Abstract
Abstract. Observations of turbulence in the planetary boundary layer are critical for developing and evaluating boundary layer parameterizations in mesoscale numerical weather prediction models. These observations, however, are expensive and rarely profile the entire boundary layer. Using optimized configurations for 449 and 915 MHz wind profiling radars during the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA), improvements have been made to the historical methods of measuring vertical velocity variance through the time series of vertical velocity, as well as the Doppler spectral width. Using six heights of sonic anemometers mounted on a 300 m tower, correlations of up to R2 = 0. 74 are seen in measurements of the large-scale variances from the radar time series and R2 = 0. 79 in measurements of small-scale variance from radar spectral widths. The total variance, measured as the sum of the small and large scales, agrees well with sonic anemometers, with R2 = 0. 79. Correlation is higher in daytime convective boundary layers than nighttime stable conditions when turbulence levels are smaller. With the good agreement with the in situ measurements, highly resolved profiles up to 2 km can be accurately observed from the 449 MHz radar and 1 km from the 915 MHz radar. This optimized configuration will provide unique observations for the verification and improvement to boundary layer parameterizations in mesoscale models.
Highlights
Observations of turbulence quantities in the planetary boundary layer (PBL) are crucial for many applications and, in particular, can be extremely informative for developing and evaluating parameterizations in numerical weather prediction models of the small scales that cannot yet be resolved
This study aims to accurately measure the total variance, as well as the individual contributions from large and small scales, with optimized wind profiling radars (WPRs) configurations and postprocessing procedures
The improvement in agreement in variance from WPR spectral widths (SW) and sonic anemometer HP can be seen from the left column to the right (c–d), but a digression is seen in the variance from WPR TS and sonic anemometer LP (a–b)
Summary
Observations of turbulence quantities in the planetary boundary layer (PBL) are crucial for many applications and, in particular, can be extremely informative for developing and evaluating parameterizations in numerical weather prediction models of the small scales that cannot yet be resolved. Turbulence measurements are predominantly relegated to high-frequency in situ observing instrumentation such as sonic anemometers, limited in their spatial coverage, or are taken by expensive aircraft platforms. Wind profiling radars (WPRs) have been shown to have capabilities of measuring turbulence, from information contained in the Doppler spectral width of the vertical velocity (Hocking, 1985; Reid, 1987; Angevine et al, 1994; Nastrom and Eaton, 1997), but the adoption of these techniques into routine use has not occurred because of the lack of precision and inability to measure the smallest turbulence values observed by sonic anemometers.
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