1

7.6 Enderby Land and Kemp Land

Enderby Land extends from 45º to 55º E while Kemp Land extends from 55º to 60º E (see Figure 7.6.1). From west to east, key stations covered in this section are:

· Molodezhnaya (67º 40´ S, 45º 50´ E, 42 m AMSL);

· Mount King (~67º 06´ S, ~52º 53´ E, ~1,120 m (+/- 6m) AMSL).

7.6.1 Molodezhnaya Station

7.6.1.1 Orography and the local environment

Molodezhnaya Station opened in February 1962 and is located on the southern shore of Alasheyev Bay (see Figure 7.6.1). The settlement is located in a small coastal oasis in the Thala Hills and is 500–600 m from the coast. The station area presents a hillocky locality with rocky ridges separated by snow–covered depressions and lakes. The Cosmonauts Sea in the station area is ice–covered much of the year. There are many icebergs. The land–fast ice width by the end of winter reaches almost 100 km. The rise to the Antarctic ice dome begins about 1.5–2.0 km from the coast. An outlet Kheis Glacier is located 15 km eastward from the station and the outlet Campbell Glacier at the same distance southwestward.

Key to numbered stations/bases/features

1 Mount King

2 Mount Cresswell

3 Moore Pyramid

4 Dovers

5 Beaver Lake/ Soyuz

6 Druzhnaya IV

7 Mount Brown AWS

Figure 7.6.1 A map showing locations in Enderby,

Kemp, Mac. Roberston, Princess Elizabeth, and

Wilhelm II Lands and adjacent areas. (Adapted from a

map provided courtesy of the Australian Antarctic Division.)

7.6.1.2 Operational requirements and activities relevant to the forecasting process

The settlement numbers more than 70 structures including: living and office buildings; a mess–room; upper–air sounding station; aerological building; power station; radio centre; and a warehouse. West of the settlement there is a runway for aircraft and 12 km to the east–southeast of the station a snow–ice airfield was constructed for heavy aircraft. At present Molodezhnaya Station is temporarily decommissioned and the information below outlines what was available before decommissioning.

7.6.1.3 Data sources and services provided

Information was received in the form of synoptic messages. Ship–borne and drifting buoy data allowed compilation of weather maps as well as pressure orography maps at 500 for 00 and 12 UTC. If necessary, the maps for 06 and 18 UTC were also prepared. The archive of synoptic maps and satellite images for all operational years is stored in St. Petersburg at the Russian Federal Service for Hydrometeorology and Environmental Monitoring’s Arctic and Antarctic Research Institute (AARI). These maps provided a possibility to review the atmospheric processes near the Earth’s surface and in the tropospheric layer in East Antarctica as well as in the Weddell Sea and in the east of the Bellingshausen Sea

In previous years, radio communication could be interrupted completely during geomagnetic perturbations in the upper atmospheric layers (magnetic storms) that were mainly observed in winter. About one or two cases of interrupted radio communication for this reason were usually observed every month from May to October. In these cases the analyst had to analyse the atmospheric processes using only meteorological satellite data received on a daily basis at Molodezhnaya.

ECMWF charts were also received. This information included surface and upper–air (500–hPa) analyses, as well as the pressure field forecasts for 24 and 72 hours. A synoptic analysis GRID code was used for processing the synoptic maps for the Southern Hemisphere while the prognostic information was invaluable for issuing short and medium–range weather forecasts.

The surface analysis maps for 00 UTC from the Australian WMC Melbourne (via HF transmitters in Canberra, Australia) were received via facsimile communication on a regular basis. In addition, a synoptic map covering the Australian continent and the adjoining oceanic area was received. A surface analysis from the South African Regional Meteorological Centre in Pretoria for 0600 UTC over the southern areas of the Indian and the Atlantic Oceans was received by facsimile on a daily basis.

Based on all aero–meteorological and satellite data received, the Molodezhnaya Weather Section prepared and disseminated the following information among the users:

· daily synoptic surface and upper–air charts for 0000 UTC;

· nephanalysis charts and “Meteosat” bulletins based on satellite data;

· semi–diurnal and daily weather forecasts for the regions of the Russian Antarctic stations and sea areas;

· three–day weather forecasts on requests for ships and stations,

· weekly and monthly reviews of synoptic processes and weather conditions for the regions of the Antarctic;

· large–scale ice charts with application by ships;

· 10–day and monthly reviews of ice conditions for the Antarctic Seas;

· ice consultations on requests;

· atmospheric circulation forms for the Southern Hemisphere and types of synoptic processes on a monthly basis.

