FINLAND’s and SWEDEN’s

ANTARCTIC and sub-ANTARCTIC “WEATHER-FORECASTING” INTERESTS

for

The International Antarctic Weather Forecasting Handbook:

IPY 2007-08 Supplement

Timo Vihma

Finnish Meteorological Institute

POB 503 (street address: Erik Palménin aukio 1)

00101 Helsinki, Finland

timo.vihma@fmi.fi

Submitted April 2008

and

Johan Sidenmark

Swedish Polar Research Secretariat

PO Box 50 003

SE-104 05 Stockholm

SWEDEN

johan.sidenmark@polar.se

Submitted February 2008

*Contributions for Section 7.5.3 Aboa, Wasa, and Svea Bases

7.5.3 Aboa, Wasa and Svea Bases

7.5.3.1 Topography and local environment

The Swedish Svea Research Station was built during the Antarctic Expedition of 1987-88 and was the first Swedish research station in Antarctica (since Maudheim in 1949 and Snow Hill Station in 1901). Svea is located in the Heimefront Range about 40 metric miles from the coast in the niche valley of Scharffenbergbotnen at 74°35´S, 11°13´ W (Swedish Polar Research Secretariat 2008).

The Finnish research station Aboa and the Swedish research station Wasa were built on the slope of the Basen nunatak in the western Dronning Maud Land in summer 1988-89 (Figure 7.5.3.1.1 (Finland-updated)). The stations are located within 200 m of each other at 73°03´S, 13°24´W making up the so–called Nordenskjöld Base. The site is 120 km inland from the marine edge of the Riiser–Larsen Ice Shelf and is at an elevation of 470 m (~1,540 ft) AMSL. The Basen nunatak reaches 550 m, and the elevation of the glacier at the base of the nunatak is approximately 200 m AMSL. The steepest slopes of the nunatak are snow-free throughout the year, and also parts of the more flat surfaces become snow-free in summer.

Figure 7.5.3.1.1 (Finland-updated). A photo of the Basen and Plugen nunataks with Aboa and Wasa stations and the airfields marked.

Aboa is operated by the Finnish Antarctic Research Programme (FINNARP). The Swedish Polar Research Secretariat is responsible for the operation of the Swedish research stations Wasa and Svea. The secretariat has no in-house research, but serves the scientific community at universities and other research institutions. At time of writing there was no Swedish permanent research projects within meteorology at Wasa or Svea

7.5.3.2 Operational requirements and activities relevant to the forecasting process

Aboa and Wasa are summer–only stations. Forecasts are required for aircraft and, less often, helicopter operations, as well as for scientific operations. Research teams use snow scooters to go for expeditions in the surrounding region. In particular, in many summers glaciologists and geologists visit the small Swedish base Svea (74°35’S, 11°13’W), which is located 200 km from Aboa and Wasa.

A snow-covered glacier approximately 2 km from Aboa / Wasa is used as an airfield. In a few cases with too soft snow surface on the glacier, a small snow-covered ice cap located at the top of the nunatak has been used as a backup airfield (Figure 7.5.3.1.1 (Finland-updated).

7.5.3.3 Data sources and services provided

Aboa has a Milos 500 automatic weather station, and the weather conditions are reported for aircraft landing and taking off. The problem is that the wind conditions on the airfield sometimes differ a lot from those at the slope of the nunatak, where Aboa is located. In summers 2006-07 and 2007-08, when meteorological research teams worked at Aboa, meteorological measurements were also made at the glacier close to the airfield, which improved the services for aircraft.

An automatic weather station operated by the University of Utrecht is located 10 km south of Aboa / Wasa.

7.5.3.4 Important weather phenomena & forecasting techniques

General overview

The site is 120 km inland of the coast at an elevation of 400 m, and is therefore affected by weather systems in the Antarctic coastal region. The monthly mean values of the basic weather variables are presented in Table 7.5.3.4.1 (Finland-updated).

During the summer season, the meteorologist at the Neumayer station sends daily weather forecasts to Aboa and Wasa, and the Aboa observations are sent to Neumayer.

Surface wind and the pressure field

The monthly mean wind speed is 5 to 6 m/s in summer and 8 to 9 m/s in winter. The maximum 10-minute wind speed observed is 35 m/s in summer and 47 m/s in winter, while the maximum gusts are 46 and 58 m/s, respectively. The most common wind direction is 30°, which is affected by the topography of the nunatak and the large-scale pressure field, with the center of the low often in the Weddell Sea. The mean sea level pressure is approximately 990 hPa in summer and 985 hPa in winter.

Upper wind, temperature and humidity

The Basen nunatak affects the upper wind conditions (see below for turbulence and hydraulic jumps).

Clouds

The cloud cover and type is mostly controlled by frontal systems. In sunny summer days with weak winds, Cumulus Humilis are sometimes generated above the Nunatak, where the snow-free rocks are strongly heated. Only visual cloud observations have been made.

