Skip to main content
SpringerLink
Log in

On cumulus mergers

Über das Verschmelzen von Cumulus-Wolken

  • Published:
Archiv für Meteorologie, Geophysik und Bioklimatologie, Serie A Aims and scope Submit manuscript

Summary

Joining together or merging is postulated to be a major way in which convective clouds become larger, enhancing their transports and impacts upon their environment. Cumulus shower merger is defined in terms of echoes from a calibrated digitized 10-cm radar reviewing a 0.9×105 km2 area in south Florida, U. S. A., which encompasses a 1.3×104 km2 experimental area for randomized seeding.

A detailed physical and statistical study is reported for three relatively undisturbed untreated days in the summer of 1973, the driest of which was a randomly selected control day for the experiment. Mergers are found to produce more than an order of magnitude more rain than unmerged echoes, while mergers of mergers (second order mergers) produce still an order of magnitude more rain. On the three days studied, merged systems produced about 86% of the rainfall over the area. Duration, echo area and rain depths are also compared for merged and unmerged systems. Each day is then analyzed individually, indicating a correlation between organization and rain amount, confirmed by other research reviewed briefly.

The location and time of merger is related to the seabreeze convergence zones as predicted by the University of Virginia Mesoscale Model with overall good agreement. Physical hypotheses suggesting the importance of downdrafts in cumulus merging are developed. The relevance of mergers to hydrology, weather modification and the large-scale impacts of convective clouds is discussed.

Zusammenfassung

Das Zusammenwachsen oder Verschmelzen von Cumulus-Wolken wird als einer der Hauptgründe für ihr Wachstum sowie für ihren Einfluß auf ihre Umgebung und auf die durch sie bewerkstelligten Transportprozesse angesehen. Das Verschmelzen von Cumulus-Schauern wird auf Grund der von einem kalibrierten und digitisierten 10-cm-Radar empfangenen Echos definiert. Das Radargerät überblickt eine Fläche von 0.9×105 km2 im Süden Floridas (U. S. A.), die ein Exerimentalgebiet von 1.3×104 km2 für randomisierte Wolkenimpfung umgibt.

Eine detaillierte physikalische und statistische Studie für drei relativ ungestörte Tage ohne Wolkenimpfung während des Sommers 1973 wird hiermit vorgelegt. Der trockenste dieser Tage war willkürlich als Kontrolltag für das Wolkenimpfungsexperiment gewählt worden. Verschmelzungsprozesse weisen um mehr als eine Größenordnung mehr Niederschlag auf als unverschmolzene Echos, während Verschmelzungen von Verschmelzungen (Verschmelzungen zweiter Ordnung) nochmals eine Größenordnung mehr Regen ergeben. An den drei untersuchten Tagen produzierten verschmolzene Systeme ungefähr 86% des über dem Untersuchungsgebiet beobachteten Regens. Andauer, Echoausmaß und Niederschlagshöhe werden für verschmolzene und unverschmolzene Wolkensysteme verglichen. Jeder Tag wird individuell analysiert, wobei eine Korrelation zwischen Wolkenorganisation und Niederschlagsbetrag angedeutet wird, die auch von anderen, kurz erwähnten Forschungsarbeiten bekräftigt wurde.

Ort und Zeit des Verschmelzens hängen von der Seewind-Konvergenzzone ab, welche durch das mesoskalare Rechenmodell der University of Virginia gut vorhergesagt wurde. Eine physikalische Hypothese über die Wichtigkeit der Absinkbewegung während des Cumulus-Verschmelzungsprozesses wird dargelegt. Die Bedeutung der Verschmelzungsvorgänge für die Hydrologie, für die künstliche Wetterbeeinflussung und für den großräumigen Einfluß konvektiver Wolken wird diskutiert.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Austin, P. M., Mason, C. K., Kraus, M. J.: Mesoscale Precipitation Patterns in New England and Their Relation to Macroscale Parameters. 12th Conf. on Radar Met., pp. 234–240, Norman, Oklahoma (1966).

  2. Battan, L. J.: Duration of Convective Radar Cloud Units. Bull. Amer. Met. Soc.32, 227–228 (1953).

    Google Scholar 

  3. Betts, A. K.: A Composite Mesoscale Cumulonimbus Budget. J. Atmos. Sci.30, 597–610 (1973).

    Google Scholar 

  4. Betts, A. K.: Convection in the Tropics. Meteorology Over the Tropical Oceans. Roy Met. Soc., pp. 105–132, Bracknell, England (1978).

