Influence of Convective Momentum Transport on Influence of Convective Momentum Transport on Tropical WavesTropical Waves

Lei Zhou State Key Lab of Satellite Ocean Environment Dynamics, SIO, Hangzhou, ChinaIn-sik Kang School of Earth and Environmental Science, Seoul National University, Seoul, Korea

Overview

Motivation: The influence of the sub-grid process, i.e., the convective momentum transport, on tropical waves.

Method: A two-layer model and the analytical solutions

Data for verification: NCEP/NCAR reanalysis, OLR, TRMM precipitation

Conclusions: Three influences of the CMT on tropical waves, especially on the mixed Rossby gravity waves1. It is important for determining the meridional scale of the tropical wave guide;

2. It can lead to the instability of the mixed Rossby gravity waves

3. It can induce upscale momentum and energy transfer from the planetary-wave scale to the large scale.

II. Two layer model

Parameterization for latent heat release:

I. Introduction

IV. Influence of CMT on the mixed Rossby gravity waves

(Wang and Xie 1996)

The thermal dynamic equation becomes where

The gravity wave speed is

III. Analytical solutions to the two layer model

The equation with one unknown variable:

Assume a wave-like solution:

Dispersion relation:

where

1. Unstable mixed Rossby gravity waves due to CMT

2. Upscale momentum transfer due to CMT

Tropical waves are influenced by many factors, such as:

The factor that is focused on and our intention: Convective momentum transport (CMT), a sub-grid process

V. Indications of the CMT-induced unstable mixed Rossby gravity waves

1. Tropical two-day waves 2. Madden-Julian Oscillations

Contact: Lei ZhouContact: Lei ZhouEmail: lzhou@sio.org.cnEmail: lzhou@sio.org.cn