Observational and modeling studies of episodic events in the antarctic ...
(University of Washington) for requesting that we publish it. We thank Jerry Mullins and Gordon Shupe of USGS (Reston, Virginia) for information about the benchmarks, and Kitt Hughes (Antarctic Support Associates) for information about the meteorological instruments.
Reference Mullins, J. 1992. Personal communication.
Observational and modeling studies of episodic events in the antarctic atmospheric boundary layer JOHN I. CARROLL, Department of Land, Air, and Water Resources, University of California, Davis, California 95616 WILLIAM D. NEFF, Wave Propagation Laboratory, National Oceanic and Atmospheric Administration, Environmental
Research Laboratory, Boulder, Colorado 80303
-40°C over periods the order of a day and is highly correlated with increased wind speed (Dalrymple 1966; Carroll 1984). Available evidence suggests that these warming events are due to enhanced turbulent transfer of heat downward through the ABL rather than horizontal advection (Neff 1980; Carroll 1984). Advances in surface-based remote-sensing technology now allow nearly continuous measurements of wind and temperature profiles in the ABL (Neff 1990). Closure schemes for parameterization of turbulence in stable conditions have improved, and a number of models have been developed and tested against tower data during nighttime stable conditions and show good quantitative agreement (for example, Sorbjan 1984; Lacser and Arya 1986a,b). Improvements in model computation of pressure gradients over sloping surfaces (Carroll, R.-Mendez-Nunez, and Tanrikulu 1987) and in use of nonhydrostatic models (R.Mendez-Nunez and Carroll 1993, in press) allow South Pole instrumentation three-dimensional modeling of small-scale flow structures in the polar boundary layer. The major objectives of this study are to determine experimentally the presence, structure, and Pyranometer Solar radiation Radiation budget behavior of transient features and their effect on the Pyrgeometer Downwelling infrared Radiation budget boundary-layer structure and near-ground fluxes at Net radiameter Net all wave radiation Radiation budget the South Pole; to use these data to verify predictions Anemometers (2) Wind speed (z = 4, 11 m) Lower wind profile of numerical models; and then to use these models to Wind vanes (2) Wind direction (z = 4, 11 m) Shear; ABL stability examine ABL dynamics. Our current experimental Platinum Air temperature 1(z); ABL stability thermometers (3) (z = 4, 11, 22 m) emphasis is on the measurement of mean profiles, Snow heat budget local near-ground turbulent fluxes, and surface enerSnow temperature Platinum gy budgets. The instruments and their functions are (z=Otol.5m) thermometers (13) Wind and temperat ure listed in the table. The mesoscale environment for (z>100 m) Doppler radar; u(z), v(z), w(z); profiles 1(z); (z>100 m) with radio these measurements is defined by five automatic sounding system weather stations, one at the South Pole and four locatWind profiles Doppler sonic u(z), v(z), w(z); (z>40 m) detecting and ed along latitude 89°S at longitudes of approximately ranging (SODAR) 0, 90°E, 90°W, and 180. In addition, the once-per-day Temperature varianice (winter) high-resolution radiosonde assents provide T(z) (z>40 m) Doppler SODAR periodic sampling of the deep atmosphere as well as a profiles Eddy correlation sh ear means to verify the nearly continuous, remotely Wind and temperature Sonic anemometer fluctuations stress and heat fI ux Local Gravity wave detection sensed wind and temperature information. The pressure variations Microbaragraphs
he antarctic interior is an ideal place to examine the role T of time-varying forcing in the onset and decay of episodic events in the stable atmospheric boundary layer (ABL). These events include the sudden warming at the surface of the antarctic plateau associated with an onset of strong surface winds and a variety of wave phenomena. Of particular interest are the effects of time-varying pressure gradient, horizontal temperature advections, and mesoscale divergence patterns on boundary-layer structure and surface fluxes of heat and momentum. Observations of the heat budget in Antarctica show a high degree of temporal variability with significant amplitudes not correlated with local insolation (Carroll 1982; Yamanouchi and Kawaguchi 1984). During the long polar night, the surface temperature may vary between -70°C and
ANTARCTIC JOURNAL - REVIEW 1993
273
instrumentation was installed in January 1993 and is expected to run for 1 year. As of this writing, data acquisition is proceeding satisfactorily. We thank the technical support staff at Amundsen-Scott South Pole Station for their assistance and K. Sharp for her efforts in running the instrumentation through the winter. Support for this research is being provided in part by National Science Foundation grants OPP 91-19364 and OPP 91-18961.
