Asian Monsoon simulation and ENSO dynamics in the CMIP coupled models

I.-S. Kang¹ and K. M. Lau²

¹Climate Environment System Research Center, Seoul National University, Korea*

²NASA/Goddard Space Flight Center, USA

*Contact information:

In-Sik Kang

Professor and Director

Climate Environment System Research Center

Seoul National University

Seoul , 151-742 Korea

Tel: +82-2-880-6718

Fax: +82-2-885-7357

email: kang@climate.snu.ac.kr

n The present subproject has two objectives:

1. To study the role of the air-sea coupled processes on the Asian Monsoon simulation.

2. To study the ENSO simulations in the coupled GCMs and its dynamics.

- East Asia Monsoon

We found that the several atmospheric GCMs, prescribed observed SST, have a poor performance for the simulation of anomalous Asian summer precipitation patterns (Kang et al. 2002; Wang et al. 2003). The models’ deficiency results from failing to simulate correctly the relationship between the local summer rainfall and SST anomalies over the warm pool region. The observed rainfall anomalies are negatively correlated with SST anomalies, whereas in nearly all atmospheric models, the rainfall anomalies are positively correlated with SST anomalies. This contrast implies that air-sea coupled processes play a critical role for the simulation of the East Asia Monsoon. Therefore, we will diagnose the Asian Monsoon simulation of the coupled GCMs, which include air-sea coupled processes, and study the role of air-sea coupled processes on the monsoon simulation.

- ENSO Dynamics

Several simple paradigms, such as the delayed oscillator and recharge oscillator, were suggested to explain the observed characteristics of the ENSO and its oscillation dynamics. But, observational studies on the ENSO dynamics often encounter some difficulties in examining the related dynamics, because of poor data problem, for example, the decomposition of Ekman and geostropic currents, estimation of boundary reflection, and others. The simple theories are applicable to not only observation but also the coupled GCMs. Different coupled GCMs simulate ENSO with different frequencies and behaviors. To a large extent, the ENSO frequency and behaviors of the Coupled GCM are related to their basic states. It was also demonstrated that the tropical Pacific oscillation has a variety of time scales: near annual time scale, TBO, ENSO, and decadal oscillations. The coupled models show some similarity and discrepancies of tropical Pacific variations compared to the observations. We want to investigate the governing dynamics of tropical oscillations using exact data set of coupled models and investigate the common success and failure of the CMIP coupled models in simulating the observed tropical Pacific variations.

n Data Requirements

1. CMIP2+ atmosphere

§ Precipitation

§ Wind (zonal and meridional wind)

§ Geopotential height

§ temperature

§ wind stress

§ heat flux (latent, sensible, radiation and fresh water flux)

2. CMIP2+ ocean:

§ Temperature (including SST)

§ Oceanic current (zonal and meridional current)

§ Sea level