Monday, 31 August 2009

Weather Stations

The problem with weather stations is that in order for them to be of any interest, you have to put them in quite inhospitable spots. This poses certain challenges for the installation team. In other words, the best place to put up a weather station would be my garage - with a nice stop for lunch halfway through - but, the best place to have a weather station collecting data would be somewhere like Cape Baird, on northern Ellesmere Island.

Nares Strait experiences frequent severe winds (occasionally, in excess of 80knots!) due to air-channeling by the high surrounding terrain. Cape Baird lies fully exposed to these winds on the tip of the Judge Daly Promontory to the west of Hall Basin at 81˚ 33’ N and 64˚ 31’ W. It’s just the nasty sort of place that’s perfect for monitoring the weather. Together with stations on Hans Island (Kennedy Channel, 80˚ 49.4’ north) and Brevoort Island (west side of Smith Sound, 78˚41’N), we hope the Cape Baird installation will allow us to gain insight into the meteorology of the 250 nautical mile strait and improve our ability to forecast weather in the area.

Foggy conditions on August 17th prevented helicopter operations and kept us from flying to Cape Baird until early evening when the wind, which had been developing since the mid-afternoon, cleared away the fog. Humfrey, David and I departed for the cape with pilot Bob Bartlett expertly flying us to shore in the gusting winds. I noted at the time that we flew oriented about 30 degrees off-heading to counter the prevailing southerly wind. The downdrafts coming off the top of the 120m-high cape were strong enough to equal the upward lift of the helicopter at full power: under neutral conditions we would have been climbing at 5m/s, as it was, we were not climbing at all- in fact we were slowly losing altitude. Undoubtedly, a lovely evening to install a weather station. We made two survey sweeps of the area to determine the best location. As we passed across the headland, we startled two large groups of Arctic hares, bright white against the brown, rocky ground.

Once we had landed and unloaded the gear (Bob kept the chopper under power to maintain stability), we had to collect rocks to hold down any equipment that weighed less than about 25kg. The solar panel, light and shaped basically like a sail, was particularly vulnerable. We later determined that the wind was gusting to up to 25m/s (90 km/hr). I found it interesting that it almost blew my toque off. I’ve never experienced conditions that could plausibly remove a snug-fitting winter cap from your head. Fortunately, the air temperature was a remarkable 6 to 7 degrees Celsius. Had it been closer to the 0-1 degree we had been having on the ship, we may have had to postpone the operation. As it was, the operating conditions were challenging but not impossible.

The first step in the installation of a weather station is to secure the tripod/mast structure. We were eager to get this step completed as the sensors would be safest attached to the mast, not pinned in boxes under rocks. The ground was rocky, but loose. David determined that while a stake was difficult to pound into the ground, it could be pulled back out with two fingers. This meant that we had to collect large rocks (30-50cm across) to hold down the tripod feet and guy-wire anchors.

Once the tripod was up, we attached the anemometer (wind-speed and direction sensor), the temperature/relative humidity probe, the pyranometer and net radiometer (solar radiation sensors) and the control box. The latter contains a barometric pressure sensor and the simple computer that polls the sensors and stores the data. Finally, we attached the Iridium antenna, the solar panel and the batteries before wiring the sensors, minimizing the exposed wiring, and activating the data-logger. It has been determined that these stations are somewhat attractive to polar bears. At the Pim Island station in Smith Sound, the aluminum bracket holding the temperature/humidity sensor was bent over 90 degrees, and the solar panel bent and scratched – presumably by a bear taking exception to the station. We hope that by pulling any excess wire inside the box and strapping the exposed wires tightly to the mast we can lessen the likelihood that a bear will find some dangling bit of electronics amusing.

Final operations before being retrieved by the helicopter were to power-up the data-logger, format the memory card, monitor the sensor data and wait until the hour mark to watch for successful operation of the Iridium transmission. This station is outfitted with a modem that allows the software to transmit data, once an hour, to an Iridium satellite. A service provider receives that transmission and sends the data directly to my inbox at the Institute of Ocean Sciences in Sidney, BC, Canada. This way, we collect the data without having to return to the station to download the data, an operation that is never guaranteed because of the uncertainty of ice conditions. In many years, it is too difficult to get within helicopter range of the station because of heavy multi-year ice in Hall Basin.

Content with the mechanical strength of the station and happy to get out of the wind, we returned to the Larsen leaving the weather station to collect and transmit data, we hope, through the next two years. It was steady enough to handle 40 knot winds. Can it survive 80 knots and a bear attack?

Dave Riedel

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