DYNAMO Singapore L3 Radiosonde Data

1.0 General Description

This is one of the upper air data sets developed for the Dynamics of the Madden-Julian Oscillation (DYNAMO) 2011-2012 project. This data set includes 365 high vertical resolution (2 second) soundings from Singapore taken by the Meteorological Service Singapore from 1 October 2011 through 31 March 2012. These data were initially processed by NCAR/EOL into the EOL Sounding Composite format and passed through a series of automated and visual checks. No data were changed during this part of the processing. The L3 version of the data had the NCAR dry bias correction applied to the Vaisala radiosondes. The Graw radiosondes had a procedure applied to make adjustments to the near-surface radiosonde data due to a change in the release procudures. See section 2.2 for more information.

1.1 Data Set Contact

Scot Loehrer
NCAR/EOL
loehrer@ucar.edu

2.0 Detailed Data Description

2.1 Detailed Format Description

All upper air soundings were converted to 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, and meteorological and wind data processors. 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:

LineLabel (padded to 35 char)Contents
1Data Type:Description of type and resolution of data.
2Project ID:Id of weather project.
3Release Site Type/Site ID:Description of the release site.
4Release Location (lon,lat,alt):Position of release site in the format described below.
5UTC Release Time (y,m,d,h,m,s):Time of release, in the 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 labels are padded to 35 characters to match the standard header lines. Records for this dataset include the following non-standard header lines.

LineLabel (padded to 35 char)Contents
6Sonde Id/Sonde Type:937046/Graw DFM-97
7  
8  
9  
10  
11  
12Nominal Release Time (y,m,d,h,m,s):Nominal time of release, in the format: yyyy, mm, dd, hh:mm:ss

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 No.WidthFormatParameterUnitsMissing Value
16F6.1TimeSeconds9999.0
26F6.1PressureMillibars9999.0
35F5.1Dry-bulb TemperatureDegrees C999.0
45F5.1Dew Point TemperatureDegrees C999.0
55F5.1Relative HumidityPercent999.0
66F6.1U Wind ComponentMeters / Second9999.0
76F6.1V Wind ComponentMeters / Second9999.0
85F5.1Wind SpeedMeters / Second999.0
95F5.1Wind DirectionDegrees999.0
105F5.1Ascent RateMeters / Second999.0
118F8.3LongitudeDegrees9999.0
127F7.3LatitudeDegrees999.0
135F5.1Elevation AngleDegrees999.0
145F5.1Azimuth AngleDegrees999.0
157F7.1AltitudeMeters99999.0
164F4.1QC for PressureCode (see below)99.0
174F4.1QC for TemperatureCode (see below)99.0
184F4.1QC for HumidityCode (see below)99.0
194F4.1QC for U Wind ComponentCode (see below)99.0
204F4.1QC for V Wind ComponentCode (see below)99.0
214F4.1QC for Ascension RateCode (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:

CodeDescription
99.0Unchecked (QC information is "missing.") ("UNCHECKED")
1.0Checked, datum seems physically reasonable. ("GOOD")
2.0Checked, datum seems questionable on physical basis. ("MAYBE")
3.0Checked, datum seems to be in error. ("BAD")
4.0Checked, datum is interpolated. ("ESTIMATED")
9.0Checked, datum was missing in original file. ("MISSING")

