UPDATED INFORMATION ON*

GERMANY’s

ANTARCTIC and sub-ANTARCTIC

 “WEATHER-FORECASTING” INTERESTS

for

The International Antarctic Weather Forecasting Handbook:

IPY 2007-08 Supplement

by

Wolfgang Seifert*,

Gert König-Langlo**,

Ralf Brauner***

* German Weather Service, Bernhard-Nocht-Str.76, D-20359 Hamburg, Germany, Wolfgang.Seifert@dwd.de

** Alfred Wegener Institute for Polar and Marine Research, PO Box 120161, 27515 Bremerhaven, Germany,

Gert.Koenig-Langlo@awi.de

*** German Weather Service, Bernhard-Nocht-Str.76, D-20359 Hamburg, Germany, Ralf.Brauner@dwd.de

Submitted February 2008

*Contributions for:

            Section 2.7.2 Ozone over Antarctica;

            Section 3.3.2.4 DMSP;

            Section 7.5.4 Neumayer Station–Atka Bay–Kohnen Station–Cape Norwegia

2.7.2 Ozone over Antarctica

In 1992 a weekly ozone sounding program – started in 1985 at the near by Georg‑Forster Station – was moved to Neumayer. Both stations are situated comparably within the area normally surrounded by the Antarctic stratospheric vortex. The measurements contribute to the “Global Atmospheric Watch” (GAW) as well as to the “Network for the Detection of Atmospheric Composition Change” (NDACC) the former “Network for the Detection of Stratospheric Change” (NDSC)

As shown from the measurements at Forster/Neumayer (Figure 2.7.2 A (Germany-updated)) the ozone layer during Antarctic spring shows remarkable inter-annual variations as well as an overall reduction of the ozone partial pressure with time. The ozone reduction is strongly corre­lated with a cooling of the stratosphere. Corresponding varia­tions or a significant trend during other seasons could not be ascertained, see Figure 2.7.2 B (Germany-updated).

Figure 2.7.2 A (Germany-updated). Time-height section of ozone partial pressure above Neumayer II from 1992 to 2005.

3.3.2.4 DMSP

DMSP satellite pictures have been received at Neumayer and at Polarstern (south of 60°S) until 2007. The high spatial resolution of the DMSP satellite pictures (500 * 500 meters) could be used for very helpful detailed ice and cloud analysis. The pictures cannot be received anymore since the orbital elements of the satellites are no longer public available.

Figure 2.7.2 B (Germany-updated): Time series of seasonally averaged ozone partial pressures (solid line) and temperatures (dotted line) in the 70 hPa level above Georg-Forster and Neumayer.

7.5.4 Neumayer Station–Atka Bay –Kohnen Station–Cape Norwegia

7.5.4.1 Topography and local environment

Neumayer (70° 41´ S, 008° 16´ W) is situated on the Ekström Ice Shelf at about 7 km distance from the southwestern part of Atka Bay (see Figure 7.5.4.1.1 (Germany-updated)). The Ekström Ice Shelf has a homogenous flat surface sloping gently upwards to the south. Except for some nunataks about 100 km south of Neumayer no ice–free land or mountains exist. The topographic conditions around the area of Cape Norwegia are nearly the same. Kohnen Station is on the Antarctic plateau (75° 00´ S, 000° 00´ E) and 2892 m above sea level. It is a summer station and used as a drilling site for the European Project for Ice Coring in Antarctica.

Figure 7.5.4.1.1 (Germany-updated). Satellite picture (DMSP, vis) received and processed at Neumayer. It shows Neumayer situated on the Ekström Ice Shelf close to the partly sea ice free Atka Bay,  the ice shelf edge (white line), the grounding line (blue lines), the vertex line from the Soråsen in the left and the Halfar Ryggen in the center (yellow line) and the traverse to SANAE IV.

