A strong katabatic wind event at Terra Nova Bay
vectors within the bulk katabatic layer shows that the flow is strongly channeled at the head of the Reeves Glacier and accelerates down along the neck of the glacier. The topographically forced drainage convergence leads to a highly asymmetric katabatic wind pattern across the glacier making the flow on the north side significantly stronger than that depicted on the south side. Thermal infrared satellite images reveal north-south temperature gradients across Nansen Ice Sheet which are probably caused by this meridional speed distribution (Bromwich in press). The corresponding flow streamlines illustrate a marked confluence zone upwind of the Reeves Glacier, in agreement with the streamlines proposed by Parish and Bromwich (1987). In addition, a minor confluence feature can be seen approximately 40 kilometers south of the main confluence zone. Bromwich, Parish, and Zorman (in press) have noted that airborne sastrugi observations upstream from the David Glacier offer strong support for a second significant confluence zone in the vicinity of Terra Nova Bay. The model-produced 12-hour katabatic wind speeds in the lowest layer suggest strong katabatic winds are confined to the steep slopes in the vicinity of Reeves Glacier. A maximum wind speed in excess of 25 meters per second is seen within the Reeves Glacier; this is well within the limits observed from the automatic weather station platforms situated along Reeves Glacier as well as from data collected during the instrumented flights of November 1987 (Parish and Bromwich in press). The strong katabatic winds issuing from Reeves Glacier can be seen to persist for extended distances. Note that a 15-meter-per-second flow can be traced well over 100 kilometers from the base of the ice slope. Again, this facet of the numerical simulations is in at least qualitative agreement with the data collected during airborne study as well as inferred from automatic weather station data and satellite imagery (Bromwich in press). We wish to thank Charles Stearns and George Weidner of the University of Wisconsin at Madison for their efforts in the construction, deployment, and data collection of the automatic weather stations. The Italian automatic weather station data
A strong katabatic wind event at Terra Nova Bay DAVID
H.
BIoMwIcH
Byrd Polar Research Center Ohio State University Columbus, Ohio 43210 THOMAS R. PARISH
Department of Atnosphcric Science University of Wyoming Laramie, Wyoming 82071
Surface winds over the sloping ice fields of Antarctica appear to be highly irregular with marked areas of confluence and difluence inland from the steep coastal ice slopes (Parish and 1989 REVIEW
presented here were made available to David H. Bromwich under the Data Exchange Agreement between the Italian National Antarctic Research Program and the Byrd Polar Research Center. This research has been supported by the National Science Foundation through grants DPP 87-16127 (to Thomas R. Parish) and DPP 87-16076 (to David H. Bromwich).
References Bromwich, D.H. In press. Satellite analyses of Antarctic katabatic wind behavior. Bulletin of the American Meteorological Society.
Bromwich, D.H., and D.D. Kurtz. 1982. Experiences of Scott's Northern Party: Evidence for a relationship between winter katabatic winds and the Terra Nova Bay polynya. Polar Record, 21, 137-146. Bromwich, D.H., T.R. Parish, and C.A. Zorman, In press. Dynamics of the confluence zone of the intense katabatic winds at Terra Nova Bay, Antarctica as derived from airborne sastrugi surveys and mesoscale numerical modeling. Journal of Geophysical Research.
Drewry, D.J. 1983. The surface of the Antarctic ice sheet. In D.J. Drewry (Ed.), Antarctica: Glaciological and geophysical folio, sheet 2. Cambridge: Scott Polar Research Institute. Kurtz, D.D., and D.H. Bromwich. 1985. A recurring, atmospherically forced polynya in Terra Nova Bay. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Continental Shelf, (Antarctic Research Series, Vol. 43.) Washington, D.C.: American Geophysical Union. Parish, T.R. 1987. Numerical simulation of the Terra Nova Bay katabatic wind regime. Antarctic Journal of the U.S., 22(5), 252-254. Parish, T.R., and D.H. Bromwich. 1987. The surface windfield over the Antarctic ice sheets. Nature, 328, 51-54. Parish, T.R., and D.H. Bromwich. 1989. Instrumented aircraft observations of the katabatic wind regime near Terra Nova Bay. Monthly Weather Review, 117, 1,570-1,585. Parish, T.R., and K.T. Waight. 1987. The forcing of Antarctic katabatic winds. Monthly Weather Review, 115, 2,214-2,226. Pickett, J.L. 1989. A mixed-layer model of katabatic winds. (MS. thesis, Department of Atmospheric Science, University of Wyoming.) Schwerdtfeger, W. 1984. Weather and climate of the Antarctic. New York: Elsevier.