The main goals addressed by weather forecasters at Molodezhnaya were hydro‑meteorological information support of activities for different scientific teams, sledge–tractor traverses, aircraft flights, navigation of ships and loading–unloading at the stations also during helicopter operations. At present, due to decommissioning of the Molodezhnaya Station, preparation is underway for organizing a new Weather Forecasting Section at the Progress Base (Prydz Bay) based on new technologies for synoptic data acquisition and processing.

7.6.1.4 Important weather phenomena and forecasting techniques used at the location

General overview

The main factor determining weather processes in the Molodezhnaya area is cyclonic activity, with cyclones passing along both zonal and meridional trajectories. During the cold half of the year the number of days with moving cyclonic eddies in the Cosmonauts Sea reaches 24 a month, on average. More than half of this number is comprised of cyclones with zonal trajectories moving along the Antarctic front. The remaining group of cyclones (8–10 cases a month, on average,) is related to the meridional tracks.

The zonal tracks are characterized in all cases by a steady western movement in the troposphere and lower stratosphere and hence by a rapid movement of surface cyclones and anticyclones from west to east. With respect to the meridional tracks, surface pressure features move with significant northerly and southerly components, resulting in the inter–latitudinal air–mass exchange in different coastal zones of the Cosmonauts Sea.

Typically, this air exchange occurs as a result of merging of the Antarctic High ridges in the troposphere with the anticyclones of the subtropical belt. Near the Earth’s surface, this relationship is expressed in the form of the blocking ridge. The locations of this ridge and of the trajectories of low–pressure systems determine the weather character in the coastal region connected with different types of meridional processes.

The influence of different meridional circulation types, which are in turn governed by the development of warm West Atlantic and East Atlantic ridges, on the weather in Molodezhnaya, is significant. In the first case, the cyclonic activity in the Falkland branch is strongly developed. However, at Molodezhnaya the weather is mainly governed by the influence of the eastern branch of the West Atlantic ridge and is distinguished by certain stability. The movement of warm and humid cyclones with intense storm activity along this trajectory also gives unstable weather in Molodezhnaya with alternating strong easterly and southeasterly (katabatic) winds with snowfall and blizzards and significant air temperature oscillations in the wintertime.

With respect to the zonal type of processes, shallow occluded cyclones with small moisture content move along the Antarctic front. They rarely approach the coast and frequently stable weather is established at Molodezhnaya without snowfall and a wind increase.

During the warm half of the year, the frequency of the movement of lows on or near to the coast, and the activity of cyclonic eddies, significantly decreases with corresponding increase of stability of weather conditions. However, extreme conditions do sometimes occur in summer and the forecasting of these events is connected with certain problems. The corresponding example will be given below. It has to be noted that global model predictions for the area of the Cosmonauts Sea and to its north, in the absence of significant orographic effects, yield quite satisfactory results in respect of the development of large–scale cyclones and blocking ridges not only for 1–2 days, but also for an extended period. These forecasts are obviously taken into account by weather forecasters and sometimes provide the only basis for forecasting for the area. On the other hand, the mesoscale systems are identified in this region with difficulty, and only from cloud images. In general, the study of these mesoscale features, which although comparatively rare in frequency, do result sometimes in significant weather deterioration, is still not well developed.

Surface wind and the pressure field

Mean–monthly wind speeds for Molodezhnaya Station are shown in Table 7.6.1.4.1 (in Appendix 2). Easterly and southeasterly winds are the most prevalent winds at Molodezhnaya: on an annual basis these winds comprise 85% of all observations at the synoptic times. From historical averages, easterly winds prevail in the summer months, and the southeasterly winds are most frequent in the other months of the year. During the period March to July the frequency of occurrence of the latter comprises around 50% with increasing southerly direction (the third by frequency of occurrence) up to 18–20%.

