Rawinsonde Budget Analyses during the TOGA COARE IOP

William M. Frank Department of Meteorology, The Pennsylvania Stage University, University Park, Pennsylvania

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Houjun Wang Department of Meteorology, The Pennsylvania Stage University, University Park, Pennsylvania

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John L. McBride Bureau of Meteorology Research Centre, Melbourne, Victoria, Australia

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Abstract

During the 120 days of the TOGA COARE intensive observation period, there was an enhanced network of rawinsonde stations covering a large portion of the equatorial West Pacific. These soundings were of sufficient quality and frequency to permit computation of line integral beat and moisture budgets over a variety of large-scale arrays. In this study an enhanced operational dataset is used to compute rainfall, surface beat, and moisture fluxes, and vertical profiles of diabatic and/or subgrid-scale heating and moistening over these arrays.

Time series of daily rainfall computed from beat and moisture budgets are presented over seven arrays, including the intensive flux array, outer sounding array, and large-scale array. Vertical profiles of apparent beat source and apparent moisture sink are analyzed and presented for different arrays and for different rainfall rates.

The mean budget-derived rainfall ranged from 4 to 12 mm day−1 over the various arrays, with the most rain occurring within the intensive flux array and the least over Papua New Guinea. Correlations between convective indicators, low-level winds, and surface fluxes indicate that convection tends to precede or be coincident with increased surface fluxes in the more active regions south of the equator but not in the less convectively active regions.

Convective heating in this region tends to be vertically distributed in a dominant single mode, apparently a characteristic blend of convective and stratiform rain heating, with a broad peak in the midtroposphere around 400–500 mb. This distribution varies surprisingly little from day to day or with rainfall intensity. In contrast, convection over Papua New Guinea differs from the maritime convection. The convection over this large island produces more beating at upper-tropospheric levels than does the surrounding maritime convection. This indicates a fundamental difference between maritime and island rainfall that may well have significant effects on global-scale circulations.

Abstract

During the 120 days of the TOGA COARE intensive observation period, there was an enhanced network of rawinsonde stations covering a large portion of the equatorial West Pacific. These soundings were of sufficient quality and frequency to permit computation of line integral beat and moisture budgets over a variety of large-scale arrays. In this study an enhanced operational dataset is used to compute rainfall, surface beat, and moisture fluxes, and vertical profiles of diabatic and/or subgrid-scale heating and moistening over these arrays.

Time series of daily rainfall computed from beat and moisture budgets are presented over seven arrays, including the intensive flux array, outer sounding array, and large-scale array. Vertical profiles of apparent beat source and apparent moisture sink are analyzed and presented for different arrays and for different rainfall rates.

The mean budget-derived rainfall ranged from 4 to 12 mm day−1 over the various arrays, with the most rain occurring within the intensive flux array and the least over Papua New Guinea. Correlations between convective indicators, low-level winds, and surface fluxes indicate that convection tends to precede or be coincident with increased surface fluxes in the more active regions south of the equator but not in the less convectively active regions.

Convective heating in this region tends to be vertically distributed in a dominant single mode, apparently a characteristic blend of convective and stratiform rain heating, with a broad peak in the midtroposphere around 400–500 mb. This distribution varies surprisingly little from day to day or with rainfall intensity. In contrast, convection over Papua New Guinea differs from the maritime convection. The convection over this large island produces more beating at upper-tropospheric levels than does the surrounding maritime convection. This indicates a fundamental difference between maritime and island rainfall that may well have significant effects on global-scale circulations.

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