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The deformation response and recrystallization behavior of a coarse, columnar-grain superalloy ingot material, Waspaloy, with a <100> fiber texture were established. For this purpose, isothermal hot compression tests were performed on cylindrical and doublecone samples at supersolvus temperatures under both monotonic (constant strain rate) and multi-hit conditions. Plastic flow showed a noticeable dependence on test direction relative to the columnar-grain orientation; the observed anisotropy in peak flow stress and flow softening were explained on the basis of the evolution of crystallographic texture during recrystallization. Similarly, anisotropy in dynamic recrystallization kinetics with respect to test direction was interpreted in terms of the effect of initial texture on the plastic work imposed per increment of macroscopic strain. Nevertheless, the broad kinetics for the coarse-grain, ingot material deformed under both monotonic and multi-hit conditions were comparable to those previously measured for fine-grain, wrought Waspaloy. Such an effect was attributed to the beneficial influence of the nucleation of recrystallization at both grain boundaries and carbide particles in the ingot material. In addition, a spatial non-uniformity in recrystallization was found in the ingot material and was interpreted in the context of the grain-boundary character and non-uniform strain at the grain/intragrain scale. A suite of tools being developed to model recrystallization phenomena during the breakdown of superalloy ingots is described. These tools include a mechanistic cellular automata; a mesoscale, mechanism-based model; and the crystal-plasticity finite-element method., Conference paper published in Materials Science Forum, v550 p129-140, 2007. Prepared in collaboration with Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/ML), Wright-Patterson AFB, OH. Prepared in cooperation with Universal Technology Corporation, Dayton, OH.

The goal of this study is to assess models for Deep Convection with special emphasis on their use in coarse resolution ocean general circulation models. A model for deep convection must contain both vertical transport and lateral advection by mesoscale eddies generated by baroclinic instabilities. The first process operates mostly in the initial phases while the second dominates the final stages. Here the emphasis is on models for vertical mixing. When mesoscales are not resolved, they are treated with the Gent and McWilliams parameterization. The model results are tested against the measurements of Lavender, Davis and Owens, 2002 (LDO) in the Labrador Sea. Specifically, we shall inquire whether the models are able to reproduce the region of "deepest convection," which we shall refer to as DC (mixed layer depths 800-1300m). The region where it was measured by Lavender et al. (2002) will be referred to as the LDO region., Pub. in Ocean Modelling, v7 p75-95, 2004.

The ability of the U.S. Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) (Trademark) to accurately forecast the height and structure of the Marine Boundary Layer (MBL) in the coastal zone is analyzed and compared to surface and aircraft observations from the Dynamics and Evolution of Coastal Stratus (DECS) field study conducted along the central coast of California from June 16 to July 22, 1999. The stratus field was found to have significant mesoscale variability within 100 km of the coast due to interaction between the mean flow and the coastal terrain. This structure is consistent with general hydraulic flow theory and the development of a low-level coastal jet. However, the specific characteristics on any given day were very sensitive to flow direction, inversion height, and synoptic conditions. With some modifications, the model predicted the general evolution of these events with qualitative fidelity, but was slow to dissipate the cloud and frequently produced surface fog versus stratus. A consistent tendency was found in the model's predictions of inversion heights 200-300 meters too low, weak inversion strengths, high integrated liquid water content, and weak buoyancy flux near the cloud top. These observed biases are consistent with underestimating the cloud top entrainment velocity and entrainment fluxes in the modeled boundary layer. An explicit entrainment parameterization was developed to better represent the sub-grid scale processes at cloud top and was tested in the single column and 3D versions of COAMPS. The entrainment parameterization was found to improve the boundary layer height and cloud liquid water content as compared to field observations, but the modeled boundary layer still exhibited a low bias, and the entrainment velocity was higher than is generally expected from field studies for this regime. (2 tables, 53 figures. 80 refs.), The original document contains color images.

The low-level jet along the coast of southern Oregon and California is examined in detail through an extensive data set and the application of COAMPS, a mesoscale model, for the purpose of improving forecasts in challenging littoral environments. The jet forms within the broad equatorward flow established by the pressure gradient between cool ocean and warm land. The inception of the jet along the coast is about 250 km south of the axis of a northeastward extension of the eastern North Pacific high, and the jet may extend equatorward and offshore for hundreds of kilometers. Wind magnitudes increase in association with a reorientation of the coastal surface pressure gradient such that an increased down-coast component exists. Within 200 kilometers of the coast, considerable diurnal and spatial variability are observed and predicted by the model. The frequently observed low-level high wind areas at specific locations along the coast are caused by the combined effects of supercritical expansion within the boundary layer and mountain wave-type flow above the marine layer over six coastal mountain areas in close proximity to the coast. While the expansion fan effects are localized near a coastal bend, it is the offshore extension of the mountain wave that accounts for the large spatial extent of the maximum wind areas offshore., The original document contains color images.

