A RAPIDLY RELOCATABLE VERSION OF THE POM

1. A RAPIDLY RELOCATABLE VERSION OF THE POM Germana Peggion USM/COAM peggion@ssc.usm.edu Daniel N. Fox Naval Research Laboratory fox@nrlssc.navy.mil http://www7320.nrlssc.navy.mil/modas S. Diego leo Initialization La Jolla (Spikes are in the raw data) • Default : cold start from MODAS with wind at -24/48hrs to build the ML. Robust, but less accurate. Everyday starts from scratch. • Diagnostic + warm start (unstable density points & turbulence scheme) • Restart from previous nowcast (not POM’s restart procedure) Los Angeles Atl. City St. Monica Day0 M0* N0*  F1  F2 M0+BC Day1 Y0  N1*  F2  F3 M1+BC Day2 Y1  N2*  F3  F4 M2+BC Cloud coverage Clear day The variability of coastal areas makes it difficult to assimilate into MODAS nowcast knowledge of the ocean's past state. For persistent cloud coverage, MODAS fields may tend to relax toward climatology. An initialization from NRLPOM solution may alleviate the problem. Static Clim. Dynamic Clim. LEO15 So California tidal circulation Hr 00 Hr 06 GOM Panama City Hr 12 Hr 18 Pensacola S. California residual tidal circulation (SSH) 1-day long-run forecasting sequence MODAS-NRLPOM @ Monterrey Bay a b c 26km 6km 1.5km Tides Model salinity SST NCOM provides BC for the regional model (no tides) that provides BC to the coastal model (with tides) MODAS-NRLPOM is a scalable, portable, and rapidly relocatable system for nowcast and short-term (2-day) forecast simulations. The system is routinely applied at the Naval Oceanographic Office (NAVO) in several areas and configurations ranging from basin-scale to inlets, from deep to coastal domains, from open-sea to semi-enclosed areas. There are two major components: 1) the Modular Ocean Data Assimilation System (MODAS) to generate a nowcast field to initialize 2) the Naval Research Laboratory Princeton Ocean Model (NRLPOM). The system is designed to find the optimal configuration with the available data to provide good solutions everywhere. The approach is quite different from most of the research application designed to findthe configuration forthebest solution for a given problem. • MODASis a static and dynamic climatology for production of 3-D nowcast temperature, T, and salinity, S, fields. • The static climatology represents historical averages • The dynamic climatology assimilates multiple data type with heavy reliance on remotely sensing data for area coverage • 3) Physical Accuracy • Initialization • - cold/warm/diagnostic • - restart from previous runs • Tides (forcing from Grenoble model) • - SSE at the boundary and/or geopotential • Boundary Conditions (always in progress !) • - radiation+relaxation (not conservative) • - coupling with other models • NRLPOMprincipal attributes are: • 1) Portability • C-preprocessor (double/single precision) • allocated memory • makefiles with compiler options • toward PC rather than HPC • Tested on Sgi-O2K, Sun platforms • Real time applications • Rapid configuration (<6hrs). • NRLPOM models executed with copies • of the same executable • - different namelist files • No data are assimilated after nowcast. • 2) User-Friendly Interface • Parameters and Flags in Namelist files, consistent with MODAS input • Namelist User (initialization, data files, configuration) • Namelist Expert (model parameters) • Namelist Levels (sigma coordinates) • Namelist Savedata (simulated tide gauges, buoys, moorings, transport values) NRLPOM Open Boundary Conditions Tides • Summary • MODAS is successful in deep/opensea • altimetry and SST are ‘reliable’ • (high correlation between surface and • subsurface features) • data are available on spatial/temporal • scales order of the dominant features • MODAS in shallow/coastal waters: • altimetry not reliable over h<200m • SST may not be available at right frequency • SST processed at 1/8º resolution (to coarse) • time & spatial scale of coastal dynamics • Working Hypothesis • MODAS field is accurate to allow NRLPOM to: • spin up the physics • provide a better nowcast • incorporate NRLPOM nowcast as nowcast • delivered product • Flather BC requires both elevation & velocity. • There exists a clamped tide solution. • SSE from Grenoble model (updated each baroclinic time step) • zero reference tide velocities • at OBC: SSE nudged to Grenoble SSE: • n+1 =(1-a) POM+ a GR • a= 3-6 hrs nudging time scale • No 1-way coupling to model with tides. • Radiation-like OBC requires reference boundary values. • Baroclinic component: from geostrophy • Barotropic values are missing: • No dynamic height in h<200m • No altimetry in coastal/shallow water • Use of other models • 1-way coupling • Only the barotropic field is necessary from other models • easy to implement • wide range of forcing models • - /z/hybrid/ coordinates Real Time Application The real-time exercise is taking place on the shelf and shelf-break off Honolulu. The model configuration is a triply-nested domain ranging approximately from 26km to 1.7km resolution. The plots illustrate the sensitivity of the innermost model to the wind forcing. Three wind data sets are compared with the wind stresses as computed from the buoy winds. The forecasted model velocities are compared with in situ measurements. A) NOGAPS wind stresses B) DAMPS_09 wind stresses C) Wind stresses computed from DAMPS_09 wind velocity. A B C