The GlacioBasis programme
3.2 Automatic Weather Sta- Sta-tions
The GlacioBasis programme operates one larger automatic weather station (AWS) and two smaller stations deployed on the glacier to obtain in situ time series
of physical parameters describing the weather at the glacier surface. The main GlacioBasis AWS was deployed in late March 2008 on A.P. Olsen Ice Cap (AWS1 in this report). AWS1 has now completed the fi fth year of uninterrupted operation and has proved very reliable, having only required minor maintenance in 2009 and 2010 to the mechanical structure of the station.
AWS2 also required some mainte-nance in May 2011 and in April 2012 to re-establish the failed frame supporting the ice ablation sonic ranger. As a part of the GEM 2012-2015 strategy, AWS2 has been equipped with radiometers and tilt sensors to measure the surface radiative energy fl uxes in this part of the upper ablation area.
AWS3 was found almost completely buried by snow, but no damage was apparent and the instruments could be reinstalled at the surface of the snow-pack. Scheduled replacement of sensors with freshly calibrated units was carried out at all stations. GlacioBasis uses the same recalibration plan as developed for PROMICE (Ahlstrøm et al. 2009). Ideally, GlacioBasis should hold a stock of spares and replacement parts in storage at Zack-enberg Research Station to increase the chances that unanticipated issues can be resolved quickly, as only one trip per year is possible. Currently, no such stock exists.
All three AWS’ worked through the few, moderately strong wind episodes recorded. To date, satellite data trans-mission indicates that the stations are working properly. During data valida-tion and calibravalida-tion, data were calibrated based on the manufacturer’s calibration report. The calibration factors are traced to the corresponding units through the device serial number using the same Glaciobase database as GEUS do to hand-le the sensors inventory for PROMICE.
Details on Glaciobase are provided by Ahlstrøm et al. 2009 and are not repeated here. Validation of the data is carried out using the same procedures established for PROMICE; again, details on this are provided by Ahlstrøm et al. 2009 and are not repeated here.
Detailed information on each AWS and a selection of the observed data are shown below, where plots show the entire availability of data starting from the establishment of the fi rst two AWS’s in late March 2008.
The AWS1 station
Description: AWS1 – A.P. Olsen Main AWS (center fl owline, lower tongue).
Coordinates: 74° 37.5’ N, 21° 22.55’ W, elevation (WGS84): 660 m a.s.l.
Measured parameters: Barometric pressure, aspirated Tair, aspirated RHair, wind speed, wind direction, downwelling SW, upwelling SW, downwelling LW, upwelling LW radia-tion, sensor T of LW radiometer, ice ablaradia-tion, ice level, snow level, eight-levels thermistor string, two axes station tilt, GPS position, diagnostics, experimental sensors (variable
from year to year, currently a passive radia-tion shield with a second Rotronics tempera-ture and humidity probe identical to the one in the aspirated radiation shield).
Time series: Uninterrupted from 29 March 2008 to today for all sensors except the sonic rangers, which had intermittent problems.
Current availability: All transmitted data (hourly summer/three-hourly winter); 10 minutes measurements from fl ash card between 29 March 2008 and 1 May 2012.
AWS1 was established 29 March 2008 and in 2012 normal maintenance and
890 900 910 920 930 940 950 960 980 970
Pressure (hPa)
–30 –40 –20 –10 0 10 20
Air temperature (°C)
0 20 40 60 80 100
Relative humidity (%)
0 5 10 15 20 25
Wind speed (m s-1)
1 Apr 2008
1 Apr 2009
1 Apr 2010
1 Apr 2011
1 Apr 2012
31 Dec 2012 a
b
c
d Figure 3.2 The complete
available time series of selected parameters at AWS1. a) barometric pres-sure, b) air temperature, c) relative humidity and d) wind speed.
scheduled calibration were carried out. The support frame for the ice ablation sonic ranger had failed and was re-established.
As a site and station especially well-suited to technical experiments and testing of new devices, an experiment started in 2011 comparing a passive Campbell scien-tifi c radiation shield against the aspirated Rotronics radiation shield that is used in all other GEUS glacier AWS. This experi-ment is being continued for a second year, to evaluate the shields performance in presence of the unusually high 2012 snow accumulation. AWS1 has been working without interruption since the day it was set up, and satellite telemetry delivers near real-time data. Complete time series of barometric pressure, air temperature, rela-tive humidity and wind speed are shown in fi gure 3.2a through 3.2d, respectively.
