FRANCE’s

ANTARCTIC and sub-ANTARCTIC

“WEATHER-FORECASTING” INTERESTS

for

The International Antarctic Weather Forecasting Handbook:

IPY 2007-08 Supplement

Christian Lafayne

(formerly of Meteo-France, now retired)

christian.lafayne@club-internet.fr

Submitted April 2008

*Contribution related to:

Section 7.2.N Amsterdam Island (need to renumber)

Section 7.2.6 Crozet Islands

Section 7.2.6 Kerguelen Islands

Section 7.11.1 Dumont d’Urville station

Pages 506- 581 of original Handbook - various tables

Editors’ note: the information regarding Amsterdam Island constitutes a new section – the Editors may need to consider the need to renumber sections.

7.2.n Amsterdam Island

7.2.n.1 Orography and the local environment

The Amsterdam Island is located in the Indian Ocean, approximately at mid-distance between La Réunion Island and the western coast of Australia, by a latitude of 37.50°S. It measures 58 km² in area, 10 km long and 7 km at its widest, oriented north-south, with a maximum altitude of 881 m AMSL (Figure 7.2 N.1 (France-updated)). Cliffs are as high as 700 m, mainly on the west side of the island.

The meteorological station (Martin de Vivies) is located on the north coast (37°46’ S, 77°35’ E), at 27 m AMSL. Surface and altitude measurements were operated by meteorologists from 1950 to 2004. An AWS is now on duty. However, radiosondes are still launched by other scientists, on a daily basis.

Figure 7.2 N.1 (France-updated). A map of the Amsterdam Island

7.2.n.2 Operational requirements and activities relevant to the forecasting process

Three times a year, from August to December, the supply vessel Marion-Dufresne II cruises between La Réunion Island and the three sub-Antarctic islands of Crozet, Kerguelen and Amsterdam. For these operations as well as for the scientists outdoor activities and fishing, forecasts are available.

7.2.n.3 Data sources and services provided

Meteorological information can be obtained from the station of Kerguelen during daytime, or from the meteorological service of Météo-France at La Réunion. From there, all types of data are available : surface and upper air observations, global (French and ECMWF) and regional NWP products, satellite imagery, sea state.

7.2.n.4 Important weather phenomena

General overview

Amsterdam Island is located in a tempered area. Its climate offers the features of an oceanic pleasant climate, wet and very windy, with four seasons of equal duration. The island is influenced, all the year long, by conditions of strong winds from W-S-W to W-N-W. The most severe storms occur in winter, from June to August.

The climate is clearly marked by the mildness of the temperature, always positive (with an absolute maximum of 26.1°C (in 1996), an absolute minimum of 1.7 °C (in 1997) and a very weak daily amplitude.

Precipitation is rarely solid, and in moderate quantities (1,100 to 1,200 mm per year), with a maximum in June and a minimum in February, but at a high frequency (159 days).

The cloudiness is rather important during all the seasons. During the second half of the year, the evaporation rate becomes higher than precipitation, leading to a relative draught.

Surface and pressure field

Located in a temperate zone, the island is, all the year long, on the polar side of the Indian Ocean High and north of the subtropical convergence of the austral oceanic waters, located at 100 km or so, south of Amsterdam. The consequence is an average sea-level pressure above 1,010 hPa.

Upper wind, temperature and humidity

The altitude parameters are indicated in TEMP messages on the GTS. Forecast fields are given by numerical weather products.

Cloud

The cloud amount is important in all seasons (about 6 oktas) so that the sunshine duration is rather short (1,550 hours a year), mainly from April to July. It does not exceed 100 hours during each of these months.

Visibility

As sea surface temperature is often higher than air temperature, the humidity remains permanently above 80% HR, inducing frequent and generally thick fog.

Surface contrast including white-out

Not relevant at this site.

Horizontal definition

Horizontal definition is generally very good, except under rain showers.

Precipitation

Precipitation are usually liquid. The annual precipitation rate is moderate, but takes place during 226 days, mainly in winter. The most rainy period occurs between January and July, with a maximum in June. Thunderstorm are not common (3 to 4 a year).

Temperature and chill factor

Considering the average temperature which is pretty high in all seasons and the small daily temperature amplitude (3°C in Winter, 6°C in Summer), although the windy conditions, wind-chill factor is not a relevant criteria at Amsterdam.

Icing

Icing has never been observed on Amsterdam Island.