Lascer, A., and S.P.S. Arya. 1986a. A numerical model study of the structure and similarity scaling of the nocturnal boundary layer (NBL). Boundary-Layer Meteorology, 35,369-386. Lascer, A., and S.P.S. Arya. 1986b. A comparative assessment of mixing-length parameterizations in the stably stratified nocturnal boundary layer (NBL). Boundary-Layer Meteorology, 36, 53-70. Neff, W.D. 1980. An observational and numerical study of the atmospheric boundary layer overlying the east Antarctic ice sheet. (Doctoral dissertation, University of Colorado.) Neff, W.D. 1990. Remote sensing of atmospheric processes over complex terrain. In W. Blumen (Ed.), Atmospheric processes in complex terrain. American Meteorology Society, Meteorological Mono-
References Carroll, J.J. 1982. Long term means and short term variability of the surface energy balance components at the South Pole. Journal of Geophysical Research, 87(C6), 4277-4286. Carroll, J.J. 1984. On the determinants of the near surface temperature regime on the South Polar Plateau. Journal of Geophysical Research, 89(D3), 4941-4952. Carroll, J.J., L. R.-Mendez-Nunez, and S. Tanrikulu. 1987. Accurate pressure gradient calculations in hydrostatic models. BoundaryLayer Meteorology, 41, 149-169. Dalrymple, P.C. 1966. A physical climatology of the antarctic plateau. In M.J. Rubin (Ed.), Studies in antarctic meteorology (Antarctic Research Series, Vol. 9). Washington, D.C.: American Geophysical Union.
graphs, 23, 173-228. R.-Mendez-Nunez, L., and J.J. Carroll. 1993. Comparison of leap frog Smolarkiewitz and MacCormack schemes applied to nonlinear equations. Monthly Weather Review, 121(2), 565-578. R.-Mendez-Nunez, L., and J.J. Carroll. In press. Application of the MacCormack scheme to non-hydrostatic atmospheric models model. Monthly Weather Review.
Sorbjan, Z. 1984. A model study of the stably stratified, steady-state atmospheric boundary layer over slightly inclined terrain. Journal ofAtmospheric Science, 41(11), 1863-1874. Yamanouchi, T., and S. Kawaguchi. 1984. Long wave radiation balance under a strong surface inversion in the katabatic wind zone, Antarctica. Journal of Geophysical Research, 89(D7), 11771-11778.
Low-level atmospheric jets and inversions on Ice Station Weddell 1 EDGAR L ANDREAS and KERRY J. CLAFFEY, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755-1290 ALEKSANDR P. MAKSHTAS, Arctic and Antarctic Research Institute, St. Petersburg, Russia 199226
uring our deployment on Ice Station Weddell 1 (ISW-1) D in 1992 (anonymous 1992; 18W-1 Group 1993), we launched radiosondes, typically at 00 and 12 Greenwich mean time (GMT) to investigate the structure of the lower atmosphere (Andreas et al. 1992). Near the end of our drift, in late May and early June, we launched simultaneous radiosondes from ISW-i and from the Akademik Fedorov at 00, 06, 12, and 18 GMT as the Fedorov approached from the northeast to help disassemble the station. Here we report some prelimi nary results from this radiosounding program. On ISW-i, we had two types of radiosondes: Tethersondes and Airsondes (both made by Atmospheric Instrumentation Research, Boulder, Colorado). Tethersondes were our primary sounding instruments because they measure pressure, temperature, humidity, and wind speed and direction. Airsondes measure only pressure, temperature, and humidity. A Tethersonde was carried aloft on a 5-meter (m)-long, torpedoshaped, helium-filled balloon that was tethered to an electric winch. Tethersondes measure wind speed with a cup anemometer; the balloon points into the wind, and a compass in the Tethersonde, thus, provides the wind direction. Occasionally, we raised the Tethersonde to over 1,000 m, but usual-
ly we profiled with it to 500-600 m. Airsondes are expendable, free-flying sondes that we launched on 1-m-diameter, spherical balloons; they commonly reached an altitude of 5 kilometers (km). The Fedorov has a CORA radiosounding system (made by Vaisala, Helsinki, Finland) that uses the Omega navigational aid signals to track the free-flying sonde. The Fedorov radiosoundings, thus, provided pressure, temperature, humidity, wind speed, and direction to altitudes over 8 km. Figures 1 and 2 show the simultaneous radiosoundings on ISW-i and from the Fedorov on 3 June 1992 at 00 GMT, when the Fedorov was 53 km northeast of ISW-1. The soundings show some obvious similarities and some important differences. Both soundings show a surface-based inversion with a temperature there of -26°C to -28°C. The inversion persists up to 400-500 m, where the temperature is about -10°C. The lowest 200 m is fairly moist (dew-point temperature only 1-2°C less than the air temperature), but the air is much drier above this level. Lastly, both soundings show wind speeds of 2-4 meters per second (m s 1) at the surface and speeds of 8-9 m s- 1 above the inversion layer. The ISW- 1 Tethersonde, however, provided much more detail than the Fedorov radiosonde. Although the Fedorov
ANTARCTIC JOURNAL - REVIEW 1993
274
Reference Mullins, J. 1992. Personal communication.
