7.13.3 Patriot Hills – Teniente Parodi

7.13.3.1 Topography and the local environment

Antarctic Logistics and Expeditions (ALE) deploys a blue ice runway at the northern side of Patriot Hills. ALE is a company that supports Antarctic expeditions, scientific research, climb ers, tourists with logistics. Because of the growing number of aviation activities ALE has done a lot to improve safety, especially on the field of meteorology.

7.13.3.2 Operational requirements and activities relevant to the forecasting process

Ever since this blue ice runway was operational the meteorological support has been done by a met-observer. But over recent years the number of intercontinental flights has increased significantly and to maintain standards concerning safety, ALE started to support their operations with weather forecasts.

The intercontinental flights happen between Punta Arenas and Chile. ALE has an office at Punta Arenas and all flights depart from there. In Patriot Hills they land on the blue ice runway. A one way flight takes about 4.30 hours.

The operation limitations for the Oekranian IL-76 aircraft are very strict:

♦ Wind speed: max of 18kt gust, during 8 hours (loading, flight, unloading)

♦ Visibility: more than 10km

♦ Good surface contrast, which implies only scattered medium or high level clouds

♦ Good horizon

♦ Temperature: less than -6°C (temperatures higher than -6°C increase slipperiness on the surface of the blue ice runway

For continental flights, ALE uses Ken Borek Twin Otters, which operate from the skiway near the camp. Half way between Patriot Hills and South Pole, ALE has a skiway at Thiels Mountains. Most frequent destinations are: South Pole, Mount Vinson, Berkner Island, Shackleton Range.

Other continental flights at Patriot Hills are performed by the US National Science Foundation (NSF) to support their science projects. The C-130 skiers operate from an other, larger skiway, approximately five kilometers North of the camp.

The blue ice runway as well as both skiways are maintained according to the highest standards.

7.13.3.3 Data sources and services provided

In 2007-08 ALE installed an all year round AWS (WX7) at the threshold of the blue ice runway. This AWS reaches WMO-standards, so Patriot Hills received a WMO number 89081. Synoptic information: LAT 80°18’00” S – LON 81°20’00”W, Elevation 905m.

In summary, the full complement of information includes:

♦ 5 Automatic Weather Stations:

♦ WX7: positioned at the threshold of the blue ice runway. All the information and observations of this new AWS you can find on http://thistle.org/wx7/index.shtml

♦ 4 RAWS (remote automatic weather stations). These AWS are only summer and are placed where ever they are needed.

♦ Dartcom Satellite Receiver: this systems allows to receive images from the polar orbiting satellites NOAA 17 and 18.

♦ Via iridium phone there is a limited email traffic possible. So a few model products are twice a day sent from Punta Arenas to Patriot Hills. This consists of a set of tephigrams, valid for Patriot Hills and Thiels Mountains and two meteograms.

♦ Metars and TAFs from Rothera and South Pole (when needed).

Meteorological products made during the summer season include:

♦ Patriot Hills TAF: daily, or on request

♦ Patriot Hills Metars, when flights are pending or going on

♦ Camp forecast, a weather forecast in plain language

♦ Medium Range Wind and Weather Forecast, used for planning the operations and activities

♦ Forecast for Mount Vinson area: to support the local guides/rangers/climbers

♦ Pilot briefings on request.

♦ Expeditions weather forecasts: on request.

7.13.3.4 Important weather phenomena & forecasting techniques

General overview

Dry katabatic airstreams prevail during a big part of the summer season. Nevertheless on occasions frontal systems or rarely mesoscale cyclones can penetrate far into the Antarctic continent. We can distinguish two different systems: firstly the frontal depressions coming in from the west, this is from the Bellingshausen/Amundsen Sea and secondly the systems coming in from the North, originating from the Weddell Sea. The latter bringing a lot of moisture at nearly all tropospheric levels. These ‘Weddell’ systems can bring bad weather for a prolonged spell: for over a week overcast conditions with intermittent snow is possible during summer. Any flying during these events is impossible.

Surface wind and the pressure field

The blue ice runway at Patriot Hills is orientated almost perpendicular on the prevailing wind direction. This results in very large crosswind component which determines the flight limitations considerably: the IL-76 can not operate when gusts exceed 18kt.

On top of this: the blue ice runway is positioned on the lee side of the Patriot Hills. As a consequence, once crossed the ridge and hitting the blue ice runway, the katabatic wind becomes very turbulent and gusty which makes it even more difficult to land safely.

As mentioned above for a safe flight the IL-76 needs a weather window (with prevailing conditions as mentioned above) of 8 hours. Last season during the period between 4 December 2007 and 24 January 2008, only 20 such periods were available. And with the knowledge that per season there are 18 flights to be done, they can not afford to miss too much of those weather windows!

Figure 7.13.3.4.1 (ALE-updated) gives an indication of the degree of windiness at the threshold of the blue ice runway at Patriot Hills while Figure 7.13.3.4.2 (ALE-updated) shows the prevailing wind direction at Patriot Hills. This wind regime is mainly katabatic. Almost 35% of the wind comes from the Southwesterly sector. Wind direction is ‘true’

Figure 7.13.3.4.1 (ALE-updated). Windspeed distribution at the threshold of the blue ice runway 02 Dec 2007 until 24 Jan 2008.