Turbulence

The altitude of the island, as well as the cliffs, may create a “mechanical” turbulence which could bring some trouble to helicopter activities (no flight by plane).

Hydraulic jump

Not relevant at this site.

Sea ice

Sea ice has never been observed around Amsterdam Island.

Wind Waves and swell

The island is very exposed to wind waves an swell. Very poor conditions occur when extra tropical storms move southwards while decreasing in intensity. Marine forecast are available from Météo-France at La Réunion Island.

Editors’ note: this table will go in Appendix 2 Climatological Data etc and needs referencing.

Amsterdam Island Station
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Year

Mean-monthly wind speed at Amsterdam Island Station (37°48' S, 77°34' E, 27 m AMSL)									(compiled drom data spanning 1971-2000)
Wind speed (m/s)	-	5.5	5.5	6.4	7.3	8.8	8.7	8.7	8.7	7.6	6.8	6.3	-

Mean number of days with gusts at Amsterdam Island Station
>= 16 m/s	7.7	6.9	7.3	10.9	16.3	22.0	21.8	21.0	21.4	17.2	12.5	10.6	175.7
>= 28 m/s	0.3	0.2	0.1	0.7	0.7	2.8	3.1	2.0	1.8	0.9	0.4	0.2	13.3

Mean-monthly precipitation at Amsterdam Island Station
Precipitation (mm)	89.1	72.1	83.0	108.7	114.1	118.9	106.6	96.6	91.1	91.2	81.7	82.4	1135.5

Mean daily maximum temperature (°C) at Amsterdam Island Station
Temperature (°C)	20.1	20.4	19.4	17.8	15.9	14.6	13.8	13.7	14.2	14.9	16.3	18.4	16.6

Mean daily temperature (°C) at Amsterdam Island Station
Temperature (°C)	17.3	17.6	16.8	15.5	13.7	12.4	11.7	11.5	11.9	12.5	13.9	15.8	14.2

Mean daily minimum temperature (°C) at Amsterdam Island Station
Temperature (°C)	14.5	14.8	14.2	13.1	11.6	10.3	9.5	9.3	9.6	10.1	11.4	13.1	11.8

Mean monthly sunshine duration (hours) at Amsterdam Island Station
duration (hours)	183.9	155.1	133.1	113.7	103.7	99.8	106.3	118.8	125.2	139.6	152.8	173.2	1605.0

7.2.6 Crozet Islands

7.2.6.1 Orography and the local environment

No update needed.

7.2.6.2 Operational requirements and activities relevant to the forecasting process

Three times a year, from August to December, the supply vessel Marion-Dufresne II navigates between La Réunion Island and the three sub-Antarctic islands of Crozet, Kerguelen and Amsterdam. For these operations as well as for the scientists outdoor activities, forecasts are available.

7.2.6.3 Data sources and services provided

Meteorological information can be obtained from the station of Kerguelen during daytime, or from the meteorological service of Météo-France at La Réunion. From there, all types of data are available: surface and upper air observations, global (French and ECMWF) and regional NWP products, satellite imagery, and sea state.

7.2.6.4 Important weather phenomena

General overview

No update needed.

Surface and pressure field

No update needed.

Upper wind, temperature and humidity

These fields are taken directly from numerical models

Cloud

No update needed.

Visibility

No update needed.

Surface contrast including white-out

No information provided.

Horizontal definition

No information provided.

Precipitation

No update needed.

Temperature and chill factor

No update needed.

Icing

No information provided.

Turbulence

Turbulence can be forecast using the wind profile of the daily radiosondes launches. These parameters are not carried out unless requested.

Hydraulic jump

No information provided.

Sea ice

No update needed.

Wind Waves and swell

No information provided.

Editors’ note: this table will go in Appendix 2 Climatological Data etc and replace the one that is there - need to check referencing.

