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Former Soviet Union Hydrological Snow Surveys, 1966-1996

Summary

The Former Soviet Union Hydrological Snow Surveys are based on observations made by personnel at 1,345 sites throughout the Former Soviet Union between 1966 and 1990, and at 238 of those sites between 1991 and 1996. These observations include snow depths at World Meteorological Organization (WMO) stations and snow depth and snow water equivalent measured over a nearby snow course transect. The station snow depth measurements are a ten-day average of individual snow depth measurements. The transect snow depth data are the spatial average of 100 to 200 individual measuring points. The transect snow water equivalent is the spatial average of twenty individual measuring points. Data were acquired from the Institute of Geography, Russian Academy of Sciences Moscow, and data were digitized in Russia under the supervision of Professor Alexander Krenke.

The development of this data set was funded by the NOAA Environmental Services, Data, and Information Management (ESDIM) program through the NOAA/NESDIS National Geophysical Data Center (NGDC).

Citing These Data:

Citations in reference lists accompanying published work should be stated:

Krenke, A. 1998, updated 2004. Former Soviet Union hydrological snow surveys, 1966-1996. Edited by NSIDC. Boulder, CO: National Snow and Ice Data Center/World Data Center for Glaciology. Digital media.

Overview Table

Table of Contents

1. Contacts and Acknowledgments:

Investigator(s) Name and Title:

Dr. Richard L. Armstrong
National Snow and Ice Data Center
University of Colorado
CIRES, 449 UCB
Boulder, CO 80309-0449 USA

Professor Alexander Krenke
Russian Academy of Sciences,
Institute of Geography
Laboratory of Dynamical and Historical Climatology
Staromonetny 29
Moscow, 109017
Russia

Technical Contact:

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

2. Detailed Data Description:

Format:

The data set includes data from 1,345 stations spread throughout the Former Soviet Union. These stations are concentrated in inhabited areas in the mid-latitudes. Available data cover January 1966 to December 1990 for all stations (however, not all stations reported data throughout this time period), and January 1991 to December 1996 for 238 of the stations. Data can be accessed from the following directories:

• product - 1966-1990 data
• update04012002 - 1991-1996 data, first update
• update02172003 - 1991-1996 data, second update
• update05152003 - 1991-1996 data, third update
• update04052004 - 1991-1996 data, fourth update

Note that updated data from 2002, 2003, and 2004 have not been combined.

The three data types in this data set are synoptic, station, and transect. Each file type contains a different type of data. All files are ASCII.

1. Synoptic data:

These files contain the snow transect measurements for a single day at all available stations. The data are stored in files with the suffix .syn. The filename itself is made up of the date of the measurements. For example, 19830110.syn indicates data from 10 January 1983. Missing data are indicated by -2 in all fields. These files contain the following parameters:

Column 1: Station number - WMO station near which the transect is based.

Column 2: Latitude - The latitude of the station (degrees North).

Column 3: Longitude - The longitude of the station (degrees East).

Column 4: Snow course type -

1 - field
2 - forest
3 - gully
4 - unknown

Column 5: Degree of snow coverage of the surrounding terrain. Values range from 0 to 10. Ten indicates 100% coverage.

Column 6: Degree of snow coverage along the route. Values range from 0 to 10. Ten indicates 100% coverage.

Column 7: Degree of ice crust coverage along the route. Values range from 0 to 10. Ten indicates 100% coverage.

Column 8: Average snow depth along the route. Value is in cm.

Column 9: Maximum snow depth along the route. Value is in cm.

Column 10: Minimum snow depth along the route. Value is in cm.

Column 11: Mean snow density. Value is in g/cm³.

Column 12: Ice crust thickness. Value is in mm.

Column 13: Thickness of snow layer which is saturated with water. Value is in mm.

Column 14: Snow water equivalent. Value is in mm.

Column 15: Snow cover features observed -

0 - even snow coverage on frozen soil without snow drifts
1 - even snow coverage on thawed soil without snow drifts
2 - even snow coverage without snow drifts, soil condition is unknown
3 - uneven snow coverage on frozen soil, little snow drifts
4 - uneven snow coverage on thawed soil, little snow drifts
5 - uneven snow coverage, soil condition is unknown, little snow drifts
6 - very uneven snow coverage on frozen soil, big snow drifts
7 - very uneven snow coverage on thawed soil, big snow drifts
8 - very uneven snow coverage, soil condition is unknown, big snow drifts
9 - snow coverage with paths of open soil

Column 16: Snow structure observed -

0 - fresh snow, like dust
1 - fresh snow, fluffy
2 - fresh snow, sticky
3 - old snow, crumbly
4 - old snow, dense
5 - old snow, wet
6 - snow crust, unconnected with snow below
7 - dense snow with snow crust on surface
8 - damp snow with snow crust on surface
9 - snow with water

Column 17: Snow course quality flag - Results of NSIDC quality control. See Quality Assessment section for further detail.

