Evaluation of the 29-km Eta Model. Part I: Objective Verification at Three Selected Stations

A subjective evaluation of the National Centers for Environmental Prediction 29-km (meso-) eta model during the 1996 warm (May-August) and cool (October-January) seasons is described. The overall evaluation assessed the utility of the model for operational weather forecasting by the U.S. Air Force 45th Weather Squadron, National Weather Service (NWS) Spaceflight Meteorology Group (SMG) and NWS Office in Melbourne, FL

Evaluation of the 29-km Eta Model for Weather Support to the United States Space Program

The Applied Meteorology Unit (AMU) conducted a year-long evaluation of NCEP's 29-km mesoscale Eta (meso-eta) weather prediction model in order to identify added value to forecast operations in support of the United States space program. The evaluation was stratified over warm and cool seasons and considered both objective and subjective verification methodologies. Objective verification results generally indicate that meso-eta model point forecasts at selected stations exhibit minimal error growth in terms of RMS errors and are reasonably unbiased. Conversely, results from the subjective verification demonstrate that model forecasts of developing weather events such as thunderstorms, sea breezes, and cold fronts, are not always as accurate as implied by the seasonal error statistics. Sea-breeze case studies reveal that the model generates a dynamically-consistent thermally direct circulation over the Florida peninsula, although at a larger scale than observed. Thunderstorm verification reveals that the meso-eta model is capable of predicting areas of organized convection, particularly during the late afternoon hours but is not capable of forecasting individual thunderstorms. Verification of cold fronts during the cool season reveals that the model is capable of forecasting a majority of cold frontal passages through east central Florida to within +1-h of observed frontal passage

An Extended Objective Evaluation of the 29-km Eta Model for Weather Support to the United States Space Program

This report describes the Applied Meteorology Unit's objective verification of the National Centers for Environmental Prediction 29-km eta model during separate warm and cool season periods from May 1996 through January 1998. The verification of surface and upper-air point forecasts was performed at three selected stations important for 45th Weather Squadron, Spaceflight Meteorology Group, and National Weather Service, Melbourne operational weather concerns. The statistical evaluation identified model biases that may result from inadequate parameterization of physical processes. Since model biases are relatively small compared to the random error component, most of the total model error results from day-to-day variability in the forecasts and/or observations. To some extent, these nonsystematic errors reflect the variability in point observations that sample spatial and temporal scales of atmospheric phenomena that cannot be resolved by the model. On average, Meso-Eta point forecasts provide useful guidance for predicting the evolution of the larger scale environment. A more substantial challenge facing model users in real time is the discrimination of nonsystematic errors that tend to inflate the total forecast error. It is important that model users maintain awareness of ongoing model changes. Such changes are likely to modify the basic error characteristics, particularly near the surface

Huts as Classrooms: A Memoir by Two Who Inhabited the Puckerbrush

The origins of the Appalachian Mountain Club’s educational programs at its huts in the White Mountains of New Hampshire, told by AMC’s first education director, John Nutter, and a former hut system manager, W. Kent Olson

Direct TEM Observation of the Movement of the Austenite-Ferrite Interface in Steels

The solid-state phase transformation from austenite to ferrite is one of the key transformations in determining the final microstructure of steels, and therefore is an important factor in the versatility of steels. An improved understanding of this process can therefore lead to greater control over final properties in steels. This thesis presents the results of cyclic partial phase transformation (CPPT) experiments using in situ hot stage TEM in order to directly observed the interface behaviour during thermal cycling in the α + γ austenite phase region, for Fe-C-Mn alloys with up to 0.33 wt% C and 1.5 wt% Mn. Hot stage TEM experiments of this type have not been reported in the literature before and are able to provide new information which is not available from other techniques commonly used to carry out CPPT experiments such as dilatometry. The observation of individual interfaces makes it possible to observe not just the kinetics of the transformation but also the interface morphology and its interaction with microstructural features. Individual interface behaviour could be classified into the three stages expected during CPPT from bulk experiments: the normal transformation, the inverse transformation and the stagnant stage. The TEM observations show that sluggish interface migration continued during the stagnant stage, without the interface becoming completely static for any significant period of time. This migration distance was measured to be <500 nm, making this difficult to detect using other techniques. Furthermore, the observations showed that the interface often displayed an evolving morphology during the normal transformation, but reverted to a more stable, often straight or smoothly curved morphology during the stagnant stage. TEM observations also showed good reversibility between cycles with the interface migrating along approximately the same path during thermal cycling, with only minor changes. Interaction with microstructural features was also observed, including the segmentation of the interface due to nearby twin boundaries and the pinning of the interface by foreign particles. Finally, the results of in situ TEM observations of the growth of bainite are presented. Two growing bainite plates were observed and the lengthening and thickening rates 3 measured. Lengthening occurred in a series of discrete steps with periods of relatively slow or no growth interspersed with periods of rapid lengthening. In contrast it was observed that the subsequent thickening of the plates was a continuous process

