0510GMT 152024510GMT 152024

2

51

41

41

3'

F

Weather and solar radiationmeasurements and

Mount Takahe and Mount Murphy,West Antarctica

M. LOSLEBEN

Mountain Research StationUniversity of Colorado

Nederland, Colorado 80466

During our geological trip to Marie Byrd Land, (party mem-bers Nick Banks, Nelia Dunbar, Pam Ellerman, Wes LeMasurier,Mark Losleben, and Bill McIntosh) took weather observationsand short-wave solar radiation measurements. These measure-ments may be some of the first ever taken in the area.

The weather was recorded one to six times each day, as condi-tions permitted, from 21 December 1984 through 18 January1985 primarily around the base of Mount Takahe (112°05'W76°17'S) but also for 5 days near Mount Murphy (111°15'W75°24'S). The Mount Murphy data is recorded at the 800-metersite, (camp 7).

Table 1 summarizes these recordings which are in-stantaneous values at the time of actual recording with theexception of temperature maximums and minimums. They arethe maximums and minimums for that Greenwich-Mean-Timeday. Time is in Coordinated Universal Time (or GreenwichMean Time) which is the local Mount Takahe time minus 17hours. Temperature was measured with a Taylor max/mm "U"tube thermometer suspended in a 1-cubic-foot cardboard box,which had slits cut to allow air flow, set on the "ground." Thisshelter worked very well with two exceptions. (1) From 13 to 16January, when air speed was virtually nil and the sun wasbright, some unrepresentative heating probably occurred in-side the box. (2) During snow storms, snow would pack insidethe box. The number of observations taken per day is shown ontable 1. Of course, the more times the following parameters aremeasured the better such values represent the true condition.Barometric pressure was read from an aneriod barometer sup-

Figure 1. Global shortwave incoming radiation (20-minute intervals) for days 11, 12, 13, and 14.

1985 REVIEW 193

plied by the Navy weather center, McMurdo Station. Accuratenorth equals approximately 112°. East equals 90°.) Visibility forcomparisons of barometric pressures can only be made amongthe day is a measure of the predominant condition for that day.those readings at the same camp or location since these are true[Good (C) means visibility of more than 12 kilometers; fair (F)pressures, not corrected to sea level. To help compare inter-means I to 12 kilometers; poor (P) means 100 meters to Icamp readings, in a rough way, the approximate elevations irikilometer; nil (N) means less than 100 meters.]meters are given on table 1 for each camp. Note camps 1, 6, andDuring the circumnavigation of Mount Takahe, three8 are the same location. Wind speeds are in knots and are the"smooth" or "calm" zones were noticed on the north, east, andrange of average speeds measured that day. Direction is thesouth sides (grid direction). These areas were separated by wellpredominate direction of the day and in grid degrees. (Gridformed sastrugi or wind-roughened surfaces. The north "calm"

Table 1. Weather observation summary for Mounts Takahe and Murphy

Date

Windrange

(in knots)

Temperature

Elevation(in degrees Celsius)

(in meters)Max.Mm.Ave.

Barometricpressure

Number of(in millibars)

observationsMax.Mm.

Predominantwind

direction(in grid

degrees)Predominant

visibility

GcF

PP

GGGGGG

GGG

NPGG

GG

G

GGGGG

NGG

1200

1300

1450

1325

(travel)1400

(travel)1200

800

1200

Camp 112/21/8412/22/8412/23/8412/24/8412/25/84

Camp 212/26/8412/27/8412/28/8412/29/8512/30/8412/31/84

Camp 301/01/8501/02/8501/03/85

Camp 401/04/8501/05/8501/06/8501/07/85

Camp 501/08/8501/09/85

Camp 601/10/85

Camp 701/11/8501/12/8501/13/8501/14/8501/15/85

Camp 801/16/8501/17/8501/18/85

-834.5

-6-5

-30

-4.52

-3

-4.5-1

-9-12-9-7

-8--10

14

-7-7

b8?10?8?

6?4.52

-1913.5

-13-5

-10-2.75

-11-8.5

-10-7.5

-10-6.5

-12-6

-16-10.2

-19-8.5

-14-8.5

-14-7.5

-12-8.8

-12-6.5

-12-5.5

-17-12.5

-14-13

-13-10.5

-13-10

-9

-16-8.5

-14

-12-9.5

-12-9.5-12-8-8

-10

-18-6.3

-20-9

823.23822.89

838.81825.94840.16

853.37847.27

846.60839.15

818.83811.72

817.81815.78

819.51817.47

819.51818.83

819.51818.83

828.65824.92

832.71831.02

807.65807.32

805.62802.24

801.90796.48

819.17816.46

819.84818.83

820.86819.51

822.55821.54

832.71827.97

826.28825.60

826.96823.56

886.90886.90

890.28891.97

893.67891.30

894.01893.67

890.62885.20

816.80812.73

816.12815.44

819.17816.80

120-1

15-222-17

00-8

00

0-2116-24

00-90-2

11-207-109-110-4

0-94-12

0

7-122-150-7

00

52-30-2

24

64

343243

233

3433

24

2

22332

226

250300

29595

90

4550

000000

330340340340

2020

202020

280150130

a Days are Coordinated Universal Time. (In month/day/year format.)

b ? denotes that the value is probably artificially high.