As mesoscale models increase in resolution there is a greater need to understand predictability on smaller scales. The predictability of a model is related to forecast skill. It is possible that the uncertainty of one scale of motion can affect the other scales due to the nonlinearity of the atmosphere. Some suggest that topography is one factor that can lead to an increase of forecast skill and therefore predictability. This study examines the uncertainty of a mesoscale model and attempts to characterize the predictability of the wind field. The data collected is from the summer, when the synoptic forcing is relatively benign. Mesoscale Model 5 (MM5) lagged forecasts are used to create a three- member ensemble over a 12-hour forecast cycle. The differences in these forecasts are used to determine the spread of the wind field. Results show that some mesoscale features have high uncertainty and others have low uncertainty, shedding light on the potential predictability of these features with a mesoscale model. Results indicate that topography is a large source of uncertainty. This is seen in all data sets, contrary to other studies. The ability of the model to properly forecast the diurnal cycle also impacted substantially on the character and evolution of forecast spread. The persistent mesoscale features were represented reasonably well, however the detailed structure of these features had a fair amount of uncertainty., The original document contains color images.

[1] Marine air intrusion and subsequent cloud formation plays a dominant role in the energy budget and mass balance of the Antarctic. However, the intrusion is very difficult to understand using the ground-based measurements alone. In this paper we present simulations of marine air intrusion into the Adelie Land, East Antarctica, using the Modele Atmospherique Regional (MAR), for July 1994 and January 1995. The model is nested into the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. The simulations show a strong influence of large-scale disturbances, over the ocean, which helped in the penetration of marine air into the interior and the formation of clouds. Each marine air intrusion episode resulted in cloud formation in July 1994. Blocking anticyclones have also been found to be responsible for much of the moisture transport far into the interior elevated locations. MAR simulations, as well as ECMWF analyses, show influence of cyclones in strengthening and prolonging the surface layer flow. The study also indicated that the influence of depressions on surface winds is pronounced during the period when the depression is approaching the Adelie Land coast.

Mesoscale models are important, useful tools for analyzing and forecasting snail-scale atmospheric phenomena. Ideally, finer grid-point resolution should make a model more likely to capture realistic small-scale structure. Because these models work to resolve phenomena that exist on very fine spatial- and time-scales, they are subject to high variability. Accurate initialization of mesoscale models is crucial to skillful short-term forecasting. This study exercises four different initialization and model physics experiments of four nested MM5 forecast domains and examines their respective short-term (f03, f06, f09, f12) forecasts. The exceptionally rich meteorological data set taken from the Southern Coast Ozone Study of 1997 (SCOS97) provides the basis for our model verification. We show that 3km and 9k resolutions produce better forecasts than the 27km resolution model, however, differences between the 3km and 9km resolution forecasts are essentially insignificant. We also show that different model initializations and physics schemes have an insignificant impact on improving the absolute accuracy of the numerical forecasts produced by a non-hydrostatic mesoscale model.

Technological advances have made atmospheric mesoscale modeling at very fine resolutions readily available to a great number of organizations. Though initial operational results show some skill with respect to synoptic scale forecasts, many of the problems associated with mesoscale error growth and predictability have been ignored. Understanding mesoscale error is critical to accurately interpreting mesoscale model results and output from tactical decision aids (TDA's). This study examines mesoscale error growth and predictability through controlled numerical model experiments. A known "true" atmosphere is created through the use of the US Navy's Coupled Oceanographic/Atmospheric Mesoscale Prediction System (COAMPS). Virtual observations are randomly sampled from this atmosphere to provide data for ingest into forecasts using the NCARIPenn State MM5 mesoscale model. Forecast results for ten cases are compared against the "true" atmospheric solution and error statistics are calculated for wind speed and geopotential height fields. Results show how error growth and predictability are affected by different variables such as boundary conditions, weather regime, sample size and sample distribution. A scale separation of error is also performed in order to assess the impact of synoptic scale error on mesoscale error.

