NCAR Technical Notes

The NCAR Technical Notes Collection comprises over 500 scientific and technical reports, issued by NCAR divisions and programs, and consists of data compilations, theoretical and numerical investigations, and experimental results.


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An Evaluation of the Rosemount Ice Detector for Aircraft Hazard Warning and for Undercooled Cloud Water Content Measurements
An Evaluation of the Rosemount Ice Detector for Aircraft Hazard Warning and for Undercooled Cloud Water Content Measurements
This report presents an evaluation of the Rosemount 871 ice detector for use as an aircraft hazard instrument and for determining liquid undercooled water content. Ice detector measurements are compared with those obtained by the more conventional heated-wire cloud water probe for -10��C stratus and -5��C cumulus icing events.
An Introduction to Atmospheric and Oceanographic Data
An Introduction to Atmospheric and Oceanographic Data
The purpose of this NCAR Instructional Aid (IA) is to serve as a "data-primer" for students and those in other fields of research who are interested in carrying out research involving the analyses of data in the atmospheric and oceanographic sciences. This IA will describe, in very general terms, the datasets most commonly used to study the atmosphere-ocean system and the formats used for archival. The datasets include observations from conventional meteorological sources such as stations and ships, from satellites, and analyzed grids produced at operational weather forecast centers. Detailed descriptions of instruments, methodologies and relative quality is not attempted. Rather, the focus is upon the broad characteristics of the data sources and the datasets. The characteristics not only include the observed variables and their spatial and temporal extent but also common problems, data limitations and sources of error. Datasets available from NCAR are used to illustrate typical archives. A bibliography containing selected references for each chapter provide the interested reader with more details. Atmospheric and oceanographic data are generally archived at data archiving and distribution centers. Addresses, both conventional and electronic, of several major data centers are provided. A discussion of the Internet includes how to find datasets using the World Wide Web. Finally, a list of commonly used abbreviations and acronyms is provided to familiarize newcomers with atmosphere/ocean jargon.
An Introduction to Genetic Algorithms for Numerical Optimization
An Introduction to Genetic Algorithms for Numerical Optimization
The paper is organized as follows. Section 1 establishes the distinction between local and global optimization and the meaning of performance measures in the context of global optimization. Section 2 introduces the general idea of a genetic algorithm, as inspired from the biological process of evolution by means of natural selection. Section 3 provides a detailed comparison of the performance of three genetic algorithm-based optimization schemes against iterated hill climbing using the simplex method. Section 4 describes in full detail the use of a genetic algorithm to solve a real data modeling problem, namely the determination of orbital elements of a binary star system from observed radial velocities. The paper closes in section 5 with reflections on matters of a somewhat more philosophical nature, and includes a list of suggested further readings.
An Introduction to the NCAR Data Storage System
An Introduction to the NCAR Data Storage System
This report is an introduction to the NCAR Data Storage System. The sections include discussions of storage on various devices and transfers of the data in a file during program execution. It is suggested to incorporate the reference manual to obtain an overall, complete understanding of the system.
An Introduction to the SCD Graphics System
An Introduction to the SCD Graphics System
This document represents the first in a series of manuals which collectively describe the Scientific Computing Division (SCD) Graphics System. Each manual in the series has been designed to provide users with complete and accurate information on how to use the SCD Graphics System. The authors and contributors to this series of documents hope that you will find the information helpful and that you will be able to make maximum use of the Graphics System for your own purposes.
An Overflow parameterization for the ocean component of the Community Climate System Model
An Overflow parameterization for the ocean component of the Community Climate System Model
The Overflow Parameterization (OFP) for the ocean component of the Community Climate System Model (CCSM) is presented. The ocean component is based on the Parallel Ocean Program Version 2, or POP2, of the Los Alamos National Laboratory (Smith et al., 2010). The OFP has two parts: the method of evaluating overflow properties based on ocean model state, and the modifications to the baroclinic and barotropic solutions to reflect the influence of the overflows. Evaluating overflow properties involves computing source water transport based on regional averages over an interior and source domain. The source overflow is implemented as a sidewall boundary condition on raised bottom topography, which replaces explicitly resolved overflow with the parameterized overflow. The parameterized overflow is assumed to flow through the ridge (implicitly) and to descend unmodified to an entrainment sidewall, where entrainment ambient water is mixed with the source water, producing the final product water. The product density is computed for the mix of source and entrainment waters, and the product injection position is found where neutral buoyancy occurs along a pre-specified product path. In POP2 the baroclinic and barotropic modes are split. Our approach is to solve the baroclinic equations without change but to modify the barotropic equation to include the effect of the parameterized overflows. We assume that the overflow sidewall velocities are total velocities at each time step, and this non-zero sidewall boundary condition is used to modify the barotropic continuity equation, as well as the vertical planar column velocities above each sidewall at source, entrainment and product locations so that local mass conservation is enforced. Overflow tracer advection is done through the source, entrainment and product sidewalls in a conservative manner. The POP2 implementation allows the user to select overflow source, entrainment and product locations and orientations. It allows for more than one product location so that the product depth can adjust to varying forcing. Various parameters can be adjusted, ideally within observational constraints, to yield overflow transports within observational uncertainties. The implementation method should be applicable to z-coordinate ocean models with the baroclinic/barotropic split as in POP2. For a thorough discussion of the climate impacts of OFP, see Danabasoglu et al. (2010).
An Overview of NCAR's Computing Environment
An Overview of NCAR's Computing Environment
The Scientific Computing Division is charged with providing computing support for research conducted by NCAR staff and for extending the computing resources of university atmospheric scientists beyond that which is otherwise available to them. The computing system within the SCD is comprised of a highly heterogenous set of hardware. This heterogeneity is partly a matter of function and partly of historical origin. The dissimilar elements of the system are integrated into a cohesive system by interfaces to two fifty-megabit per second communication channels which are the basis for the NCAR internal network. Configuration and performance details of all of the SCD hardware are given in Appendix A of this section of the User's Guide.
An Overview of the Scientific Computing Division
An Overview of the Scientific Computing Division
This document is an expanded revision of An Overview of NCAR's Computing Environment (NCAR/TN-177+IA). It contains a new chapter describing the various departments within SCD and the major components of the SCD computing systems, as well as three appendices containing technical information for the interested reader. The other chapters have been updated to include the latest information on subjects of interest to visitors and users of SCD's computing equipment.
Analysis of 1988 and 1989 Measurements of Stellar Spectra With the Lowell Observatory/High Altitude Observatory Solar-stellar Spectrograph
Analysis of 1988 and 1989 Measurements of Stellar Spectra With the Lowell Observatory/High Altitude Observatory Solar-stellar Spectrograph
Report on reducing spectral data to obtain useful measures of stellar activity which includes topics such as the Echelle Spectrograph Stellar Spectra, a summary of Solar Observations and associated conclusions/recommendations.

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