McMurdo Dry Valleys

High frequency measurements from Lake Fryxell Meteorological Station (FRLM) in Taylor Valley, Antarctica from 1993 to present

Abstract: 

As part of the McMurdo Dry Valleys Long Term Ecological Research program, meteorological data are collected from various locations throughout the McMurdo Dry Valleys of Antarctica. This data package contains 15-minute data from the Lake Fryxell Meteorological Station (FRLM), located in Taylor Valley. BOYM was established in 1993, during the 93/94 field season.

Dataset ID: 

7010

Associated Personnel: 

829
828
190
17
63
191

Short name: 

FRLM

Purpose: 

Meteorological data are collected year-round at each of MCM LTER stations. Data are manually downloaded from the meteorological stations during the austral summer. Raw 15 minute data (Level 0) are processed and provided as Level 1 data on the MCM LTER website. Field notes, sensor information, processing procedures, QA/QC, and metadata are provided in the Meteorological Post Processing Documentation and Task Lists for each field season at the following address: http://www.mcmlter.org/data/meteorology/tasks/task_lists.htm 

Methods: 

When the McMurdo Dry Valley LTER project began in December, 1993, a lake-ice meteorology station was already set up at Lake Fryxell. It was a 6 foot tower built by Rich Harnish in ~1989, but had not collected data for at least a year. Peter Doran, noting that the problem was power related (since the battery was under water and the voltage was less than 5), righted the station, and rebuilt it with new power supply, a new wind monitor, new CR10, new solar panel, and added a quantum sensor. The under water light sensors were not hooked up again nor was the barometric pressure sensor. The lake-ice station was operated from 7 December 1993 to 6 January 1994 (this lake-ice station is located in the same table as the Lake Fryxell shore station and is noted with the METLOCID=FRIM). At that time, it was decided that maintenance of the records at the site of the old Fryxell land station was more important than the ice station so the ice station was cannibalized to re-establish the Lake Fryxell shore station, (which had been destroyed by wind the previous winter (METLOCID=FRLM)). The station was based on a 6 foot tripod which set it apart from the other Taylor Valley stations, but a 10 foot tower was subsequently installed in year 2. The land station is located a few meters above the old site to avoid rising lake levels. On June 25, 2001 @ 0230 the station mast broke and blew over, breaking the wind monitor. Station was taken apart on November 16, 2001, with the sensors except wind temporally set up on what was left of the station. On November 27, 2001 the station was reconstructed and was made operational again. Mark all values from June to November as bad or questionable except the soil temperatures 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: 10 minutes from December 7, 1993 to January 6, 1994 and January 7, 1994 to January 12, 1994, three hours from January 6, 1994 to January 7, 1994 and January 12, 1994 to November 28, 1994, 20 minutes between November 28, 1994 and November 21, 1995, and 15 minutes thereafter. This has resulted in approximately 20 values being recorded for final storage in every output interval. Primary measurements made on Lake Fryxell meteorology station, instrumentation used, and time of initiation are shown in the following table: In 2007, it was realized that the RH error was still present in parts of the dataset. Hasan Basagic made the above corrections to the FRLM dataset for the date range 1/23/2004 11:15 - 12/21/2006 13:30 (102,058 records). In September, 2007 the information manager (Chris Gardner) removed all old RH data and re-inserted then newly calculated values and associated comments. The original files are archive in the 'submitted data' section of the mcmlter server.

Sampling and Averaging Intervals For Sampling frequency and Data Logger output and averaging intervals please visit: http://mcmlter.ltenet.edu/data/meteorology/methods/Interval_Dates.pdf

Seasonal Task Summary To view the data post-processing steps for each season please visit: http://mcmlter.lternet.edu/data/meteorology/tasks/task_lists.htm

Data sources: 

FRLM_AIRT
FRLM_RADN
FRLM_RH
FRLM_SOILT
FRLM_SURF
FRLM_WIND
FRLM_WVAPD

Maintenance: 

On August 16, 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 and flagging of WDirStd values between Nov 28, 1994 @ 15:40 and Nov 30,
 1994 @ 14:00. The task sheet in frl94501.dat and frl94502.dat both indicated the
 WDirStD should be flagged, but only the data covering frl94502.dat had been flagged.
 2. Removal of all RichNo and RichNo Comments from 11/21/1995 12:40:00 to
 1/24/1996 12:15:00, since data was not collected after 11/21/95.
 3. addition of PAR values for the entire portion of 1997. This data was accidently dropped
 and needed to be added back.
 4. removal of all commas from the comments fields, since commas cause spreadsheet
 software packages to add additional columns.
 
 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 24, 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=RH_orig/((A*temp*temp)+(B*temp)+C) where
 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.
 
 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.
 
 On May 6, 2003, radiation values were omitted between June 25, 2001 @ 0230 to Nov 27, 2001
 because station was blown over.
 
On 2006, metadata was standardized to EML by Chris Gardner and Inigo San Gil
 
On 2014, metadata was enhanced using the DEIMS system

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