Crozet Island Station
Month	Jan	Fev	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Year

Precipitation at Crozet Island Station (46°26' S, 51°51' E, 146 m AMSL) (mm)									(compiled drom data spanning 1974-2000)
Daily maximum precipitation	63.8	84.4	102.3	89.7	72.4	89.4	61.3	76.2	91.7	76.8	68.0	68.6	102.3
Mean monthly precipitation	178.0	162.0	204.0	222.0	214.0	201.0	203.0	236.0	208.0	199.0	186.0	200.0	2413.0

Mean daily temperature in a month (°C)
Mean daily maximum temperature	10.9	11.5	10.8	9.5	7.8	6.9	6.6	5.9	6.2	7.0	8.1	9.4	8.4
Mean daily temperature	7.7	8.4	7.9	6.7	5.2	4.1	3.8	3.2	3.4	4.1	5.1	6.4	5.5
Mean daily minimum temperature	4.5	5.2	4.9	3.9	2.5	1.4	1.1	0.6	0.6	1.2	2.2	3.3	2.6

Mean monthly wind speed
Wind speed (ms^-1)	10.2	9.5	9.9	10.2	10.8	11.5	11.6	11.5	11.5	10.7	10.3	10.5	10.8

Mean monthly MSLP
Pressure (hPa)	1005.9	1012.4	1012.3	1009.7	1009.1	1006.1	1009.9	1008.3	1008.5	1005.4	1002.3	1004.2	1007.8

7.2. Kerguelen Islands

7.2.7.1 Orography and the local environment

No update needed.

7.2.7.2 Operational requirements and activities relevant to the forecasting process

The observing programme includes three-hourly observations. Radiosounding are made daily at 12 UTC, giving upper air measurements up to 22 km.

7.2.7.3 Data sources and services provided

Meteorological data, including NWP outputs, satellite imagery and messages are received through Internet from the meteorological service of Météo-France at La Réunion. Forecast for the weather conditions and the sea state can thus be delivered.

7.2.7.4 Important weather phenomena

General overview

The general weather conditions over Kerguelen can be classified in four main typical situations. They are described hereafter in their synoptic context, and, for each of them, indications on the sensible parameters are given.

Ø North-West situation (NW): there is a low coming from NW, i.d. from South Africa. In this zone, the tropical warm air coming from Madagascar Island and the cold air issued from the low latitudes converge. In some cases, the cyclogenesis can be very vigorous in the vicinity of Marion and Crozet Islands. There is a large through at 500 hPa, oriented South Africa – Queen Maud Island. Strong jets from NW are observed from radiosoundings, and a large zone of subsidence is seen behind the cold front. The sensible weather depends largely on the relative position of the low, but the general characters are similar.

Ø West situation (W): in this case, the most frequent situation, there is a moving low circulating in the south of Kerguelen. Coming from the 45°S and associated with a through at 500 hPa, the low is then oriented towards the south-east. The warm front is slightly pronounced.

Ø Rear of a depression situation (RD) : the characteristics of the cold air behind the depressions is linked to its origin, generally located near the Dronning Maud Land, the delay this air mass takes to reach Kerguelen and the season. The satellite pictures give a good idea of the activity of the atmosphere.

Ø Anticyclonic situation (A) : the Archipelago is concerned either by a high pressure zone or a wedge following a disturbance. The first case occurs during 3 to 5 days and is common in summer; the second one does not exceed 2 days.

Surface wind and pressure field

Ø NW: in phase with the initial vorticity in the lower layers, the low will deep rapidly (10 hPa in 6 hours) and move quickly toward the South-East, arriving to the Archipelago with a pressure near 980 hPa, sometimes 960 hPa. The wind is, in a first stage, oriented north-east, with a speed between 25 and 35 kt. Then, the warm front passes and the wind turns to north-west. At the station, wind gusts are frequent, reaching 70 to 80 kt.

Ø W: before the arrival of the disturbance, the wind from the north-west sector is weak. A foehn effect is important on the west side of the island. In some cases, wind speeds of 50 kt with gusts at 75 kt have been measured, associated with a variation of the pressure up to -7 hPa in three hours.

Ø RD: very strong gusts of about 45-50 kt.

Ø A: if the wind speed is around 10 kt or less, then see breeze is always observed in the middle of the day.

Upper wind, temperature and humidity

The sub-Antarctic zone (40°S, 55°S) is a continuous active cyclogenesis area where westerly jet streams are often encountered. Depending on the position of the various air masses, three types of jet streams can be defined:

Ø the west jets which can persist 48 hours;

Ø the northwest jets, the strongest, with warm air ahead and cold air behind, some hours later;

Ø the southwest jets with cold air ahead and warm air behind, some hours later, and which are found in front of the wedge.

The altitude of the tropopause may vary from 6-8 km with a temperature of -45°C in the sub-Antarctic zone to 12-16 km in the tropical air, with a temperature of -70°C.