The results of the inorganic and organic analyses of aerosol samples collected on the east and west sides of Hong Kong during a dust episode (9-10 May 1996) are reported. The origin of the dust was traced to Northern China. The dust reached Hong Kong by way of the East China Sea. The characteristics of the inorganic elements and organic compounds were quite different from the non-episodic samples collected on 1-2 April 1996, EPD (Environmental Protection Department, Special Administrative Region, Hong Kong, China) results for April-May 1994, and our early studies (Zheng et al., 1997. Atmospheric Environment 31(2), 227-237.). Results from X-ray spectrometry showed pronounced increase in the relative abundance of Al, Fe, Ca, S and Cl in the dust samples compared to the non-episodic samples. The high abundance of Cl in the dust samples suggested the aerosols experienced long-range transport by way of the sea. ICP-MS analysis revealed higher concentrations of Fe, Ca, S and Pb in the episodic samples relative to the values measured during April-May 1994 by EPD. The high Ca content in the soil samples is a characteristic of northern Chinese crustal material (Liu et al., 1985). Hong Kong aerosols are characterized by high octadecenoic acid concentration due to heavy urbanization and Chinese-style stir-fry cooking. A much lower C-18 : 1/C-18 : 0 ratio was found in the episodic samples, however, suggesting the aerosols were transported from a long distance. The high ratio of greater than or equal to C-20/ < C-20 in n-alkanoic acids, the high input of n-alkanes and n-alkanols from plant waxes, and the unusually similar distribution of the organic compounds in the east and west samples suggested the existence of non-local sources on 9-10 May 1996. The compositions and distributions of lipids in the aerosol samples collected during the episode corresponded well with those of the eolian dust samples over the Atlantic and Pacific Oceans. Back trajectories and low altitude (< 3 km

On 25 August a controlled burn on the former Fort Ord property raged out of control. The sea breeze was responsible for transporting the acrid smoke into the Salinas Valley. The PSUINCAR mesoscale model, MMS, was run at 4 km grid resolution twice using two different PBL schemes (MRF and Burk-Thompson) and then verified by observations from several local mesoscale networks, including wind profiler data. The MM5 simulation was able to depict the 3-D structure of the sea breeze and differentiate between the local mountain- valley forcing and the large-scale sea breeze forcing. These two individual forcing mechanisms were responsible for an observed double surge in the time series of winds at Fort Ord. Further investigation is needed into the surface parameterization/land use tables to improve the surface forcing.

A meso-beta scale numerical model is described that is designed specifically for operational use on relatively small computers. A major aspect of the model is that it treats the boundary layer as a single model layer of known structure whose depth can evolve during the integration. The model equations are recast in a coordinate system, referred to as boundary-layer coordinates, based on the depth of the evolving boundary layer. The model described here does not include condensation processes, but it does include a radiation parameterization, schemes governing the structure of the stable and unstable boundary layers and the transitions between these regimes, and parameterizations for the fluxes of heat and moisture between the boundary layer and the earth's surface. Simulations have been carried out with a prototype model that has five layers and 20 km resolution in the fine grid mesh of its nested domain. The results of these simulations show that the model is capable of reproducing such mesoscale phenomena as mountain lee waves and the Florida sea-breeze circulation fairly well. Results are also presented of some preliminary simulations for the complex terrain of southern New England that demonstrate the need for carefully prepared terrain fields in numerical models.

Starting with computer code for a research model developed by Seitter and Colby (1992), initial steps were taken to make the model a real-time forecasting tool. Several procedures are required to initialize and run the model from real data. The code to automate this process has been written and tested. In addition, an error condition in the interactive nesting region related to terrain has been corrected.

In this thesis a vertical, two dimensional, grid-point mesoscale model is developed, using the equations of motion and thermodynamics in a dry flow. A non-dimensional vertical coordinate s is used. The hydrostatic assumption is made. To avoid the sensitivity of the continuity equation, several derived equations are used based on the first law of thermodynamics, the pressure tendency equation, and the top boundary condition, which was that the vertical motion was zero at the top boundary. These derived equations include the equation for prediction of density, Richardson's equation for vertical motion, and the pressure tendency at the top of the model. A simplified calculation of dry, subgrid convection is made to prevent instability. The equations are integrated using explicit finite differences with a time step of 2 minutes.

