Editorial Type:
Article
Article Type:
Research Article

Drop Growth Due to High Supersaturation Caused by Isobaric Mixing

Alexei V. Korolev Meteorological Service of Canada, Toronto, Ontario, Canada

Search for other papers by Alexei V. Korolev in
Current site
Google Scholar
PubMed Close
and
George A. Isaac Meteorological Service of Canada, Toronto, Ontario, Canada

Search for other papers by George A. Isaac in
Current site
Google Scholar
PubMed Close
Print Publication:
01 May 2000
DOI:
https://doi.org/10.1175/1520-0469(2000)057<1675:DGDTHS>2.0.CO;2
Page(s):
1675–1685
Restricted access

Abstract

A new conceptual model is proposed for enhanced cloud droplet growth during condensation. Rapid droplet growth may occur in zones of high supersaturation resulting from isobaric mixing of saturated volumes with different temperatures. Cloud volumes having a temperature different from the general cloud environment may form due to turbulent vertical motions in a temperature lapse rate that is not pseudoadiabatic. This mechanism is most effective in the vicinity of cloud-top inversions. It is also shown that the isobaric mixing of saturated and dry volumes with different temperatures may also lead to high supersaturations. The high supersaturations are associated with zones of molecular mixing, and they have a characteristic size of the order of millimeters with a characteristic lifetime near tenths of a second. Some small proportion of cloud droplets, over many supersaturation events, may grow large enough to grow effectively through collision–coalescence. This hypothesis of isobaric mixing may help explain freezing and warm drizzle formation.

Corresponding author address: Dr. Alexei V. Korolev, Cloud Physics Research Division, Meteorological Service of Canada, 4905 Dufferin Street, Toronto, ON M3H 5T4, Canada.

Email: alexei.korolev@ec.gc.ca

Abstract

A new conceptual model is proposed for enhanced cloud droplet growth during condensation. Rapid droplet growth may occur in zones of high supersaturation resulting from isobaric mixing of saturated volumes with different temperatures. Cloud volumes having a temperature different from the general cloud environment may form due to turbulent vertical motions in a temperature lapse rate that is not pseudoadiabatic. This mechanism is most effective in the vicinity of cloud-top inversions. It is also shown that the isobaric mixing of saturated and dry volumes with different temperatures may also lead to high supersaturations. The high supersaturations are associated with zones of molecular mixing, and they have a characteristic size of the order of millimeters with a characteristic lifetime near tenths of a second. Some small proportion of cloud droplets, over many supersaturation events, may grow large enough to grow effectively through collision–coalescence. This hypothesis of isobaric mixing may help explain freezing and warm drizzle formation.

Corresponding author address: Dr. Alexei V. Korolev, Cloud Physics Research Division, Meteorological Service of Canada, 4905 Dufferin Street, Toronto, ON M3H 5T4, Canada.

Email: alexei.korolev@ec.gc.ca

Save
Cover Journal of the Atmospheric Sciences
Journal of the Atmospheric Sciences

  • Baker, M. B., and J. Latham, 1979: The evolution of droplet spectra and rate of production of embryonic raindrops in small cumulus clouds. J. Atmos. Sci.,36, 1612–1615.

  • Beard, K. V., and H. T. Ochs III, 1993: Warm rain initiation: An overview of microphysical mechanisms. J. Appl. Meteor.,32, 608–625.

  • Bohren, C. F., and C. H. Albrecht, 1998: Atmospheric Thermodynamics. Oxford University Press, 402 pp.

  • Broadwell, J. E., and R. E. Breidenthal, 1982: A simple model of mixing and chemical reaction in a turbulent shear layer. J. Fluid Mech.,125, 397–410.

  • Cober, S. G., J. W. Strapp, and G. A. Isaac, 1996: An example of supercooled drizzle droplets formed through a collision coalescence process. J. Appl. Meteor.,35, 2250–2260.

  • Cooper, W. A., 1989: Effect of variable droplet growth histories on droplet size distributions. Part I: Theory. J. Atmos. Sci.,46, 1301–1311.

  • Gerber, H., 1991: Supersaturation and droplet spectral evolution in fog. J. Atmos. Sci.,48, 2569–2588.

  • Haman, K. E., A. Makulski, and S. P. Malinovski, 1997a: A new ultrafast thermometer for airborne measurements in clouds. J. Atmos. Oceanic Technol.,14, 217–227.