7.5.4.2 Operational requirements and activities relevant to the forecasting process

In 1981, the first Georg von Neumayer Station was established on the Ekstrom Ice Shelf as a research observatory for geophysical, meteorological and atmospheric chemistry measurements, as well as a logistics base for summer expeditions. Ice movements and heavy snow deposits demanded the construction of a new station. In March 1992 a new station (called Neumayer) was completed some kilometres south from the original site. A third station (Neumayer III) will replace Neumayer in March 2009, which is 52 m above sea level.

Normally, nine people live and work at Neumayer during Antarctic winter. The station participates in international networks initiated by the Word Climate Research Programme such as the Baseline Surface Radiation Network (BSRN), the Network for the Detection of Atmospheric Composition Change (NDACC) and the Global Atmospheric Watch (GAW). The most intensive research activities take place in the summer seasons. More than 30 people live at the station in addition to the crew.

In summer season 2002/2003 a weather forecast service was established at Neumayer. This was caused by the international project DROMLAN (Dronning Maud Land Air Network), which provide an airlink with international flights between Cape Town and Novolazarevskaja/Troll with an Iljushin76. Connecting flights are done with a Basler DC3 from Novolazarevskaja/Troll and Neumayer. But also all other activities are supported for all partners in the DROMLAN community. The covered region is between Halley (BAS, UK) and eastward to Syowa (JARE, Japan) (Figure 7.5.4.2.1 (Germany-updated)).

The weather forecast service is supported by the German Weather Service (DWD), who provided the meteorologist/forecaster for the season.

Figure 7.5.4.2.1 (Germany-updated). Dronning Maud (Queen Maud) Land and the typical flight routes within the DROMLAN air network.

Beside the forecast service at Neumayer the Alfred Wegener Institute for Polar Research in Bremerhaven operates the research vessel ("Polarstern") that cruises in the southern summer around Antarctica (Figure 7.5.4.2.2 (Germany-updated).). Two helicopters are stationed on board of Polarstern.

Figure 7.5.4.2.2 (Germany-updated). “Google Earth” overlay depicting any upper air sounding ever performed from Polarstern. Each dot is a link to the measured data retrievable via the Publishing Network for Geoscientific & Environmental Data PANGAEA (http://www.pangaea.de/)

7.5.4.3 Data sources and services provided

The forecast service starts in the beginning of the summer season around end of October in Cape Town and finish in February or March. In the past seasons up to 3500 individual forecasts for aircrafts, stations, traverses, ships and other field activities have been worked out and distributed via email, VHF and Iridium. The service is available 24 hours a day, the regular service hours are from 06:00 to 22:00 UTC (contact: neumayer-fcst@awi.de  ) 

Additionally to the data of the meteorological observatory at Neumayer forecast products, observations, satellite pictures from Meteosat are received via email at Neumayer Station with the permanent satellite data link (128 kB).  Therefore the forecaster had the advantage to get access to different products of the numerical weather forecast models of the ECMWF and AMPS at any time. A satellite picture receiving station (SeaSpace, VCS) for highly spatially and timely resolved multi-cannel pictures from the NOAA, FenYun and MetOp satellites (e.g. Figure 7.5.4.3.1 (Germany-updated)) can receive up to 16 passes a day (http://www.awi.de/en/go/meteorological_observatories). These images with a horizontal resolution down to 1000 m are very important for the individual flight forecasts in the DROMLAN community.

The meteorological observatory supports the forecast service with synoptic observations every three hours which are transferred directly into the GTS by email and into the Internet address below: http://www.awi.de/en/go/meteorological_observatories. Once a day (at about 11:00 UTC) a radiosonde is launched to measure the vertical profiles of air pressure, temperature, humidity, wind vector and ozone (weekly). The resulting TEMP–CODE is available without delay at http://www.awi.de/en/go/meteorological_observatories and via the GTS.

