• Benjamin, T. B., 1968: Gravity currents and related phenomena. J. Fluid Mech., 31B , 209248.

  • Carbone, R. E., J. D. Tuttle, D. A. Ahijevych, and S. B. Trier, 2002: Inferences of predictability associated with warm season precipitation episodes. J. Atmos. Sci., 59 , 20332056.

    • Search Google Scholar
    • Export Citation
  • Carlson, T. N., S. G. Benjamin, G. S. Forbes, and Y. F. Li, 1983: Elevated mixed layers in the regional severe storm environment: Conceptual model and case studies. Mon. Wea. Rev., 111 , 14531473.

    • Search Google Scholar
    • Export Citation
  • Crook, N. A., and J. B. Klemp, 2000: Lifting by convergence lines. J. Atmos. Sci., 57 , 873890.

  • Grossman, R. L., and D. R. Durran, 1984: Interaction of low-level flow with the western Ghat mountains and offshore convection in the summer monsoon. Mon. Wea. Rev., 112 , 652672.

    • Search Google Scholar
    • Export Citation
  • Grossman, R. L., and O. Garcia, 1990: The distribution of deep convection over ocean and land during the Asian summer monsoon. J. Climate, 3 , 10321044.

    • Search Google Scholar
    • Export Citation
  • Houze Jr., R. A., S. G. Geotis, F. D. Marks Jr., and A. K. West, 1981: Winter monsoon convection in the vicinity of north Borneo. Part I: Structure and time variation of the clouds and precipitation. Mon. Wea. Rev., 109 , 15951614.

    • Search Google Scholar
    • Export Citation
  • Johnson, R. H., and D. L. Priegnitz, 1981: Winter monsoon convection in the vicinity of north Borneo. Part II: Effects on large-scale fields. Mon. Wea. Rev., 109 , 16151628.

    • Search Google Scholar
    • Export Citation
  • Johnson, R. H., and J. F. Bresch, 1991: Diagnosed characteristics of precipitation systems over Taiwan during May–June 1987 TAMEX. Mon. Wea. Rev., 119 , 25402557.

    • Search Google Scholar
    • Export Citation
  • Kingsmill, D. E., 1995: Convection initiation associated with a sea-breeze front, a gust front, and their collision. Mon. Wea. Rev., 123 , 29132933.

    • Search Google Scholar
    • Export Citation
  • Kousky, V. E., 1980: Diurnal rainfall variation in northeastern Brazil. Mon. Wea. Rev., 108 , 488498.

  • Lahey, J. F., 1973: On the origin of the dry climate in northern South America and the southern Caribbean. Coastal Deserts: Their Natural and Human Environments, D. H. K. Amiran and A. W. Wilson, Eds., The University of Arizona Press, 75–90.

    • Search Google Scholar
    • Export Citation
  • Lanicci, J. M., and T. T. Warner, 1991: A synoptic climatology of the elevated mixed-layer inversion over the southern Great Plains in spring. Part I: Structure, dynamics, and seasonal evolution. Wea. Forecasting, 6 , 198213.

    • Search Google Scholar
    • Export Citation
  • Mahrer, Y., and R. A. Pielke, 1977: The effects of topography on sea and land breezes in a two-dimensional numerical model. Mon. Wea. Rev., 105 , 11511162.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., 2001: Water's two height scales: The moist adiabat and the radiative troposphere. Quart. J. Roy. Meteor. Soc., 127 , 22532266.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., and R. A. Houze Jr., 1995: Diabatic divergence profiles in tropical mesoscale convective systems. J. Atmos. Sci., 52 , 18071828.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., T. T. Warner, M. Xu, and A. J. Negri, 2003: Diurnal patterns of rainfall in northwestern South American. Part I: Observations and context. Mon. Wea. Rev., 131 , 799812.

    • Search Google Scholar
    • Export Citation
  • Meyer, J. H., 1971: Radar observations of land breeze fronts. J. Appl. Meteor., 10 , 12241232.

  • Negri, A. J., R. F. Adler, E. J. Nelkin, and G. J. Huffman, 1994: Regional rainfall climatologies derived from Special Sensor Microwave Imager (SSM/I) data. Bull. Amer. Meteor. Soc., 75 , 11651182.

    • Search Google Scholar
    • Export Citation
  • Neumann, J., 1951: Land breezes and nocturnal thunderstorms. J. Meteor., 8 , 6067.

  • Oerlemans, J., 1980: A case study of a subsynoptic disturbance in a polar outbreak. Quart J. Roy. Meteor. Soc., 106 , 313325.

  • Ohsawa, T., H. Ueda, T. Hayashi, A. Watanabe, and J. Masumoto, 2001: Diurnal variations of convective activity and rainfall in tropical Asia. J. Meteor. Soc. Japan, 79 , 333352.

    • Search Google Scholar
    • Export Citation
  • Pielke, R. A., and M. Segal, 1986: Mesoscale circulations forced by differential terrain heating. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 516–548.

    • Search Google Scholar
    • Export Citation
  • Poveda, G., and O. J. Mesa, 2000: On the existence of Lloró (the rainiest locality on Earth): Enhanced ocean–land–atmosphere interaction by a low-level jet. Geophys. Res. Lett., 27 , 16751678.

    • Search Google Scholar
    • Export Citation
  • Ramage, C. S., 1964: Diurnal variation of summer rainfall over Malaya. J. Trop. Geogr., 19 , 6268.

  • Ricciardulli, L., and P. D. Sardeshmukh, 2002: Local time- and space scales of tropical deep convection. J. Climate, 15 , 27752790.