Sample Data

The following is a sample record of DYNAMO Singapore high resolution sounding data in 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:                         Meteorological Service Singapore Radiosonde/Ascending
Project ID:                        DYNAMO
Release Site Type/Site ID:         WSSS Singapore/Changi / 48698
Release Location (lon,lat,alt):    103 48.00'E, 01 20.00'N, 103.800, 1.333, 14.0
UTC Release Time (y,m,d,h,m,s):    2011, 10, 01, 00:00:00
Radiosonde Type:                   Vaisala RS92-SGP
/
/
/
/
/
Nominal Release Time (y,m,d,h,m,s):2011, 10, 01, 00:00:00
 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 1008.5  27.9  25.5  87.0   -0.5    2.6   2.6 170.0 999.0  103.800   1.333 999.0 999.0    14.0 99.0 99.0 99.0 99.0 99.0  9.0
   2.0 1007.3  27.8  22.8  74.0   -1.1    1.9   2.2 149.0   5.5 9999.000 999.000 999.0 999.0    25.0 99.0 99.0 99.0 99.0 99.0 99.0
   4.0 1005.8  27.8  22.8  74.0   -1.3    1.6   2.0 141.0   6.5 9999.000 999.000 999.0 999.0    38.0 99.0 99.0 99.0 99.0 99.0 99.0
   6.0 1004.4  27.7  22.9  75.0   -1.3    1.4   1.9 137.0   6.5 9999.000 999.000 999.0 999.0    51.0 99.0 99.0 99.0 99.0 99.0 99.0
   8.0 1003.1  27.6  22.8  75.0   -1.4    1.3   1.9 134.0   5.5 9999.000 999.000 999.0 999.0    62.0 99.0 99.0 99.0 99.0 99.0 99.0
  10.0 1001.9  27.5  22.9  76.0   -1.3    1.2   1.8 133.0   5.5 9999.000 999.000 999.0 999.0    73.0 99.0 99.0 99.0 99.0 99.0 99.0
  12.0 1000.4  27.4  23.0  77.0   -1.3    1.2   1.8 132.0   6.5 9999.000 999.000 999.0 999.0    86.0 99.0 99.0 99.0 99.0 99.0 99.0
  14.0  998.7  27.2  22.9  77.0   -1.4    1.2   1.9 131.0   7.5 9999.000 999.000 999.0 999.0   101.0 99.0 99.0 99.0 99.0 99.0 99.0
  16.0  997.3  27.2  22.8  77.0   -1.5    1.3   2.0 130.0   6.5 9999.000 999.000 999.0 999.0   114.0 99.0 99.0 99.0 99.0 99.0 99.0
  18.0  995.8  27.0  22.9  78.0   -1.6    1.3   2.1 129.0   6.5 9999.000 999.000 999.0 999.0   127.0 99.0 99.0 99.0 99.0 99.0 99.0
  20.0  994.6  26.9  23.0  79.0   -1.7    1.4   2.2 129.0   5.5 9999.000 999.000 999.0 999.0   138.0 99.0 99.0 99.0 99.0 99.0 99.0
  22.0  993.4  26.8  22.9  79.0   -1.8    1.5   2.3 130.0   5.5 9999.000 999.000 999.0 999.0   149.0 99.0 99.0 99.0 99.0 99.0 99.0
  24.0  991.9  26.7  22.8  79.0   -1.9    1.6   2.5 131.0   6.5 9999.000 999.000 999.0 999.0   162.0 99.0 99.0 99.0 99.0 99.0 99.0
  26.0  990.7  26.6  22.9  80.0   -1.9    1.7   2.6 132.0   5.0 9999.000 999.000 999.0 999.0   172.0 99.0 99.0 99.0 99.0 99.0 99.0
  28.0  989.5  26.5  22.8  80.0   -1.9    1.9   2.7 134.0   5.5 9999.000 999.000 999.0 999.0   183.0 99.0 99.0 99.0 99.0 99.0 99.0
  30.0  988.3  26.4  22.7  80.0   -1.9    2.0   2.8 137.0   5.5 9999.000 999.000 999.0 999.0   194.0 99.0 99.0 99.0 99.0 99.0 99.0
  32.0  987.1  26.2  22.8  81.0   -1.9    2.2   2.9 140.0   5.5 9999.000 999.000 999.0 999.0   205.0 99.0 99.0 99.0 99.0 99.0 99.0
  34.0  985.7  26.2  22.7  81.0   -1.8    2.4   3.0 143.0   6.5 9999.000 999.000 999.0 999.0   218.0 99.0 99.0 99.0 99.0 99.0 99.0
  36.0  984.5  26.1  22.6  81.0   -1.8    2.5   3.1 145.0   5.5 9999.000 999.000 999.0 999.0   229.0 99.0 99.0 99.0 99.0 99.0 99.0
  38.0  983.3  26.0  22.7  82.0   -1.6    2.6   3.1 148.0   5.0 9999.000 999.000 999.0 999.0   239.0 99.0 99.0 99.0 99.0 99.0 99.0
  40.0  982.1  25.8  22.5  82.0   -1.6    2.7   3.1 149.0   5.5 9999.000 999.000 999.0 999.0   250.0 99.0 99.0 99.0 99.0 99.0 99.0
  42.0  980.9  25.7  22.6  83.0   -1.5    2.7   3.1 150.0   5.5 9999.000 999.000 999.0 999.0   261.0 99.0 99.0 99.0 99.0 99.0 99.0
  44.0  979.9  25.6  22.5  83.0   -1.5    2.7   3.1 151.0   4.5 9999.000 999.000 999.0 999.0   270.0 99.0 99.0 99.0 99.0 99.0 99.0
  46.0  978.7  25.6  22.5  83.0   -1.5    2.7   3.1 151.0   5.0 9999.000 999.000 999.0 999.0   280.0 99.0 99.0 99.0 99.0 99.0 99.0
  48.0  977.5  25.5  22.6  84.0   -1.5    2.6   3.0 150.0   5.5 9999.000 999.000 999.0 999.0   291.0 99.0 99.0 99.0 99.0 99.0 99.0
  50.0  976.3  25.4  22.2  83.0   -1.5    2.5   2.9 149.0   5.5 9999.000 999.000 999.0 999.0   302.0 99.0 99.0 99.0 99.0 99.0 99.0

2.2 Data Remarks

The L3 version of this data set was released 2 April 2013.

