Comparison of Convective Boundary Layer Characteristics from Aircraft and Wind Lidar Observations

• Published in: Journal of atmospheric and oceanic technology 2019-07, Vol.36 (7), p.1381-1399
• Main Authors: Adler, Bianca, Kiseleva, Olga, Kalthoff, Norbert, Wieser, Andreas
• Format: Article
• Language: English
• Subjects: Airborne observation; Aircraft; Aircraft performance; Boreal ecosystems; Boundary layers; Flight; Heterogeneity; Horizontal flight; Leg; Lidar; Lidar measurements; Mean winds; Mixed layer; Observatories; Research aircraft; Statistical methods; Storms; Time series; Urban areas; Velocity; Vertical velocities; Wavelength; Weather; Wind; Wind direction
• ISSN: 0739-0572; 1520-0426
• DOI: 10.1175/JTECH-D-18-0118.1

During the Convective Storm Initiation Project experiment, which was conducted in summer 2005 in southern England, vertical velocity in the convective boundary layer (CBL) was measured simultaneously with a research aircraft and a wind lidar. The aircraft performed horizontal flight legs approximately parallel to the prevailing wind direction and centered over the lidar. This measurement setup allows for the comparing of CBL characteristics (CBL depth z i , integral length scale l w , spectral peak wavelength λ m , and vertical velocity variance ) from temporal (lidar) and spatial (aircraft) measurements. For this, the lidar time series are transferred into space using the mean wind. While the statistics of the aircraft data are all based on the 34-km flight legs, the averaging interval for the lidar is either 1 h or a longer period that corresponds to the 34-km leg. Although the l w and λ m values from aircraft and lidar measurements are in the same range (100–200 and 500–2000 m) and agree well on the average, the correlation for individual legs is very low ( R 2 < 0.17). One possible explanation is the large uncertainty that arises from the transfer of the lidar time series to space. For , the agreement between aircraft and lidar is better for individual legs ( R 2 ≥ 0.63), but the mean absolute difference in is about 2.5 times as large as the statistical error. We examine the nonstationarity and heterogeneity for the lidar and aircraft samples and can exclude these as the major sources for the large differences between lidar and aircraft data.