Polarstern's meteorological office is staffed with one meteorologist (forecaster) and one Information Technology (IT) assistant. Synoptic observations are made every three hours and transferred directly into the GTS and into the internet where the cruise track and the most recent data are freely available (http://www.awi.de/en/infrastructure/ships/polarstern/where_is_polarstern/). With a permanent satellite data link (64 kB) the ship–meteorological office receives via email or other satellite communication, analyses and forecast charts of surface pressure, 500–hPa, and sea state up to 144 h ahead based on ECMWF and AMPS. Observations from the GTS are also available. One radiosonde is launched every day at 11:00 UTC while for flight operations other radiosondes are launched if required. All meteorological data from 25 year of Polarstern cruises are published in the WDC-MARE Report 0004 (König-Langlo et al, 2006). The meteorologist on board produces forecasts for Polarstern, helicopters and other operations in the local area.

Figure 7.5.4.3.1 (Germany-updated). Example of a full scale satellite picture received and processed at Neumayer.

7.5.4.4 Important weather phenomena and forecasting techniques used in the location

General overview

During the summer season the weather is dominated by low–pressure systems moving across the northern Weddell Sea from the Antarctic Peninsula in an easterly direction with periods of two to seven days. Ahead of the low–pressure systems relative warm air with high humidity streams in from a northeasterly direction mostly accompanied by moderate to strong snowfall and winds between 10 and 20 m/s (~20 and 40 Kt ), sometimes above 25 m/s (~50 kt). Sometimes fog develops due to the high dew–points in relation to the cold water.

Moderate to strong south or southwesterly winds with cold, dry air and good visibility are found at the rear of the low–pressure systems with cloudy to fair sky. It can often be observed that eastward moving lows lose their speed if they move to a position under an upper low– pressure system. One of the most frequent positions where lows become stationary is situated east of Neumayer, near Novolazarevskaya or Syowa: this gives mostly clear weather with katabatic flows over the Neumayer region.

During summer season DROMLAN weather forecast service provides twice daily a weather forecast for all stations and field parties with a 5 days outlook. Aviation forecasts for intercontinental flights between South Africa and Antarctica and feeder flights in Antarctica can be transmitted via email with attached satellite images, upper air winds at different flight levels and other flight relevant forecasts and hazards.

The ship meteorological office on Polarstern produces surface pressure analyses at 0000 and 1200 UTC, and occasionally at 0600 UTC. The analyses cover the operational area of Polarstern usually including the Antarctic Peninsula, the Weddell Sea and Neumayer regions. The analysis of frontal systems is supported by satellite imagery in combination with surface observations.

Synoptic scale weather systems are quite well forecast by using the ECMWF and AMPS models. Difficulties sometimes occur when a low–pressure system is moving up against the barrier of the Antarctic Peninsula. Low–pressure developments leeward are sometimes not predicted by the model but they can be analysed well by satellite imagery. Model forecasts often produce speeds of movement of these lows that are too fast, with phase differences of more than 12 hours.

The development of polar lows is hardly ever observed during anticyclonic conditions, at the ice edge north and northwest of Neumayer region. Analysis and forecast of these systems is only possible using satellite imagery and in situ data. Especially in the summer season, the forecasting of polar lows near Neumayer is very important for flight operations, field parties or other logistic work. In polar lows, visibilities can change rapidly to poor conditions due to drifting snow and precipitation accompanied by a low cloud base.

Surface wind speed and pressure field

Neumayer is a rather windy site with an averaged wind speed of 9 m s-1 (Table 7.5.4.1.1 (Germany-updated)). Severe easterly storms are common. They can reach wind velocities well above 30 m s-1. Only during sum­mer blizzards are less frequent.

