Daily simulation using the 3-dimensional atmosphere-ocean regional coupled model, CReSS-NHOES over the CINDY/DYNAMO observation region

To examine the structure and development processes of mesoscale convective systems (MCSs) over the tropical oceanic region, we have examined daily simulations over the tropical western Pacific Ocean during the PALAU2008 and PALAU2010, and over the tropical Indian Ocean during the MISMO2006 using a cloud-resolving model (Cloud Resolving Strom Simulator: CReSS) developed at Nagoya University, Japan. The CReSS model employed a slab-ocean scheme to simulate the vertical heat conductivity under the sea surface. In this scheme, temperature of sea water under the surface was prescribed by initial sea surface temperature (SST). Although release of sensible and latent heat flux from the sea surface forced to modulate SST distributions as well as temperature below the surface, it was unrealistic to provide the vertical profile of temperature of sea water using this method. It goes without saying that it is important to recognize the air-sea interaction to simulate convective activity realistically.

Recently, Non Hydrostatic Ocean model for the Earth Simulator (NHOES) is coupled with the CReSS model and the three-dimensional atmosphere-ocean coupled model named the CReSS-NHOES is developed. This study shows preliminary results applied on the daily simulations using the CReSS-NHOES over the CINDY/DYNAMO observation region.

Three types of sensitivity experiment are carried out to clarify the effect of the coupled model and horizontal grid resolutions over the array of the CINDY/DYNAMO region. One is the CReSS-NHOES two-way coupled simulation with horizontal grid spacing of 0.045 degree (approximately 4.8 km). Another two simulations are the CReSS simulations without coupling the NHOES with horizontal grid spacing of 0.045 and 0.0225 degrees (approximately 2.4 km). The Global Spectral Model (GSM: Horizontal grid resolution is about 50 km) data provided by Japan Meteorological Agency (JMA) are used as the initial and boundary conditions of the atmosphere in CReSS and CReSS-NHOES. Three-dimensional Navy Coastal Ocean Model (NCOM) data provided by Naval Research Laboratory are used as the initial and boundary conditions of the ocean in CReSS-NHOES. Daily simulation is carried out for 36 hours from 12 UTC every day.

Now we are accumulating the results of daily simulation. We reproduced the existence of low equivalent temperature airmass in the middle troposphere at the southeastern corner of the array: a fixed point of the R/V Mirai (80.5E, 8S) using CReSS in October. Also, relatively deep oceanic mixed layer depth with 60-80 m is reproduced at the same fixed point using CReSS-NHOES. We will analyze the reproduction of the atmospheric and oceanic fields, and heating profiles in comparison with the sounding observations in the array. We will apply a satellite simulator to validate the horizontal distributions of cloud properties in comparison with the satellite observations of FY2D-IR and TRMM.