See text for definitions.d No data.

None.

194

ANTARCTIC JOURNAL

zone was the largest in the area and also had the deepest softsnow, whereas the west side had no "smooth" area at all. Thepredominant wind direction as "read" from the snow appearsto have been from grid north-northwest and then split to "bend"around the mountain.

Solar radiation was recorded from 10 to 17 January 1985 at theGill Bluff camp (112°44'W 76°13'S) near Mount Takahe but onlythe entire days of 11 to 16 January are shown in table 2. This istotal incoming (direct plus diffuse), short-wave (285- to 2,800-nanometer) radiation reaching the ground. Short-wave radia-tion is that which clouds block out when they cover the sun.This was sensed with an Epply precision spectral pyranometer,recorded on a Campbell CR-21 logger and powered by a solarphotovoltaic panel.

Table 2. Mount Takahe daily radiation totals

Energy

In Kilojoules perDay square meterIn Langleysa

11 16,435(16,698)b393(399)12 16,779(17,047)401(407)13 14,771(15,007)353(359)14 15,296(15,541)365(371)15 14,563(14,796)348(354)16 13,811(14,032)330(335)Average 15,276(15,520)365(371)

Percentage ofcalculated value60.7(62.3)50.0(51.6)

a 1 Langley equals 1 calorie per square centimeter.

Numbers in parentheses are the recorded values plus 1.6 percent

The surrounding topography was a flat (less than 1°) ice sheetwith this exception: Mount Takahe was to the grid north anddescribed a relatively smooth arc of height 8° above the horizontapering to the horizon on both sides. The azimuth of the 5°altitude point on each side was 55°.

The instrument used has not yet been officially recalibratedsince returning from Antarctica; however, an initial check

against the National Oceanic and Atmospheric Administration(Boulder, Colorado) short-wave reference indicates the instru-ment is now reading about 1.6 percent low using the pre-antarctic calibration. Therefore, the true values lie between thereported values and 1.6 percent higher than these reportedvalues. (See table 2.)

Figures 1 and 2 show the total incoming radiation in 20-minute totals by day with the total for that day in the lower rightcorner. The ordinate is energy in kilojoules per square meterwhile the abscissa is time in Greenwich Mean Time hours. Byvisual observation at the site, days 11 and 12 were fairly clear,and day 16 was overcast.

To gain a little perspective, some comparisons were madewith other sites and with calculations. I did all the calculationsaccording to the Smithsonian Meteorological Tables (Sixth edi-tion) and assume a transmissivity coefficient of 0.70. This coeffi-cient was chosen because studies conducted by Jacobs (1973)indicated an average transmission coefficient of 0.70 to 0.75.

According to Jacobs (1978), the arctic station of Resolute(74°43'N) received an average daily total of 390 Langleys for themonth of July, which would correspond to January in the Ant-arctic. This value is 62.6 percent of the calculated value of directplus diffuse short wave reaching the ground at Resolute. TheMount Takahe values ranged from a high of 63.2 to 60.7 percentto a low of 51.6 to 50.0 percent of their corresponding calculatedvalues.

Thus, for these 6 days in January, this antarctic site comparedclosely, though a bit lower, to a similar (by latitude) arctic site.Some possible mitigating factors could have been the proximityof Mount Takahe and greater cloud coverage.

Compared to a high altitude, mid-latitude site (3,749 meterselevation, 40°N) the average daily total in July 1984 was 552Langleys. Mount Takahe (1,200 meters, 76°S) was 371 Langleys.Even though the sun shines for 24 hours in Antarctica, its raysmust penetrate a thicker atmosphere to reach the Earth'ssurface.

The author wishes to thank all the members of the field party,Rudy Haas, the National Oceanic and Atmospheric Admin-istration, and Ruth Cameron for their help in making this articlepossible. This research was supported in part by National Sci-ence Foundation grant DPP 80-20836 to W.E. LeMasurier.

