Data granularity is one file per station per time period.

Each file contains:

• Number of soundings in the file
• Header of first sounding
• Transmission levels for first sounding (one measurement level per record)
• Header of second sounding
• Transmission levels for second sounding (one measurement level per line) etc.

The number of soundings in the file appears only once as the first line of each file and occupies columns 9-12. For variables and formats contained in the sounding headers, see the section titled: Variables in Header of Each Sounding. For variables and formats contained in the transmission levels, see the section titled: Variables in Transmission Levels of Each Sounding.

Variables in Header of Each Soundings

STATION

North Pole station number. Missing values are -99. Occupies columns 1-3.

STN_IND

STATION NUMBER INDICATOR: Positive single digit. Specifies the type of station number given in the Condigital station variable.

0 = WBAN NUMBER
1 = AIR FORCE AUGMENTED WMO NUMBER
2 = SHIP CALL SIGN
3 = MOBILE PLATFORM CALL SIGN
4 = MOBILE PLATFORM ID (Assigned by NCDC)
5 = WMO/CARDS NUMBER
6 = FIXED PLATFORM CALL SIGN
7 = OTHER STATION NUMBER (Origin unknown)
8 = RESERVED
9 = NO STATION NUMBER

Missing values are 9. Occupies column 5.

 

ELEV

ELEVATION: The height of the launch site in meters used in Condigital soundings. Missing values are 9999.9. Occupies columns 7-13.

Four-digit year of sounding observation. Missing values are 9999. Occupies columns 15-18.

MONTH

Two-digit month of sounding observation. Missing values are 99. Occupies columns 20-21.

DAY

Two-digit day of sounding observation. Missing values are 99. Occupies columns 23-24.

GMT_HOUR

Two-digit GMT hour of sounding observation. Usually 00, 06, 12, or 18. However, for those days that had more than four soundings, there will be soundings with additional hours. Missing values are -9. Occupies columns 26-27.

GMT_MINUTE

Two-digit GMT minute of sounding observation. Missing values are -9. Occupies columns 28-29.

STD_GMT_TIME

Two-digit standard GMT time from Aerostan data set. Missing values are -9. Occupies columns 31-32.

LOCAL_TIME

Three-digit local time used in Floppy soundings. Missing values are -9. Occupies columns 34-36.

RELSE_TIME

The hour and minute of the actual release, expressed as HHMM. Used in Condigital soundings. Missing values are 9999. Occupies columns 38-41

LATITUDE

The station latitude in degrees North. Missing values are 99.99. Occupies columns 43-47.

LONGITUDE

The station longitude in degrees East. Missing values are 999.99. Occupies columns 49-54.

MIN_ALTITUDE

Altitude in meters of first transmission level in sounding. Missing values are -9999999. Negative values generally indicate cases where the surface pressure is < 1000 mb and the first reported level is the mandatory 1000 mb level. Occupies columns 56-63.

MAX_ALTITUDE

Altitude in meters of last transmission level in sounding. Missing values are -9999999. Occupies columns 65-72.

OBSN_TYPE

Type of observation given in Condigital soundings:

01 = radio/rawinsonde
02 = rocketsonde
03 = satellite
04 = dropsonde
05 = aircraft flight level report
06 = Profiler
07 = PIBAL
08 = APOB
09 = RAWIN (RADAR winds only)
10 = Rawinsonde (RADAR winds)
11 = Radiosonde (optical theodolite)
12 = Rawinsonde (OMEGA NAVAID)
13-98 = reserved

Missing values are 99. Occupies columns 74-75.

 

QC_EFFORT

Used in Condigital soundings.

QUALITY CONTROL EFFORT: Intended for use in conjunction with the DATA_SRCE field for determining if the appendices of the Condigital documentation must be referenced for decoding the ELEMENT QUALITY flags. If QC EFFORT=0, the ELEMENT QUALITY flags defined within the body of this document apply, regardless of the DATA_SRCE. If the QC EFFORT > 0, the ELEMENT QUALITY flags will be defined in Appendix nn of the Condigital document (where nn = the value contained in the DATA_SRCE element).

0 = NCDC QC after 12/92
1 = NCDC QC prior to 1/93
2 = QC at source
3-7 = reserved
8 = no QC
9 = unknown

Missing values are 9. Occupies column 77.

