ROMS in Alaska Waters

Kate Hedstrom, ARSC/UAFEnrique Curchitser, IMCS/Rutgers

August, 2007

Overview

• GLOBEC and related modeling– NEP runs so far– Forcing– Plans– Tides

• CCSM connection– CORE forcing, POP global ocean for

boundaries– Coupling underway at NCAR

The Model• ROMS ocean

– Coupled ecosystem models– Now with an adjoint and tangent linear for

data assimilation

• Ice model from Paul Budgell– EVP dynamics (Arakawa C grid)– Mellor-Kantha thermodynamics– Oceanic molecular sublayer under the ice

for improved behavior

NEP Implementation

• 10 km average horizontal resolution• Run1:

– 30 vertical layers– IC’s and BC’s from NPac– Daily fluxes from NCEP hindcast (modified)– 1996-2002, 1960-1970

• Run2:– 42 vertical layers– Six-hourly fluxes from Common Ocean-ice Reference

Experiments (CORE) reanalysis– IC’s and BC’s from CCSM (POP) forced by CORE– 1958-2004

Evaluation of Latest Simulation

• We are much happier with the heat fluxes from CORE

• Ice area seems quite realistic• Still could do better:

– Not enough fresh water input at the coast– Stratification in general isn’t quite right, will

perhaps be improved by tidal mixing– We want a shallower minimum depth

• We also need to add an ecosystem model for GLOBEC, plus need to test the new NEMURO implementation

Ice Area and Volume

Zoom In

Tides in the Bering Sea

• We have an effort underway to evaluate the tides in the model with Zigmunt Kowalik and Seth Danielson

• We started with the 4 km Bering Sea domain in 2-d with four tidal constituents

• We are ultimately interested in the complex 3-d structure

CCSM Coupling

• Thanks to the CORE group’s products, we no longer need to run the large NPAC domain (proof of one-way coupling)

• The CCSM model does fine for its resolution, but fails in regions needing more resolution (coastal upwelling)

• The idea is to couple ROMS to CCSM, where ROMS is part of a “composite ocean” providing a better sea surface temperature to the atmosphere

CCSM

CCSM Strategy

• The coupling interval is one day, with the atmosphere running ahead

• The composite ocean will receive hourly winds, etc. and interpolate to ROMS grid(s)

• POP runs for that day, sends “curtains” out for ROMS nests

• ROMS runs for that day• Composite ocean merges SST from POP and ROMS for CAM

Conclusions

• We are excited about this opportunity to work with the CCSM group

• A similar effort is underway to add WRF as a regional atmospheric model

• One of the people we’ve been working with is on the ESMF team at NCAR and wants to make a standalone ESMF-ready version of ROMS