    Google Scholar 

  5. Bjerknes, J.: Saturated Adiabatic Ascent of Air Through Dry Adiabatically Descending Environment. Quart. J. R. Met. Soc.64, 325–330 (1938).

    Google Scholar 

  6. Browing, K. A.: The Structure and Mechanisms of Hailstorms. Hail: A Review of Hail Science and Hail Suppression. Met. Monographs16, No. 38. Amer. Met Soc., pp. 1–43, Boston, Mass. (1977).

    Google Scholar 

  7. Byers, H. R., Braham, R. R., Jr.: The Thunderstorm: Report of the Thunderstorm Project, 287 pp. Washington, D. C.: U. S. Government Printing Office 1949.

    Google Scholar 

  8. Chen, C.-H., Orville, H. D.: Effects of Mesoscale Convergence on Cloud Convection. Submitted to J. Appl. Met. (1979).

  9. Cotton, W. R.: Theoretical Cumulus Dynamics. Rev. Geophys.13, 419–448 (1975).

    Google Scholar 

  10. Cotton, W. R., Pielke, R. A.: Weather Modification and Three-Dimensional Mesoscale Models. Bull. Amer. Met. Soc.57, 788–796 (1976).

    Google Scholar 

  11. Cotton, W. R., Pielke, R. A., Gannon, P. T.: Numerical Experiments on the Influence of the Mesoscale Circulation on the Cumulus Scale. J. Atmos. Sci.33, 252–261 (1976).

    Google Scholar 

  12. Cotton, W. R., Tripoli, G. J.: Effects of Mesoscale Convergence on Three-Dimensional Simulations of Large Cumulus Clouds. Submitted to J. Atmos. Sci. (1979).

  13. Cressman, G. P.: The Influence of the Field of Horizontal Divergence on Convective Cloudiness. J. Met.3, 85–88 (1946).

    Google Scholar 

  14. Cunning, J., Thomas, J., Gannon, P.: Mesoscale Response of the Florida Environment to Convection-a Case Study. Preprint Vol. Tenth Conf. on Severe Local Storms, Amer. Met. Soc., pp. 126–132, Omaha, Nebraska (1977).

  15. Eden, J. C.: Guide to Computer Programs Used in the Statistical Analysis of Florida Cumulus Seeding Experiments. NOAA Tech. Memorandum ERL WMPO-14, 117 pp., Boulder, Colorado (1974).

  16. Frank, H., Lhermitte, R. M.: Cell Interaction and Merger in a South Florida Thunderstorm. 17th Conf. Radar Meteor. Amer. Soc., pp. 151–156, Seattle, Washington (1976).

  17. Frank, N. L., Moore, P. L., Fisher, G. E.: Summer Shower Distribution Over the Florida Peninsula as Deduced From Digitized Radar Data. J. Appl. Met.6, 309–316 (1967).

    Google Scholar 

  18. Fritsch, J. M.: Cumulus Dynamics: Local Compensating Subsidence and Its Implications for Cumulus Parameterization. Pageoph.113, 851–867 (1975).

    Google Scholar 

  19. Fritsch, J. M., Chappell, C. F.: Numerical Prediction of Convectively Driven Mesoscale Pressure Systems. Preprint Vol. Fourth Conf. on Weather Forecasting and Analysis and Aviation Meteorology, Amer. Met. Soc., pp. 77–87 (1978).

  20. Gannon, P. T.: Influence of Earth Surface and Cloud Properties on the South Florida Seabreeze. NOAA Tech. Report ERL 402 NHEML 2, 91 pp., U. S. Dept. of Commerce, Boulder, Colorado (1978).

    Google Scholar 

  21. Gerrish, R., Hiser, H. W.: Mesoscale Studies of Instability Patterns and Winds in the Tropics. Rept. 7, 63 pp. U. S. Army Elec. Labs., Fort Monmouth, New Jersey (1965).

    Google Scholar 

  22. Herndon, A., Woodley, W. L., Miller, A. H., Samet, A., Sern, H.: Comparison of Gage and Radar Methods of Convective Precipitation Measurement, NOAA Tech. Memo. ERL OD-18, Boulder, Colorado (1973).

  23. Hill, G. E.: Factors Controlling the Size and Spacing of Cumulus Clouds as Revealed by Numerical Experiments. J. Atmos. Sci.31, 646–673 (1974).

