
	Some uncertainties remain about the accuracy of the data because of the 
	uncertainties in the elevation data and flight level heights, and the assumption of 
	a constant temperature for the first ~20 seconds.  IN ADDITION, IT IS POSSIBLE THAT 
	(if needed the flight level altitude can be found in the header) AND THE LOWEST 

	3.2  JOSS Quality Control Processing
        This dataset underwent am 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 JOSS can be found in Loehrer et al. 
	(1996)	and Loehrer et al. (1998).
     	3.2.1  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 IHOP 2002 Lear and Falcon dropsonde data sets.  
	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        < -99.9C 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        < -45 m/s or > 0 m/s     P, T, RH        B

         3.2.2  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 values.  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               increasing/equal         None          None
     Altitude           increasing/equal         P, T, RH        Q
     Pressure           decreasing/equal         P, T, RH        Q
                        > 3 mb/s or < -3 mb/s    P, T, RH        Q
                        > 5 mb/s or < -5 mb/s    P, T, RH        B
     Temperature        < -15 C/km               P, T, RH        Q
                        < -30 C/km               P, T, RH        B
          from surface to 250 mb:
                        > 100 C/km (not applied
                                   at p < 250mb) P, T, RH        Q
                        > 200 C/km (not applied
                                   at p < 250mb) P, T, RH        B
          for pressures < 250 mb:
                        >   100 C/km (not applied
                                   at p > 150mb) P, T, RH        Q
                        >   200 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

	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.