Cloud

Ø NW: Sc and As are important with Ci which can be seen on satellite pictures.

Ø RD: in winter, numerous Cb ; in summer, Sc embedded with Cu and Cb.

Ø W: numerous Ac len and Ci in the south direction.

Ø A: the sky is generally clear, due to the fact that the Sc are stopped eastwards, far from the Archipelago as it can be shown on satellite pictures.

Visibility

No update needed.

Surface contrast including white-out

No update needed.

Horizontal definition

No update needed.

Precipitation

Ø NW: snow in winter up to an altitude of 200m, turning to rain in the warm sector. In winter, when the cold front passes over Kerguelen, rain and snow are more severe.

Ø W: ahead the front, the rain is weak, becoming more intense when it passes over Kerguelen. Due to the strong wind, the true amount of rain is higher than measured.

Ø RD: in winter, frequent snow or small hail showers; in summer, small hail or snow pellets showers.

Ø A: no precipitation.

Temperature and chill factor

Ø NW: in the warm sector, the increase of temperature can reach 7 to 10 °C.

Ø W: 7 to 9°C in winter and 13 to 15°C in summer in the warm sector, with an important decrease of the temperature behind the cold front.

Ø RD: between 0°C and +2°C in winter, with a temperature lapse rate of -1°C/100m. The temperature can decrease rapidly from 4 to 6°C and the chill factor is then very important. In summer, the temperature is comprised between +4°C and +7°C.

Ø A: due to the foehn effect, the temperature are particularly high, considering the latitude : from 15°C to 20°C

Icing

No update needed.

Turbulence

Turbulence can be forecast using the wind profile of the daily radiosondes launches. These parameters are not carried out unless requested.

Hydraulic jump

No update needed.

Sea ice

No update needed.

Wind Waves and swell

No update needed.

Editors’ note: this table will go in Appendix 2 Climatological Data etc and replace the one that is there - need to check referencing.

Kerguelen Station
Month	Jan	Fev	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Year

Mean-monthly precipitation at Kerguelen Island Station (49°21' S, 70°14' E, 29 m AMSL)									(compiled drom data spanning 1971-2000)
Precipitation (mm)	52.0	45.6	65.0	67.2	73.3	67.5	72.1	65.0	65.7	54.7	50.8	57.2	736.1

Mean daily temperature in a month (°C)
Mean daily maximum temperature	11.8	12.0	11.1	9.2	7.2	5.5	5.1	5.1	5.7	7.3	8.9	10.6	8.3
Mean daily temperature	8.0	8.3	7.4	5.9	4.1	2.7	2.3	2.2	2.6	3.9	5.3	6.9	5.0
Mean daily minimum temperature	4.3	4.5	3.8	2.7	1.0	-0.1	-0.6	-0.7	-0.5	0.5	1.7	3.3	1.7

Mean-monthly wind speed
Wind speed (ms-1 )	9.6	9.3	9.4	9.5	9.1	9.5	9.8	10.4	10.4	10.2	9.9	9.6	9.7

Mean number of days with gusts
>= 16 m/s	25.7	23.1	26.3	25.6	25.9	25.8	27.2	28.3	27.0	26.8	25.7	25.8	312.9
>= 28 m/s	4.4	3.0	4.8	5.4	6.5	7.0	7.8	7.7	8.2	5.9	3.7	4.0	68.1

Mean monthly MSLP
Pressure (hPa)	1000.9	1005.9	1007.1	1004.6	1001.4	998.9	1001.2	1001.2	1000.2	1001.4	999.2	999.0	1001.7

Mean monthly sunshine duration (hours) at Kerguelen Island Station
Duration (hours)	193.9	163.0	147.1	114.7	93.6	73.1	83.8	106.7	217.5	151.9	178.7	191.0	1624.9

7.11.1 Dumont d’Urville Station

7.11.1.1 Orography and the local environment

No update needed.

7.11.1.2 Operational requirements and activities relevant to the forecasting process

No update needed.

7.11.1.3 Data sources and services provided

The meteorological observing tasks include three-hourly synoptic observations and one daily upper air radiosounding at 00Z. Ozone soundings are also provided, with about 20 launches per year. The station is opened from 23 to 13Z. High resolution images from polar orbiting satellites are received directly. The forecasts are issued for local activities and the routing of the supply ship during summer period using charts elaborated by the Australian Bureau of Meteorology and high resolution satellite imagery. Metar and Speci messages are exchanged with the Terra Nova Bay station when planes fly between the two bases and Dome C.