This study investigates the feasibility of using a high resolution simple diagnostic model (WOCSS) initialized from a coarser grid full physics prognostic model (COAMPS) to obtain mesoscale winds. This approach using COAMPS 81, 27, and 9 km forecast model soundings to initialize WOCSS at 3 km is compared to COAMPS forecast at 3km horizontal resolution alone. Four case studies were collected during various weather regimes in Central California. Observations were collected from 5 different agencies and were used for verification of the models. The sensitivity of various WOCSS parameters were also explored. The results showed that overall the COAMPS(9km)/WOCSS approach provides winds as good as COAMPS at 3 km at a greatly reduced computation time. The COAMPS/WOCSS methodology performed particularly well during non-frontal situations where low-level inversions were present. Separation of the surface observation data by agency revealed large errors from data networks with low maintenance, monitoring and site specifications standards. The highest flow surface in WOCSS was the only parameter that displayed any significant sensitivity. Further work is needed to test the advantages of this sensitivity. COAMPS/WOCSS mesoscale forecast winds may prove to be very useful as input to emergency response applications such as dispersion and trajectory modeling., http://archive.org/details/performanceofhig109455242, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

The low-level jet along the coast of southern Oregon and California is examined in detail through an extensive data set and the application of COAMPS, a mesoscale model, for the purpose of improving forecasts in challenging littoral environments. The jet forms within the broad equatorward flow established by the pressure gradient between cool ocean and warm land. The inception of the jet along the coast is about 250 km south of the axis of a northeastward extension of the eastern North Pacific high, and the jet may extend equatorward and offshore for hundreds of kilometers. Wind magnitudes increase in association with a reorientation of the coastal surface pressure gradient such that an increased down-coast component exists. Within 200 kilometers of the coast, considerable diurnal and spatial variability are observed and predicted by the model. The frequently observed low-level high wind areas at specific locations along the coast are caused by the combined effects of supercritical expansion within the boundary layer and mountain wave-type flow above the marine layer over six coastal mountain areas in close proximity to the coast. While the expansion fan effects are localized near a coastal bend, it is the offshore extension of the mountain wave that accounts for the large spatial extent of the maximum wind areas offshore., http://archive.org/details/thecalifornicoas109459873, Lieutenant Commander, United States Navy, Approved for public release; distribution is unlimited.

This research focuses on the evaluation of a mesoscale model in simulating coastal sea-breeze circulations. Measurements for this purpose were made from a mesonetwork consisting of 36 towers and five Doppler Wind Profilers as part of the Weather Information Network Display System at Cape Canaveral Air Force Station, Florida. The tower measurements provides observations of wind, temperature, and humidity from at least one level on each tower, while 17 of the towers have two common levels that allow calculations of surface momentum flux and sensible and latent heat fluxes. For this research, two five-day periods are chosen for analyses and model verification of temporal and spatial variability of sea breeze circulations against high-resolution simulations from the U.S. Navys Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPSTM). In addition to traditional statistical method of model evaluation, this research also evaluated how the error statistics vary spatially relative to distance from the coastline, an unprecedented approach to studies in this region. Results from this study suggests general adequacy of COAMPSTM in simulating the diurnal variation of the sea breeze circulation. However, significant errors result in some of the variables, such as surface fluxes., http://archive.org/details/mesoscalesimulat1094532874, Captain, United States Air Force, Approved for public release; distribution is unlimited.

Performance of high resolution mesoscale models has been in a continuous state of refinement since their inception. Mesoscale models have become quite skillful in forecasting synoptic scale events such as mid-latitude cyclones. However, atmospheric forcing becomes a much more complicated process when faced with the challenge of forecasting near topography along the coastline. Phenomena such as gap flows, blocked flow winds and low level stratification become important to predictability at these scales. The problem is further complicated by the dynamics of a frontal passage event. The skill of mesoscale models in predicting these winds is not as well developed. This study examines several forecasts by the Coupled Ocean Atmospheric Mesoscale Prediction System (COAMPS) during frontal passage events for the Winter of 2003-2004. An attempt is made to characterize the predictability of the wind speed and direction both before and after frontal passage along the California coast. Synoptic forcing during this time is strong due to the effects of the mid-latitude cyclones propagate across the Pacific. The study's results indicate that the wind field predictability is subject to several consistent errors associated with the passage of fronts over topography. These errors arise due to difficulty in the model capturing weak thermal advection events and topographic wind funneling. The deficiencies in model representation of topography contributes to these errors., http://archive.org/details/evaluationofcoam109452281, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