  • ——, S. P. Malinowski, and R. Busen, 1997b: Ultrafast aircraft thermometer. Proc. WMO Workshop on Measurements of Cloud Properties for Forecasts of Weather Climate, Rep. 30, Mexico City, Mexico, WMO, 116–124.

  • Hinze, J. O., 1959: Turbulence. An Introduction to its Mechanism and Theory. McGraw-Hill, 586 pp.

  • Hudson, J. G., 1984: Cloud condensation nuclei measurements within clouds. J. Climate Appl. Meteor.,23, 42–51.

  • Isaac, G. A., S. G. Cober, A. V. Korolev, J. W. Strapp, A. Tremblay, and D. L. Marcotte, 1998: Overview of the Canadian Freezing Drizzle Experiment I, II, and III. Preprints, Conf. on Cloud Physics, Everett, WA, Amer. Meteor. Soc., 447–450.

  • Kabanov, A. S., I. P. Mazin, and V. I. Smirnov, 1970: The effect of the spatial inhomogeneity newly-formed drops on their size spectrum in a cloud. Izv. Acad. Sci. USSR, Atmos. Oceanic Phys.,6, 149–155.

  • Knollenberg, R. G., 1981: Techniques for probing cloud microstructure. Clouds, Their Formation, Optical Properties, and Effects, P. V Hobbs and A. Deepak, Eds., Academic Press, 15–92.

  • Korolev, A. V., 1994: A study of bimodal droplet size distribution in stratiform clouds. Atmos. Res.,32, 143–170.

  • ——, and I. P. Mazin, 1993: Zones of increased and decreased droplet number concentration in stratiform clouds. J. Appl. Meteor.,32, 760–773.

  • ——, J. W. Strapp, G. A. Isaac, and A. N. Nevzorov, 1998: The Nevzorov airborne hot-wire LWC–TWC probe: Principal of operation and performance characteristics. J. Atmos. Oceanic Technol.,15, 1495–1510.

  • Krueger, S. K., 1993: Linear eddy modeling and mixing in stratus clouds. J. Atmos. Sci.,50, 3078–3090.

  • Latham, J., and R. L. Reed, 1977: Laboratory studies of the effect of mixing on the evolution of cloud droplet spectra. Quart. J. Roy. Meteor. Soc.,103, 279–306.

  • MacPherson, J. I., and G. A. Isaac, 1977: Turbulent characteristics of some Canadian cumulus clouds. J. Appl. Meteor.,16, 81–90.

  • Mason, B. J., 1957: The Physics of Clouds. Oxford, 481 pp.

  • Mazin, I. P., 1966: The stochastic condensation and its effect on the formation of cloud drop size distribution. Proc. Int. Conf. on Cloud Physics, Toronto, ON, Canada, IAMAP, 67–71.

  • ——, V. I. Silaeva, and M. A. Strunin, 1984: Turbulent fluctuations of horizontal and vertical wind velocity components in various cloud forms. Izv. Acad. Sci. USSR, Atmos. Oceanic Phys.,20, 6–11.

  • Paluch, I. R., and C. A. Knight, 1984: Mixing and the evolution of cloud droplet size spectra in a vigorous continental cumulus. J. Atmos. Sci.,41, 1801–1805.

  • Pobanz, B. M., J. D. Marwitz, and M. K. Politovitch, 1994: Conditions associated with large drop region. J. Appl. Meteor.,33, 1366–1372.

  • Rogers, R. R., 1976: A Short Course in Cloud Physics. Pergamon Press, 227 pp.

  • Stepanov, A. S., 1976: Influence of turbulence on the size spectrum of cloud drops during condensation. Izv. Acad. Sci. USSR, Atmos. Oceanic Phys.,12, 167–173.

  • Telford, J. W., T. S. Keck, and S. K. Chai, 1984: Entrainment at cloud tops and the droplet spectra. J. Atmos. Sci.,41, 3170–3179.

  • Vali, G., R. D. Kelly, J. French, S. Haimov, D. Leon, R. E. McIntosh, and A. Pazmany, 1998: Finescale structure and microphysics of coastal stratus. J. Atmos. Sci.,55, 3540–3564.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 544 231 37
PDF Downloads 183 40 2