Bromwich 1987). Where air from a large section of the ice sheet becomes focused (a "confluence zone"), the supply of cold air to downwind coastal sectors is considerably enhanced, and the resulting katabatic winds are intensified and more persistent. Confluence zones seem to be the dominant features of the antarctic surface windfield and may be responsible for the majority of the boundary-layer transport of air across the antarctic periphery (Parish and Bromwich 1986). Terra Nova Bay is a region with intense katabatic winds that are sustained by an inland confluence zone and is viewed as a prototype of this climatically important coupling. We are conducting an in-depth investigation to describe the kinematics and dynamics of this representative wind regime. Completed analyses include establishment of the time-averaged characteristics of the confluence zone from aerial photography of the snow surface and from mesoscale numerical modeling (Bromwich, Parish, and Zorman in press). An important finding was that within about 180 kilometers of the coast, the broadscale confluence zone becomes organized into two smaller confluence zones focused on the Reeves and David 223
glaciers. In addition, two aircraft missions were carried out to elucidate the spatial variations of the boundary-layer winds and temperatures from the inland confluence zone, down the steep coastal ice slopes and for hundreds of kilometers offshore (Parish and Bromwich 1989). Notable results were that the strong katabatic winds only become established near the head of Reeves Glacier, and that the katabatic airstream was followed for 200 kilometers beyond the foot of the terrain slope. One of the most comprehensive antarctic arrays of automatic weather stations (AWS) is deployed in support of this project. In 1988, it consisted of five U.S. units (numbers 05, 09, 21, 23, and 27) and four platforms belonging to the Italian National Antarctic Research Program (stations 50, 51, 52, and 53). Observations from these sites are used to describe a 9-day katabatic wind event at Terra Nova Bay during March 1988 which had a well-defined start and finish. Figure 1 presents a sequence of surface-wind speed readings at 3-hour intervals from automatic weather stations along the western shore of Terra Nova Bay and at the head of Reeves Glacier (see figure 2 for the locations). Because wind directions during winter at these two sites do not vary that much (Bromwich and Parish 1988), wind-speed variations almost solely monitor changes in the intensity of the katabatic airstream that blows down Reeves Glacier and crosses Nansen Ice Sheet to reach Inexpressible Island. The selected event started around the middle of 14 March and ended on 22 March in 1988. The 9-day average wind speed at Inexpressible Island was 16.9 meters per second and the strongest speed was 36 meters per second; these 3-meter-height values are close to the typical March conditions reported by Bromwich (1989) of 18.2 and 34 meters per second, respectively. The wind-speed record displays major maxima and min ima at intervals of about 1.5 days. The wind speeds measured by AWS 09 at the head of Reeves Glacier follow the general trend of the Inexpressible Island values. Notable differences do occur, as for example during the first half of 18 March when the variations are anticorrelated.
32
'I •-. Inexpressible Island AWS 05 AWS 09 at Head of Reeves Glacier
28
fl A
24
•
20 Wind Speed 16 ms 12
TV ; •,
1 •'\ I
II .
I
7 \J\,
kV''
I \,.
bd
v
8]/\J \ 151 .
4
ti 11•
k
I I
of I
4 16 18 20 22 March 1988
Figure 1. Time series of surface-wind speeds measured by automatic weather stations (AWS) on Inexpressible Island (AWS 05) and at the head of Reeves Glacier (AWS 09), 14-22 March 1988. AWS 05 winds are measured at a height of 1.5 meters and at 3 meters on AWS 09. (ms -1 denotes meters per second.)