Observational and modeling studies of episodic events in the antarctic atmospheric boundary layer JOHN I. CARROLL, Department of Land, Air, and Water Resources, University of California, Davis, California 95616 WILLIAM D. NEFF, Wave Propagation Laboratory, National Oceanic and Atmospheric Administration, Environmental
Research Laboratory, Boulder, Colorado 80303
-40°C over periods the order of a day and is highly correlated with increased wind speed (Dalrymple 1966; Carroll 1984). Available evidence suggests that these warming events are due to enhanced turbulent transfer of heat downward through the ABL rather than horizontal advection (Neff 1980; Carroll 1984). Advances in surface-based remote-sensing technology now allow nearly continuous measurements of wind and temperature profiles in the ABL (Neff 1990). Closure schemes for parameterization of turbulence in stable conditions have improved, and a number of models have been developed and tested against tower data during nighttime stable conditions and show good quantitative agreement (for example, Sorbjan 1984; Lacser and Arya 1986a,b). Improvements in model computation of pressure gradients over sloping surfaces (Carroll, R.-Mendez-Nunez, and Tanrikulu 1987) and in use of nonhydrostatic models (R.Mendez-Nunez and Carroll 1993, in press) allow South Pole instrumentation three-dimensional modeling of small-scale flow structures in the polar boundary layer. The major objectives of this study are to determine experimentally the presence, structure, and Pyranometer Solar radiation Radiation budget behavior of transient features and their effect on the Pyrgeometer Downwelling infrared Radiation budget boundary-layer structure and near-ground fluxes at Net radiameter Net all wave radiation Radiation budget the South Pole; to use these data to verify predictions Anemometers (2) Wind speed (z = 4, 11 m) Lower wind profile of numerical models; and then to use these models to Wind vanes (2) Wind direction (z = 4, 11 m) Shear; ABL stability examine ABL dynamics. Our current experimental Platinum Air temperature 1(z); ABL stability thermometers (3) (z = 4, 11, 22 m) emphasis is on the measurement of mean profiles, Snow heat budget local near-ground turbulent fluxes, and surface enerSnow temperature Platinum gy budgets. The instruments and their functions are (z=Otol.5m) thermometers (13) Wind and temperat ure listed in the table. The mesoscale environment for (z>100 m) Doppler radar; u(z), v(z), w(z); profiles 1(z); (z>100 m) with radio these measurements is defined by five automatic sounding system weather stations, one at the South Pole and four locatWind profiles Doppler sonic u(z), v(z), w(z); (z>40 m) detecting and ed along latitude 89°S at longitudes of approximately ranging (SODAR) 0, 90°E, 90°W, and 180. In addition, the once-per-day Temperature varianice (winter) high-resolution radiosonde assents provide T(z) (z>40 m) Doppler SODAR periodic sampling of the deep atmosphere as well as a profiles Eddy correlation sh ear means to verify the nearly continuous, remotely Wind and temperature Sonic anemometer fluctuations stress and heat fI ux Local Gravity wave detection sensed wind and temperature information. The pressure variations Microbaragraphs
he antarctic interior is an ideal place to examine the role T of time-varying forcing in the onset and decay of episodic events in the stable atmospheric boundary layer (ABL). These events include the sudden warming at the surface of the antarctic plateau associated with an onset of strong surface winds and a variety of wave phenomena. Of particular interest are the effects of time-varying pressure gradient, horizontal temperature advections, and mesoscale divergence patterns on boundary-layer structure and surface fluxes of heat and momentum. Observations of the heat budget in Antarctica show a high degree of temporal variability with significant amplitudes not correlated with local insolation (Carroll 1982; Yamanouchi and Kawaguchi 1984). During the long polar night, the surface temperature may vary between -70°C and
ANTARCTIC JOURNAL - REVIEW 1993
273
instrumentation was installed in January 1993 and is expected to run for 1 year. As of this writing, data acquisition is proceeding satisfactorily. We thank the technical support staff at Amundsen-Scott South Pole Station for their assistance and K. Sharp for her efforts in running the instrumentation through the winter. Support for this research is being provided in part by National Science Foundation grants OPP 91-19364 and OPP 91-18961.