The main factor controlling the wind direction is the surface pressure distribution. As indicated on mean surface pressure analyses, the zone of north to south surface pressure gradient (easterly geostrophic wind) covers the coastal region of the Cosmonauts Sea up to latitude 65º S. In the winter months, the climatic circumpolar trough axis is located slightly more to the south and in the summer months slightly north of this latitude.

Thus the main wind types for the coastal Antarctic regions (cyclonic, katabatic and transient) have quite a steady direction in Molodezhnaya, but the wind speeds change sharply and over a wide range. Particularly intense and persistent cyclonic winds are observed as maritime lows move to the coast. Thaws and heavy snowfalls accompany them. The katabatic wind following the cyclonic wind can have hurricane force lifting enormous amounts of freshly fallen snow into the air.

The katabatic (gravitational) wind occurs above the steep slope of the dome whose height reaches 2,500 m some 350 km distant from Molodezhnaya. The conditions for consistently gusty winds in the nighttimes with a gust speed range from 0 to 25–30 m s^–1 (0 to ~50–60 kt) are created at the beginning of autumn. At this time, the ocean produces a warming effect and the cold katabatic flow penetrates far over the sea. In winter, in connection with air cooling in the coastal area above the sea ice, the katabatic wind becomes irregular. Sometimes katabatic winds decrease only at the dome foot and calm weather persists at the station. Continuous katabatic wind at the station is observed in the presence of relatively warm air masses near the coast.

The development of katabatic winds at the station is related to cyclonic activity near the coast. The highest wind speeds are observed in the rear part of the cyclones when the katabatic and cyclonic wind vectors coincide. Strong katabatic winds are formed above Molodezhnaya with appearance of strong southerly jet currents in the troposphere above the dome. These jets form strong lower level flows that merge with the surface katabatic flow at the northwestern slope of the ice sheet ridge, which is directed from the centre of East Antarctic towards Enderby Land. The surface relief features induce separate jets depending on the slope forms and relative positions. Note that appearance of snow eddies above Mount Vechernyaya in the Hays Glacier outlet area is one of the direct signs of the beginning of subsidence and downslope flow at Molodezhnaya. Typically, if the direction of the downslope flow at Molodezhnaya is 140º, then it is 160º at the airfield near Mount Vechernyaya.

The subsiding downslope flow becomes especially gusty at the end of winter. Its strong jets can interact with the relief irregularities contributing to the occurrence of eddies. The southeasterly wind speed reaches 40 and even 50 m s^–1 (~80–100 kt) with an almost complete loss of visibility. In summer, the katabatic wind can also be significant (with individual gusts up to 25–30 m s^–1 (~50–60 kt) but this is rare and typically occurs in the night–time (between 1 and 5 AM local time.). The diurnal heating of the dome slope induces a pressure decrease and air advection from the sea towards the dome. Only with the passage of an east‑southeasterly jet current in the troposphere can the katabatic wind persist in the daytime, but it is less intense.

The number of days with storm force winds at Molodezhnaya has been as great as 221 a year, with as many as 174 blizzards in a year. The largest average monthly speed occurs in May and is 14.5 m s^–1 (~28 kt). The maximum speeds are about 40 m s^–1 (~80 kt) and occur from April to October: the maximum gust reported (54 m s^–1 (~105 kt)) being in May.

The presence of wind data from permanent stations, ships, buoys and automated weather stations is necessary for the synoptic analysis of the surface pressure field and 850‑hPa field. It is also important to take into account the influence of the orography of the area, as the observations do not necessarily reflect the general character of the air–mass transfer in the given area. This should also be taken into account in updating the model pressure forecasts that should be used with caution south of 70º S.

Upper wind, temperature and humidity

No specific information on forecasting has been obtained.

Clouds

The amount of total cloud, on average, for a year in the Molodezhnaya area is 5.5 oktas. The months with high cloud amount are April and March when the average cloud amount is 6.2 oktas. The largest frequency of occurrence of overcast conditions (6 to 8 oktas) is 72% and is observed during the same period. This statistic does not decrease significantly in the other months of the year. In other words, gloomy weather predominates at Molodezhnaya. However, the frequency of occurrence of clear sky is observed in 20 to 30% of observations at standard times in all months of the year, except for March and April. Active cyclonic activity in the Antarctic coast zone is a cause of constantly significant cloud cover. Upper and low clouds typically prevail. However, as deep cyclones leave the ice–free sea, multi–layered cloud systems accompany the passage of the main and secondary frontal zones, including low stratus and cumulus clouds with precipitation in the form of snow.

