photosynthetically active radiation

Daily measurement summaries from Lake Vanda Meteorological Station (VAAM), McMurdo Dry Valleys, Antarctica (1994-2019, ongoing)


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 package contains daily measurement summaries derived from 15-minute data generated by the Lake Vanda Meteorological Station (VAAM), located in Wright Valley. VAAM was established in 1994, during the 94/95 field season.

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During the 1994-1995 field season, the Lake Vanda meteorological station was constructed near the mouth of the Onyx River. 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 20 minutes between November 24, 1994 and December 30, 1994, every hour between December 30, 1994 and November 21, 1995, and every 15 minutes thereafter. This has resulted in approximately 20 values being recorded for final storage in every output interval.


On September 9, 1999, the data manager added the 1998-1999 data to this dataset. In the process,at the  request of Thomas Nylen, she did some fine-tuning of the data. Revisions included:
 1. Removal and flagging of WDir and WDirStd values on Nov 25, 1994 @ 9:20. Since windspeed was zero (0),
 it made no sense to have values for wind direction.
 2. Addition of PAR values between Dec 30, 1994 @ 17:00 and Jan 20, 1995 @ 15:00.
 On June 1, 2000, the 1999-2000 data was posted. In the process, Denise Steigerwald changed thelayout 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 andminor adjustments were made to the metadata.
 On June 1, 2000, relative humidity (RH) values were corrected for a systematic error in themeasurement created  by an instrument manufacturer error. All RH data with air temperaturesbelow 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 tha n or equal to 100 were changed to 99.99and 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, maximumsand counts of the  records represented in the Oracle database's meteorology tables.

Additional information: 

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:  meteorological tasks lists


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