NDLI: The Contribution of Variability of Lift-induced Upwash to the Uncertainty in Vertical Winds Determined from an Aircraft Platform

Content Provider	Springer Nature Link
Author	Garman, Karl E. Wyss, Phil Carlsen, Mark Zimmerman, James R. Stirm, Brian H. Carney, Thomas Q. Santini, Robert Shepson, Paul B.
Copyright Year	2007
Abstract	Aircraft-based vertical flux measurements fill a gap in the spatial domain for studies of biosphere–atmosphere exchange. To acquire valid flux data, a determination of the deviation from the mean vertical wind, w′, is essential. When using aircraft platforms, flux measurements are subject to systematic and random errors from airflow distortion caused by the lift-induced upwash ahead of the aircraft. Although upwash is typically considered to be a constant quantity over periods used for calculating fluxes, it can vary significantly over short (and longer) periods due to changes in aircraft lift. The characterization of such variations in upwash are of undeniable importance to flux measurements, especially when real-time computations of w′ are required. In this paper, the variability in upwash was compared to the calculated upwash from the model of Crawford et al. (Boundary-Layer Meteorol, 80:79–94, 1996) using data taken during a long-period (phugoid mode) free oscillation of the aircraft. The cyclic variation of lift during the free oscillation offers an ideal scenario in which to acquire in-flight data on the upwash that is present, as well as to test the capability of upwash correction models. Our results indicate that while this model corrects for much of the mean upwash, there can be significant variations in upwash on a time scale that is important to flux measurements. Our results suggest that use of the measured load factor could be an easily implemented operational constraint to minimize uncertainty in w′ due to changing upwash from changing aircraft lift. We estimate, using the phugoid data, and from variations in aircraft attitude and airspeed in flux-measurement configuration, that the uncertainty in w caused by variable upwash is approximately ± 0.05 m s−1.
Starting Page	461
Ending Page	476
Page Count	16
File Format	PDF
ISSN	00068314
Journal	Boundary-Layer Meteorology
Volume Number	126
Issue Number	3
e-ISSN	15731472
Language	English
Publisher	Springer Netherlands
Publisher Date	2007-11-23
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Aircraft measurements Airflow Flow distortion Lift-induced upwash Phugoid Upwash Vertical flux Atmospheric Protection/Air Quality Control/Air Pollution Meteorology/Climatology
Content Type	Text
Resource Type	Article
Subject	Atmospheric Science

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