Visibility: blowing snow and fog

Good visibility conditions generally prevail at Molodezhnaya. The frequency of occurrence of visibility greater than 10 km comprises 85–88% of all observation times in the summer months notably decreasing in winter. Blizzards are the main factor restricting visibility, hence to predict deteriorating visibility means to correctly predict the wind increase accompanied with snowfall or snow–drift. The latter occurs in the presence of non–compact snow cover and wind speeds greater than 7–9 m s^–1 (~ 14–17 kt). Since strong winds predominate in many Antarctic coastal regions, the number of days with blizzards is more than 170 days a year. In winter, they comprise 18–22 days a month but in summer they typically do not exceed 1–2 days per month.

The presence of a cyclone is the most dangerous synoptic situation connected with occurrence of strong blizzards. When the station is influenced by the rear sector of a low, the storm force winds can persist for a long time. Drifting snow is obviously a less dangerous phenomenon than blizzards, but they are quite frequent in winter. In summer, their frequency of occurrence notably decreases as non–compact snow cover is quite seldom observed at this time of the year.

Advective sea fogs at Molodezhnaya are very rare, occurring during periods of light wind speed. These are purely local phenomena and are of short duration.

Ice fog is an even rarer phenomenon compared to sea fog in summer. After a strong blizzard, a fine snow dust remains in the air at the station and especially in the vicinity of the station at the dome slope at low wind speeds. This snow dust remains in the suspended state for many hours and may result in the snow haze phenomenon with visibility reducing to 4 km. A successful forecast of such a phenomenon by an experienced forecaster is quite possible.

Surface contrast including white–out

White–out presents a significant danger for aviation flights under Antarctic conditions. In sunny weather, with discontinuous and thin stratus clouds over a uniform snow surface, there is no contrast and the horizon is not discernible. An example of a dangerous synoptic situation is a period when a subtropical high–pressure ridge in the Cosmonauts Sea area merges with the Polar High ridge. This leads to the formation of a southerly jet at the eastern periphery of the high–pressure ridge typically at the tropopause height. A zone of continuous mainly stratocumulus cloud is formed on the dome at the contact of warm and cold air masses. Some times the southeasterly winds can increase and the horizontal visibilities reduce in the snowfall. Orientation in space above the dome is very difficult under these conditions since the horizon blends with the snow surface. Then when the wind decreases, and visibility improves and the sun is at a sufficient height, a no less dangerous situation can appear – the white–out. There is a rule, according to which the flights above the dome, especially inland, are better undertaken with a cloud–free forecast.

Horizontal definition

See the section on surface contrast above.

Precipitation

In accordance with the features of the development of cyclonic activity, the maximum precipitation is observed at Molodezhnaya in autumn, during March and April. A secondary maximum is observed at the end of winter and at the beginning of spring, namely, in August and September. The minimum precipitation occurs in the summer months – December and January. Typically, less than 350 mm of precipitation falls in solid form except for rare cases in the summer months.

One usually pays attention to the similar physical–geographical conditions and atmospheric circulation conditions of Mirny and Molodezhnaya. This similarity is manifested in the characteristics of clouds and precipitation. In addition, both stations, similar to the entire coast of East Antarctica, are characterised by significant air dryness and comparatively low relative humidity values. The yearly average comprises 65% for Molodezhnaya and 71% for Mirny. For the ice–covered coastal areas, the low humidity values are connected with air drying at discharges. The annual humidity variations as well as water–vapour elasticity at Molodezhnaya is very weakly pronounced.

The forecast of cloud and precipitation depends typically on the correct forecasting of the development of the synoptic situation provided upper–air synoptic data and satellite data are available.

Temperature and chill factor

The temperature regime at Molodezhnaya, similar to other Antarctic areas is influenced by solar radiation, the underlying surface character and atmospheric circulation. According to the “Atlas of the Antarctic” this region belongs to the coastal climatic zone in the form of a narrow coastal strip including outlet glaciers, land–fast ice, oases and areas with snow–free hills and rocks.

