Editorial Type:
Article
Article Type:
Research Article

Cloud Trails Past the Lesser Antilles

Daniel J. Kirshbaum Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, Québec, Canada

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Jonathan G. Fairman Jr. School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester, United Kingdom

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Print Publication:
01 Apr 2015
DOI:
https://doi.org/10.1175/MWR-D-14-00254.1
Page(s):
995–1017
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Abstract

Observations and cloud-resolving simulations of elongated cloud plumes (or “cloud trails”) past the Lesser Antilles islands in the Caribbean Sea are presented. Analysis of one year of visible satellite images reveals that each island forms cloud trails on 30%–40% of days, typically in the afternoon in response to diurnal island heating. On around 10% of days the cloud bands are very well organized, with lengths of and durations of min. Radiosonde analysis suggests that the well-organized events are favored by moderate-to-strong trade winds (6–10 m s−1) and stronger trade inversions. The simulated cloud trails, which are consistent with observations in their morphology and diurnal cycle, are organized by quasi-linear bands of thermally forced convergence within the heated island wake. They are sensitive to overland surface fluxes, inversion strength and height, terrain height, and trade-wind speed. While surface fluxes control the strength of the wake thermal circulations, the inversion controls precipitation and the disruption of cloud trails by subcloud cold pools. The impacts of terrain height and wind speed are multifaceted, including control over (i) the mechanical flow regime, (ii) the intensity of wake turbulence, (iii) the cloud-trail length, (iv) the wake thermal anomaly, and (v) elevated-heating effects (which strengthen the thermal convergence). Dimensional analysis is used to develop empirical scalings for the wake thermal circulation, which describe the suite of numerical sensitivity tests reasonably well.

Corresponding author address: Daniel J. Kirshbaum, Department of Atmospheric and Oceanic Sciences, McGill University, Room 945, Burnside Hall, 805 Sherbrooke St. West, Montréal, QC H3A 0B9, Canada. E-mail: daniel.kirshbaum@mcgill.ca

Abstract

Observations and cloud-resolving simulations of elongated cloud plumes (or “cloud trails”) past the Lesser Antilles islands in the Caribbean Sea are presented. Analysis of one year of visible satellite images reveals that each island forms cloud trails on 30%–40% of days, typically in the afternoon in response to diurnal island heating. On around 10% of days the cloud bands are very well organized, with lengths of and durations of min. Radiosonde analysis suggests that the well-organized events are favored by moderate-to-strong trade winds (6–10 m s−1) and stronger trade inversions. The simulated cloud trails, which are consistent with observations in their morphology and diurnal cycle, are organized by quasi-linear bands of thermally forced convergence within the heated island wake. They are sensitive to overland surface fluxes, inversion strength and height, terrain height, and trade-wind speed. While surface fluxes control the strength of the wake thermal circulations, the inversion controls precipitation and the disruption of cloud trails by subcloud cold pools. The impacts of terrain height and wind speed are multifaceted, including control over (i) the mechanical flow regime, (ii) the intensity of wake turbulence, (iii) the cloud-trail length, (iv) the wake thermal anomaly, and (v) elevated-heating effects (which strengthen the thermal convergence). Dimensional analysis is used to develop empirical scalings for the wake thermal circulation, which describe the suite of numerical sensitivity tests reasonably well.

Corresponding author address: Daniel J. Kirshbaum, Department of Atmospheric and Oceanic Sciences, McGill University, Room 945, Burnside Hall, 805 Sherbrooke St. West, Montréal, QC H3A 0B9, Canada. E-mail: daniel.kirshbaum@mcgill.ca
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  • Banta, R. M., 1990: Atmospheric Processes over Complex Terrain. Meteor. Monogr., No. 45, Amer. Meteor. Soc., 323 pp.

  • Barthlott, C., and D. J. Kirshbaum, 2013: Sensitivity of deep convection to terrain forcing over Mediterranean islands. Quart. J. Roy. Meteor. Soc., 139, 1762–1779, doi:10.1002/qj.2089.