Table 7.5.4.1.1 (Germany-updated). Monthly averaged wind speeds in m s-1

at a height of 10 m above ground between 1982 and 2005

          Month      MeanFF10   MeanMaxFF10       MaxMaxFF10

      1             6.68                     20.16                           28.32

      2             7.71                     21.54                           28.81

      3             9.22                     24.30                           28.81

      4             9.90                     26.76                           32.96

      5             9.61                     26.69                           32.41

      6             9.78                     27.69                           35.49

      7             9.62                     28.14                           36.52

      8            10.11                    29.89                           36.52

      9             9.49                     26.83                           32.92

     10             9.24                    27.39                           33.95

     11             9.71                    25.26                           33.95

     12             7.09                    21.34                           30.35

The surface wind observations are performed with a wind speed resolution of 1 knot (0.5144 m s-1) and a resolution of the wind direction of 10°. The two-dimensional frequency distribution depicted in Figure 7.5.4.4.1 (Germany-updated). (König-Langlo et al. 1998) is based directly on these observations with wind speeds exceeding 2.5 knots. Certain wind directions are correlated with rather distinct wind speeds. Two combinations occur most frequently at Neumayer: The synoptic disturbances are responsible for the maxi­mum at 90° and 25 knots, the katabatic flows for the combination around 180° and 10 knots. The medium strong westerly winds are associated with super geostrophic flows resulting from a high pressure ridge north of Neumayer. Northerly winds hardly ever occur.

Figure 7.5.4.4.1 (Germany-updated). Two-dimensional frequency distribution of wind speed and wind direction in percent of all observations with a wind speed exceeding 2.5 knots. The class widths are 5 knots and 20°, respectively.

Wind direction and wind speed can be forecast using the hand drawn analysis of surface pressure and the model data (wind vectors or surface pressure gradients) with corrections due to local orography. In anticyclonic situations with light synoptic pressure gradients katabatic flows tend to dominate.

Since Neumayer is positioned at the southern edge of the circumpolar low-pressure belt surrounding whole Antarctica the mean sea-level pressure of the station is just 986.5 hPa. According to van Loon at al. (1984a, 1984b) a half-year cycle in the pressure data with minima during spring and au­tumn should exist. To a certain extend this cycle is detectable in the full dataset, but mostly hidden behind synoptic disturbances if only single years are regarded.

For the area around Cape Norwegia the easterly geostrophic wind is enhanced by katabatic winds. The increase in wind speed reaches 5 to 10 m s–1 (~10 to 20 kt). Thus wind speeds up to 28 m s–1 (~55 kt) are measured near the Cape. The katabatic winds can be calculated and forecast in combination with the ground temperature (sea surface temperature), the temperature on the mountain plateau and slope of the ice sheet. This katabatic effect is shown in Figure 7.5.4.4.2 and Figure 7.5.4.4.3. Figure 7.5.4.4.2 shows the frequency distribution of the measured wind forces between 24 January and 2 February 1998 on Polarstern near Cape Norwegia. The frequency distribution of wind direction for wind speeds greater or equal 14 m s–1 (~28 kt) is shown in Figure 7.5.4.4.3.. It is evident that the highest values correspond to easterly and northeasterly directions. While cruising near Cape Norwegia it is important to know that a high wind speed is generated due to the katabatic effect.

Figure 7.5.4.4.2 (Germany – original). Frequency distribution of Beaufort scale wind–force measurements taken in the period 24th January 1998 and 02nd February 1998 on board Polarstern.

Figure 7.5.4.4.3 (Germany – original). Frequency of wind directions for speeds greater than 14 m s-1 (28 knots) measured on board Polarstern between 24 January 1998 and 02 February 1998.

Upper wind, temperature and humidity

The prevailing easterly surface wind dominates the troposphere just within the lowest 2 km. Only between November and February do easterlies exist at any higher levels (see Figure 7.5.4.4.4 (Germany-updated)). During the rest of the year, a pronounced circumpolar cy­clonic vortex, with westerly winds increasing with height, is well established. This vortex is strongest within the strato­sphere but also present in the troposphere above 5 km. The whole upper air climatology of Antarctica is go­verned by this vortex. In the stratosphere the flow is driven by horizontal temperature gradients that are maintained by radiative heating and cooling. During the austral summer, the Antarctic stratosphere receives more solar radiation than lower latitudes and thus becomes relatively warm, generating a weak easterly circulation. From February onward, as solar heating decreases, the Antarctic stratosphere cools rapidly, and an intense westerly vortex develops until the stratosphere warms once again in the austral spring. The meridional components of the upper air wind field are comparable weak

Figure 7.5.4.4.4 (Germany-updated). Typical annual time-height section of zonal wind in m s-1 from daily radiosonde soundings at Neumayer. Positive values denote wind from west to east; negative values denote wind from east to west.

