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McCarren, D.

Publications and source records attributed to McCarren, D..

The Earth System Prediction Suite: Toward a Coordinated U.S. Modeling Capability

The Earth System Prediction Suite (ESPS) is a collection of flagship U.S. weather and climate models and model components that are being instrumented to conform to interoperability conventions, documented to follow metadata standards, and made available either under open-source terms or to credentialed users. Furthermore, the ESPS represents a culmination of efforts to create a common Earth system model architecture, and the advent of increasingly coordinated model development activities in the United States. ESPS component interfaces are based on the Earth System Modeling Framework (ESMF), community-developed software for building and coupling models, and the National Unified Operational Prediction Capability (NUOPC) Layer, a set of ESMF-based component templates and interoperability conventions. Our shared infrastructure simplifies the process of model coupling by guaranteeing that components conform to a set of technical and semantic behaviors. The ESPS encourages distributed, multiagency development of coupled modeling systems; controlled experimentation and testing; and exploration of novel model configurations, such as those motivated by research involving managed and interactive ensembles. ESPS codes include the Navy Global Environmental Model (NAVGEM), the Hybrid Coordinate Ocean Model (HYCOM), and the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS); the NOAA Environmental Modeling System (NEMS) and the Modular Ocean Model (MOM); the Community Earth System Model (CESM); and the NASA ModelE climate model and the Goddard Earth Observing System Model, version 5 (GEOS-5), atmospheric general circulation model.

54 ENVIRONMENTAL SCIENCES↗

Continuous wave cavity ring-down spectroscopy for velocity distribution measurements in plasma

We report the development of a continuous wave cavity ring-down spectroscopic (CW-CRDS) diagnostic for real-time, in situ measurement of velocity distribution functions of ions and neutral atoms in plasma. This apparatus is less complex than conventional CW-CRDS systems. We provide a detailed description of the CW-CRDS apparatus as well as measurements of argon ions and neutrals in a high-density (10{sup 9} cm{sup −3} < plasma density <10{sup 13} cm{sup −3}) plasma. The CW-CRDS measurements are validated through comparison with laser induced fluorescence measurements of the same absorbing states of the ions and neutrals.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Instability limits for spontaneous double layer formation

We present time-resolved measurements that demonstrate that large amplitude electrostatic instabilities appear in pulsed, expanding helicon plasmas at the same time as particularly strong double layers appear in the expansion region. A significant cross-correlation between the electrostatic fluctuations and fluctuations in the number of ions accelerated by the double layer electric field is observed. No correlation is observed between the electrostatic fluctuations and ions that have not passed through the double layer. These measurements confirm that the simultaneous appearance of the electrostatic fluctuations and the double layer is not simple coincidence. In fact, the accelerated ion population is responsible for the growth of the instability. The double layer strength, and therefore, the velocity of the accelerated ions, is limited by the appearance of the electrostatic instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