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Commonwealth Glacier Meteorological Station Monthly Averages
As part of the McMurdo Dry Valleys Long Term Ecological Research program (MCM LTER), meteorological data is collected from various locations throughout the McMurdo Dry Valleys of Antarctica. This package contains monthly averages derived from 15-minute data generated by the Commonwealth Glacier Meteorological Station (COHM), located in Taylor Valley. COHM was established in 1993, during the 93/94 field season.
Data set ID:
McMurdo Dry Valleys Long-Term Ecological Research (LTER): LTER automatic weather network (LAWN)
Commonwealth Glacier Meteorological Station
At the start of the 1993-1994 field season, the Commonwealth Glacier meteorological station was constructed at the same coordinates as stake 11 on the glacier's mass balance grid. The station was set up to sample sensors every 30 seconds and send summary statistics (for example, averages and maximums) to solid-state storage modules every:
3 hours between November 22 and December 3, 1993,
30 minutes between December 3 and December 24, 1993,
30 minutes for the main array andamp; every 24 hours for the max/min thermal infrared between December 24, 1993 and; January 12, 1994,
6 hours for the main array andamp; every 24 hours for the max/min thermal infrared between January 12, 1994 and; January 18, 1994,
20 minutes between January 18, 1994 and November 27, 1995,
15 minutes thereafter.
This has resulted in approximately 20 values being recorded for final storage in every output interval.
Sampling and Averaging Intervals
For Sampling frequency and Data Logger output and averaging intervals please visit
Seasonal Task Summary
To view the data post-processing steps for each season please visit the
Tasks Lists page
While processing the 1997-98 files, Peter Doran identified an error in the LWRadIn values for the Commonwealth station in 1996-97's data from Julian day 319 of 1996 at 15:45 local time to Julian day 27 of 1997 at 9:00 local time. To correct the LWRadIn values during this period the values needed to be multiplied by 0.800514. The data manager at INSTAAR did this and provided updated versions of the data sets in May, 1999.
On August 18, 1999, the data manager added the 1998-1999 data to this dataset. In the process, she did some fine-tuning of the data, which included:
1. removal of the relative humidity values from November 14, 1996 through December 4, 1996, as requested by Peter Doran. Since the temperatures were bad during this period, and relative humidity is based on temperature, the RH data needed to be voided as well. They had been marked as subjectively voided in the comments field, but needed the
values removed from the RH field.
2. removal of records on 5/20/1994 2:00:00 and 5/20/1994 11:00:00. These contained
3. removal of SwRadOut values on 12/25/1994 13:00:00, 12/25/1994 13:20:00, and 12/25/1994 13:40:00. These records had very high SwRadOut and no SwRadIn values, so Peter Doran determined that it was best to delete the 3 SwRadOut values.
4. removal of ThmIR values of -999.99 from the 1994 data. This was a level 0 campbell code and should not have been in the level 1 data set.
5. making the file layout consistent from year to year. This results in many null values being present for periods when certain values were not collected. However, it simplifies combining data from different years.
6. making corrections so that the files containing data for a given year started on January 1 at 0:00 and ended on December 31 at 23:45. Up to this point, records for January 1 between 0:00 and 12:45 were appearing in the previous year's file.
On August 31, 1999, at the request of Thomas Nylen, more updates were made including:
1. removal of wind direction and wind direction standard deviation values for records where
wind speed = 0;
2. removal of all commas from the comments fields, since commas cause spreadsheet
software packages to add additional columns;
3. addition of relative humidity values from Jan 23, 1995 @ 14:20 to Nov 27, 1995 @ 10:20. The task sheet gives no explanation nor data to indicate why it was omitted. The data looks good when plotted, so it was decided to include it.