 

DATA_SRCE

DATA SOURCE/FORMAT: This field indicates the data source for the Condigital soundings only. See appendices keyed to the data source values for details concerning the original source.

00 = TD6103 (NMC)
01 = TD6201 (U.S. National data set prior to 1/93)
02 = Standard Nonreal-Time Data Transfer Format
(Mostly MicroART - post 12/92)
03 = Mini Rawin System Format (MRS)
04 = TDAT/WDAT Format
06 = Manuscript
07 = Range standard
08 = MIT
09 = NCAR
10 = TDF54
11 = TDF56
12 = other PC-based, semiautomated reduction system
13 = Canadian upper air archives
14 = Former USSR
15 = Peoples' Republic of China (PRC)
16 = Argentina
17 = British Antarctica
18 = Hong Kong
19 = Korea
18-98 = reserved
99 = unknown

Missing values are 99. Occupies columns 79-80.

 

NUM_LVLS

NUMBER OF LEVELS: This is the number of data levels found in the sounding. Missing values are 0. Occupies columns 82-84.

INST_CODE

INSTRUMENT CODE: Seven-character string from Aerostan data set. Missing values are "???????." Occupies columns 86-92.

CLOUD_AMOUNT

CLOUD AMOUNT from Aerostan data set. Tenths of sky covered. Missing values are -9. Occupies columns 94-95.

CLOUD_AMOUNT_QLTY

CLOUD AMOUNT QUALITY from Aerostan data set. Missing values are -9. Occupies columns 97-98. 0 = No quality control
1 = correct
2 = doubtful value
3 = error
4 = corrected value
5 = original value missing; value produced
9 = missing data

LOWER_CLOUD

LOWER INFERIOR CLOUDS from Aerostan data set. Missing values are -9. Occupies columns 100-101.

0 = absence of clouds
1 = cumulus humilis
2 = cumulus humilis together with stratocumulus
3 = cumulonimbus calvus together with cumulus, stratocumulus or stratus
4 = stratocumulus cumulogenitus
5 = stratocumulus
6 = stratus and/or fractonimbus
7 = fractonimbus under altostratus or nimbostratus
8 = cumulus humilis together with cumulus congestus
9 = cumulonimbus capillatus, stratocumulus, stratus

LOWER_CLOUD_QLTY

LOWER INFERIOR CLOUDS QUALITY from Aerostan data set. Missing values are -9. Occupies columns 103-104. Refer to CLOUD_AMOUNT_QLTY for values.

CLOUD_HEIGHT

CLOUD HEIGHT from Aerostan data set (height of cloud base). Missing values are -9. Occupies columns 106-107.

0 = < 50 m
1 = 50-100 m
2 = 100-200 m
3 = 200-300 m
4 = 300-600 m
5 = 600-1000 m
6 = 1000-1500 m
7 = 1500-2000 m
8 = 2000-2500 m
9 = > 2500 m

CLOUD_HEIGHT_QLTY

CLOUD HEIGHT QUALITY from Aerostan data set. Missing values are -9. Occupies columns 109-110. Refer to CLOUD_AMOUNT_QLTY for values.

MID_CLOUD

MIDDLE CLOUD TYPE from Aerostan data set. Missing values are -9. Occupies columns 112-113.

1 = altostratus translucidus
2 = altostratus opacus or nimbostratus
3 = altocumulus translucidus
4 = altocumulus translucidus lenticularis
5 = altocumulus translucidus duplicatus or altocumulus opacus
6 = altocumulus cumulogenitus
7 = altocumulus opacus or duplicatus
8 = altocumulus cumuliformis, floccus, or castellatus
9 = altocumulus together with cirrus

MID_CLOUD_QLTY

MIDDLE CLOUD SHAPE QUALITY from Aerostan data set. Missing values are -9. Occupies columns 115-116. Refer to CLOUD_AMOUNT_QLTY for values.

HIGH_CLOUD

HIGH_LEVEL CLOUDS TYPE from Aerostan data set. Missing values are -9. Occupies columns 118-119.

