Sensitivity of Tropical Pacific Convection to Dry Layers at Mid- to Upper Levels: Simulation and Parameterization Tests

Abstract

Abstract Numerical forecast experiments are carried out to investigate the implications of observed moisture variability in the tropical Pacific for deep convection. The study uses a series of quasi-cloud-resolving model forecasts with a triple-nested version of the Naval Research Laboratory's Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). The forecasts are carried out for a dry tongue episode in the tropical western Pacific in November 1998. During a 24-h forecast, a number of convective cells develop in an area of deep convection near the edge of the simulated dry tongue in the COAMPS 3-km mesh inner grid, which is located in the southern portion of the domain of the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) field program. The forecast is repeated multiple times using a moisture profile from a TOGA COARE dry tongue episode to modify the lateral boundary conditions for the 3-km mesh grid over layers of varying depth and altitude. The entrai...