    Google Scholar 

  24. Holle, R. L., Cunning, J., Thomas, J., Gannon, P., Teijeiro, L.: A Case Study of Mesoscale Convection and Cloud Merger Over South Florida. 11th Tech. Conf. on Hurricanes and Tropical Meteorology, Miami Beach, Florida, Amer. Met. Soc., pp. 428–4235 (1977).

  25. Holle, R. L., Maier, M. W.: Cloud Interaction and the Formation of the 15 June 1973 Tornado in the FACE Mesonetwork. NOAA Tech. Memo. ERL-WMPO33, 55 pp. (1976).

  26. Leary, C. A., Houze, R. A., Jr.: The Structure and Evolution of Convection in a Tropical Cloud Cluster. J. Atmos. Sci.36, 437–457 (1979).

    Google Scholar 

  27. Lilly, D. K.: Dynamical Structure and Evolution of Thunderstorms and Squall Lines. Ann. Rev. Earth Planet Sci.7, 117–161 (1979).

    Google Scholar 

  28. Ludlam, F. H., Scorer, R. S.: Reviews of Modern Meteorology 10: Convection in the Atmosphere. Quart. J. R. Met. Soc.79, 317–341 (1953).

    Google Scholar 

  29. Mahrer, Y., Pielke, R. A.: The Effects of Topography on Sea and Land Breezes in Two-Dimensional Numerical Model. Mon. Weath. Rev.105, 1151–1162 (1977).

    Google Scholar 

  30. Mahrer, Y., Pielke, R. A.: A Test of an Upstream Spline Interpolation Technique for the Advective Terms in a Numerical Mesoscale Model. Mon. Weath. Rev.106, 818–830 (1978).

    Google Scholar 

  31. Malkus, J. S.: Effects of Wind Shear on Some Aspects of Convection. Trans. Amer. Geophys. Union30, 19–25 (1949).

    Google Scholar 

  32. Malkus, J. S.: Recent Advances in the Study of Convective Clouds and Their Interaction With the Environment. Tellus4, 71–87 (1952).

    Google Scholar 

  33. Malkus, J. S.: The Slopes of Cumulus Clouds in Relation to External Wind Shear. Quart. J. R. Met. Soc.78, 530–542 (1952).

    Google Scholar 

  34. Malkus, J. S.: Some Results of a Trade Cumulus Clouds Investigation. J. Met.11, 220–237 (1954).

    Google Scholar 

  35. Malkus, J. S.: On the Formation and Structure of Downdrafts in Cumulus Clouds. J. Met.12, 350–357 (1955).

    Google Scholar 

  36. Malkus, J. S., Riehl, H.: Cloud Structure and Distributions Over the Tropical Pacific Ocean, 229 pp. Univ. of California Press, Berkeley (1964).

    Google Scholar 

  37. Malkus, J. S., Scorer, R. S.: The Erosion of Cumulus Towers. J. Met.12, 43–57 (1955).

    Google Scholar 

  38. Malkus, J. S., Williams, R. T.: On the Interaction Between Severe Storms and Large Cumulus Clouds. Met. Monographs5, 59–64 (1963).

    Google Scholar 

  39. Moncrieff, M. W., Miller, M. J.: The Dynamics and Simulation of Tropical Cumulonimbus and Squall Lines. Quart. J. R. Met. Soc.102, 373–394 (1976).

    Google Scholar 

  40. National Center for Atmospheric Research: Report of the U. S. GATE Central Program Workshop, 723 pp. Ed. R. Greenfield (1977).

  41. Pielke, R.: A Three-Dimensional Numerical Model of the Sea Breezes Over South Florida. Mon. Weath. Rev.102, 115–139 (1974).

    Google Scholar 

  42. Pielke, R. A., Cotton, W. R.: A Mesoscale Analysis Over South Florida for a High Rainfall Event. Mon. Weath. Rev.105, 343–362 (1977).

    Google Scholar 

  43. Pielke, R. A., Cotton, W. R.: The Evolutionary Characteristics of Sea and Lake-Breeze Generated Convective-Mesoscale Systems Over South Florida. Submitted to Mon. Weath. Rev. (1979).

  44. Pielke, R. A., Mahrer, Y.: The Numerical Simulation of the Airflow Over Barbados. Mon. Weath. Rev.104, 1392–1402 (1976).

    Google Scholar 

  45. Pielke, R. A., Mahrer, Y.: A Numerical Study of the Airflow Over Irregular Terrain. Beitr. Physik Atmos.50, 98–113 (1977).