1 = cirrus filosus
2 = cirrus densus
3 = cirrus nothus
4 = cirrus uncinus
5 = cirrus, cirrostratus
6 = cirrus, cirrostratus
7 = cirrostratus (all sky)
8 = cirrostratus (part of sky)
9 = cirrocumulus

HIGH_CLOUD_QLTY

HIGH_LEVEL CLOUDS SHAPE QUALITY from Aerostan data set. Missing values are -9. Occupies columns 121-122. Refer to CLOUD_AMOUNT_QLTY for values.

One or more of the following three text fields will appear at the end of each sounding's header in columns 124-325. For a given sounding, COMMENTS and OTHERFILEDATA may or may not be present but ORIGINAL_LATLON will always be there. No matter how many of the following three text fields are present, they will always occur in the order given below and will always begin in column 121.

Variables in Transmission Levels of Each Sounding

COMMENTS

May or may not be present. Floppy data set contained key sequences of unknown meaning. If they were present for a given sounding, they will appear directly after HIGH_CLOUD_QLTY. This field can be 0 to 100 characters long (when present, usually contains 3-10 characters).

OTHERFILEDATA

May or may not be present. Soundings which are the product of merging two different sources may contain a text field containing the following:

TXT: YEAR MONTH DAY GMT_HOUR GMT_MINUTE LATITUDE LONGITUDE 3km data: PRESSURE TEMPERATURE HUMIDITY WIND_DIRECTION WIND_VELOCITY DPDP.

These are alternate values for some of the header and 3km level variables. This text field will start with the letters "TXT: " and continue with values for the above listed variables. After the value for LONGITUDE is given, the words "3km data:" may appear with the above listed variables following.

ORIGINAL_LATLON

Will be present in every sounding. Most soundings have new latitude and longitude position data from one of two independent sources, with the exception of those soundings whose dates were out of range for the independent sources. All soundings have this text field, which begins with the words "Old latlon" and follows with the position data from its original source. (Old latlon, LATITUDE LONGITUDE.)

LEVEL_CODE

LEVEL CODE is from the Aerostan data set. Missing values are 99. Occupies columns 1-2.

01 = surface
02 = significant level (not at mandatory level)
03 = tropopause (significant level)
04 = significant level for wind (not at mandatory level)
05 = max wind (not at mandatory level)
06 = level of wind shift (not at mandatory level)
10 = mandatory level (for pressure or altitude)
11 = surface and standard level coincide
12 = significant level (occurs at mandatory level)
13 = tropopause (occurs at mandatory level)
14 = significant wind level (occurs at mandatory level)
15 = max wind (occurs at mandatory level)
16 = wind shift (occurs at mandatory level)

ALTITUDE

Height of the pressure level in whole meters. Missing values are -999999. Occupies columns 4-10.

A_ALT_QLTY

Aerostan's quality indicator for the ALTITUDE field. Missing values are -9. Occupies columns 12-13. Refer to CLOUD_AMOUNT_QLTY for values.

K_ALT_QLTY

Kahl's quality indicator for the ALTITUDE field. Occupies column 15.

0 = FAIL
1 = PASS

PRESSURE

AIR PRESSURE of the data level in hPa. Missing values are 9999.99. Occupies columns 17-23.

A_PRES_QLTY

Aerostan's quality indicator for the PRESSURE field. Missing values are -9. Occupies columns 25-26. Refer to CLOUD_AMOUNT_QLTY for values.

K_PRES_QLTY

Kahl's quality indicator for the PRESSURE field. Occupies column 28.

0 = FAIL
1 = PASS

TEMPERATURE

AIR TEMPERATURE in degrees Celsius. Missing values are 99.99. Occupies columns 30-35.

A_TEMP_QLTY

Aerostan's quality indicator for the TEMPERATURE field. Missing values are -9. Occupies columns 37-38. Refer to CLOUD_AMOUNT_QLTY for values.

K_TEMP_QLTY

Kahl's quality indicator for the TEMPERATURE field. Occupies column 40.

0 = FAIL
1 = PASS

HUMIDITY

RELATIVE HUMIDITY ranging from 0 to 100 percent. Missing values are -99.9. Occupies columns 42-46.

K_HUMID_QLTY

Kahl's quality indicator for the HUMIDITY field. Occupies column 48.