224
I64'E
(\f
Priestley W4Priestley GI.
+4
I68E
Tinker SI
) @C0mpbeI1G 74 S
+4-47
-25.9
(%N\)%6 > ROSS
Northern Foot ills
Reeves Nev 23( Reeves GI.
\q
SEA
4.0
..-. -leo 53 Larsen GI. —Inexpressible Is 05 Nansen TerrcNovcj Ice 25.6BC')' Sheet ECOOL-,i \ 00 25
WARM
' Clarke GI.
76'S
7 6'S
.\ +5 I60E\
64' E
4.9 -14.9
Franklin Is
13
I68'E—
Figure 2. Regional conditions accompanying strong katabatic winds at Inexpressible Island, 1500 universal coordinated time 15 March to 0000 universal coordinated time 16 March 1988. For each automatic weather station site (numbered dots) the vector-averaged wind at 3 meters height has been plotted according to the following convention. Direction from which the wind blows is shown by the orientation of the line drawn to each automatic weather station location. Resultant speed is denoted by symbol attached to the direction line: no symbol means less than 1.3 meters per second; half a barb equals 2.5 meters per second; a full barb 5 meters per second; and a flag 25 meters per second. For all sites except 13 and 51, the wind direction hardly changed, so that the vector-average and the scalar-average speeds are nearly identical. Numbers entered vertically next to each automatic weather station give the departure of the station air pressure from its March 1988 average (pressure anomaly in hectopascals) and the potential temperature in degrees celsius. The solid and dashed lines are isopleths of pressure anomaly and potential temperature, respectively.
To provide a detailed description of the regional windfield, two 12-hour periods centered on the strongest and lightest wind speeds recorded at Inexpressible Island during the 9-day interval have been considered. These periods, respectively, are from 1500 universal coordinated time (about 12 hours behind local time at McMurdo Station) 15 March to 0000 universal coordinated time 16 March and from 0600 to 1500 universal coordinated time on 22 March. Figure 2 summarizes the average strong-wind conditions. Vector-average winds at 3-meter height, mean potential temperatures, and pressure anomaly values have been plotted. The latter two variables were used by Bromwich and Parish (1988) to compare temperature and pressure readings from automatic weather station sites near Terra Nova Bay but at very different heights above sea level. The 25-meter-per-second winds at Inexpressible Island are associated with weak pressure gradients over the southwestern Ross Sea and coastal air temperatures which are about 10°C lower than those offANTARCTIC JOURNAL
shore. These results are qualitatively consistent with the typical winter katabatic conditions described by Bromwich (1989). Marked pressure gradients are present over the polar plateau, and a trough projects from the plateau toward the Northern Foothills. The potential temperature at the head of Reeves Glacier is 0.9°C lower than at Inexpressible Island, reflecting the more intense vertical mixing at the latter site due to the stronger winds (Parish and Bromwich 1989). In conjunction with the high winds at Inexpressible Island, speeds are generally above average throughout the Terra Nova Bay region; only at the Priestley Glacier site (AWS 52) are wind speeds about average. As noted by Bromwich and Parish (1988), station 50 is generally near the northern edge of the katabatic jet from Reeves Glacier. Here it is embedded within the katabatic airstream which then appears to reach station 53 with a 4.4°C increase in potential temperature. Figure 3 describes the average conditions during light winds at Inexpressible Island. In contrast to the strong-wind case, pressure gradients over the Ross Sea are marked but weak upslope from Reeves Glacier. The distribution of pressure anomaly values is inverted relative to figure 2 with the largest values over the plateau. A trough projecting westward from Terra Nova Bay overlies the northern halves of Reeves Glacier and Nansen Ice Sheet. Bromwich (1989) also found that strong east-west pressure gradients over the ocean were typically associated with light winds at Inexpressible Island. The thermal contrast between the coast and offshore has decreased from 10°C in the strong-wind period to about 3.5°C here. This decrease is consistent with a dramatic decrease in the transport of cold katabatic air into the Terra Nova Bay region. Wind speeds are much lower than in figure 2, although the decrease is not as marked at Priestley Glacier (site 52). Generally, it appears that wind speed changes in a coherent fashion throughout the Terra Nova Bay area, reflecting a close coupling between the interior confluence zone and the coastal katabatic winds. The 8-meter-per-second winds at station 53 may result from a localized acceleration of katabatic winds from Priestley Glacier down the lee side of the Northern Foothills. The results from this examination of a strong katabatic wind event at Terra Nova Bay during March 1988 can be summarized as follows. The change from the strongest to the lightest winds at Inexpressible Island was associated with coherent variations of wind, temperature, and pressure throughout the area. Several of these changes can be rationalized in terms of the coupling between the interior confluence zone and the coastal katabatic winds. This research was supported by National Science Foundation grants DPP 87-16076 to D.H. Bromwich and DPP 87-161 27 to T.R. Parish. The Italian automatic weather station data used here were made available to Bromwich under the Data Exchange Agreement between the Italian National Antarctic Research Program and the Byrd Polar Research Center. Collection
1989 REVIEW
168E
164E irt
160E f
'Aviator GI -20 Priest Nee
?4SJ
(
-9351
-I
Pri estley ley GI Tinker GI.