The upper wind can be predicted using the model forecasts in combination with the daily radiosonde data from Neumayer and Polarstern. Usually the circumpolar vortex, with increasing westerly winds with height, prevails while an easterly wind is observed mostly in the lowest two kilometers of the troposphere. Only between November and February do easterly winds exist in levels above two kilometers.

Surface inversions can be detected by analyzing radiosonde data. The inversions are normally created by radiative cooling during clear sky conditions or by descending air masses in anticyclonic situations. The thickness of the inversions extends during wintertime approximately two kilometers while in summer it is typically less than one kilometer. Inversions caused by radiative cooling become unstable near noon. In anticyclonic situations inversions become well established and assist in maintaining cloud cover.

Clouds

The annually averaged total cloud amount at Neumayer is 5.1 octa. During darkness, the total cloud amount can only be observed while the moon or stars are visible. Therefore, the tendency toward lower total cloud amounts during winter is questionable. The mean annual sunshine duration accumu­lates to 1430 hours. The lowest annual sunshine hours were recorded 1983 (1134 hours) while the highest value was reached in 2003 (2047 hours). The overall tendency is to­wards a significant increase of the sunshine duration.

The cloud cover and type are mainly related to frontal systems. The heights of cloud bases are determined by a laser ceilometer. Cloud bases and tops are also calculated by analysis of the actual radiosonde ascent. Cloud forecasts can be made by studying the high–resolution satellite imagery in combination with measured cloud tops and bases with consideration of the general synoptic situation.

A special effect is often observed near Neumayer Station in relation to cloud cover. On the southern flank of low–pressure systems the sky becomes suddenly filled with scattered clouds, or the sky clears in correlation with wind direction veering from 90° to 110°. This happens while mild north–northeasterly origin air masses are replaced by cold and dry air masses due to katabatic flows.

Another typical situation is often observed when frontal systems approach Neumayer. The start of precipitation with a descending cloud base occurs just before frontal systems reach Neumayer. This is an effect of the easterly winds (see Fig07) caused by strong ageostrophic components in front of the low–pressure system due to the orography.

Visibility: blowing snow and fog

Visibility is an important parameter in the Antarctic region estimated by the 3-hourly visual observations with landmarks and measured continuously. At Neumayer the visibility is frequently limited from blowing snow since drifting and blowing snow events are common. Frequently, precipitation events are hidden behind severely blowing snow events. Drifting or blowing snow is reported in 40 % of all visual observations. Depending on the surface conditions, snow begins to drift at wind speeds between 6 and 12 m s-1 (Figure 7.5.4.4.5 (Germany-updated)). If the saltated snow reaches heights above the eye level of the observer, the phenomenon is called blowing snow. Drifting and blowing snow events are restricted to synoptic disturbances, which are connected mainly with the advection of air masses from the east.

Figure 7.5.4.4.5 (Germany-updated). Accumulated frequency distribution of snow drift observations at Neumayer stations versus wind velocity 10 m above the snow surface.

The onset of blowing snow is rather independent of the snow surface conditions and the season (see Figure 7.5.4.4.5 (Germany-updated)) and can limit the visibility to less than 10 m. Thus, all vehicles from Neumayer – including the skidoos – are equipped with GPS. Safety ropes around the station exists for the orientation of the pedestrians. According to Figure 7.5.4.4.5 (Germany-updated) blowing snow may start at about 10 m s-1. In 50% of all observations blowing snow was observed at 15 m s-1, independently of the season and surface conditions. The katabatic winds at Neumayer never reach this limit. Table 7.5.4.4.2 (Germany-updated) shows the annual cycle of the percentage of wind speeds above 10 and 15 m s-1 associated with blowing snow events and reduced visibility.

Table 7.5.4.4.2 (Germany-updated). Annual cycle of the percentage of wind speeds above 10 and 15 m s-1 associated with blowing snow events and reduced visibility.