The albedo value at Molodezhnaya is quite significant, but much less than at Mirny. From the middle of spring and up to the beginning of autumn, the value of absorbed radiation flux and the full balance in bare areas become much greater compared to the surrounding snow surface. The annual balance, unlike Mirny, is positive: around 7 months positive at Molodezhnaya but 4 months at Mirny. A comparatively large radiation heat flux to the underlying surface in summer is compensated by the heat lost in warming the near surface air layer. The summer at Molodezhnaya is warmer and the winter is colder than at Mirny, but the air temperature multiyear averages at both stations are negative in all months.

Mean–monthly temperatures for Molodezhnaya Station are shown in Table 7.6.1.4.2 (in Appendix 2) The maximum monthly average temperature is in January with a record maximum of +9.0ºC. August is the most severe month (~ –19ºC mean temperature) with a record minimum of –42.0ºC. Air temperature variations from day–to–day are related to the atmospheric circulations, primarily to the track of cyclones from the northern oceanic regions to the coast. The pattern of development of such systems is sometimes quite complicated being connected with the study of large–scale circulation modification over extensive areas. For example, such phenomenon as the formation of significant air temperature increases (several degrees higher than the multi–year norm) at Molodezhnaya in summer can be connected to the variant of the process beginning 1–2 weeks earlier in the Australian sector at the development of the meridional Ma circulation form. According to this variant a sharp large–scale warming in the tropospheric layer begins with the formation of a strong blocking ridge and the surface high south of Tasmania. A steady southward warm air transport is established at the ridge southern periphery with cyclones developing at the West Australian branch. This contributes to an intensified coastal high and its displacement south–westward to the near–pole area resulting in a sharp air temperature increase along its pathway, for example up to above zero values at Vostok Station then changing its direction the high moves towards the Cosmonauts Sea. A significant air temperature increase at Molodezhnaya and at Syowa occurs with increasing southeasterly flows. Warm air flowing from the high down the ice dome slopes from a height of more than 3,000 m, warms additionally as a result of the Foehn effect and an almost daily incoming solar radiation. Some times the air temperature in the coastal oases can rise to 8–12ºC.

The forecasters at Molodezhnaya developed in this way many variants of typical processes leading to the anomalous weather conditions in different seasons.

Icing

No specific information on forecasting has been obtained.

Turbulence

In weather forecasting for the coastal Antarctic regions, it is necessary to constantly make observations of turbulence occurring both at a height in the jet streams and near the surface especially at the ice slopes. Typically, a westerly and southwesterly jet occurs above the region of a low that has moved from temperate latitudes along the meridional trajectory 12–18 hours beforehand. Strong heat advection from the north in the frontal sector leads to the development of continuous low clouds, snowfall and precipitation in the form of drizzle. Under such conditions clouds and warm air extends to the plateau over 400–500 km away where the strongest turbulence is observed at the contact with cold air, which is often accompanied with icing of aircraft.

During the sinking flow in winter the largest eddy formation occurs when a mass of very cold air forms near the coast above the fast ice while the katabatic wind mixed with the upper layer air has a higher temperature. In these cases strong jets occur at the contact of cold air and interact with it. The irregular relief contributes to eddy formation. Occasionally, tornado–like eddies with a 10–150 m diameter are observed with the wind speeds of 50 m s^–1 (~100 kt).

The winter and spring flow is sometimes manifested in occurrences of eddy waves with a horizontal axis descending from the ice slopes. In the rear part of the eddy a strong downward flow is felt while at the frontal wave there is a sudden deterioration of visibility due to rising snow dust.

The effect of the aforementioned and similar phenomena on the landing aircraft can be very dangerous. There is a large gap of detailed observations of turbulence and a need for projects investigating these phenomena using modern instruments and equipment, as well as experience of investigating the dynamic and thermodynamic processes in the boundary atmospheric layer, for example, during the international winter expedition to the Weddell Sea in 1989.

Hydraulic jumps

No specific information on forecasting has been obtained.