-:
Camp bell GI.
+I7-_._ 109 WARM
I
I0L•7f'•"
Reeves
.0 09
1^^ 3.8
arsen GI..
( \
•
ROSS SEA
/
Terra Nova
—\ Bay David j I I,• I
a2Gl. —2
7__
r
.
__
-4
76S
16 * E
1/I
l64E
Franklin Is.
13
l68 E
Figure 3. Same as figure 2, but for light wind conditions at Inexpressible Island, 0600 to 1500 universal coordinated time 22 March 1988. Once again directional variability was small.
and distribution of U.S. automatic weather station data is funded by National Science Foundation grant DPP 86-06385 to Charles R. Stearns. References Bromwich, D.H. 1989. An extraordinary katabatic wind regime at Terra Nova Bay, Antarctica. Monthly Weathi'r Review, 117(3), 688-695. Bromwich, D.H., andT.R. Parish. 1988. Mesoscale cyclone interactions with the surface windfield near Terra Nova Bay, Antarctica. Atitarctic Jouriial of the U.S., 23(5), 172-175. Bromwich, D.H., T.R. Parish, and C.A. Zorman. In press. The confluence zone of the intense katabatic winds at Terra Nova Bay, Antarctica as derived from airborne sastrugs surveys and mesoscale numerical modeling. Journal of Geophysical Research.
Parish, T.R., and D.H. Bromwich. 1986. The inversion wind pattern over West Antarctica. Mont/ih Weather Review, 114, 849-860. Parish, T.R., and D.H. Bromwich. 1987. The surface windfield over the Antarctic ice sheets. Nat ore, 328, 51-54. Parish, T.R., and D.H. Bromwich. 1989. Instrumented aircraft observations of the katabatic wind regime near Terra Nova Bay. Monthl y Went/icr Review, 117, 1,570-1,585.
225
A strong katabatic wind event at Terra Nova Bay DAVID
H.
BIoMwIcH
Byrd Polar Research Center Ohio State University Columbus, Ohio 43210 THOMAS R. PARISH
Department of Atnosphcric Science University of Wyoming Laramie, Wyoming 82071
Surface winds over the sloping ice fields of Antarctica appear to be highly irregular with marked areas of confluence and difluence inland from the steep coastal ice slopes (Parish and 1989 REVIEW
presented here were made available to David H. Bromwich under the Data Exchange Agreement between the Italian National Antarctic Research Program and the Byrd Polar Research Center. This research has been supported by the National Science Foundation through grants DPP 87-16127 (to Thomas R. Parish) and DPP 87-16076 (to David H. Bromwich).
References Bromwich, D.H. In press. Satellite analyses of Antarctic katabatic wind behavior. Bulletin of the American Meteorological Society.