  • Rotunno, R., 1983: On the linear theory of the land and sea breeze. J. Atmos. Sci., 40 , 19992009.

  • Saito, K., T. Keenan, G. Holland, and K. Puri, 2001: Numerical simulation of the diurnal evolution of tropical island convection over the Maritime Continent. Mon. Wea. Rev., 129 , 378400.

    • Search Google Scholar
    • Export Citation
  • Schafer, R., P. T. May, T. D. Keenan, K. McGuffie, W. L. Ecklund, P. E. Johnston, and K. S. Gage, 2001: Boundary layer development over a tropical island during the Maritime Continent Thunderstorm Experiment. J. Atmos. Sci., 58 , 21632179.

    • Search Google Scholar
    • Export Citation
  • Wai, M. M-K., P. T. Welsh, and W-M. Ma, 1996: Interaction of secondary circulations with the summer monsoon and diurnal rainfall over Hong Kong. Bound.-Layer Meteor., 81 , 123146.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., N. E. Graham, and C. Gautier, 1993: Comparison of the highly reflective cloud and outgoing longwave radiation datasets for use in estimating tropical deep convection. J. Climate, 6 , 331353.

    • Search Google Scholar
    • Export Citation
  • Warner, T. T., B. E. Mapes, and M. Xu, 2003: Diurnal patterns of rainfall in northwestern South America. Part II: Model simulations. Mon. Wea. Rev., 131 , 813829.

    • Search Google Scholar
    • Export Citation
  • Wilson, J. W., and D. L. Megenhardt, 1997: Thunderstorm initiation, organization, and lifetime associated with Florida boundary layer convergence lines. Mon. Wea. Rev., 125 , 15071525.

    • Search Google Scholar
    • Export Citation
  • Yan, H., and R. A. Anthes, 1987: Effect of latitude on the sea breeze. Mon. Wea. Rev., 115 , 936956.

  • Yang, G-Y., and J. Slingo, 2001: The diurnal cycle in the Tropics. Mon. Wea. Rev., 129 , 784801.

  • Zuidema, P., 2003: Convective clouds over the Bay of Bengal. Mon. Wea. Rev., 131 , 780798.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 472 262 18
PDF Downloads 423 252 14

Diurnal Patterns of Rainfall in Northwestern South America. Part III: Diurnal Gravity Waves and Nocturnal Convection Offshore

View More View Less
  • 1 NOAA–CIRES Climate Diagnostics Center, Boulder, Colorado
  • | 2 Program in Atmospheric and Oceanic Sciences, University of Colorado, and Research Applications Program, National Center for Atmospheric Research,* Boulder, Colorado
Restricted access

Abstract

Afternoon/evening near-coastal convection over land is easily understood as a response to solar heating of the land, turbulent transfer of heat and moisture to the boundary layer, and lifting of air by vigorous sea-breeze fronts. Subtler processes apparently underlie the late night and morning convection that is prevalent over coastal waters throughout the Tropics. Sensitivity tests using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), and further diagnoses of the control run described in Part II, are used to explore these processes.

Prior studies have speculated that “land-breeze” circulations, analogous but opposite to the sea breeze, drive offshore convection at night. However, nighttime radiative cooling of land and the associated thermal breezes are much weaker than the corresponding daytime processes, especially under humid tropical skies. Analysis of model mean soundings reveals that modest (fractions of a degree Celsius) temperature changes near the 800-hPa level change the sign of the buoyancy of low-level air, from negative (inhibited) to positive (convecting) after about midnight in the coastal zone. These diurnal temperature changes are seen to be signatures of a diurnal gravity wave with a propagation speed of ∼15 m s−1, similar to the speed of motion of the diurnal seaward sweep of convection seen in satellite data as well as in the model. This wave radiates from the diurnally oscillating heat source of the daytime mixed layer, raised up into the stratified layers of the atmosphere by elevated terrain. A surprising finding is that the model mean rainfall field is almost the same in a simulation without diurnally varying solar radiation.

Corresponding author address: Brian Mapes, CIRES, 216 UCB, Boulder CO 80309-0216. Email: bem@cdc.noaa.gov

Abstract

Afternoon/evening near-coastal convection over land is easily understood as a response to solar heating of the land, turbulent transfer of heat and moisture to the boundary layer, and lifting of air by vigorous sea-breeze fronts. Subtler processes apparently underlie the late night and morning convection that is prevalent over coastal waters throughout the Tropics. Sensitivity tests using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), and further diagnoses of the control run described in Part II, are used to explore these processes.

Prior studies have speculated that “land-breeze” circulations, analogous but opposite to the sea breeze, drive offshore convection at night. However, nighttime radiative cooling of land and the associated thermal breezes are much weaker than the corresponding daytime processes, especially under humid tropical skies. Analysis of model mean soundings reveals that modest (fractions of a degree Celsius) temperature changes near the 800-hPa level change the sign of the buoyancy of low-level air, from negative (inhibited) to positive (convecting) after about midnight in the coastal zone. These diurnal temperature changes are seen to be signatures of a diurnal gravity wave with a propagation speed of ∼15 m s−1, similar to the speed of motion of the diurnal seaward sweep of convection seen in satellite data as well as in the model. This wave radiates from the diurnally oscillating heat source of the daytime mixed layer, raised up into the stratified layers of the atmosphere by elevated terrain. A surprising finding is that the model mean rainfall field is almost the same in a simulation without diurnally varying solar radiation.

Corresponding author address: Brian Mapes, CIRES, 216 UCB, Boulder CO 80309-0216. Email: bem@cdc.noaa.gov

Save