15 Minute Data (Level 1)

Processed from raw 15 minute data (Level 0)

High frequency measurements from Howard Glacier Meteorological Station (HODM) 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 package contains 15-minute data from the Howard Glacier Meteorological Station (HODM), located in Taylor Valley (Latitude: -77.67121, Longitude: 163.07732, Elevation: 472 meters above sea level). HODM was established in 1993, during the 93/94 field season.

Dataset ID: 

7012

Associated Personnel: 

822
823
167
9
166
168

Short name: 

HODM

Purpose: 

Meteorological data is collected year-round at each of MCM LTER stations. Data is 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 1993-1994 field season, the Howard Glacier meteorological station was constructed at the same coordinates as stake 31 on the glacier's mass balance grid (latitude of 77-40-17.36222 S, longitude of 163-04-44.83507 E, and elevation of 472.49343 meters above sea level).  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 20, 1993 and November 27, 1995, and every 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:
    

Data sources: 

HODM_AIRT
HODM_ICESURFCHANGE
HODM_ICET
HODM_RADN
HODM_RH
HODM_WIND
HODM_WVAPD

Maintenance: 

 
Metadata standardized in 2007 by Gardner and San Gil.
 
Data and metadata was moved to DEIMS in 2014 (Inigo San Gil)

Quality Assurance: 

 On September 3, 1999, at the request of Thomas Nylen, the data manager did some fine-tuning
 of the data. This included:
 1. Deletion of flags for ice temperature measurements from Nov 20, 1993 @ 16:30 to Dec
 24, 1993 @ 14:30. Instruments were not installed during this time;
 2. Removal and flagging of WDir values for measurements taken between Nov 23, 1994 @
 10:20 and Jan 23, 1995 @ 13:20 where WSpd = 0. Since the wind speed values during
 this time were flagged as bad, the original database query probably did not flag the WDir
 data when WSpd =0.
 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 30, 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 7, 2003, SwRadIn and SwRadOut values between 11/20/1993 4:30:00 PM and
 11/23/1994 8:00:00 AM flagged as questionable because the values are significantly lower than
 the other stations during the same time period. It appears the pyranometers were either tilted or
 installed improperly. Also SwRadIn and SwRadOut values between 11/25/1997 @ 1445 and
 01/10/1998 1430 because the wrong multiplier was used. The SwRadIn values were divided by
 109.29 and multiplied by 115.61 and the SwRadOut were divided by 108.7 and multiplied by
 116.41.
 On June 29, 2004, wind direction between 11/20/1993 16:30 to 11/27/1995 15:00 was flagged
 because the data is about +25 degrees off from the true direction. This was determined by
 comparing the daily wind direciton over the entire 10 years of record. Additionally, between
 11/27/1995 15:30 to 11/25/1997 13:30, the wind direction data was flagged because it is about -
 10 degrees off from the true direction.
 

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