Bromwich, D.H., and D.D. Kurtz. 1982. Experiences of Scott's Northern Party: Evidence for a relationship between winter katabatic winds and the Terra Nova Bay polynya. Polar Record, 21, 137-146. Bromwich, D.H., T.R. Parish, and C.A. Zorman, In press. Dynamics of the confluence zone of the intense katabatic winds at Terra Nova Bay, Antarctica as derived from airborne sastrugi surveys and mesoscale numerical modeling. Journal of Geophysical Research.
Drewry, D.J. 1983. The surface of the Antarctic ice sheet. In D.J. Drewry (Ed.), Antarctica: Glaciological and geophysical folio, sheet 2. Cambridge: Scott Polar Research Institute. Kurtz, D.D., and D.H. Bromwich. 1985. A recurring, atmospherically forced polynya in Terra Nova Bay. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Continental Shelf, (Antarctic Research Series, Vol. 43.) Washington, D.C.: American Geophysical Union. Parish, T.R. 1987. Numerical simulation of the Terra Nova Bay katabatic wind regime. Antarctic Journal of the U.S., 22(5), 252-254. Parish, T.R., and D.H. Bromwich. 1987. The surface windfield over the Antarctic ice sheets. Nature, 328, 51-54. Parish, T.R., and D.H. Bromwich. 1989. Instrumented aircraft observations of the katabatic wind regime near Terra Nova Bay. Monthly Weather Review, 117, 1,570-1,585. Parish, T.R., and K.T. Waight. 1987. The forcing of Antarctic katabatic winds. Monthly Weather Review, 115, 2,214-2,226. Pickett, J.L. 1989. A mixed-layer model of katabatic winds. (MS. thesis, Department of Atmospheric Science, University of Wyoming.) Schwerdtfeger, W. 1984. Weather and climate of the Antarctic. New York: Elsevier.
Bromwich 1987). Where air from a large section of the ice sheet becomes focused (a "confluence zone"), the supply of cold air to downwind coastal sectors is considerably enhanced, and the resulting katabatic winds are intensified and more persistent. Confluence zones seem to be the dominant features of the antarctic surface windfield and may be responsible for the majority of the boundary-layer transport of air across the antarctic periphery (Parish and Bromwich 1986). Terra Nova Bay is a region with intense katabatic winds that are sustained by an inland confluence zone and is viewed as a prototype of this climatically important coupling. We are conducting an in-depth investigation to describe the kinematics and dynamics of this representative wind regime. Completed analyses include establishment of the time-averaged characteristics of the confluence zone from aerial photography of the snow surface and from mesoscale numerical modeling (Bromwich, Parish, and Zorman in press). An important finding was that within about 180 kilometers of the coast, the broadscale confluence zone becomes organized into two smaller confluence zones focused on the Reeves and David 223
glaciers. In addition, two aircraft missions were carried out to elucidate the spatial variations of the boundary-layer winds and temperatures from the inland confluence zone, down the steep coastal ice slopes and for hundreds of kilometers offshore (Parish and Bromwich 1989). Notable results were that the strong katabatic winds only become established near the head of Reeves Glacier, and that the katabatic airstream was followed for 200 kilometers beyond the foot of the terrain slope. One of the most comprehensive antarctic arrays of automatic weather stations (AWS) is deployed in support of this project. In 1988, it consisted of five U.S. units (numbers 05, 09, 21, 23, and 27) and four platforms belonging to the Italian National Antarctic Research Program (stations 50, 51, 52, and 53). Observations from these sites are used to describe a 9-day katabatic wind event at Terra Nova Bay during March 1988 which had a well-defined start and finish. Figure 1 presents a sequence of surface-wind speed readings at 3-hour intervals from automatic weather stations along the western shore of Terra Nova Bay and at the head of Reeves Glacier (see figure 2 for the locations). Because wind directions during winter at these two sites do not vary that much (Bromwich and Parish 1988), wind-speed variations almost solely monitor changes in the intensity of the katabatic airstream that blows down Reeves Glacier and crosses Nansen Ice Sheet to reach Inexpressible Island. The selected event started around the middle of 14 March and ended on 22 March in 1988. The 9-day average wind speed at Inexpressible Island was 16.9 meters per second and the strongest speed was 36 meters per second; these 3-meter-height values are close to the typical March conditions reported by Bromwich (1989) of 18.2 and 34 meters per second, respectively. The wind-speed record displays major maxima and min ima at intervals of about 1.5 days. The wind speeds measured by AWS 09 at the head of Reeves Glacier follow the general trend of the Inexpressible Island values. Notable differences do occur, as for example during the first half of 18 March when the variations are anticorrelated.