    • Search Google Scholar
    • Export Citation

  • Bryan, G. H., J. C. Wyngaard, and J. M. Fritsch, 2003: Resolution requirements for the simulation of deep moist convection. Mon. Wea. Rev., 131, 2394–2416, doi:10.1175/1520-0493(2003)131<2394:RRFTSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Carbone, R. E., J. W. Wilson, T. D. Keenan, and J. M. Hacker, 2000: Tropical island convection in the absence of significant topography. Part I: Life cycle of diurnally forced convection. Mon. Wea. Rev., 128, 3459–3480, doi:10.1175/1520-0493(2000)128<3459:TICITA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Crook, N. A., 2001: Understanding Hector: The dynamics of island thunderstorms. Mon. Wea. Rev., 129, 1550–1563, doi:10.1175/1520-0493(2001)129<1550:UHTDOI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Crook, N. A., and D. F. Tucker, 2005: Flow over heated terrain. Part I: Linear theory and idealized numerical simulations. Mon. Wea. Rev., 133, 2552–2564, doi:10.1175/MWR2964.1.

    • Search Google Scholar
    • Export Citation

  • Davison, J. L., R. M. Rauber, L. DiGirolamo, and M. A. LeMone, 2013: A revised conceptual model of the tropical marine boundary layer. Part I: Statistical characterization of the variability inherent in the wintertime trade wind regime over the western tropical Atlantic. J. Atmos. Sci., 70, 3005–3024, doi:10.1175/JAS-D-12-0321.1.

    • Search Google Scholar
    • Export Citation

  • Dorman, C. E., 1994: Guadalupe Island cloud trail. Mon. Wea. Rev., 122, 235–242, doi:10.1175/1520-0493(1994)122<0235:GICT>2.0.CO;2.

  • Fovell, R. G., 2005: Convective initiation ahead of the sea-breeze front. Mon. Wea. Rev., 133, 264–278, doi:10.1175/MWR-2852.1.

  • Kirshbaum, D. J., 2013: On thermally forced circulations over heated terrain. J. Atmos. Sci., 70, 1690–1709, doi:10.1175/JAS-D-12-0199.1.

    • Search Google Scholar
    • Export Citation

  • Kirshbaum, D. J., and R. B. Smith, 2009: Orographic precipitation in the tropics: Large-eddy simulations and theory. J. Atmos. Sci., 66, 2559–2578, doi:10.1175/2009JAS2990.1.

    • Search Google Scholar
    • Export Citation

  • Kirshbaum, D. J., and A. L. M. Grant, 2012: Invigoration of cumulus cloud fields by mesoscale ascent. Quart. J. Roy. Meteor. Soc., 138, 2136–2150, doi:10.1002/qj.1954.

    • Search Google Scholar
    • Export Citation

  • Kirshbaum, D. J., and C.-C. Wang, 2014: Boundary layer updrafts driven by airflow over heated terrain. J. Atmos. Sci., 71, 1425–1442, doi:10.1175/JAS-D-13-0287.1.

    • Search Google Scholar
    • Export Citation

  • Kirshbaum, D. J., R. Rotunno, and G. H. Bryan, 2007: The spacing of orographic rainbands triggered by small-scale topography. J. Atmos. Sci., 64, 4222–4245, doi:10.1175/2007JAS2335.1.

    • Search Google Scholar
    • Export Citation

  • Kundu, P. M., and I. M. Cohen, 2002: Fluid Mechanics. 2nd ed. Elsevier Science, 730 pp.

  • Malkus, J. S., 1963: Tropical rain induced by a small heat source. J. Appl. Meteor., 2, 547–556, doi:10.1175/1520-0450(1963)002<0547:TRIBAS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Malkus, J. S., and A. E. Bunker, 1952: Observational studies of the airflow over Nantucket island during the summer of 1950. Papers in Physical Oceanography and Meteorology, Vol. XII, No. 2, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 50 pp.

  • Matthews, S., J. M. Hacker, J. Cole, J. Hare, C. N. Long, and R. M. Reynolds, 2007: Modification of the atmospheric boundary layer by a small island: Observations from Nauru. Mon. Wea. Rev., 135, 891–905, doi:10.1175/MWR3319.1.

    • Search Google Scholar
    • Export Citation

  • McFarlane, S. A., C. N. Long, and D. M. Flynn, 2005: Impact of island-induced clouds on surface measurements: Analysis of the ARM Nauru Island effect study data. J. Appl. Meteor., 44, 1045–1065, doi:10.1175/JAM2241.1.

    • Search Google Scholar
    • Export Citation

  • Minder, J., R. B. Smith, and A. D. Nugent, 2013: The dynamics of ascent-forced orographic convection in the tropics: Results from Dominica. J. Atmos. Sci., 70, 4067–4088, doi:10.1175/JAS-D-13-016.1.