    Google Scholar 

  46. Pielke, R. A., Mahrer, Y.: Verification Analysis of the University of Virginia Mesoscale Model Prediction Over South Florida for 1 July 1973. Mon. Weath. Rev.106, 1568–1589 (1978).

    Google Scholar 

  47. Plank, V. G.: The Size of Cumulus Clouds in Representative Florida Populations. J. Appl. Met.8, 46–67 (1969).

    Google Scholar 

  48. Saunders, P. M.: An Observational Study of Cumulus. J. Met.18, 451–467 (1961).

    Google Scholar 

  49. Schlesinger, R. E.: A Three-Dimensional Numerical Model of an Isolated Thunderstorm. Part I. Comparative Experiments for Variable Ambient Wind Shear. J. Atmos. Sci.35, 690–713 (1978).

    Google Scholar 

  50. Scorer, R. S., Ludlam, F. H.: Bubble Theory of Penetrative Convection. Quart. J. R. Met. Soc.79, 94–103 (1953).

    Google Scholar 

  51. Simpson, J.: Downdrafts as Linkages in Dynamic Cumulus Seeding Effects. Submitted to J. Appl. Met. (1979).

  52. Simpson, J., Dennis, A. S.: Cumulus Clouds and Their Modification. Weather Modification, Chap. 6, pp. 229–280 (Hess, W. N., ed.). New York: Wiley 1974.

    Google Scholar 

  53. Simpson, J., Woodley, W. L.: Seeding Cumulus in Florida — New 1970 Results. Science172, 117–126 (1971).

    Google Scholar 

  54. Simpson, J., Woodley, W. L.: Florida Area Cumulus Experiment 1970–1973 Rainfall Results. J. Appl. Met.14, 734–744 (1975).

    Google Scholar 

  55. Sims, A. L., Mueller, E. A., Stout, G. E.: Investigations of Quantitative Determination of Point and Areal Precipitation by Radar Echo Measurements. Quart. Tech. Rep., 1 July 63-30 Sept. 1963, 27 pp., Met. Lab., Illinois State Water Survey, Urbana (1963).

    Google Scholar 

  56. Snedecor, G. W., Cochran, W. G.: Statistical Methods. The Iowa State University Press, Ames, Iowa (1967).

    Google Scholar 

  57. Staff, Experimental Meteorology Laboratory: 1973 Florida Area Cumulus Experiment (FACE) Operational and Preliminary Summary. NOAA Techn. Memo. ERL WMPO-12, 254 pp., Boulder, Colorado (1974).

  58. Thomas, J., Jordan, J.: Measurement of Convective Rainfall Within the FACE Target Area. Abstract Vol. 7th Conf. on Weather Modification, Amer. Met. Soc., Banff, Alberta, Canada (1979).

  59. Ulanski, S., Garstang, M.: The Role of Surface Divergence and Vorticity in the Life Cycle of Convective Rainfall. Part I: Observation and Analysis. J. Atmos. Sci.35, 1047–1062 (1978).

    Google Scholar 

  60. Ulanski, S., Garstang, M.: The Role of Surface Divergence and Vorticity in the Life Cycle of Convective Rainfall. Part II; Descriptive Model. J. Atmos. Sci.35, 1063–1069 (1978).

    Google Scholar 

  61. Ulanski, S., Garstang, M.: Some Aspects of Florida Convective Rainfall. Water Resources Research14, 1133–1139 (1978).

    Google Scholar 

  62. Warner, C., Simpson, J., Van Helvoirt, G.: Shallow and Deep Convection: Day 261 of GATE. Tech. Report No. 4, Cloud Populations and Their Interactions With the Boundary Layer. Dept. of Environmental Sciences, 90 pp. University of Virginia, Charlottesville, Virginia.

  63. Welch, B. L.: The Significance of the Difference Between Two Means When the Population Variance Are Unequal. Biometrika (Cambridge, England)29, 350–359 (1938).

    Google Scholar 

  64. Westcott, N. E.: Radar Characterization of South Florida Convective Rainfall. Proc. Sixth Conf. on Planned and Inadvertent Weather Modification, pp. 190–193. Champaign-Urbana, Illinois. Amer. Met. Soc. (1977).

    Google Scholar 

  65. Westcott, N. E.: Radar Characterization of South Florida Rainfall, 74 pp. M. S. Thesis, Dept. of Environmental Sciences, University of Virginia, Charlottesville, Virginia (1977).