32
'I •-. Inexpressible Island AWS 05 AWS 09 at Head of Reeves Glacier
28
fl A
24
•
20 Wind Speed 16 ms 12
TV ; •,
1 •'\ I
II .
I
7 \J\,
kV''
I \,.
bd
v
8]/\J \ 151 .
4
ti 11•
k
I I
of I
4 16 18 20 22 March 1988
Figure 1. Time series of surface-wind speeds measured by automatic weather stations (AWS) on Inexpressible Island (AWS 05) and at the head of Reeves Glacier (AWS 09), 14-22 March 1988. AWS 05 winds are measured at a height of 1.5 meters and at 3 meters on AWS 09. (ms -1 denotes meters per second.)
224
I64'E
(\f
Priestley W4Priestley GI.
+4
I68E
Tinker SI
) @C0mpbeI1G 74 S
+4-47
-25.9
(%N\)%6 > ROSS
Northern Foot ills
Reeves Nev 23( Reeves GI.
\q
SEA
4.0
..-. -leo 53 Larsen GI. —Inexpressible Is 05 Nansen TerrcNovcj Ice 25.6BC')' Sheet ECOOL-,i \ 00 25
WARM
' Clarke GI.
76'S
7 6'S
.\ +5 I60E\
64' E
4.9 -14.9
Franklin Is
13
I68'E—
Figure 2. Regional conditions accompanying strong katabatic winds at Inexpressible Island, 1500 universal coordinated time 15 March to 0000 universal coordinated time 16 March 1988. For each automatic weather station site (numbered dots) the vector-averaged wind at 3 meters height has been plotted according to the following convention. Direction from which the wind blows is shown by the orientation of the line drawn to each automatic weather station location. Resultant speed is denoted by symbol attached to the direction line: no symbol means less than 1.3 meters per second; half a barb equals 2.5 meters per second; a full barb 5 meters per second; and a flag 25 meters per second. For all sites except 13 and 51, the wind direction hardly changed, so that the vector-average and the scalar-average speeds are nearly identical. Numbers entered vertically next to each automatic weather station give the departure of the station air pressure from its March 1988 average (pressure anomaly in hectopascals) and the potential temperature in degrees celsius. The solid and dashed lines are isopleths of pressure anomaly and potential temperature, respectively.
To provide a detailed description of the regional windfield, two 12-hour periods centered on the strongest and lightest wind speeds recorded at Inexpressible Island during the 9-day interval have been considered. These periods, respectively, are from 1500 universal coordinated time (about 12 hours behind local time at McMurdo Station) 15 March to 0000 universal coordinated time 16 March and from 0600 to 1500 universal coordinated time on 22 March. Figure 2 summarizes the average strong-wind conditions. Vector-average winds at 3-meter height, mean potential temperatures, and pressure anomaly values have been plotted. The latter two variables were used by Bromwich and Parish (1988) to compare temperature and pressure readings from automatic weather station sites near Terra Nova Bay but at very different heights above sea level. The 25-meter-per-second winds at Inexpressible Island are associated with weak pressure gradients over the southwestern Ross Sea and coastal air temperatures which are about 10°C lower than those offANTARCTIC JOURNAL
shore. These results are qualitatively consistent with the typical winter katabatic conditions described by Bromwich (1989). Marked pressure gradients are present over the polar plateau, and a trough projects from the plateau toward the Northern Foothills. The potential temperature at the head of Reeves Glacier is 0.9°C lower than at Inexpressible Island, reflecting the more intense vertical mixing at the latter site due to the stronger winds (Parish and Bromwich 1989). In conjunction with the high winds at Inexpressible Island, speeds are generally above average throughout the Terra Nova Bay region; only at the Priestley Glacier site (AWS 52) are wind speeds about average. As noted by Bromwich and Parish (1988), station 50 is generally near the northern edge of the katabatic jet from Reeves