The AWS2 station
Description: AWS2 – A.P. Olsen small AWS (center fl owline, middle tongue, just up-fl ow of lake and lateral glacier conup-fl uence).
Coordinates: 74° 38.6’ N, 21° 28.2’ W, elevation (WGS84): 880 m a.s.l.
Measured parameters: Aspirated Tair, as-pirated RHair, wind speed, wind direction, ice level, snow level, GPS position, down-welling SW, updown-welling SW, downdown-welling LW, upwelling LW radiation, sensor T of LW radiometer and two axes station tilt diagnostics.
Time series: Uninterrupted from 31 March 2008 until today for all sensors except the sonic rangers, which had intermittent problems.
Current availability: 10 minutes measure-ments from fl ash card from 31 March 2008 to 1 May 2012. There is no satellite data telemetry; therefore data is only retrieved once a year in the fi eld.
This AWS is a smaller version of AWS1 and it is not equipped with satellite trans-mission. In 2012, the metal frame support-ing the sonic ranger measursupport-ing ice ablation had collapsed. The frame was re-establis-hed, data downloaded and the scheduled recalibration plan was implemented. Data
–40 –30 –20 –10 0 10 20
Air temperature (°C)
0 20 40 60 80 100
Relative humidity (%)
0 5 10 15 20 25
Wind speed (m s-1)
a
b
c
1 Apr 2008
30 Sep 2008
1 Apr 2009
30 Sep 2009
1 Apr 2010
1 Oct 2010
1 Apr 2011
1 Oct 2011
1 Apr 2012
Figure 3.3 The complete available time series of selected parameters at AWS2. a) air temperature, b) relative humidity and c) wind speed.
retrieval in the fi eld is required for this station, therefore the plots in fi gure 3.3 stop in early May 2012. Further data will be retrieved upon the next revisit in spring 2013. Air temperature, relative humidity and wind speed are shown in fi gure 3.3a through 3.3c, respectively.
The AWS3 station
Description: AWS3 – A.P. Olsen summit (at the wide open fl at just SSW of A.P.
Olsen summit).
Coordinates: 74° 38.9’ N, 21° 39.1’ W, elevation (WGS84): 1475 m a.s.l.
Measured parameters: Aspirated Tair, aspirated RHair, wind speed, wind direc-tion, downwelling SW, upwelling SW, downwelling LW, upwelling LW, sensor T of the LW radiometer, ice and snow level, eight-levels thermistor string, two axes station tilt, GPS fi x, diagnostics.
Time series: From 6 August 2009 to 19 Oc-tober 2010, for all sensors except the sonic rangers which had intermittent problems with a four days gap for unknown reasons
just before the revisit 11 May 2010. On 19 October 2010 transmission stopped abruptly during moderately high wind conditions and resumed spontaneously 13 March 2011, resulting in a data gap during the winter. The station has been operating uninterruptedly ever since.
Current availability: 10 minutes measure-ments from fl ash card from 6 August 2009 to 1 May 2012, then one- or three-hourly transmitted data until next revisit (see above for gaps).
Notes: Fitted for extension with one ad-ditional thermistor string.
This AWS was setup by helicopter in August 2009. It is equipped with a subset of the sensors on AWS1 and it was found in good working order upon revisit in May 2012. This station is equipped with an ‘alpine type’ wind monitor instru-ment, which features a special surface colour and is designed to better cope with riming. Figure 3.4a through 3.4c show air temperature, relative humidity and wind speed from ASW3.
–40 –20 –30 –10 0 10 20
Air temperature (°C)
0 20 40 60 80 100
Relative humidity (%)
0 5 10 15 20 25
Wind speed (m s-1)
a
b
c
1 Apr 2008
1 Apr 2009
1 Apr 2010
1 Apr 2011
1 Apr 2012
30 Dec 2012 Figure 3.4 The complete
available time series of selected parameters at AWS3. a) air temperature, b) relative humidity and wind speed (c).