Comparisons of Crosswind Velocity Profile Estimates Used in Fast-Time Wake Vortex Prediction Models

Five methods for estimating crosswind profiles used in fast-time wake vortex prediction models are compared in this study. Previous investigations have shown that temporal and spatial variations in the crosswind vertical profile have a large impact on the transport and time evolution of the trailing vortex pair. The most important crosswind parameters are the magnitude of the crosswind and the gradient in the crosswind shear. It is known that pulsed and continuous wave lidar measurements can provide good estimates of the wind profile in the vicinity of airports. In this study comparisons are made between estimates of the crosswind profiles from a priori information on the trajectory of the vortex pair as well as crosswind profiles derived from different sensors and a regional numerical weather prediction model

NASA AVOSS Fast-Time Wake Prediction Models: User's Guide

The National Aeronautics and Space Administration (NASA) is developing and testing fast-time wake transport and decay models to safely enhance the capacity of the National Airspace System (NAS). The fast-time wake models are empirical algorithms used for real-time predictions of wake transport and decay based on aircraft parameters and ambient weather conditions. The aircraft dependent parameters include the initial vortex descent velocity and the vortex pair separation distance. The atmospheric initial conditions include vertical profiles of temperature or potential temperature, eddy dissipation rate, and crosswind. The current distribution includes the latest versions of the APA (3.4) and the TDP (2.1) models. This User's Guide provides detailed information on the model inputs, file formats, and the model output. An example of a model run and a brief description of the Memphis 1995 Wake Vortex Dataset is also provided

Evaluation of Fast-Time Wake Models Using Denver 2006 Field Experiment Data

The National Aeronautics and Space Administration conducted a series of wake vortex field experiments at Denver in 2003, 2005, and 2006. This paper describes the lidar wake vortex measurements and associated meteorological data collected during the 2006 deployment, and includes results of recent reprocessing of the lidar data using a new wake vortex algorithm and estimates of the atmospheric turbulence using a new algorithm to estimate eddy dissipation rate from the lidar data. The configuration and set-up of the 2006 field experiment allowed out-of-ground effect vortices to be tracked in lateral transport further than any previous campaign and thereby provides an opportunity to study long-lived wake vortices in moderate to low crosswinds. An evaluation of NASA's fast-time wake vortex transport and decay models using the dataset shows similar performance as previous studies using other field data

Atmospheric Turbulence Estimates from a Pulsed Lidar

Estimates of the eddy dissipation rate (EDR) were obtained from measurements made by a coherent pulsed lidar and compared with estimates from mesoscale model simulations and measurements from an in situ sonic anemometer at the Denver International Airport and with EDR estimates from the last observation time of the trailing vortex pair. The estimates of EDR from the lidar were obtained using two different methodologies. The two methodologies show consistent estimates of the vertical profiles. Comparison of EDR derived from the Weather Research and Forecast (WRF) mesoscale model with the in situ lidar estimates show good agreement during the daytime convective boundary layer, but the WRF simulations tend to overestimate EDR during the nighttime. The EDR estimates from a sonic anemometer located at 7.3 meters above ground level are approximately one order of magnitude greater than both the WRF and lidar estimates - which are from greater heights - during the daytime convective boundary layer and substantially greater during the nighttime stable boundary layer. The consistency of the EDR estimates from different methods suggests a reasonable ability to predict the temporal evolution of a spatially averaged vertical profile of EDR in an airport terminal area using a mesoscale model during the daytime convective boundary layer. In the stable nighttime boundary layer, there may be added value to EDR estimates provided by in situ lidar measurements

Rethinking english language support : reflections from chinese international students on communicating orally in english in the study abroad context

Australian universities are currently emphasizing such graduate qualities as English language proficiency. However, this can be problematic for many international students who may still be struggling to communicate orally in English while participating in their chosen course of study. Indeed, the English language proficiency of international students has often received negative attention from the Australian media, employers, and academics. Several government reviews have recommended ongoing English language support for international students that extends beyond existing English language entry requirements, English Academic Preparation programs, and Post-entry Language Assessments. At the same time, there has been a critique of responses to these issues which focus on language proficiency—and simply place the onus on international students to increase their English language proficiency—without taking issues of intercultural communicative competence into account, along with calls for institutional frameworks to better support student experience. This thesis is one contribution to this debate, supported and informed by an exploration of lived experiences of Chinese students engaging with oral English language use and other supports. Not only are Chinese students the largest cohort of international students in Australia, but English education in China also does not appear to prepare them effectively to communicate orally in English. Very different sociocultural backgrounds can also make it difficult for this cohort to engage both academically and socially in Australian higher education. These issues comprise road blockers that can limit English language practice opportunities and negatively affect academic success. iii This thesis shines a light on this cohort’s oral English language experiences in the study abroad context via engagement of Max van Manen’s (1990, 2014) frameworks for phenomenologically oriented qualitative research. Drawing on the lived experiences of Chinese students and a critical review of the regulatory frameworks that inform sectoral and institutional English language proficiency models, this thesis argues for an English language proficiency support framework that integrates insights from intercultural communicative competence into oral English language proficiency as well as the development of curriculum, course delivery, and assessments.Doctor of Philosoph