Rain on small tropical islands

[1] A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997–2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow rather than elevated surface heating.

[1]  W. Boos,et al.  Dominant control of the South Asian monsoon by orographic insulation versus plateau heating , 2010, Nature.

[2]  Ronald B. Smith,et al.  Orographic Precipitation in the Tropics: Large-Eddy Simulations and Theory , 2009 .

[3]  A. Anders,et al.  Very high resolution precipitation climatologies from the Tropical Rainfall Measuring Mission precipitation radar , 2009 .

[4]  David B. Wolff,et al.  Comparisons of Reflectivities from the TRMM Precipitation Radar and Ground-Based Radars , 2009 .

[5]  Eric D. Maloney,et al.  The role of surface heat fluxes in tropical intraseasonal oscillations , 2008 .

[6]  T. Yasunari,et al.  Intraseasonal Variability in Diurnal Rainfall over New Guinea and the Surrounding Oceans during Austral Summer , 2008 .

[7]  Bin Wang,et al.  Diurnal Precipitation Regimes in the Global Tropics , 2008 .

[8]  E. Maloney,et al.  Surface Fluxes and Tropical Intraseasonal Variability: a Reassessment , 2008, 0805.1508.

[9]  Phillip B. Schafer,et al.  Orographic Precipitation in the Tropics: Experiments in Dominica , 2008 .

[10]  J. Qian,et al.  Why Precipitation Is Mostly Concentrated over Islands in the Maritime Continent , 2008 .

[11]  S. Sherwood,et al.  Resonant Response of Deep Convection to Surface Hot Spots , 2006 .

[12]  Kenneth P. Bowman,et al.  Comparison of TRMM Precipitation Retrievals with Rain Gauge Data from Ocean Buoys , 2005 .

[13]  G. Roe.  OROGRAPHIC PRECIPITATION , 2005 .

[14]  Jeffrey A. Jones,et al.  A Hybrid Surface Reference Technique and Its Application to the TRMM Precipitation Radar , 2004 .

[15]  E. Williams,et al.  Islands as miniature continents: Another look at the land-ocean lightning contrast , 2004 .

[16]  Christopher R. Williams,et al.  Uncertainties in Oceanic Radar Rain Maps at Kwajalein and Implications for Satellite Validation , 2004 .

[17]  Sulochana Gadgil,et al.  The Indian monsoon and its variability , 2003 .

[18]  Nobuhiro Takahashi,et al.  Four-year result of external calibration for Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) satellite , 2003, IEEE Trans. Geosci. Remote. Sens..

[19]  Ralph Ferraro,et al.  Next generation of NOAA/NESDIS TMI, SSM/I, and AMSR‐E microwave land rainfall algorithms , 2003 .

[20]  E. Williams,et al.  The physical origin of the land–ocean contrast in lightning activity , 2002 .

[21]  Katsuhiko Nishikawa,et al.  Development of precipitation radar onboard the Tropical Rainfall Measuring Mission (TRMM) satellite , 2001, IEEE Trans. Geosci. Remote. Sens..

[22]  Jeffrey A. Jones,et al.  Use of the Surface Reference Technique for Path Attenuation Estimates from the TRMM Precipitation Radar , 2000 .

[23]  Robert A. Houze,et al.  Comparison of Radar Data from the TRMM Satellite and Kwajalein Oceanic Validation Site , 2000 .

[24]  David A. Seal,et al.  The Shuttle Radar Topography Mission , 2007 .

[25]  K. Emanuel,et al.  Temperature profiles in radiative-convective equilibrium above surfaces at different heights , 1999 .

[26]  Thomas M. Smith,et al.  A High-Resolution Global Sea Surface Temperature Climatology for the 1961–90 Base Period , 1998 .

[27]  C. Kummerow,et al.  The Tropical Rainfall Measuring Mission (TRMM) Sensor Package , 1998 .

[28]  R. Houze,et al.  The natural variability of precipitating clouds over the western Pacific warm pool , 1998 .

[29]  Christian Kummerow,et al.  A simplified scheme for obtaining precipitation and vertical hydrometeor profiles from passive microwave sensors , 1996, IEEE Trans. Geosci. Remote. Sens..

[30]  Thomas M. Smith,et al.  A High-Resolution Global Sea Surface Temperature Climatology , 1995 .

[31]  M. Mcphaden,et al.  Estimating Rainfall in the Tropics Using the Fractional Time Raining. , 1994 .

[32]  J. Kutzbach,et al.  Sensitivity of Eurasian Climate to Surface Uplift of the Tibetan Plateau , 1993, The Journal of Geology.

[33]  Matthew McGranaghan,et al.  Rainfall Enhancement over the Hawaiian Islands , 1988 .

[34]  Y. Mahrer,et al.  On the effects of Islands' geometry and size on inducing sea breeze circulation , 1985 .

[35]  Peter J. Webster,et al.  Mechanisms of Monsoon Low-Frequency Variability: Surface Hydrological Effects , 1983 .

[36]  C. Dorman.  Comments on “Comparison of Ocean and Island Rainfall in the Tropical Pacific” , 1982 .

[37]  Frank D. Marks,et al.  Winter Monsoon Convection in the Vicinity of North Borneo. Part I: Structure and Time Variation of the Clouds and Precipitation , 1981 .

[38]  G. Holland,et al.  Diurnal Variations of Convection over the “Maritime Continent” , 1980 .

[39]  Robert W. Burpee.  Peninsula-Scale Convergence in the South Florida Sea Breeze , 1979 .

[40]  J. Neumann,et al.  A Theoretical Study of the Sea and Land Breezes of Circular Islands , 1974 .

[41]  L. B. Leopold.  THE INTERACTION OF TRADE WIND AND SEA BREEZE, HAWAII , 1949 .