                 Month       Above 10 m s-1          Above 15 m s-1

           1                       20                                 5

           2                       28                                10

           3                       37                                19

           4                       40                                22

           5                       39                                21

           6                       39                                21

           7                       39                                20

           8                       37                                24

           9                       38                                20

          10                      37                                16

          11                      43                                18

          12                      24                                  6

Fog

Fog sometimes develops near the Neumayer region on the forward side of low–pressure systems due to the high dew–point of the air over the cold water or the shelf ice. Also sea smoke exists when cold air due to katabatic flow moves over warm open water. For prediction of visibility including fog, satellite imagery, in situ observations and radiosonde data processed with special software is used.

Surface contrast including white–out

Even in summer poor surface contrast or white–out is observed in the vicinity of Neumayer. Precipitation and an opaque cloud layer mostly accompany these situations on the forward side of low–pressure systems. But also under high pressure poor surface contrast is possible in overcast conditions of low stratus or stratocumulus layers. On the ice blowing snow additionally influences shelf the surface contrast.

A forecast of surface contrast can be done by using satellite imagery bearing in mind the general synoptic situation as well as using a regression formula (Equation 7.5.4.4.1 (Germany-original)) developed during several expeditions with Polarstern.

CON = 0.00002*VIS + 0.0634*RH + 0.0014*SUN –0.135*ICE – 0.9462*COV + 4.092656

Equation 7.5.4.4.1 (Germany-original)     where:

            VIS is the horizontal visibility in km;

            RH is the relative humidity in percent;

            SUN is the relative azimuth angle in degrees between observer and sun position;

            ICE and COV are cover of ice and cloud in oktas.

Surface contrast is poor for CON <= 2 and very good for CON 9 to 10. Poor surface conditions over the sea, known as "glassy sea“, are sometimes observed on Polarstern in light air with sea state like a "mirror“.

Horizontal definition

Since Neumayer is situated on a homogeneous ice shelf the horizon is free of any obstacles. Only some near by icebergs in the Atka Bay and north of the station can be seen visible. Rarely the Halfar Ryggen can be guessed. The Soråsen cannot be seen at any time. A far as no sea ice exists a pronounced water blink north of Neumayer is visible which clearly marks the horizon even during totally overcast conditions. In case of precipitation the horizon become poor or nil very quick. Also snowdrift gives a remarkable reduction in the contrast on the ground.

Precipitation

Precipitation is possible during all seasons of the year. Most of the precipitation is slight to moderate with snow brought by frontal systems. Either drifting or blowing snow makes the quantification very difficult. The annual snow accumulation is about 750 mm. During summer drizzle and rainfall occur rarely. Even with high pressure, snow, light rainfall and showers are possible in combination with low stratus.  This low stratus reduces the horizontal definition to poor or nil and in most cases white out can be observed.

Temperature and chill factor

The annual averaged temperature at Neumayer is -16.0 °C (Table 7.5.4.4.3 (Germany-updated)) The day-to-day temperature variations are largest during win­ter, when the temperature variations between the air masses from the interior of Antarctica and the surrounding ocean are most pronounced. An additional reduction of the temperature variations in summer results from some minor melting processes, which tend to constrain near surface air temperatures to 0 °C. Within the last 25 years remarkable year-to-year temperature variations were measured but no sig­nificant trend can be observed (Figure 7.5.4.4.6 (Germany-updated).). This situation is in con­trast to measurements at the Antarctic Peninsular where a significant warming took place, but it is typical for the majority of all other Antarctic stations.

Figure 7.5.4.4.6 (Germany-updated). Time series of the annually averaged air temperature at Neumayer 2 m above the snow surface.