0 = FAIL
1 = PASS

WIND_DIRECTION

WIND DIRECTION ranging from 0 to 360 degrees. Missing values are 999. Occupies columns 50-52.

A_WIND_DIR_QLTY

Aerostan's quality indicator for the WIND DIRECTION field. Missing values are -9. Occupies columns 54-55. Refer to CLOUD_AMOUNT_QLTY for values.

K_WIND_DIR_QLTY

Kahl's quality indicator for the WIND_DIRECTION field. Occupies column 57.

0 = FAIL
1 = PASS

WIND_VELOCITY

WIND VELOCITY in meters/second. Missing values are -99.9. Occupies columns 59-63.

A_WIND_SPD_QLTY

Aerostan's quality indicator for the WIND VELOCITY field. Missing values are -9. Occupies columns 65-66. Refer to CLOUD_AMOUNT_QLTY for values.

K_WIND_SPD_QLTY

Kahl's quality indicator for the WIND_VELOCITY field. Occupies column 68.

0 = FAIL
1 = PASS

LVL_QUAL

LEVEL QUALITY INDICATOR: Denotes the results of Condigital's quality controls applied to this level. Range is 0 to 9 as follows:

Missing values are 9. Occupies column 70.

DPDP

DEW POINT DEPRESSION (DEW POINT DEFICIT) at the current level in degrees Celsius. Missing values are 99.9. Occupies columns 72-75.

A_DPD_QLTY

Aerostan's quality indicator for the DEW POINT DEFICIT field. Missing values are -9. Occupies columns 77-78. Refer to CLOUD_AMOUNT_QLTY for values.

K_DPD_QLTY

Kahl's quality indicator for the DPDP field. Occupies column 80.

0 = FAIL
1 = PASS

TYP_LVL

TYPE OF LEVEL: Condigital's code indicating the reason for selection of the level. Range of values is 00-99.

ELEMENT_QLTY

Condigital field. ELEMENT QUALITY FLAGS: These fields contain the result of any quality control procedures for identifying suspect and doubtful individual elements, and elements that failed QC checks. Descriptions of the element quality flags are contained in the appendices, which are keyed to the DATA_SRCE field. If, for example, the DATA_SRCE is 01 (source = TD6201), the appendix is numbered 02, etc. The Element Quality is assigned a value equivalent to the least correct flag.

The range of values is listed in each applicable appendix. Although the range of values for element quality flags are specific for each data source, as a general rule, any combination of ASCII characters, except lowercase letters and "#," is allowed in this element.

Missing values are "??????????????." Occupies columns 86-99.

 

NCDC_USE

Condigital field: Reserved for internal NCDC use. Missing values are *quot;??." Occupies columns 101-102.

The parameters for this data set represent an archive of rawinsonde measurements of wind direction and speed, atmospheric pressure, humidity, air temperature, and geopotential height as well as surface-based observations of cloud cover such as amount, type, and height.

Spatial Coverage

North polar regions:

• Minimum latitude: 70 N
• Maximum latitude: 90 N
• Minimum longitude: 180 W
• Maximum longitude: 180 E

Spatial Coverage Map

Locations of profiles measured by rawinsonde at Soviet drifting ice stations during 1954-1990. The stations drift with the prevailing winds and surface currents in the Arctic Ocean. Taken together, the measurements provide reasonably complete coverage over the Arctic ice cap. At any given time, however, data are only available at locations along the drift path.

The following is an excerpt of soundings taken from April 20, 1954 to April 14, 1955.