    • Search Google Scholar
    • Export Citation

  • Nordeen, M. L., P. Minnis, D. R. Doelling, D. Pethick, and L. Nguyen, 2001: Satellite observations of cloud plumes generated by Nauru. Geophys. Res. Lett., 28, 631–634, doi:10.1029/2000GL012409.

    • Search Google Scholar
    • Export Citation

  • Nuijens, L., and B. Stevens, 2012: The influence of wind speed on shallow marine cumulus convection. J. Atmos. Sci., 69, 168–184, doi:10.1175/JAS-D-11-02.1.

    • Search Google Scholar
    • Export Citation

  • Schär, C., and R. B. Smith, 1993: Shallow-water flow past isolated topography. Part I: Vorticity production and wake formation. J. Atmos. Sci., 50, 1373–1400, doi:10.1175/1520-0469(1993)050<1373:SWFPIT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Skamarock, W. C., and Coauthors, 2008: A description of the Advanced Research WRF version 3. NCAR Tech. Note NCAR/TN-475+STR, 113 pp. [Available online at http://www.mmm.ucar.edu/wrf/users/docs/arw_v3_bw.pdf.]

  • Smith, R. B., 1989: Hydrostatic airflow over mountains. Advances in Geophysics, Vol. 31, Academic Press, 1–41, doi:10.1016/S0065-2687(08)60052-7.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., A. C. Gleason, P. A. Gluhosky, and V. Grubiŝić, 1997: The wake of St. Vincent. J. Atmos. Sci., 54, 606–623, doi:10.1175/1520-0469(1997)054<0606:TWOSV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., P. Schafer, D. J. Kirshbaum, and E. Regina, 2009a: Orographic enhancement of precipitation inside Hurricane Dean. J. Hydrometeor., 10, 820–831, doi:10.1175/2008JHM1057.1.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., P. Schafer, D. J. Kirshbaum, and E. Regina, 2009b: Orographic precipitation in the tropics: Experiments in Dominica. J. Atmos. Sci., 66, 1698–1716, doi:10.1175/2008JAS2920.1.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., and Coauthors, 2012: Orographic precipitation in the tropics: The Dominica experiment. Bull. Amer. Meteor. Soc., 93, 1567–1579, doi:10.1175/BAMS-D-11-00194.1.

    • Search Google Scholar
    • Export Citation

  • Smolarkiewicz, P. K., R. M. Rasmussen, and T. L. Clark, 1988: On the dynamics of Hawaiian cloud bands: Island forcing. J. Atmos. Sci., 45, 1872–1905, doi:10.1175/1520-0469(1988)045<1872:OTDOHC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Souza, R. L. D., 1972: A study of atmospheric flow over a tropical island. Ph.D. thesis, Florida State University, 203 pp.

  • Stevens, B., and A. Seifert, 2008: Understanding macrophysical outcomes of microphysical choices in simulations of shallow cumulus convection. J. Meteor. Soc. Japan, 86A, 143–162, doi:10.2151/jmsj.86A.143.

    • Search Google Scholar
    • Export Citation

  • Warren, R. A., D. J. Kirshbaum, R. S. Plant, and H. W. Lean, 2014: A ‘Boscastle-type’ quasi-stationary convective system over the UK southwest peninsula. Quart. J. Roy. Meteor. Soc., 140, 240–257, doi:10.1002/qj.2124.

    • Search Google Scholar
    • Export Citation

  • Yang, Y., and Y.-L. Chen, 2008: Effects of terrain heights and sizes on island-scale circulations and rainfall for the island of Hawaii during HaRP. Mon. Wea. Rev., 136, 120–146, doi:10.1175/2007MWR1984.1.

    • Search Google Scholar
    • Export Citation

  • Yang, Y., S.-P. Xie, and J. Hafner, 2008a: Cloud patterns lee of Hawaii island: A synthesis of satellite observations and numerical simulation. J. Geophys. Res., 113, D15126, doi:10.1029/2008JD009889.

    • Search Google Scholar
    • Export Citation

  • Yang, Y., S.-P. Xie, and J. Hafner, 2008b: The thermal wake of Kauai island: Satellite observations and numerical simulations. J. Climate, 21, 4568–4586, doi:10.1175/2008JCLI1895.1.

    • Search Google Scholar
    • Export Citation
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