The L3 version had the following corrections applied by Colorado State University:

For the Vaisala RS92 radiosondes (prior to 21 Decemeber 2011) the RH data were corrected using the NCAR dry bias correction (Wang et al. 2013).

When the switch was made from Vaisala to Graw sonde on 21 Dec. 10Z 2011, their launching procedure also changed to launching from inside a building. This resulted in suspicious low-level (lowest 15-20 hPa or about 40 seconds after launch) T and Td data in about 90% of the sondes. In most cases, the surface data which came from a source indepedent of the sonde was correct.

To mitigate this questionable data the following procedure was delevoped. A visual editor was used to mark questionable low-level data. If surface data was good, new data was generated by linearly interpolating from the surface point to the first good data value. If surface data was questionable, the lowest three good data points were used to determine a gradient which was used to extrapolate the data down to the surface.

This procedure effectively removed the questionable low-level data.

2.3 Station List

ID SITE LONG LAT ELEV (m)
WSSS Singapore/Changi 48698 103.80000 1.33300 14.0
The station utilized Vaisala RS93-SGP radiosondes through the 0000 UTC sounding on 21 December 2011. After that sounding the station utilized GRAW DFM-09 radiosondes. The header records for each sonde specify the sonde type.

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 NCAR/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. NCAR/EOL conducted the following gross limit checks on the DYNAMO Singapore 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.

ParameterGross Limit CheckParameter(s) FlaggedFlag Applied
Pressure < 0 mb or > 1050 mb PB
Altitude < 0 m or > 40000 m P, T, RHQ
Temperature < -90 °C or > 45 °C TT
Dew Point < -99.9 °C or > 33 °C
> Temperature
RH
T, RH
Q
Q
Relative Humidity < 0% or > 100% RHB
Wind Speed < 0 m/s or > 100 m/s
> 150 m/s
U, V
U, V
Q
B
U Wind Component < 0 m/s or > 100 m/s
> 150 m/s
U
U
Q
B
V Wind Component < 0 m/s or > 100 m/s
> 150 m/s
V
V
Q
B
Wind Direction < 0° or > 360° U, VB
Ascent Rate < -10 m/s or > 10 m/s P, T, RHQ

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 2-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.

ParameterVertical Consitency CheckParameter(s) FlaggedFlag Applied
Time decreasing / equal NoneNone
Altitude decreasing / equal P, T, RHQ
Pressure increasing / equal
> 1 mb/s or < -1 mb/s
> 2 mb/s or < -2 mb/s
P, T, RH
P, T, RH
P, T, RH
Q
Q
B
Temperature < -15 °C/km
< -30 °C/km
> 50 °C/km (not applied at p < 250 mb)
>100 °C/km (not applied at p < 2 50 mb)
P, T, RH
P, T, RH
P, T, RH
P, T, RH
Q
B
Q
B
Ascent Rate change of > 3 m/s or & lt; -3 m/s
change of > 5 m/s or < -5 m/s
P
P
Q
B

3.3 Visual Quality Checks

Each sounding was visually examined for data quality issues. Any issues found were flagged in the data file and/or noted in Section 3.4.

3.4 Data Quality Issues

The GRAW soundings often had odd behavior near the surface. Most soundings have a 5-10 records of high ascension rates (8+ m/s) followed by another 5-10 records of low ascension rates (3 or less m/s) before the more typical values around 5m/s are reached. For this reason the first 15 records of each soundings after the surface record have had all parameters flagged as questionable.

Also in the GRAW data many soundings have a very dry RH layer just above the surface. These have also been flagged as questionable.

The 201201221000 sounding has bad temperature values from ~445-385mb.

The soundings at 201201242300 and 201202251000 appear to have the radiosonde sitting at the surface for a period of time after data collection has started. These data have been flagged as questionable.

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.

Wang, J., L. Zhang, A. Dai, F. Immler, M. Sommer and H. Voemel, 2013: Radiation dry bias correction of Vaisala RS92 humidity data and its impacts on historical radiosonde data. J. Atmos. Oceanic Technol., accepted.