500

400

KJ/M2300

200

100

005101520245101520240

500

400

KJ/M2300

200

tOO

GUT GUTFigure 2. Global shortwave incoming radiation (20-minute intervals) for days 15 and 16.

1985 REVIEW 195

Jacobs, J.D. 1973. Synoptic energy budget studies in the eastern Baffin Island-Davis Strait region. (Unpublished Doctoral Thesis, University of Colo-rado, Department of Geography.)

Smithsonian Meteorological Tables, (Sixth Revised Edition). Prepared byRobert J. List, Fourth Reprint Issued 1968. (Smithsonian Mis-cellaneous Collections, Volume 114.) Washington, D.C.: Smithso-nian Institution Press.

References

Jacobs, J.D. 1978. Radiation climate of Broughton Island. In R.G. Barry,and J.D. Jacobs, (Eds.). Energy budget studies in relation to fast-ice breakupprocesses in Davis Strait.

Katabatic wind interaction withInexpressible Island, Terra Nova Bay

D.H. BROMWICH

Institute of Polar StudiesOhio State University

Columbus, Ohio 43210

Each winter, Terra Nova Bay (figure 1) is kept mostly free ofice by strong katabatic winds which continually blow down theReeves Glacier from the east antarctic plateau and cross the flatNansen Ice Sheet (Bromwich and Kurtz 1984). High windspeeds and low air temperatures lead to very high ice produc-tion rates in this recurring polynya (Kurtz and Bromwich 1985);the ice is continually blown away by the wind keeping the wateropen. Formulation of these ideas depended upon historical,regional, and satellite data. Quantitative in situ observations arebeing acquired to test these inferences. The katabatic outflow ismonitored by an automatic weather station (Aws) which is lo-cated on the southern part of Inexpressible Island. Data forFebruary through April 1984 and February through April 1985reveal that the katabatic wind nearly always blows from thedirection of the Reeves Glacier (from 3000 with a directionalconstancy of 0.98) at an average speed of 17.1 meters per sec-ond. These values are very close to those inferred from 1912historical records (Bromwich and Kurtz 1982, 1984) and suggestthat this site is the second windiest in the Antarctic. Because theAWS (at 78 meters above sea level) is situated within 3 kilometersof terrain which rises to elevations well in excess of 200 meters, itis important to ascertain whether AWS measurements accuratelyreflect the upwind katabatic flow. This report summarizes whatis known about the island's perturbation of the airflow.

The U.S. Navy and U.S. Geological Survey have pho-tographed the western side of Inexpressible Island in five sum-mers between 1956 and 1984. All the air photographs show anaccumulation zone below the western cliffs which is sur-rounded on three sides by bare, probably wind-swept ice. Thetypical configuration is sketched in figure 1; the widest parts ofthe zone lie to the north of the southern tip of the 200-metercontour. To the west of the highest point on the island, the zoneis about 1 kilometer across and its top is estimated to be 30meters above the Nansen Ice Sheet (Skinner personal com-munication). Because this large feature has been observed dur-ing numerous summers from both ground and air, it is likely tobe permanent (Chinn personal communication).

$ :6' Vegetation

Cape

Z_ Washington

Nansei k :a '3 Terra....,/Harsel1 (%490,InexpresslbleA

\\ ,VTeoll N Is. !\ A20fFIce Ale RussellNova

Hells Gateo- AWS - Snow Cave 119121

- Sheet-Bay

on 8 January, 1975

a AnemometerResultant wind directionOceanHigh terrainFast or Boy iceElevation contours in metersSpot elevation in motorsAccumulation zone

DovId 6/. A;;:lb'Ce

75'30

163E -I64E -165E

Figure 1. Location map adapted from U.S. Geological Survey1:250,000 reconnaissance series. Elevation contours in 200-meterincrements have been added to labelled glaciers and InexpressibleIsland, but omitted from "high terrain" and nunataks (N).

D. Skinner of the New Zealand Geological Survey has stud-ied the geology of Inexpressible Island (Skinner 1983) on threeseparate occasions, most recently during the 1982— 1983 australsummer. He generously supplied the author with all availablemeteorological observations (Skinner et al. 1983; Skinner per-sonal communciation). These data identify frequent summerconditions which allow the accumulation zone to persistundiminished.

On seven of the days between 7 and 18 January 1983, galeforce katabatic winds (speeds exceeding 15 meters per second)from the Reeves Glacier interacted with Inexpressible Island;generally light winds prevailed the remainder of the time. Fig-ure 2 summarizes the observed interaction on all these daysbetween the strong winds (sustained speeds of 25 meters persecond were frequently estimated) and the topography of thenorthern two-thirds of the island. The gale force winds rose

196 ANTARCTIC JOURNAL