Lucy F. Smedstad

Integrated Modeling of the Battlespace Environment

The goal of the Battlespace Environments Institute (BEI) is to integrate Earth and space modeling capabilities into a seamless, whole-Earth common modeling infrastructure that facilitates interservice development of multiple, mission-specific environmental simulations and supports battlefield decisions, improves interoperability, and reduces operating costs.

Real-time ocean data assimilation and prediction with global NCOM

The Naval Research Laboratory (NRL) at Stennis Space Center has developed a global implementation of the Navy Coastal Ocean Model (NCOM). Global NCOM encompasses the open ocean to 5 m depth in a curvilinear global model grid with 1/8 degree grid spacing at 45/spl deg/N, extending from 80/spl deg/S to a complete Arctic cap with grid singularities mapped into Canada and Russia. The model employs 40 vertical sigma-z levels, with sigma in the upper ocean and coastal regions, and z in the deeper ocean. The real-time system uses Navy Operational Global Atmospheric Prediction System (NOGAPS) 3-hourly wind stresses and heat fluxes. Operationally available sea surface temperature (SST) and altimetry (SSH) data are incorporated into NAVOCEANO Modular Ocean Data Assimilation System (MODAS) and Navy Layered Ocean Model (NLOM) analyses and forecasts of SSH and SST. These in turn are combined with the MODAS synthetic database to yield three-dimensional fields of temperature and salinity for assimilation into global NCOM. We describe the analysis and forecast system, present selected evaluations of the model performance, and discuss planned upgrades to the model and data assimilation methods.

Global river inflow with Navy Coastal Ocean Model

One of the primary concerns driving the development of U.S. Navy global models has been improved performance and nesting support in shelf and nearshore regions with short notice applicability anywhere on the globe. A global implementation of the Navy Coastal Ocean Model (NCOM) is a product of some of the efforts to meet this need. One purpose of Global NCOM is to provide a global capability for initializing, nesting, and evaluating fixed and relocatable coastal ocean models. In support of that objective, a database of river flow estimates is needed. Perry et al. (1996) provides a start with estimates of annual mean river discharges for 981 of the largest global rivers. However, many rivers exhibit a strong seasonal variability, which we would like to reflect in our ocean models. Through the use of multiple Internet sources and published data sets we have expanded on the Perry (1996) data to provide a global database of monthly mean river discharge and incorporated this data in global and nested NCOM runs. Where sufficient data is unavailable to construct monthly means, a seasonal cycle is imputed from nearby rivers and scaled to the appropriate annual mean. Real time discharge rates are routinely available for almost no rivers outside of the United States, so a monthly mean is likely to be the most appropriate estimate of real time flow for analyses and forecasts in most areas. The monthly river outflow can contribute to more accurate seasonal representation of areas near coastlines. Seasonality particularly affects the polar areas, where river outflow can become quite small during winter months and quite large during the summer melting season. Multiannual daily USGS observations for selected US rivers are used to quantify the improvement in estimation of daily flow by the monthly means versus a multiannual mean. Case studies examine the impact of river input into NCOM.

An Expansion of Glider Observation STrategies to Systematically Transmit and Analyze Preferred Waypoints of Underwater Gliders

The Glider Observation STrategies (GOST) system provides real-time assistance to ocean glider pilots by suggesting preferred ocean glider waypoints based on ocean forecasts and their uncertainties. Restrictions on waterspace, preferred operational areas, and other glider trajectories are also taken into account. Using existing operational regional Navy Coastal Ocean Model (RNCOM) output, demonstrations of glider waypoint calculation are ongoing in Navy operational areas. After the ocean forecast models and GOST components run at the Navy DoD Supercomputing Resource Center (Navy DSRC), GOST-suggested glider paths are transferred to the Glider Operations Center (GOC). The glider pilots at the GOC import this information into their Unmanned Systems Interface (USI), developed at the University of Washington, Applied Physics Laboratory (APL-UW) to evaluate the suggested glider paths, make adjustments, and update waypoints for the gliders. The waypoints being sent are visualized and analyzed using graphic capabilities to convey guidance uncertainty developed under a grant to the University of New Orleans (UNO) and added under the Environmental Measurements Path Planner (EMPath) system within GOST. USI forwards automatic messages from the gliders with recent glider location, speed, and depth to GOST for the next cycle. Over the course of these demonstrations, capabilities were added or modified including use of initial glider bearing, preferred path, refinement of glider turn frequency, correction of glider speed, and introduction of glider rendezvous locations. Automation has been added with help from the modeling group at the Naval Oceanographic Office (NAVOCEANO). GOST supports NAVOCEANO’s ongoing efforts to direct and recover gliders, to safely navigate in changing ocean conditions, and to provide feedback to improve ocean model prediction.

An interactive HTML ocean nowcast GUI based on Perl and JavaScript

Abstract We describe the use of Hyper Text Markup Language (HTML), JavaScript code, and Perl I/O to create and validate forms in an Internet-based graphical user interface (GUI) for the Naval Research Laboratory (NRL) Ocean models and Assimilation Demonstration System (NOMADS). The resulting nowcast system can be operated from any compatible browser across the Internet, for although the GUI was prepared in a Netscape browser, it used no Netscape extensions. Code available at: http://www.iamg.org/CGEditor/index.htm

An explicit grid-independent interpolation algorithm

We present an explicit interpolation method for ocean model initial conditions that avoids the grid dependence that is present when using explicit polynomial interpolation on gridded fields. In grid dependent algorithms, grid size changes artificially alter the influence distance. Optimal Interpolation (01) is theoretically preferred over other polynomial interpolation methods such as bi-linear interpolation because it avoids the above problems. But it can be computationally prohibitive, as it requires a large matrix solve to compute optimal multipliers (weights). With 01, the actual error gain is rarely significant. The method presented here is an inverse distance weighting (IDW) method originally developed for irregularly spaced data. Here we consider whether IDW performs as well as 01 when used to initialize an ocean model forecast. We developed an explicit linear-time IDW implementation. In contrast, 01 requires inverting a (usually) full, often ill-conditioned matrix. We found no degradation of one and two-week forecast skill, when compared to 01, in a realistic numerical simulation of the Gulf Stream Region in the North Atlantic, when initialized from quality assured data. In comparison, bi-linear interpolation on the same curvilinear computational grid degraded forecast skill to an