4. addition of ice temperature values (at 20 cm and 1 m depths) from Nov 27, 1995 @ 12:15 to Jan 24, 1996 @ 10:30. Up to this point, the values were omitted from the data column and flagged. Looking at the values before and after this time period, the ice temperature data was also flagged, but the values were left in the data column. The data appears to be continuous across each of these time periods, and it was not logical why one period was omitted, but the before and after values were not. The data between Nov 27, 1995 @ 12:15 and Jan 24, 1996 @ 10:30 was therefore placed back, though flagged.
5. addition of wind direction values from Dec 19, 1995 @ 15:15 to Jan 24, 1996 @ 10:15. The task list stated that the arm was rotated 13 degrees on Jan 24. According to Peter Doran, the data should be left, but flagged.
6. removal of ThmIR values between 12/19/1995 11:15 and 12/19/1995 13:00.
7. updating of SwRadIn and SwRadOut values between Nov 25, 1997 @ 13:00 and Jan 16, 1998 @ 9:45. The wrong multiplier was used for SwRadIn and SwRadOut between Nov 25, 1997 @ 13:00 and Jan 16, 1998 @ 9:45. Two flags for SwRadOut, 01/02/1998 11:30 and 01/02/1998 12:00 were removed with the recalculated values.
8. removal of LwRadIn2 and LwRadOut2 values between Jan 1, 1999 and Jan 22, 1999 @ 10:15. These values were bad for the whole dataset.
9. removal of 1998-99 IceT20cm values above 0 (above the range limit).
In May 2000, the 1999-2000 data was posted. In the process, Denise Steigerwald changed the layout of the files so that they were sorted by category (air temperatures, humidity, radiation, wind etc.) rather than by year. Files containing monthly and daily averages were generated and minor adjustments were made to the metadata.
On May 17, 2000, relative humidity (RH) values were corrected for a systematic error in the measurement created by an instrument manufacturer error. All RH data with air temperatures below freezing were corrected using the vapor pressure over ice (rather than over water which was used initially). The error became quite large for very cold temperatures (the correction could grow to around 30%). The formula used for the correction was:
RH_corr = corrected relative humidity
RH_orig = original relative humidity
temp = air temperature
A = 4.165E-5
B = 9.7E-3
C = 1.0
For example, with an air temperature of -2.3 and RH_orig of 50.6, the RH_corr will be 51.7.
Records that showed corrected RH values greater than or equal to 100 were changed to 99.99 and flagged.
On June 6, 2000, the dataset showing longwave radiation measurements was updated. Thomas Nylen had gone through values recorded before January 22, 1999 and made some changes to these values and their corresponding flags (comments). Many of the fields were originally left blank but have now been assigned an appropriate number.
In June 2000, summary files were added to the web containing daily and monthly statistics.
These were generated by creating "views" of daily and monthly means, minimums, maximums and counts of the records represented in the Oracle database's meteorology tables.
In April 2003, the LwRadOut2 data were adjusted between 01/20/1999 12:45 PM and 01/23/2003 04:15 PM to account for erroneous dome thermister measurements made by the Eppley precision spectral pyranometer. The problem was identified by Eppley when recalibrating the instrument. The dome and case temperatures should be about the same,
especially in the winter. The voltage measured by the dome thermister was consistently 9% higher than the case thermister. To correct the problem the dome thermister were divided by 1.09 and the LwRadOut2 values were calculated again using the methods outlined in Procedures for Correcting Eppley Pyrgeometer Data. The revised values were on average 11.2% higher than the previous calculated values.
In 2006, metadata was standardized (Chris Gardner and Inigo San Gil) to the EML format.
in 2014, metadata was enhanced using the Drupal Ecological Information Management System (Inigo San Gil)
Meteorological data is collected year-round at each of the stations in the McMurdo Dry Valleys of Antarctica.
After retrieving this data (usually every January), the parameters that are recorded are processed from level 0 (raw) to level 1 (processed, provided on the web). The raw data file descriptions and task lists summarize what was done to get from level 0 to level 1 for all station found at the following link: M
eteorological Tasks Lists
about Commonwealth Glacier Meteorological Station Monthly Averages