Evaluation of wind profiles from the NERC MST radar, Aberystwyth, UK

Abstract

Abstract. This study quantifies the uncertainties in winds measured by the Aberystwyth Mesosphere-StratosphereTroposphere (MST) radar (52.4 • N, 4.0 • W), before and after its renovation in March 2011. A total of 127 radiosondes provide an independent measure of winds. Differences between radiosonde and radar-measured horizontal winds are correlated with long-term averages of vertical velocities, suggesting an influence from local mountain waves. These local influences are an important consideration when using radar winds as a measure of regional conditions, particularly for numerical weather prediction. For those applications, local effects represent a source of sampling error additional to the inherent uncertainties in the measurements themselves. The radar renovation improved the signal-tonoise ratio (SNR) of measurements, with a corresponding improvement in altitude coverage. It also corrected an underestimate of horizontal wind speeds attributed to beam formation problems, due to pre-renovation component failure. The root mean square error (RMSE) in radar-measured horizontal wind components, averaged over half an hour, increases with wind speed and altitude, and is 0.8-2.5 m s −1 (6-12 % of wind speed) for post-renovation winds. Pre-renovation values are typically 0.1 m s −1 larger. The RMSE in radial velocities is < 0.04 m s −1 . Eight weeks of special radar operation are used to investigate the effects of echo power aspect sensitivity. Corrections for echo power aspect sensitivity remove an underestimate of horizontal wind speeds; however aspect sensitivity is azimuthally anisotropic at the scale of routine observations (≈ 1 h). This anisotropy introduces random error into wind profiles. For winds averaged over half an hour, the RMSE is around 3.5 % above 8 km, but as large as 4.5 % in the mid-troposphere.

Intercomparisons of Tropospheric Wind Velocities Measured by Multi-Frequency Wind Profilers and Rawinsonde

“…In light of the fact that the correlations of the u and v components between different radar measurements are significantly high (0.95-0.99) and their RMSDs are also very consistent with each other (0.91-1.24 ms −1 ), it can be reasonably inferred that the RMSDs of the VHF radar-measured u and v components are comparable to those between different radar pairs. In this context, the RMSD of horizontal wind velocity related to the VHF radar measurements in the present study (approximately 0.956 ms −1 on average) is essentially consistent with that obtained by Lee et al [37].…”

“…They found that the RMSDs were between 0.8 ms −1 for low wind velocities (10-15 ms −1 ) below 5 km and 2.5 ms −1 for high winds (40-45 ms −1 ) at higher altitudes. As seen in Figure 5, the magnitudes of horizontal wind velocities for our cases are in the range of 5-17 ms −1 , which corresponds to the low wind velocity case defined by Lee et al [37]. In light of the fact that the correlations of the u and v components between different radar measurements are significantly high (0.95-0.99) and their RMSDs are also very consistent with each other (0.91-1.24 ms −1 ), it can be reasonably inferred that the RMSDs of the VHF radar-measured u and v components are comparable to those between different radar pairs.…”

“…Strauch et al [29] compared the wind velocities measured by 50 MHz and 405 MHz wind profilers and found that the RMSD of the horizontal wind velocities was 1.071 ms −1 which is approximately 14% larger than that measured by the 52 MHz and 449 MHz wind profilers, as shown in Figure 5 and Table 3. On the basis of a pair of radial velocities observed by off-zenith radar beams pointed in opposite directions for the Aberystwyth VHF radar operating at 46.5 MHz, Lee et al [37] analyzed the RMSDs of the pair of horizontal wind velocities by removing vertical wind velocities from the observed radial velocities, which were directly measured by a vertically pointed radar beam. They found that the RMSDs were between 0.8 ms −1 for low wind velocities (10-15 ms −1 ) below 5 km and 2.5 ms −1 for high winds (40-45 ms −1 ) at higher altitudes.…”

Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region

“…mesosphere-stratosphere-troposphere (MST) radar techniques (e.g. Hooper et al, 2008;Lee et al, 2014) provide additional coverage over 0-20 km. Under clear-sky conditions the Rayleigh-Mie-Raman (RMR) lidar (Baumgarten, 2010;Hildebrand et al, 2012) measures winds throughout the middle atmosphere above Andenes, northern Norway but requires complex laser transmission and detection equipment and is not portable.…”

Evaluation of multifrequency range imaging technique implemented on the Chung–Li VHF atmospheric radar

“…Among the capabilities of VHF-MST radar, continuous measurement of three-dimensional winds with a temporal resolution of several minutes and a vertical resolution of several hundred meters are praiseworthy (Lee et al, 2014). In addition to the air motion characterized by the wind field, small-scale structures of refractivity irregularities, such as thin layers with a thickness of tens of meters, exist commonly in the atmosphere and can reflect dynamic behavior of the atmosphere directly.…”