Thermodynamic characteristics of air flowing into and out of precipitating convection over the west Pacific warm pool

Abstract

AbstractAircraft data from the Tropical Ocean/Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment (TOGA‐COARE) indicate the validity of current conceptual models used in cumulus parametrization theories. This study makes use of 1 s (˜ 100m) measurements of temperature, dew‐point temperature and pressure taken along the aircraft flight tracks and airborne radar data. The radar data are used to determine the location, depth and horizontal extent of the convection and to categorize the thermodynamic data according to whether the measurements were obtained in precipitation areas or in regions of inflow to convection.Inflow regions had the highest values of equivalent potential temperature (θe), both in the boundary layer and lower free atmosphere, where the convection was deepest and most horizontally extensive, implying a relationship of θe to both the depth and breadth of convection. The observations suggest that the thickness of the layer of high‐θe air may determine the sustainability and, therefore, the horizontal extent of warm‐pool convection. The spectrum of values of θe in the boundary layer of inflow regions was broad, indicating that the field of θe was highly non‐uniform at the 1 s (˜100m) scale sampled by the aircraft.The boundary‐layer air in precipitating regions also exhibited a broad spectrum of θe values, indicating the presence of both outflow from downdraughts and a significant amount of air with characteristics similar to inflow regions. The lowest values in the distribution were about 345 K, suggesting that air parcels transported down into the boundary layer originated from no higher than about 1500 m, or that they underwent substantial mixing.