1 - Raw snow density increased by a factor of 10 (e.g., raw data .6 reset to .06)
2 - Raw snow density missing a decimal point (e.g., raw data 6 reset to .06)
3 - Average snow depth out of range (> 200 cm); set to agree with SWE and density data
4 - Snow water equivalent out of range (> 400 mm); set to agree with depth and density data
5 - Suspect data; out of range values, however the error was unknown so no data were changed

2. Station data:

These files contain data from the meteorological station itself. These data are monthly station summaries rather than daily measurements. The filename includes the WMO station number and the suffix .sta. For example, 38974.sta indicates a file of station data from station 38974. Missing data are indicated by -2 in all fields. These files contain the following parameters:

Header information:

Region - political region which the data station resides in
Station number - the WMO station number
Latitude - The latitude of the station (degrees North)
Longitude - The longitude of the station (degrees East)
Elevation - The elevation of the station (meters ASL)

Column 1: Month - The month summarized in the record.

Column 2: Year - The four digit year of the data record.

Column 3: Surroundings of the stake - The physical surroundings of the stake at which data were taken

1 - open
2 - closed
3 - mixed

Column 4: Number of days of snow cover within the month.

Column 5: Mean snow height at the station for the first 10 days of the month.

Column 6: Mean snow height at the station for the second 10 days of the month.

Column 7: Mean snow height at the station for the final days of the month. Note: this mean is not always the mean of 10 days (e.g., February has a mean for 8 days and December has a mean for 11 days).

Column 8: Station data quality - Results of NSIDC quality control. See Quality Assessment section for further details.

1 - Mean values increased by a factor of 100 (e.g., data of 6 700 8 reset to 6 7 8)
2 - Mean values between 0 and 1; decreased by a factor of 100 (e.g., data of 6 .07 8 reset to 6 7 8)
3 - More days of snow in raw data than are in the month (e.g., 34 reset to 31)
4 - Raw data value of zero greater than two standard deviations from the mean; data value is set to missing
5 - Suspect data but unknown error; data unchanged

3. Transect data:

These files contain the averages of data taken during the snow transect. Transects were to be taken on the 10th, 20th, and final day of the month. However, transects occur throughout the month. This data product only includes the three most common days of measurement (the 10th, 20th, and final day). Data taken on other days has been omitted. Field and forest transects comprise the majority of transect types, and only these are included in this data product. The filename includes the WMO station number and the suffix .trn. For example; 38974.trn contains transect data from station 38974. Missing data are indicated by -99 in all fields. These files contain the following parameters:

Header information

Region - political region which the data station resides in
Station number - the WMO station number
Latitude - The latitude of the station (degrees North)
Longitude - The longitude of the station (degrees East)
Elevation - The elevation of the station (meters ASL)

Column 1: Month - The month summarized in the record.

Column 2: Year - The year of the data record.

Column 3: Transect type - 01 indicates field transacts.

Column 4: Snow course date - The date on which the transect was taken. Either the 10th, 20th, or last day of the month.

Column 5: The average snow depth along the transect (field transect)

Column 6: Snow water equivalent along the transect (field transect)

Column 7: Transect type - 02 indicates forest transacts.

Column 8: The average snow depth along the transect (forest transect)

Column 9: Snow water equivalent along the transect (forest transect)

Column 10: Snow course quality flag - Results of NSIDC quality control. See Quality Assessment section for further detail.

1 - Raw snow density increased by a factor of 10 (e.g., raw data .6 reset to .06)
2 - Raw snow density missing a decimal point (e.g., raw data 6 reset to .06)
3 - Average snow depth out of range (> 200 cm) set to agree with SWE and density data
4 - Snow water equivalent out of range (> 400 mm) set to agree with depth and density data
5 - Suspect data; out of range values, however the error is unknown so no data was changed

Note that some stations have data from both a field transect and a forest transect. The quality flag reflects errors found in either transect. If errors are found in both transects, the quality flag is set to 5.

File and Directory Structure:

Data can be accessed from the following directories:

• product - 1966-1990 data
• update04012002 - 1991-1996 data, first update
• update02172003 - 1991-1996 data, second update
• update05152003 - 1991-1996 data, third update
• update04052004 - 1991-1996 data, fourth update

File Naming Convention:

There are three types of data file within this data product. Each file type encompasses a different type of data. All files are ASCII. The three data types included are: synoptic, station, and transect. Synoptic data files have a filename made up of the date of the measurements, plus a suffix of .syn (for example, 19830110.syn indicates data from 10 January 1983). Station filenames include the WMO station number and the suffix .sta (for example, 38974.sta indicates a file of station data from station 38974). Transect filenames include the WMO station number and the suffix .trn (for example; 38974.trn contains transect data from station 38974).

Spatial Coverage:

The data set includes data from 1,345 stations spread throughout the Former Soviet Union. These stations are concentrated in inhabited areas in the mid-latitudes.

The red squares represent locations updated on 2002-04-01. Green squares represent updates from 2003-02-17. Light blue squares represent updates from 2003-05-15. Yellow squares represent updates from 2004-04-05. The blue diamonds represent the entire data set.