Sea ice

The drifting ice zone in the Cosmonauts Sea is mainly formed during winter with maximum intensity in October-November, when under average climatic conditions the ice edge reaches 58⁰ S. In the summer season the drifting ice zone decreases and the ice decays rapidly. It is due to location of the eastern part of Cosmonauts Sea that is in the western peripheral area of a vast current system with prevailing conditions for the outflow drift.

The most favourable conditions for mooring at Molodezhnaya usually occur from the third 10-day period of February till the second 10-day period of March. During this time it is often possible for ships to access the shore through clear water, or by leads where the ice concentration is not greater than 3/10.

The thickness of the fast ice in Alasheev's Bay does not usually exceed 100-140 cm. The width of fast ice is significant during pre-spring months, about 70 km on average, therefore the most reasonable period for mooring the station for disembarkation on the ice moorage is after the break-up of fast ice. From the second half of February till the end of March fast ice is destroyed in 70 % of all cases, and if it remains, then its width does not exceed 20-30 km and its strength characteristics are strongly reduced.

In the station area there are deltas of outlet glaciers, which are responsible for higher concentration of icebergs in Alasheev's Bay. From the station it is possible to observe up to several tens of icebergs along the horizon, mostly drifting very slowly in winter.

Wind waves and swell

No specific information on forecasting has been obtained.

7.6.2 Mount King

7.6.2.1 Orography and the local environment

The coastline, which bounds eastern Enderby and western Kemp Lands, protrudes like a mushroom–shaped knob some 100 km, beyond the general line of the coast (see Figures 7.6.1 and 7.6.2.1.1) and gives a more maritime climate on this part of the coast, especially once the sea ice on the northern coast breaks up (the second week in January has been noted on one occasion).

Another factor influencing local weather patterns is the basically north–south ridge line running east of Knuckey Peaks down to the 1,500 m contour into a saddle shaped landform and then rising to a dome bounded by the 2,000 m contour through which rises Mount Elkins. Mount King sits on the western side of this saddle. Another spur of the ridge from the plateau extends northwest towards Perov Nunataks.

Other notable features are the large valley formed by the Robert and Wilma Glaciers to the east, the Seaton and Rippon Glaciers north of these and all running into the King Edward Ice Shelf, the Beaver Glacier (Figure 7.6.2.1.1) to the west of Mount King and the Napier Mountains running northwest from Mount Elkins. The modifications these terrain features make to weather produced by synoptic scale systems are significant. Dramatic changes can occur over short distances and in short time intervals.

7.6.2.2 Operational requirements and activities relevant to the forecasting process

A temporary summer camp was operated by Australia at Mount King from 1975 to 1980 inclusive after a similar camp was sited at the much worse weather location of Knuckey Peaks (67°48' S 53°30' E). (These peaks are just visible in Figure 6.6.4.1 that was taken from the Mount King camp looking south-southeast.)

Figure 7.6.2.1.1 A map–segment showing the locations of some features in Enderby Land.

(Adapted from a map provided courtesy of the Australian Antarctic Division.)

7.6.2.3 Important weather phenomena and forecasting techniques used at the location

General overview

The descriptions of weather reported here come mostly from four reports from operational forecasters charged with forecasting for ANARE expeditions in 1975–76, 1976–77, 1977–78, and 1979–80. A summary of the conditions experienced during these summers is given in Table 7.6.2.4.1 (in Appendix 2).

7.6.2.4 Data sources and services provided

The Mount King camp is closed. If there was a forecast service required it would most probably be provided by forecasters located at Davis Station.

It appears that the weather experienced in Enderby Land in the 1976–77 summer was more clement than in other years, this is supported by the number of flying days lost due to weather (15% compared to 20% in 1975–76): moreover, above average geopotential heights, temperatures and pressures were recorded over the Antarctic during the 1976–77 summer. By way of contrast the weather experienced in Enderby Land in the summer of 1977–78 was worse than the previous two seasons and there was a 31% loss of flying time. In 1976–77 the upper trough persisted in the Molodezhnaya area giving an east to northeasterly trajectory to upper winds over Enderby Land. For the 1977–78 summer a closed upper circulation (very evident at 500 hPa) persisted to the west of Syowa, giving a mainly upper northwest flow over Enderby Land. The surface winds remained their normal easterly. As in previous years, coastal lows stagnated in Lutzow–Holm Bay, but this year instead of dissipating they eventually moved eastwards around the Enderby Land coast, often splitting into two centres when near Proclamation Island. The three blizzards that occurred at Mount King during the 1977–78 summer formed when these coastal lows deepened suddenly between Sheelagh Island and Proclamation Island.

