precipitation

High frequency measurements from Explorers Cove Meteorological Station (EXEM) in Taylor Valley, Antarctica from 1997 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 package contains 15-minute data from the Explorers Cove Meteorological Station (EXEM), located in Taylor Valley (Latitude: -77.588733, Longitude: 163.417523, Elevation: 25 meters above sea level). EXEM was acquired from USGS in 1997, during the 97/98 field season.

Dataset ID: 

7008

Associated Personnel: 

818
819
159
11
160
161

Short name: 

EXEM

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) is processed and provided as Level 1 data on the MCM LTER website. Field notes, sensor information, processing procedures, QA/QC, and metadata is 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: 

At the start of the first McMurdo LTER field season (1993-1994), Explorers Cove station was one of only two meteorological stations operating on the floor of the McMurdo Dry Valleys. The U.S. Geological Survey continued to manage the station. From November 24, 1995 to February 26, 1996, precipitation levels were sampled every hour for the long-term ecological research program.On February 26, 1996, the signal from the precipitation gage went dead and remained so until new equipment was installed in November, 1997. As a result there is a gap in the data collected at Explorers Cove meteorological station.In November, 1997, a new station with all new sensors mounted on Clow's old tripod was set up. At that time, 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 15 minutes. This has resulted in approximately 20 values being recorded for final storage in the more recent output intervals.In 2014, the data loggers lost most of the season data, and the streamed record is spotty.Sampling and Averaging Intervals For Sampling frequency and Data Logger output and averaging intervals please visit: http://www.mcmlter.org/data/meteorology/methods/Interval_Dates.pdfSeasonal Task Summary To view the data post-processing steps for each season please visit: http://www.mcmlter.org/data/meteorology/tasks/task_lists.htm

Data sources: 

EXEM_AIRT
EXEM_PPT
EXEM_RADN
EXEM_RH
EXEM_SOILT
EXEM_WIND

Maintenance: 

On September 6, 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 the removal and flagging of precipitation values between Nov 21, 1997 @ 11:00 and Jan 13, 1998 @ 9:30. This was done at the request of Thomas Nylen. 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 correctio n 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.

In 2006, metadata Chris Gardner and Inigo San Gil standardized the metadata to the EML.

In 2014, metadata was refined further using the Drupal Ecological Information Management System (Inigo San Gil)

In 2016, data from 2013 through 2016 onwards was recovered and posted - Maciek, San Gil.

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