Station CORE

The CORE met station was established in May 2004 at the location of an ice core extracted by the Japanese team led by Shuhei Takahashi. This station has been the most troublesome of all of them. In addition to standard weather instruments, it also has a 13.5m thermistor string into the ice and initially had many strain meters, tiltmeters, and compasses that we had installed in the firn. Troubles included one of the instruments shorting out and draining the battery during the first summer and a programming error in one of the AT/RH instruments that led us on a wild goose chase for quite a while.

Overview

Program May 2004 - Aug 2004
Wiring Diagram May 2004 - Aug 2004

Equipment failures:
- A short occurred in one of the compasses sometime in June, and all measurements should be considered suspect until examined in detail, as the battery drain may have affected them. The small solar panel was not quite enough to keep up with the short, and some time in early July the logger quit. The battery was replaced 20 July 2004 and the shorted equipment isolated. Listing over the summer likely adversely affected the sonic ranger measurements.
- The relative humidity measurements at both heights are suspect from May - Oct 2004. See the notes for details, but the 3m height never worked accurately until a program error was found in late-September, and the 1m height may also have had instrument problems.

May 2004

The station was located about 5 meters away from the site of a core drill site, within view of the Japanese camera taking pictures of a snow stake. A decision was made to place the station here largely due to the firn study, where we wanted to measure whether the firn was sliding over the ice or not. Here the firn depth was only 2.5 m or so, making it easy to access the firn/ice contact. A better location for this station would have been further upglacier at the deepest firn area found, and likely a long-term met station will be placed there instead.

Instruments:
- Met One C034A wind set: S/N x3096: 1.43 m (cups to snow)
- Net Radiometer: REBS S/N Q98270 (9.01 Top, 11.13 bottom): 1.36 m above snow
- SR50M-45: S/N c1494 (loaner from Anthony): height not recorded
- 3m (nominal) AT/RH (HMP45 S/N U2340003): height not recorded, 2.62 m based on Aug measurements
- 1m (nominal) AT/RH (HMP45 ): height not recorded, 1.65 m based on August measurements
- Tipping bucket
- Freewave radio telemetry
- A 13.5 m thermistor string (depth not recorded clearly, but 3 thermistor exposed in photo, so about 12m (verifies with recollection and vague note))
- Plus Erin's strain meters, tilt meters, and compasses

The CORE met station is on the right, with thermistor string dropping into the hole beside the sonic ranger and net rad. Note the camera and japanese ablation stake to the left; CORE met is in the camera frame.


My instruments are on the mux on the left, Erin's on the right.


With the battery and radio, just before closing the box.

20 July 2004

A day trip was made to determine why the CORE site stopped telemetering data. It was found that the battery was completely drained, likely due to a short in the compasses. The battery was replaced with a small one. The station was also listing, and bracing was added to keep it upright. It was a heavy melt year; note that this will affect SR50 measurements. Possibly splashed water into tipping bucket for testing. The station was left in running condition.

August 2004

The station was found working in August, with the exception of the relative humidity measurements. However, it was clearly listing to the west and certainly would not survive another summer (maybe not even this summer), so we tore it down and reset the poles more deeply into the ice, adding tetra-type cross-bracing, also set into the ice.

Instrument heights (before station reset, 12 Aug 04):
- AT/RH 3m nominal: 2.84 m (snow to sensor)
- AT/RH 1m nominal: 1.87 m (snow to sensor)
- Wind set: 2.67 m (vane to snow)

Instrument heights (after reset, 16 Aug 04):
- AT/RH 3m nominal: 3.06 m (sensor to snow)
- AT/RH 1m nominal: 2.10 m (sensor to snow)
- wind vane: 2.20 m (vane to snow)
- 6 thermistors of 25 thermistor string showing
- Net rad: 1.95m
- SR50: 1.63 m

Notes:
- Wind vane was rotated ~15degrees towards south from SW
- Installed new 1 m AT/RH (the 1 m sensor from JJMC, S/N Z0620014)

The CORE station, as it was found in August, before resetting.

The new and improved CORE station.

Erin's instruments, partially melted out.

September 2004

We made two day trips to CORE met to attempt to fix the broken relative humidity sensor. We replaced the lower AT/RH with a freshly calibrated one (24 Sept 04), but the next morning discovered that this was not the broken one, but the 3 m AT/RH was. I swapped nearly everything there the next day (25 Sept 04), including the cable, and concluded that it was either a bad logger port or an error in the program, so I wired the 3m RH to the next port in sequence on the mux and decided to figure it out at home using the telemetry, as it was cold and windy. It turned out to be an error in the program (the mux relay was not sequenced), but the offsets and multipliers used in the program turned the AT measurement into a realistic RH measurement, so it was hard to diagnose this initially.