The upper low west of Syowa kept the relatively moist northwest flow over Enderby Land and probably helped the progression of the coastal lows. It was significant that the only substantial period of nil cloud occurred when there was no northerly component in the upper winds at Mount King and Molodezhnaya.

Most deteriorations in weather at Mount King in 1977–78 moved in from the northwest quadrant. On only two occasions was the previously (1976–77) common "cloud band and snow showers from the east" observed. Most often middle level cloud thickened from the west as a coastal low moved eastwards past Molodezhnaya. The cloud base then gradually lowered and snow would begin falling in the Tula Mountains. This low cloud and snow would then gradually build up towards Mount King.

During the December of 1979–80, in response to the long wave pattern, the lows moved over the ocean well to the north with the main cyclonic activity being along 50º S. This suddenly changed in early January and for the remainder of this season the cyclones tracked along the coast and even south of Mount King on one occasion. It is interesting to note that this change in cyclone paths coincided with the final break–out of the sea ice from Amundsen and Casey Bays, which increased the moisture available over Enderby Land.

Mount King is fairly sheltered from north and north–easterly airstreams, slightly more exposed to easterly and south–easterly airflows and quite open to westerlies. The Robert and Wilma Glaciers form an area of pronounced cloudiness in easterly airstreams because moist air both converges and rises up the valley. If the stream is sufficiently developed and moist, this cloud follows a natural channel off to the west–southwest to encompass Knuckey Peaks and McLeod Nunataks. If cloud in the King Edward Ice Shelf area is more extensive in an easterly air–stream, low cloud north of Wilma Glacier moves east to the vicinity of Bird ridge, but middle cloud from this area usually extends as far as Mount King, and produces white–out.

South–easterly airstreams are usually drier and the above effect is less noticeable. These streams produced good weather at Knuckey Peaks that otherwise had very poor weather overall compared to Mount King. One problem with some moist southeasterly airstreams is cloud formation northwest of Seaton and Rippon Glaciers that produces white–out looking inland of Rippon Depot.

Northeasterly airstreams are almost invariably very moist and produce extensive low cloud on the windward side of the Napier Mountains. Mount King's protected position delays the cloud build–up some six to ten hours but eventually a good cover of stratocumulus drifts across. Mount King does however seem to have less precipitation and wind than a more exposed position.

The most frequent path followed by the lows that produce poor weather in Enderby Land is from a point usually near 50º S latitude and west of Marion Island to a pronounced stagnation point north of Prydz Bay. These lows sometimes amalgamate with pre–existing weak lows in the Antarctic coastal trough to produce a fair sized blow at Mawson and strong winds right along the coast, probably as far as Cape Ann. The effect at Mount King depends on how close to the coast the lows come, their strength and local effects but will at least bring increasing cloud, wind and snowdrift.

Extended periods of fine weather occur when a strong ridge from the polar high extends northwards over Enderby Land to the coast.

Surface wind and the pressure field

The predominant surface wind direction is easterly. It would seem from the earlier discussion that most weather comes from the east when the long wave pattern is conducive to an upper east to northeast airflow over Enderby Land. On the other hand a persistent upper northwesterly to westerly flow over Enderby Land is also associated with weather arriving from those directions, even if the surface airflow was easterly

Early in the 1979–80 season a high correlation was noted between the value of Mawson's MSL pressure minus Molodezhnaya's MSL pressure and the velocity of the surface wind at Mount King. High positive values (i.e. northerly gradient) were associated with the strongest easterly winds at Mount King. Negative values were associated with light easterly or even westerly winds. The reason for this correlation appears to be the barrier the continental ice dome presents to a northerly flow. The barrier deflects the flow westwards. The wind increase appears to lag the Mawson–Molodezhnaya pressure difference value by approximately six hours.

Upper wind, temperature and humidity

NWP would be used to forecast upper–air information along with radiosonde date from Mawson and Molodezhnaya.

