ALBERT

Description: Diel fluctuations can comprise a significant portion of summer discharge in small to medium catchments. The source of these signals and the manner in which they are propagated to stream gauging sites is poorly understood. In this work we analyze stream discharge from 15 subcatchments in Dry Creek, Idaho, Reynolds Creek, Idaho, and the HJ Andrews, Oregon. We identify diel signals in summer low flow, determine the lag between the diel signals and evapotranspiration demand, and identify seasonal trends in the evolution of the lag at each site. The lag between vegetation water use and streamflow response increases thorough the summer at each subcatchment, with the rate of increase a function of catchment stream length and other catchment characteristics such as geology, vegetation, and stream geomorphology. These findings support the hypothesis that variations in stream velocity are the key control on the seasonal evolution of the observed lags. Copyright © 2012 John Wiley & Sons, Ltd.

Description: The Center TRACON Automation System (CTAS) is a new support system that is designed to assist air traffic controllers in the management of arrival traffic. CTAS will provide controllers with more information about current air traffic, enabling them to provide clearances for efficient, conflict-free descents that help achieve an orderly stream of aircraft at the final approach fix. CTAS is a computer-based system that functions as a "ground-based FMS" that can predict flight trajectories and arrival times for all incoming aircraft. CTAS uses an aircraft's cruise airspeed; current air traffic, winds and temperature; performance characteristics of the aircraft type; and individual airline preferences to create a flight profile from cruise altitude to the final approach fix. Controllers can use this flight profile to provide a descent clearance that will allow an aircraft to fly an efficient descent and merge more smoothly with other arriving aircraft. A field test of the CTAS Descent Advisor software was conducted at the Denver Center for aircraft arriving at the Stapleton International Airport from September 12-29. CTAS Descent clearances were given to a NASA flight test aircraft and to 77 airline flights that arrived during low traffic periods. For the airline portion of the field test, cockpit procedures and pilot briefing packages for both FMS equipped and unequipped aircraft were developed in cooperation with an airline. The procedures developed for the FMS equipped aircraft were to fly a VNAV descent at a controller specified speed to cross a metering fix at a specified altitude and speed. For nonFMS aircraft, the clearance also specified a CTAS calculated top-of-descent point. Some CTAS related flight deck issues included how much time was available to the pilots' for compliance, the amount of information that needed to be interpreted in the clearance and possible repercussions of misunderstandings. Data collected during the study ranged from subjective data (including the airline pilots' opinions and comments about the new descent clearances and procedures) to objective data (including observations of aircraft performance from the flight deck). This paper will present data and the resulting changes in the design of the procedures and clearance phraseology.