Table 7.5.4.4.3 (Germany-updated). Monthly averaged air temperature and extreme temperatures in °C at a height of 2 m above ground between 1982 and 2005

Month   MeanTemp   MeanMaxTemp    MaxMaxTemp   MeanMinTemp    MinMinTemp

     1       -4.1                     1.2                             4.3                  -16.4                            -23.8

     2       -8.1                    -0.1                            3.6                  -21.6                            -26.5

     3      -12.7                  -2.4                             1.1                  -29.2                            -33.0

     4      -17.6                  -4.2                             0.8                  -35.1                            -39.1

     5      -20.5                  -6.1                            -0.2                 -38.3                            -44.3

     6      -22.1                  -7.5                            -3.1                 -39.6                            -44.7

     7      -24.0                  -9.7                            -3.9                  -41.4                           -45.6

     8      -24.9                 -10.6                           -3.9                 -41.8                            -47.3

     9      -23.1                  -9.5                            -2.6                 -40.8                            -45.9

    10     -18.1                  -6.3                             0.8                  -34.5                            -42.6

    11     -10.1                  -1.6                             1.5                  -25.2                            -32.6

    12      -4.8                    0.8                              2.8                  -17.0                            -24.2

The relative humidity varies mostly between 70 and 95%. Since the relative humidity is defined with respect to water it must be lower during winter time and can reach 100% only when the air temperature is above zero °C. During precipitation events and blowing snow – when easterly winds are predominant - the relative humidity is comparable high. Southerly and westerly winds are comparable dry. Only the hardly existing northerly winds are very humid and warm.

Forecasting of temperature during the summer season is mostly related to the synoptic situation. In summer the temperature can be slightly above freezing ahead of low–pressure systems or in sky clear conditions without wind. Following the passage of lows, in combination with katabatic winds, temperatures down to –25°C are observed. With wind speeds from 5 to 7 m s–1 (~10 to 15 kt) wind chill temperatures below –50°C can be calculated using the formula of Schwerdtfeger (1984).

Icing

Icing is normally tied to frontal systems. Light, moderate and severe icing is observed in the vicinity of Neumayer. Supercooled droplets are observed only occasionally at Neumayer Station. Analysis and forecasting of this parameter is prepared by using the radiosonde data processed by special software and by use of the so called "–8D–curve" (see Section 6.6.9.1).

Turbulence

Turbulence is correlated to the general synoptic situation and the local orography. Forecasts of turbulence are provided using radiosonde data and by calculating the vertical wind profile.

Hydraulic jumps

Hydraulic jumps have not yet been investigated near Neumayer region.

Sea ice

Atka Bay is mostly covered with close fast ice (first–year and some parts multi–year–ice) with some icebergs of medium size. Only from January to March does Atka Bay experience open ice conditions, or is free of ice. Pack ice is located about 15 km north of Neumayer. Sometimes, strong southwesterly to westerly winds open a coastal polynya. The sea ice state can be well analysed with AVHRR satellite images received during clear sky situation at Neumayer or from http://iup.physik.uni-bremen.de:8084/amsr/regions.html . Forecasts in relation to sea ice cover in Atka Bay are done using model surface winds in combination with satellite imagery.

Figure 7.5.4.4.7 (Germany-updated). Sea Ice Maps for Antarctica, University of Bremen

Wind waves and swell

In summer wave heights between one to four meters are observed in the outer Atka Bay and at the northern edge of the pack ice due to eastward moving lows north of Neumayer region. But mostly in the inner Atka Bay the sea is subdued by fast ice. Waves and swell forecasts are needed for logistic work if Polarstern is alongside the ice shelf edge. Predictions of sea state are done using model surface wind with the WMO standard wave prediction algorithm.

Model sea state forecasts can be used if no fast ice exists windward. The quality of wave forecasts from models in Antarctic waters such as in the Weddell Sea, around the Antarctic Peninsula, and in regions with sparse meteorological data, are relatively poor. Forecasts for four to six hours ahead can be produced using the techniques presented in the WMO (1988) handbook of wave analysis and forecasting.

References cited by Seifert et al.

Birnbaum, G., Brauner, R., Ries, H.(2006).Synoptic situations causing high precipitation rates on the Antarctic plateau: observations from Kohnen Station, Dronning Maud Land, Antarctic science, 18(2), 279-288,

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