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
hock@ucar.edu
Junhong Wang
junhong@ucar.edu
Kate Beierle
kbeierle@ucar.edu
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
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
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 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
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 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
specification
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,
7287.0
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,
4782.0
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
data.
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!!!
THESE SOUNDINGS WERE RECENTLY CORRECTED FOR ERRORS IN GEOPOTENTIAL HEIGHT AND WERE
RE-RELEASED MAY 1, 2003
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
THE GEO-POTENTIAL HEIGHTS FOR SOME OF THE SOUNDINGS MAY STILL HAVE PROBLEMS THAT
HAVE YET TO BE FOUND. THEREFORE, WE RECOMMEND TAKING CAUTION WHEN USING THE
ALTITUDE DATA. WE ALSO RECOMMEND NOT USING THE FLIGHT LEVEL DATA (AT time=0s)
BECAUSE OF THE MODIFICATIONS MADE TO IT. IT SHOULD ALSO BE KEPT IN MIND THAT
THE FIRST AVAILABLE ALTITUDE IS NOT NECESSARILY THE FLIGHT LEVEL ALTITUDE
(if needed the flight level altitude can be found in the header) AND THE LOWEST
LEVEL IN THE FINAL DATASET DOES NOT NECESSARILY REPRESENT THE SURFACE DATA.
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.