    Google Scholar 

  66. Westcott, N. E., Simpson, J.: Population Study of Radar Echoes Over South Florida. Submitted to J. Appl. Met. (1979).

  67. Wiggert, V., Andrews, G. F.: Digitizing, Recording, and Computer Processing Weather Data at EML. NOAA Tech. Memo. ERL WMPO-17, pp. 1–25 (1974).

  68. Wiggert, V., Lockett, G. J., Ostlund, S.: Radar Rainshower Growth Histories and Their Variation With Wind Speed and Echo Motion Over South Florida. Submitted to Mon. Weath. Rev. (1979).

  69. Wiggert, V., Ostlund, S.: Computerized Rain Assessment and Tracking of South Florida WSR-57 Weather Radar Echoes. Bull. Amer. Met. Soc.56, 17–26 (1975).

    Google Scholar 

  70. Wiggert, V., Ostlund, S., Lockett, G. J., Stewart, J. V.: Computer Software for the Assessment of Growth Histories of Weather Radar Echoes. NOAA Tech. Mem. ERL WMPO-35, 85 pp. Boulder, Colorado (1976).

  71. Wilson, J. W.: Evaluation of Precipitation Measurements With the WSR-57 Weather Radar. J. Appl. Met.3, 164–174 (1964).

    Google Scholar 

  72. Woodley, W. L., Jordan, J. A., Simpson, J., Biondini, R., Flueck, J.: NOAA's Florida Area Cumulus Experiment Rainfall Results: 1970–1976. In press.

  73. Woodley, W. L., Norwood, J., Sancho, B.: Some Aspects of South Florida Showers and Thunderstorms. Weatherwise24, 106–113 (1971).

    Google Scholar 

  74. Woodley, W. L., Olsen, A., Herndon, A., Wiggert, V.: Optimizing the Measurement of Convective Rainfall in Florida. NOAA Tech. Mem. ERL WMPO-18, 99 pp. Boulder, Colorado (1974).

  75. Woodley, W. L., Olsen, A. R., Herndon, A., Wiggert, V.: Comparison of Gage and Radar Methods of Convective Rain Measurement. J. Appl. Met.14, 909–928 (1975).

    Google Scholar 

  76. Woodley, W. L., Sax, R. I.: The Florida Area Cumulus Experiment: Rationale, Design, Procedures, Results and Future Course. NOAA Tech. Rept. ERL 354-WMPO 6, 204 pp. (1976).

  77. Woodley, W. L., Simpson, J., Biondini, R., Berkeley, J.: Rainfall Results, 1970–1975: Florida Area Cumulus Experiment. Science195, 735–742.

  78. Woodley, W. L., Simpson, J., Biondini, R., Jordan, J.: NOAA's Florida Area Cumulus Experiment Rainfall Results 1970–1976. Sixth Conf. on Inadvertent and Planned Weather Modification, pp. 206–209. Champaign-Urbana, Illinois, Amer. Met. Soc. (1977).

    Google Scholar 

Download references

Author information

Author notes

  1. Joanne Simpson

    Present address: Goddard Laboratory of Atmospheric Sciences, National Space and Aeronautics Administration, 20771, Greenbelt, MD, USA

  2. R. A. Pielke

    Present address: Department of Environmental Sciences, University of Virginia, 22903, Charlottesville, VA, USA

  3. Nancy E. Westcott

    Present address: Atmospheric Sciences Section, Illinois State Water Survey, 61801, Urbana, IL, USA

  4. R. J. Clerman

    Present address: The Mitre Corporation, 22101, McLean, VA, USA

Authors and Affiliations

  1. Department of Environmental Sciences, University of Virginia, 22903, Charlottesville, VA, USA

    Joanne Simpson, Nancy E. Westcott & R. J. Clerman

Authors
  1. Joanne Simpson
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Nancy E. Westcott
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. R. J. Clerman
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. R. A. Pielke
    View author publications

    You can also search for this author in PubMed Google Scholar

Additional information

With 11 Figures

Rights and permissions

Reprints and permissions

About this article

Cite this article

Simpson, J., Westcott, N.E., Clerman, R.J. et al. On cumulus mergers. Arch. Met. Geoph. Biokl. A. 29, 1–40 (1980). https://doi.org/10.1007/BF02247731

Download citation

  • Received:

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF02247731

Keywords

Search

Navigation