A coupled regional air-sea model, its performance and climate drift in simulation of the East Asian summer monsoon in 1998

Abstract

A regional climate model is coupled to a regional ocean model in this study, its performance in simulating the East Asian summer monsoon in 1998 is discussed, and the cold drift of the simulated sea-surface temperature (SST) that appears in the coupled model system and the reasons for its existence are found. The atmospheric component of the coupled model system is a regional climate model named P -σ RCM, and the oceanic component of the coupled model is based on the Princeton ocean model (POM). By simulation-to-observation comparison, it is shown that the coupled model has a certain ability to simulate the seasonal propagation of the monsoon rain belt, the associated low-level southwest wind and the western Pacific subtropical high from May to August in 1998. It can reproduce the East Asian summer monsoon onset during the third dekad of May and its evolution process after the onset. From the coupled simulation results, it is also found that the south-to-north inflow in the southern South China Sea (SCS) and the summer monsoon current to the south of Sri Lanka do not occur until after mid-May, indicating that the ocean surface currents in the SCS and the Bay of Bengal regions are closely related with the SCS summer monsoon. The coupled simulation results show some differences with the individual uncoupled P -σ RCM and POM. The obvious difference between the coupled and the uncoupled POM (also observation) is a cold tendency of simulated SST in the coupled model system. Two experimental groups are performed to investigate the reasons for the 'cold drift'. The results confirm that the 'cold drift' is mainly caused by the disagreement of the surface heat fluxes produced by the atmosphere model with those required by the POM. Therefore, a more accurate description and parameterization of the physical process in the atmosphere model is an important way to decrease the differences.

A review on regional dynamical downscaling in intraseasonal to seasonal simulation/prediction and major factors that affect downscaling ability

“…Recently, fully coupled atmosphere-ocean RCMs have been used for dynamic downscaling studies (e.g., Aldrian et al, 2005;Ren and Qian, 2005;Seo et al, 2007;Artale, et al, 2010;Ratnam et al, 2013). In general, these studies reported an improvement in dynamic downscaling due to coupled models.…”

Preliminary results of a regional air-sea coupled model over East Asia

“…Recently, efforts have been made to construct a RACM over East Asia. Ren and Qian [31] used a p-σ RCM coupling with the revised Princeton Ocean Model (POM) to simulate the summer monsoon. Yao and Zhang [32] developed a regional air-sea coupled climate model based on RegCM3 and POM to simulate the summer precipitation over China.…”

A regional ocean–atmosphere coupled model developed for CORDEX East Asia: assessment of Asian summer monsoon simulation

“…The major deficiency is that FROALS tends to underestimate the SST over the western North Pacific (WNP) north of 10°N, with the largest bias of approximately 2 °C. The cold biases of the simulated SST over WNP are the common biases in regional ocean-atmosphere coupled models (Ren and Qian 2005;Fang et al 2010;Zou and Zhou 2013a) and in many CMIP5 models (Fig. 3 in Song and Zhou 2014b).…”

“…Regional climate models (RCMs) have been widely used as a useful tool for regional climate studies (Giorgi and Mearns 1999;Leung et al 2003;Wang et al 2004b;Christensen et al 2007). In the past 10 years, many regional ocean atmosphere coupled models have been developed with focus on the South China Sea monsoon (Lu et al 2000), the East Asian monsoon (Ren and Qian 2005;Yao and Zhang 2010;Fang et al 2010;Cha et al 2016), the Indian monsoon (Ratnam et al 2009), and the western North Pacific monsoon (Zou and Zhou 2011, 2013a. However, no model has focused on the entire Asian monsoon.…”