Temporal Coverage:

Available data cover January 1966 to December 1990 for all 1,345 stations (however, not all stations reported data throughout this time period), and January 1991 to December 1996 for 238 of these stations.

Parameter or Variable:

Parameter Description:

These observations include snow depths at World Meteorological Organization (WMO) stations and snow depth and snow water equivalent measured over a nearby snow course transect. The station snow depth measurements are a ten-day average of individual snow depth measurements. The transect snow depth data are the average of snow depth from 100 to 200 points along the transect. The transect snow water equivalent is the average of snow water equivalent at twenty points.

Error Sources:

This data set is based upon hand-digitized analog records. Bad data values could have been introduced in the process of keying the data from the original log books. Degradation of the original records and human error could have resulted in missing or inaccurate data values.

Quality Assessment:

NSIDC implemented a quality control process to identify errors and correct the data where possible. However, users are encouraged to do their own quality control on these data.

In the first step of the quality control process, out-of-range values were identified and, where possible, correction algorithms were developed. The data ranges used were

	Mean snow height at the station:  0-200 
	Amount of days with snow cover in a month:  0-31 
	Degree of snow or ice coverage:  0-10
	Average snow height along the route:  0-200 
	Mean snow density:  0-0.60
	Snow water equivalent of the snow itself:  0-400
	Snow cover features and structure:  0-9

As indicated by the data quality flags, corrections of some of the errors in depth, snow density, and snow water equivalent were effected. These errors made up a small percentage of all errors (see the table below for actual numbers of corrected entries).

The most common correction error occured for station data, when data fields that should have been recorded as missing were instead recorded as zero. An algorithm to correct these errors checked the monthly mean for each station. If the "zero" value in question was more than two standard deviations below the mean, it was assumed to be missing data and the value was reset to missing (-2).

Note that some stations reported no snow for an entire winter. In areas with low snowfall, this is possible, so these records were not removed from the data set.

In the transect files, each of the types of snow course is checked individually, but the flag set does not make a distinction between the "field" and the "forest;" therefore, if the flag is set it could be either of the two.

The data for "days with snow cover" are very inconsistent, and therefore suspect. The value of zero in this field is often inconsistent with other data from the station.

Statistics on quality control for station and transect records:

Data for 1966 - 1990:
Total number of station records examined: 195936
Total number of transect records examined: 495593

Total Errors (by error flag)

Data for 1991 - 1996, update 2002-04-01:
Total number of station records examined: 4397
Total number of transect records examined: 10482

Total Errors (by error flag)

Data for 1991 - 1996, update 2003-02-17:
Total number of station records examined: 2149
Total number of transect records examined: 6697

Total Errors (by error flag)

Data for 1991 - 1996, update 2003-05-15:
Total number of station records examined: 3530
Total number of transect records examined: 11549

Total Errors (by error flag)

Data for 1991 - 1996, update 2004-04-05:
Total number of station records examined: 2796
Total number of transect records examined: 8459

Total Errors (by error flag)

3.Data Acquisition and Processing:

Data Acquisition Methods:

The original analog records were digitized (keyed) at the Institute of Geography, Moscow, under the supervision of Professor Alexander Krenke. The analog records were a collection of individual entries taken by observers in the field. Snow depth measurements were made at the station with a fixed snow measuring rod. Snow survey measurements were made using a portable snow measuring rod and a snow weighing balance. Snow depth data were taken at a meteorological enclosure, on a daily basis, in the vicinity of the station. The daily data were then averaged at the end of a ten-day period into a single value. This averaging would be done three times per month with the final period in the month containing from eight to eleven days of data, depending on the month.

Snow surveys were carried out at regular intervals. Each snow survey was carried out not more than five kilometers from the station and not closer than one-half of a kilometer to railroads, highways, or settlements with industrial plants. The snow survey routes were laid out to cross the typical terrain of the region. Routes in open areas were 2000 meters in length. Routes in partially forested areas were 1000 meters, and routes in heavily forested areas were 500 meters. Snow surveys were carried out on the 10th, 20th, and the last day of each month during the snow cover season. During snow melt, surveys were carried out every five days. The suggested frequency of snow surveys was not always followed, and thus data may have been collected on any given day throughout the month (although only data from the 10th, 20th, and final day of the month are included in the NSIDC data set). Snow depth and snow weight were measured at specified intervals along the route. State of the snow, thickness of layers, and snow characteristics were noted along the route. Upon completion of the snow survey, the measurements were averaged across the entire route and were then used to calculate snow density and snow water equivalent.

Data Source:

Data were acquired from the Institute of Geography, Russian Academy of Sciences Moscow, and data were digitized under the supervision of Professor Alexander Krenke.

4.Document Information:

Document Creation Date:

2002-04-08

Document Revision Date:

2004-04-16

Document URL:

http://nsidc.org/data/docs/noaa/g01170_fsu_snow/index.html