Glacier. Here it is embedded within the katabatic airstream which then appears to reach station 53 with a 4.4°C increase in potential temperature. Figure 3 describes the average conditions during light winds at Inexpressible Island. In contrast to the strong-wind case, pressure gradients over the Ross Sea are marked but weak upslope from Reeves Glacier. The distribution of pressure anomaly values is inverted relative to figure 2 with the largest values over the plateau. A trough projecting westward from Terra Nova Bay overlies the northern halves of Reeves Glacier and Nansen Ice Sheet. Bromwich (1989) also found that strong east-west pressure gradients over the ocean were typically associated with light winds at Inexpressible Island. The thermal contrast between the coast and offshore has decreased from 10°C in the strong-wind period to about 3.5°C here. This decrease is consistent with a dramatic decrease in the transport of cold katabatic air into the Terra Nova Bay region. Wind speeds are much lower than in figure 2, although the decrease is not as marked at Priestley Glacier (site 52). Generally, it appears that wind speed changes in a coherent fashion throughout the Terra Nova Bay area, reflecting a close coupling between the interior confluence zone and the coastal katabatic winds. The 8-meter-per-second winds at station 53 may result from a localized acceleration of katabatic winds from Priestley Glacier down the lee side of the Northern Foothills. The results from this examination of a strong katabatic wind event at Terra Nova Bay during March 1988 can be summarized as follows. The change from the strongest to the lightest winds at Inexpressible Island was associated with coherent variations of wind, temperature, and pressure throughout the area. Several of these changes can be rationalized in terms of the coupling between the interior confluence zone and the coastal katabatic winds. This research was supported by National Science Foundation grants DPP 87-16076 to D.H. Bromwich and DPP 87-161 27 to T.R. Parish. The Italian automatic weather station data used here were made available to Bromwich under the Data Exchange Agreement between the Italian National Antarctic Research Program and the Byrd Polar Research Center. Collection
1989 REVIEW
168E
164E irt
160E f
'Aviator GI -20 Priest Nee
?4SJ
(
-9351
-I
Pri estley ley GI Tinker GI.
-:
Camp bell GI.
+I7-_._ 109 WARM
I
I0L•7f'•"
Reeves
.0 09
1^^ 3.8
arsen GI..
( \
•
ROSS SEA
/
Terra Nova
—\ Bay David j I I,• I
a2Gl. —2
7__
r
.
__
-4
76S
16 * E
1/I
l64E
Franklin Is.
13
l68 E
Figure 3. Same as figure 2, but for light wind conditions at Inexpressible Island, 0600 to 1500 universal coordinated time 22 March 1988. Once again directional variability was small.
and distribution of U.S. automatic weather station data is funded by National Science Foundation grant DPP 86-06385 to Charles R. Stearns. References Bromwich, D.H. 1989. An extraordinary katabatic wind regime at Terra Nova Bay, Antarctica. Monthly Weathi'r Review, 117(3), 688-695. Bromwich, D.H., andT.R. Parish. 1988. Mesoscale cyclone interactions with the surface windfield near Terra Nova Bay, Antarctica. Atitarctic Jouriial of the U.S., 23(5), 172-175. Bromwich, D.H., T.R. Parish, and C.A. Zorman. In press. The confluence zone of the intense katabatic winds at Terra Nova Bay, Antarctica as derived from airborne sastrugs surveys and mesoscale numerical modeling. Journal of Geophysical Research.
Parish, T.R., and D.H. Bromwich. 1986. The inversion wind pattern over West Antarctica. Mont/ih Weather Review, 114, 849-860. Parish, T.R., and D.H. Bromwich. 1987. The surface windfield over the Antarctic ice sheets. Nat ore, 328, 51-54. Parish, T.R., and D.H. Bromwich. 1989. Instrumented aircraft observations of the katabatic wind regime near Terra Nova Bay. Monthl y Went/icr Review, 117, 1,570-1,585.
225