Visibility: blowing snow and fog

The visibility is often reduced by blowing snow and fog. Blowing snow is observed both nearby the stations on the slope of the nunatak and on the glacier below. Fog is more common on the glacier, where the airfield locates. There is not much information on the conditions in seasons other than summer.

Surface contrast including white–out

The bare rocks of the nunatak provide surface contrast also during overcast conditions, but further from the nunatak, white-out conditions can occur. There are, however, no statistics available.

Horizontal definition

The snow-free slopes of the Basen and Plugen nunataks help to identify the horizon.

Precipitation

Precipitation is not measured at the stations. Due to drifting snow, the snow accumulation varies a lot spatially, being on average 200 mm of water equivalent in a year.

Temperature and chill factor

The monthly mean temperature ranges from -9 to -5°C in summer (December – February), and from -22 to -19°C in winter (June – August). The minimum temperatures observed in December, January and February are -15.4, -25.4, and -23.9°C, respectively. The lowest temperature observed is -42.0°C (in May). No calculations have been made on the chill factor.

Icing

Icing is frequently observed e.g. on weather masts. Aircraft icing is potentially a problem in this area since there is a plentiful supply of super-cooled water droplets.

Turbulence

The Basen nunatak generates mountain lee waves particularly during northerly winds. These are common, as the center of a low-pressure system often locates in the Weddell Sea. The airfield locates at the lee side of the nunatak, and the breaking of the lee waves generates turbulence.

Hydraulic jumps

Studies on possible hydraulic jumps on the lee side of the Basen nunatak are under work..

Sea ice

Not relevant at this location.

Wind waves and swell

Not relevant at this location.

Table 7.5.3.4.1 (Finland-updated). The monthly mean values and standard deviations of the wind speed (WS), gust wind speed, air temperature (T), and atmospheric pressure (p) at Aboa. Also the recorded minimum and maximum values as well as the directional constancy of wind (dc) and gust coefficient are shown (Kärkäs 2004).

	WS (m s^-1)	WS max (m s^-1)	Gust (m s^-1)	Gust max (m s^-1)	Gust/WS	dc	T (°C)	T max (°C)	T min (°C)	p (hPa)	p max (hPa)	p min (hPa)
Jan	5.4±1.1	30.3	9.1±5.9	41.2	1.60	0.73	-5.2±1.3	9.7	-25.4	931.4±3.6	952.1	912.5
Feb	6.0±1.5	35.0	10.1±6.3	45.8	1.59	0.85	-8.7±1.5	5.9	-23.9	929.9±3.2	948.9	909.1
Mar	6.9±1.6	34.5	11.1±6.5	44.7	1.55	0.84	-13.5±1.4	-0.3	-31.2	926.3±2.9	945.2	891.1
Apr	7.1±1.6	35.0	11.0±6.7	42.2	1.55	0.88	-17.5±1.0	-5.9	-37.0	926.5±3.5	947.0	898.8
May	7.7±1.7	35.0	12.4±8.1	45.3	1.56	0.86	-19.0±1.2	-6.4	-42.0	925.6±4.5	950.0	892.2
Jun	9.1±3.1	41.2	13.6±8.3	48.3	1.55	0.90	-19.4±1.5	-5.9	-38.6	929.8±5.7	964.1	883.1
Jul	7.7±2.1	42.7	12.5±8.3	54.5	1.55	0.85	-21.5±2.1	-7.3	-41.2	926.3±4.7	952.1	887.3
Aug	9.0±2.2	47.3	14.2±9.1	57.6	1.53	0.88	-21.9±2.7	-5.0	-37.4	923.8±3.9	963.8	876.8
Sep	8.3±1.7	47.3	13.5±8.9	57.1	1.50	0.89	-20.8±2.0	-5.5	-40.2	926.7±4.2	986.8	890.6
Oct	7.7±1.4	42.7	12.2±8.4	50.0	1.50	0.86	-16.1±1.6	0.5	-35.4	924.6±2.8	950.1	890.7
Nov	8.6±2.0	44.8	13.4±9.2	56.6	1.49	0.89	-10.6±0.9	3.2	-27.2	926.9±3.7	947.9	895.1
Dec	6.4±2.6	30.3	10.2±6.4	41.2	1.57	0.75	-5.5±1.8	9.1	-15.4	929.8±5.1	947.7	904.1

Reference cited by Vihma

Kärkäs, E., 2004, Meteorological conditions of the Basen Nunatak in western Dronning Maud Land, Antarctica, during the years 1989-2001, Geophysica, 40, 39-52.

Reference Obtained by the Editors

Swedish Polar Research Secretariat 2008: The Svea Research Station Retrieved. 29 July 2007 from http://www.polar.se/english/logistics/svea_station.html on 21 August 2008