Lascer, A., and S.P.S. Arya. 1986a. A numerical model study of the structure and similarity scaling of the nocturnal boundary layer (NBL). Boundary-Layer Meteorology, 35,369-386. Lascer, A., and S.P.S. Arya. 1986b. A comparative assessment of mixing-length parameterizations in the stably stratified nocturnal boundary layer (NBL). Boundary-Layer Meteorology, 36, 53-70. Neff, W.D. 1980. An observational and numerical study of the atmospheric boundary layer overlying the east Antarctic ice sheet. (Doctoral dissertation, University of Colorado.) Neff, W.D. 1990. Remote sensing of atmospheric processes over complex terrain. In W. Blumen (Ed.), Atmospheric processes in complex terrain. American Meteorology Society, Meteorological Mono-
References Carroll, J.J. 1982. Long term means and short term variability of the surface energy balance components at the South Pole. Journal of Geophysical Research, 87(C6), 4277-4286. Carroll, J.J. 1984. On the determinants of the near surface temperature regime on the South Polar Plateau. Journal of Geophysical Research, 89(D3), 4941-4952. Carroll, J.J., L. R.-Mendez-Nunez, and S. Tanrikulu. 1987. Accurate pressure gradient calculations in hydrostatic models. BoundaryLayer Meteorology, 41, 149-169. Dalrymple, P.C. 1966. A physical climatology of the antarctic plateau. In M.J. Rubin (Ed.), Studies in antarctic meteorology (Antarctic Research Series, Vol. 9). Washington, D.C.: American Geophysical Union.
graphs, 23, 173-228. R.-Mendez-Nunez, L., and J.J. Carroll. 1993. Comparison of leap frog Smolarkiewitz and MacCormack schemes applied to nonlinear equations. Monthly Weather Review, 121(2), 565-578. R.-Mendez-Nunez, L., and J.J. Carroll. In press. Application of the MacCormack scheme to non-hydrostatic atmospheric models model. Monthly Weather Review.
Sorbjan, Z. 1984. A model study of the stably stratified, steady-state atmospheric boundary layer over slightly inclined terrain. Journal ofAtmospheric Science, 41(11), 1863-1874. Yamanouchi, T., and S. Kawaguchi. 1984. Long wave radiation balance under a strong surface inversion in the katabatic wind zone, Antarctica. Journal of Geophysical Research, 89(D7), 11771-11778.
Low-level atmospheric jets and inversions on Ice Station Weddell 1 EDGAR L ANDREAS and KERRY J. CLAFFEY, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755-1290 ALEKSANDR P. MAKSHTAS, Arctic and Antarctic Research Institute, St. Petersburg, Russia 199226
uring our deployment on Ice Station Weddell 1 (ISW-1) D in 1992 (anonymous 1992; 18W-1 Group 1993), we launched radiosondes, typically at 00 and 12 Greenwich mean time (GMT) to investigate the structure of the lower atmosphere (Andreas et al. 1992). Near the end of our drift, in late May and early June, we launched simultaneous radiosondes from ISW-i and from the Akademik Fedorov at 00, 06, 12, and 18 GMT as the Fedorov approached from the northeast to help disassemble the station. Here we report some prelimi nary results from this radiosounding program. On ISW-i, we had two types of radiosondes: Tethersondes and Airsondes (both made by Atmospheric Instrumentation Research, Boulder, Colorado). Tethersondes were our primary sounding instruments because they measure pressure, temperature, humidity, and wind speed and direction. Airsondes measure only pressure, temperature, and humidity. A Tethersonde was carried aloft on a 5-meter (m)-long, torpedoshaped, helium-filled balloon that was tethered to an electric winch. Tethersondes measure wind speed with a cup anemometer; the balloon points into the wind, and a compass in the Tethersonde, thus, provides the wind direction. Occasionally, we raised the Tethersonde to over 1,000 m, but usual-
ly we profiled with it to 500-600 m. Airsondes are expendable, free-flying sondes that we launched on 1-m-diameter, spherical balloons; they commonly reached an altitude of 5 kilometers (km). The Fedorov has a CORA radiosounding system (made by Vaisala, Helsinki, Finland) that uses the Omega navigational aid signals to track the free-flying sonde. The Fedorov radiosoundings, thus, provided pressure, temperature, humidity, wind speed, and direction to altitudes over 8 km. Figures 1 and 2 show the simultaneous radiosoundings on ISW-i and from the Fedorov on 3 June 1992 at 00 GMT, when the Fedorov was 53 km northeast of ISW-1. The soundings show some obvious similarities and some important differences. Both soundings show a surface-based inversion with a temperature there of -26°C to -28°C. The inversion persists up to 400-500 m, where the temperature is about -10°C. The lowest 200 m is fairly moist (dew-point temperature only 1-2°C less than the air temperature), but the air is much drier above this level. Lastly, both soundings show wind speeds of 2-4 meters per second (m s 1) at the surface and speeds of 8-9 m s- 1 above the inversion layer. The ISW- 1 Tethersonde, however, provided much more detail than the Fedorov radiosonde. Although the Fedorov
ANTARCTIC JOURNAL - REVIEW 1993
274