7.11.1.4 Important weather phenomena

General overview

No update needed.

Surface and pressure field

No update needed.

Upper wind, temperature and humidity

The altitude parameters are indicated in TEMP messages on the GTS. Forecast fields are given by numerical weather products.

Cloud

In situation of katabatic winds, no clouds are observed, except some cumulus humilis on top of the snow wall. Ahead or near cyclonic systems, high level clouds are frequent (most often As, Ci and Cs, but no Cc). Within these systems, St, Sc, As and Ns are the most common clouds. Between two depressions, the sky is generally clear. Only very rare isolated Sc or Cu can be seen, and, in that case, they are not extended.

Visibility

In summer, in case of strong winds blowing from South-East sector, at 15 m/s during several days and gusts reaching sometimes 30 to 50 m/s, then the phenomena of drifting snow and blowing snow are frequent, reducing the visibility to some meters.

Surface contrast including white-out

With a yearly average number of 60 days with visibility less than 1 km and 100 days of snow falls, the surface contrast is often very poor.

Horizontal definition

Horizontal definition is generally weak during quite all the year. Aircraft operations are allowed only from November to March, when the weather can be fine.

Precipitation

No update needed.

Temperature and chill factor

No update needed.

Icing

Icing, as a result of a deposit of liquid hydrometeor in a super-cooled state on an object, is very seldom because liquid precipitation itself is quite never observed.

Turbulence

Turbulence can be forecast using the wind profile of the daily radiosondes launches. These parameters are not carried out unless requested.

Hydraulic jump

No update needed.

Sea ice

No update needed.

Wind Waves and swell

The ECMWF WAM model is used for forecasting the wind waves and swell on demand of the supply ship when operating in the vicinity of Terre Adelie.

Editors’ note: this table will go in Appendix 2 Climatological Data etc and replace the one that is there - need to check referencing.

Dumont d'Urville Station
Month	Jan	Fev	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Year

Mean daily temperature in a month (°C) at Dumont d'Urville Station (66°40' S, 140°01'E, 43 m AMSL)
Mean daily maximum temperature	1.0	-1.7	-7.0	-11.8	-13.4	-12.5	-14.5	-14.1	-12.3	-9.7	-3.5	0.6	-8.2
Mean daily temperature	-1.2	-4.1	-9.5	-14.4	-16.2	-15.3	-17.6	-17.2	-15.2	-12.9	-6.8	-1.9	-11.0
Mean daily minimum temperature	-3.5	-6.5	-12.1	-17.0	-19.0	-18.0	-20.6	-20.3	-18.1	-16.1	-10.2	-4.4	-13.8

Extremums of daily temperature (°C)
Maximum daily temperature	9.8	6.5	3.4	1.1	2.6	3.1	3.2	0.4	0.8	2.9	5.5	9.9	9.9
Minimum daily temperature	-10.5	-17.9	-25.1	-29.3	-32.3	-33.4	-35.7	-37.5	-36.8	-31.5	-22.4	-14.1	-37.5

Maximum wind gust speed
Wind speed (m/s)	52	58	61	57	68	61	55	66	63	58	54	51	68

Mean number of days with gusts
>= 16 m/s	22.5	25.0	26.6	24.3	24.5	25.9	24.5	25.6	24.2	24.8	23.3	22.6	293.8
>= 28 m/s	6.5	10.9	9.2	10.3	9.9	12.2	10.2	10.1	12.5	8.8	7.2	7.7	115.5

Mean monthly MSLP
Maximum monthly pressure (hPa)	1018.9	1017.0	1019.4	1028.9	1033.0	1030.2	1033.5	1027.7	1026.0	1012.8	1016.2	1019.7	1023.6
Mean monthly pressure (hPa)	991.2	988.8	986.2	987.6	989.9	992.5	991.0	987.9	983.6	982.9	986.3	989.6	1023.6
Minimum monthly pressure (hPa)	961.2	948.8	933.2	936.2	940.8	948.8	946.5	943.1	943.9	946.0	954.5	952.8	1023.6

Mean monthly sunshine duration (hours) at Dumont d'Urville Station
duration (hours)	261.2	194.2	177.2	111.7	54.8	7.0	27.5	85.4	152.8	267.9	373.0	352.2	2037.9