The ability of the U.S. Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) (Trademark) to accurately forecast the height and structure of the Marine Boundary Layer (MBL) in the coastal zone is analyzed and compared to surface and aircraft observations from the Dynamics and Evolution of Coastal Stratus (DECS) field study conducted along the central coast of California from June 16 to July 22, 1999. The stratus field was found to have significant mesoscale variability within 100 km of the coast due to interaction between the mean flow and the coastal terrain. This structure is consistent with general hydraulic flow theory and the development of a low-level coastal jet. However, the specific characteristics on any given day were very sensitive to flow direction, inversion height, and synoptic conditions. With some modifications, the model predicted the general evolution of these events with qualitative fidelity, but was slow to dissipate the cloud and frequently produced surface fog versus stratus. A consistent tendency was found in the model's predictions of inversion heights 200-300 meters too low, weak inversion strengths, high integrated liquid water content, and weak buoyancy flux near the cloud top. These observed biases are consistent with underestimating the cloud top entrainment velocity and entrainment fluxes in the modeled boundary layer. An explicit entrainment parameterization was developed to better represent the sub-grid scale processes at cloud top and was tested in the single column and 3D versions of COAMPS. The entrainment parameterization was found to improve the boundary layer height and cloud liquid water content as compared to field observations, but the modeled boundary layer still exhibited a low bias, and the entrainment velocity was higher than is generally expected from field studies for this regime. (2 tables, 53 figures. 80 refs.) ANNOTATION: The Role of Cloud-Top Entrainment in Coastal Stratocumulus-Topped Boundary Layer, http://archive.org/details/coastalstratocum109459928, Lieutenant Commander, United States Navy, Approved for public release; distribution is unlimited.

On 25 August a controlled burn on the former Fort Ord property raged out of control. The sea breeze was responsible for transporting the acrid smoke into the Salinas Valley. The PSUINCAR mesoscale model, MMS, was run at 4 km grid resolution twice using two different PBL schemes (MRF and Burk-Thompson) and then verified by observations from several local mesoscale networks, including wind profiler data. The MM5 simulation was able to depict the 3-D structure of the sea breeze and differentiate between the local mountain- valley forcing and the large-scale sea breeze forcing. These two individual forcing mechanisms were responsible for an observed double surge in the time series of winds at Fort Ord. Further investigation is needed into the surface parameterization/land use tables to improve the surface forcing., http://archive.org/details/acasestudyofmont109458057, Civilian, Naval Postgraduate School, Approved for public release; distribution is unlimited.

This report describes the results of a one-year program to gather meteorological data at Vandenberg AFB, CA. The purpose of the program was to obtain data that would allow characterization of the mean flow and turbulence in complex terrain. One full year of data, 24 hours a day, was obtained so that the full range of meteorological conditions at the site would be experienced and to establish statistical validity. The principal goal of the study is to characterize the turbulence, providing a data base for modeling diffusion in complex terrain. Immediate applications being addressed are: Space Shuttle exhaust hazard, site specific diffusion at Vandenberg, and generic features of flow and turbulence in complex, coastal terrain. Because the data may ultimately be used for modeling a wide variety of situations, such as continuous plumes, burst releases, rocket exhaust, the data acquisition procedures must be well designed. Specifically, sampling must be done so that the full range of the turbulence spectrum that is important for all types of diffusion is acquired. The purpose of this report is to describe the status of the data that has been obtained and to outline how to use it. Auxiliary data has been obtained and several analyses have been performed. These are also described., U.S. Air Force, Space Division, Funding number: N00244-07-1-0017., Approved for public release; distribution is unlimited.

Several issues associated with grid resolution and the sub-grid scale (SGS) parameterizations in a mesoscale model are addressed in this study. Of particular concern is the issue concerning increasingly high-resolution mesoscale atmospheric numerical models in that sub-grid scale parameterization of atmospheric processes becomes unclear when the grid resolution becomes comparable to the length scale of the phenomenon. These issues are studied through the careful analysis of in situ data and mesoscale model testing. In this study, we perform observational analysis to better understand the scales of turbulence in various environmental conditions. We then explore the capability of the U.S. Navy's current Coupled Ocean-atmosphere Mesoscale Prediction System (COAMPS(tm)), using a real case study of a cold air outbreak over the Japan/East Sea. We analyze the model's ability to perform accurately within the resolvable scales and to accurately represent the boundary layer turbulence mixing when the resolution is high. Based on results from the above analysis, we modify the existing parameterizations towards more realistic representations of the turbulent processes over a relatively wide range of grid resolution, and test this modification within COAMPS(tm)., http://archive.org/details/turbulenceparame109459835, Lieutenant Commander, United States Navy, Approved for public release; distribution is unlimited.