Observations of magnetic fields and clustering functions in prestellar cores

In this thesis, I present SCUBA polaximetry data of three prestellar cores, L1544, L43 and L183. I also present SCUBA scan-map observations of three molecular clouds, Orion B, L1689, and RCrA. I use the Chandrasekhar-Fermi technique to measure the magnetic field strength in LI544, L43 and LI83, and find that each core is approximately magnetically critical or slightly supercritical. I measure the core mass function for prestellar cores in the Orion B molecular cloud and find that above 1 M0, the data are best fitted by a power-law of the form diV/dlog M cx M 15. The mass function has a peak at approximately 1 Mq. This core mass function is comparable with the Salpeter slope of M-1,35. I also determine the mean surface density of companions Ec(0) for the Orion B region, and find that it is best fitted by a power law of the form &pound;c(0) oc 0 03. This is smaller than the slope of 9 6 that is typically found for young stars in most molecular clouds. However, this slope is consistent with my data at the extreme limits of my la error bars. My value of T,c(0) oc 0 3 is comparable with the slope of 9 0 2 that is found for the nearby Orion Trapezium association. I find that the L1689 molecular cloud has a comparable rate of star formation to the neighbouring and more massive LI688. In addition, the star formation in LI689 occurs in a number of filaments that are parallel both to each other, and to similar filaments in L1688. I conclude that these observations indicate that the star formation is being influenced by the nearby Sco OB2 association. I compare the RCrA data to previous surveys of the region, and discover a previously unknown Class 0 source

Adaptation of Mesoscale Weather Models to Local Forecasting

Methodologies have been developed for (1) configuring mesoscale numerical weather-prediction models for execution on high-performance computer workstations to make short-range weather forecasts for the vicinity of the Kennedy Space Center (KSC) and the Cape Canaveral Air Force Station (CCAFS) and (2) evaluating the performances of the models as configured. These methodologies have been implemented as part of a continuing effort to improve weather forecasting in support of operations of the U.S. space program. The models, methodologies, and results of the evaluations also have potential value for commercial users who could benefit from tailoring their operations and/or marketing strategies based on accurate predictions of local weather. More specifically, the purpose of developing the methodologies for configuring the models to run on computers at KSC and CCAFS is to provide accurate forecasts of winds, temperature, and such specific thunderstorm-related phenomena as lightning and precipitation. The purpose of developing the evaluation methodologies is to maximize the utility of the models by providing users with assessments of the capabilities and limitations of the models. The models used in this effort thus far include the Mesoscale Atmospheric Simulation System (MASS), the Regional Atmospheric Modeling System (RAMS), and the National Centers for Environmental Prediction Eta Model ( Eta for short). The configuration of the MASS and RAMS is designed to run the models at very high spatial resolution and incorporate local data to resolve fine-scale weather features. Model preprocessors were modified to incorporate surface, ship, buoy, and rawinsonde data as well as data from local wind towers, wind profilers, and conventional or Doppler radars. The overall evaluation of the MASS, Eta, and RAMS was designed to assess the utility of these mesoscale models for satisfying the weather-forecasting needs of the U.S. space program. The evaluation methodology includes objective and subjective verification methodologies. Objective (e.g., statistical) verification of point forecasts is a stringent measure of model performance, but when used alone, it is not usually sufficient for quantifying the value of the overall contribution of the model to the weather-forecasting process. This is especially true for mesoscale models with enhanced spatial and temporal resolution that may be capable of predicting meteorologically consistent, though not necessarily accurate, fine-scale weather phenomena. Therefore, subjective (phenomenological) evaluation, focusing on selected case studies and specific weather features, such as sea breezes and precipitation, has been performed to help quantify the added value that cannot be inferred solely from objective evaluation

The properties of SCUBA cores in the Perseus molecular cloud: the bias of clump-finding algorithms

We present a new analysis of the properties of star-forming cores in the Perseus molecular cloud, identified in SCUBA 850 micron data. Our goal is to determine which core properties can be robustly identified and which depend on the extraction technique. Four regions in the cloud are examined: NGC1333, IC348/HH211, L1448 and L1455. We identify clumps of dust emission using two popular automated algorithms, CLFIND and GAUSSCLUMPS, finding 85 and 122 clumps in total respectively. Some trends are true for both populations: clumps become increasingly elongated over time and are consistent with constant surface brightness objects, with an average brightness ~4 to 10 times larger than the surrounding molecular cloud; the clump mass distribution (CMD) resembles the stellar intial mass function, with a slope alpha = -2.0+/-0.1 for CLFIND and alpha = -3.15+/-0.08 for GAUSSCLUMPS, which straddle the Salpeter value. The mass at which the slope shallows (similar for both algorithms at M~6 Msun) implies a star-forming efficiency of between 10 and 20 per cent. Other trends reported elsewhere depend on the clump-finding technique: we find protostellar clumps are both smaller (for GAUSSCLUMPS) and larger (for CLFIND) than their starless counterparts; the functional form, best-fitting to the CMD, is different for the two algorithms. The GAUSSCLUMPS CMD is best-fitted with a log-normal distribution, whereas a broken power law is best for CLFIND; the reported lack of massive starless cores in previous studies can be seen in the CLFIND but not the GAUSSCLUMPS data. Our approach highlights similarities and differences between the clump populations, illustrating the caution that must be exercised when comparing results from different studies and interpreting the properties of continuum cores.Comment: 19 pages, 17 figures, accepted for publication by MNRA