Validation of a UHF spaced antenna wind profiler for high‐resolution boundary layer observations

Abstract

Abstract. In this paper we apply a spaced antenna technique derived from the recent work of Doviak et al. [1996a] and Holloway et al. [this issue] to wind measurement with a small UHF boundary layer profiler. We discuss the implementation of the technique, averaging and quality control strategies, and some advantages and limitations of spaced antenna methods over conventional Doppler beam swinging wind profilers in the boundary layer. Such advantages include a relaxation of the assumption of a horizontally uniform wind field and the possibility of high temporal resolution wind profiles. In this regard we present velocity measurements derived from this UHF system with time resolution of about 30 s and compare these measurements with in situ sonic anemometer data taken on a 300-m tower. Finally, we present an example of a high-resolution time-height cross section of atmospheric winds. This example, collected in stratiform precipitation, shows the intriguing situation of a wind speed maximum (jet) which closely follows the height of the melting layer over several hours even as this height changes by several hundred meters. IntroductionIn the past decade a growing number of "clear-air" wind profilers have been used to probe the troposphere and lower stratosphere. Spaced antenna (SA) techniques are an alternative to the more common DBS technique. They use a single vertically directed transmitted beam, and the diffraction pattern formed by energy backscattered from the atmosphere is received using three or more spatially separated receiving antennas. Although not specifically developed for this purpose, SA measurement techniques can relax the assumption of uniform wind because the vector wind is measured within one radar pulse volume rather than at several separated volumes. Another potential benefit of SA techniques is that less time may be needed for the measurement 1279

Clear air boundary layer spaced antenna wind measurement with the Multiple Antenna Profiler (MAPR)

“…This facility has a 300 m high instrumented tower, and other remote sensors are often present for testing. MAPR was located approximately 600 m south of the tower, the same location as in the earlier tests reported in Cohn et al (1997). It was deployed as part of an NCAR Integrated Sounding System (ISS, Parsons et al, 1994), which includes a CLASS rawinsonde system and makes comparisons with co-located rawinsonde wind measurements possible.…”

“…Each receiver chain processes the signal from one of four antenna panels. Cohn et al (1997) describe this configuration in more detail.…”

“…Thus, the SA and DBS wind measurement techniques each have advantages in complementary situations (high time resolution in strong SNR, and longer dwell times in weaker conditions). Cohn et al (1997) described MAPR and presented measurements of vertical profiles of winds with 30-second time resolution and 60-m altitude resolution. Their study compared winds measured by MAPR against an anemometer on the 300 m Boulder Atmospheric Observatory (BAO; Kaimal and Gaynor, 1983) tower.…”

“…4 The antenna parameter a h Cohn et al (1997) used the parameter a h , described in Holloway et al (1997), to evaluate MAPR performance against a theoretical expectation. The theoretical value of this parameter is solely a function of the transmitting and receiving antenna patterns.…”

“…Spaced antenna (SA) wind measurement techniques are applied to Multiple Antenna Profiler (MAPR) data to evaluate its performance in clear air conditions. MAPR is a multiple antenna 915 MHz wind profiler developed at the National Center for Atmospheric Research (NCAR) and described in Cohn et al (1997), designed to make high resolution wind measurements. Previous reported measurements with MAPR were restricted to precipitation because of low signal to noise (SNR) and signal to ground-clutter (SCR) ratios.…”