Clouds

Apart from blizzards, the main cause of deteriorating weather at Mount King appears to be broad bands of cloud moving westward accompanied by light snow or virga and snowdrift (usually slight). Only occasionally do these bands make the camp inoperative for helicopter operations and then at most for about six hours as the band moves through. Possibly a diurnal effect operates because the improvements often happen in the evening. Usually the degree of effect can be judged from the nature of the cloud. If there are several cloud layers to the east, or the depth of cloud appreciable, then it is likely that the cloud will eventually move over most of Enderby Land with some deterioration at Mount King.

This location, being west of the ice ridge joining the ice dome near Mount Elkins to the main ice plateau enjoys some protection from adverse conditions: to reach the camp the easterly airflow undergoes subsidence, the resulting warming being sufficient to evaporate much of the cloud.

On some occasions front–like cloud bands associated with maritime lows passed through Mawson with a north–south orientation and headed westwards to subsequently affect eastern Enderby Land. On other occasions, these lows themselves became stationary or moved westwards.

The early identification of major lows coming in from the northwest is straight forward provided observations from Marion Island and satellite imagery are available, but the accurate timing of weather deterioration at the coast is difficult because of the lack of data to the immediate north. The rate of movement of east to west moving cloud bands can usually be fairly accurately assessed.

The other interesting synoptic scale feature of the area is the pronounced stagnation area for low–pressure systems near Lutzow–Holm Bay. These lows produce onshore winds and cloud in the Molodezhnaya coastal region with occasional snow but rarely do they move further eastwards to produce significant blows for eastern Enderby Land.

A feature of all these systems, particularly those moving in from around 50º S, is the advection of relatively warm air from over the relatively warm sea to the north. This southward flowing air is cooled by contact with progressively colder sea water and eventually the continent itself. Moreover, a general upslide occurs as the maritime air becomes relatively more buoyant with respect to the colder continental air mass. This mechanism is a significant cloud producer with associated white–out problems. So whenever an approaching low turns the basic wind flow on the coast from Mawson to Enderby Land (from southeasterly, easterly, to northeasterly), increasing cloud can be expected.

Visibility: fog

An infrequent but interesting airstream direction at Mount King is from the west. On infrequent occasions a weak low may move inland near Molodezhnaya producing a light onshore airflow over the coast further to the east. Low cloud formed in this way may move up the valleys between mountains. On Beaver Glacier the cloud will generally move as far as Mount Reed with the wind at Mount King calm or a light easterly during the day. On one reported occasion in late January, the wind at Mount King swung to a very light westerly in the late afternoon. Within two hours the low cloud had drifted up towards Mount King and enveloped the camp in fog. On other occasions distant fog was observed to the northwest of the camp in the morning.

On two occasions in 1976–77 fog enveloped the Mount King camp following a set pattern: stratus formed about the mountains to the north and north–west during the late afternoon. At about 2100 h (local) the low stratus/fog appeared to form just west of the camp and when the surface wind gave way to a light westerly at about 2200, the fog moved over. For the next few hours it would fluctuate, usually going when the easterly wind sprung up. By about 0200 local the fog retreated west of the camp but was still to be seen in the distance until around 0700 local time. In the example shown in Figure 6.6.4.1, the wind sock indicated that a light easterly was blowing keeping the surface clear of fog: shortly after the picture was taken the easterly ceased and the fog enveloped the camp.

Fog at Mount King was more common in the 1977–78 season. Usually it formed on relatively clear afternoons in the Beaver Glacier and drifted eastwards to envelop Mount King by mid–evening. In this sequence, a light easterly wind often persisted at the camp until the fog was within one or two miles. When the surface wind at Mount King turned westerly by mid–afternoon, fog on two occasions actually formed over the camp, rather than drifting in.

Surface contrast including white–out

White–out conditions were most commonly created by an overcast of cloud causing the ice surface to appear to blend in with the cloud. At Mount King, a chain of mountains runs approximately westward to the coast, and, provided cloud did not cover the peaks, these rock formations did provide some visual reference in white–out conditions and a relatively safe path for the aircraft. However, there is no such relief in other directions and cloud will readily cause white–out problems.