723
003 9  9999.9 1954 04 20 0000 -9 166 9999 86.60 182.80     3850    13000 99 9 99 018 
??????? -9 -9 -9 -9 -9 -9 -9 -9 -9 -9     Old latlon 86.60 182.85 E
99    3850 -9 1  600.00 -9 1 -32.10 -9 1 -99.9 0 210 -9 1   5.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    4000 -9 1  587.00 -9 1 -33.30 -9 1 -99.9 0 208 -9 1   5.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    5000 -9 1  509.00 -9 1 -40.80 -9 1 -99.9 0 204 -9 1   7.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    5120 -9 1  500.00 -9 1 -41.50 -9 1 -99.9 0 204 -9 1   7.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    5820 -9 1  448.00 -9 1 -48.90 -9 1 -99.9 0 215 -9 1   6.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    6000 -9 1  439.00 -9 1 -48.90 -9 1 -99.9 0 217 -9 1   6.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    6620 -9 1  400.00 -9 1 -48.90 -9 1 -99.9 0 207 -9 1   6.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    7000 -9 1  377.00 -9 1 -48.90 -9 1 -99.9 0 210 -9 1   7.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    7360 -9 1  357.00 -9 1 -48.90 -9 1 -99.9 0 207 -9 1   7.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??
99    7810 -9 1  334.00 -9 1 -45.50 -9 1 -99.9 0 197 -9 1   7.0 -9 1 9 99.9 -9 0 -99 
?????????????? ??

Following the experience in assembling the Historical Arctic Rawinsonde Archive (Serreze et al. 1992; Kahl et al. 1993), it was decided that all data values present in the individual soundings, including quality indicators, would be retained. This approach gives users the option of making their own determination of data quality. Nevertheless, a rudimentary quality control procedure, which is described briefly below and more fully in Serreze et al. 1992, has been applied. This procedure consists of identifying "gross" errors, such as negative wind speeds, and also "probable" errors, such as extreme values. The latter two quality checks, which give codes of 0 (failed) or 1 (passed) are referred to as "Kahl's quality indicators." Only the Aerostan and Condigital data sets contain quality indicators prior to being processed by Kahl. Refer to the Summary of Individual Data Sources section of this document.

Gross errors, such as negative wind speeds, negative geopotential heights, geopotential height decreasing with decreasing pressure, etc., were flagged first. Data values that passed this check were subjected to a "seasonally adjustable limits check," which is described in the following excerpt from Serreze et al. (1992).

The seasonally adjustable limits check worked as follows. Data from all [land-based] stations for 1987 were stratified by season into 15 atmospheric layers bounded by pressure levels. Seasons are defined as December-February (winter), March-May (spring), June-August (summer) and September-November (autumn). Since all checks are based on pressure, no check on the pressure values, themselves, is performed.

Initial frequency histograms of geopotential height, temperature, wind direction, and wind speed were compiled for each layer and for each season in 1987. Extreme outliers were eliminated by discarding values that were more than four standard deviations from the respective means. Since wind speed does not follow a normal distribution, these values were first converted into log wind speed. Means and standard deviations for the remaining data were then recomputed. Using these data as representative sample means and standard deviations of the complete data set, any value that was greater than +/- 4 standard deviations from the sample mean for the respective season and layer was then flagged. The means and standard deviations used in the limits check are given in the Appendix.

An implicit assumption in the error checking routine is that the layer mean is representative of the mean for any level within that layer. Since a large number of atmospheric levels are used in the check, this is a tolerable assumption for testing temperature, wind direction, and wind speed. It was found to be inappropriate for geopotential height, however, due to the logarithmic decay of pressure with increasing elevation.

To check the geopotential heights, this logarithmic relationship was used. Taking the log of pressure at the bottom (P1) and top (P2) of the layer in which the observed pressure (P) fell, a weight, W, was calculated:

W = [LOG(P)-LOG(P2)]/[LOG(P1)-LOG(P2)] (1)

Next, ZL1 and ZH1, respectively, are defined as the lowest and highest allowable geopotential height at the base of the layer, and similarly ZL2 and ZH2 as the lowest and highest allowed limits of the top of the layer (with limits taken as +/- 4 standard deviations from the mean). Then ZL and ZH are calculated, which by incorporating the weight W, define the limits of allowable geopotential height for the value of P:

ZL = W*[ZL1-ZH1] + ZH1 (2)

ZH = W*[ZL2-ZH2] + ZH2 (3)

The allowable value of Z at pressure level P in the sounding is thus

ZL <= Z <= ZH (4)

Since atmospheric moisture can be highly variable, with considerable uncertainties in cold Arctic conditions, the dew point depression data was simply screened to flag negative values and any values exceeding an arbitrary high threshold of 35C. Those wishing to use these data are referred to Elliot and Gaffen (1991) who provide an overview of problems in rawinsonde moisture data.