Abstract
Abstract. In this paper, we develop an estimator for the vertical flux of horizontal momentum with arbitrary beam pointing, applicable to the case of arbitrary but fixed beam pointing with systems such as the Poker Flat Incoherent Scatter Radar (PFISR). This method uses information from all available beams to resolve the variances of the wind field in addition to the vertical flux of both meridional and zonal momentum, targeted for high-frequency wave motions. The estimator utilises the full covariance of the distributed measurements, which provides a significant reduction in errors over the direct extension of previously developed techniques and allows for the calculation of an error covariance matrix of the estimated quantities. We find that for the PFISR experiment, we can construct an unbiased and robust estimator of the momentum flux if sufficient and proper beam orientations are chosen, which can in the future be optimized for the expected frequency distribution of momentum-containing scales. However, there is a potential trade-off between biases and standard errors introduced with the new approach, which must be taken into account when assessing the momentum fluxes. We apply the estimator to PFISR measurements on 23 April 2008 and 21 December 2007, from 60–85 km altitude, and show expected results as compared to mean winds and in relation to the measured vertical velocity variances.
Highlights
Geophysical vertical flux of horizontal momentum measurements were pioneered by Lhermitte (1983) and Vincent and Reid (1983), the former for studying the spectral variance in underwater tidal channels and the latter for assessing the vertical structure of wave motions in the atmosphere
We have applied the technique described in this paper to Poker Flat Incoherent Scatter Radar (PFISR) data from 23 April 2008, which has been described and analysed in detail by Nicolls et al (2010)
We have demonstrated a technique to estimate the covariance matrix of the wind field, including wind variances and momentum fluxes, using arbitrary, distributed measurements of line-of-sight winds
Summary
Geophysical vertical flux of horizontal momentum measurements were pioneered by Lhermitte (1983) and Vincent and Reid (1983), the former for studying the spectral variance in underwater tidal channels and the latter for assessing the vertical structure of wave motions in the atmosphere. Vincent and Reid (1983) developed a technique for ground-based radars to estimate radial velocity variances and corresponding momentum fluxes in the mesosphere and lower thermosphere (MLT) using dual co-planar narrow radar beams. This technique has since been widely used by HF and VHF radars (e.g., Reid and Vincent, 1987; Fritts and Vincent, 1987; Fukao et al, 1988; Reid et al, 1988; Fritts and Yuan, 1989; Fritts et al, 1990; Sato, 1990, 1993, 1994; Tsuda et al, 1990; Wang and Fritts, 1990, 1991; Hitchman et al, 1992; Nakamura et al, 1993; Murayama et al, 1994; Murphy and Vincent, 1993, 1998). This technique is applicable to phased array radars such as the Advanced Modular Incoherent Scatter Radar (AMISR) class of radars
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
