Determination of Planetary Boundary Layer Height on Short Spatial and Temporal Scales: A Demonstration of the Covariance Wavelet Transform in Ground-Based Wind Profiler and Lidar Measurements*

Abstract

This article explores the application of the covariance wavelet transform (CWT) to lidar and, for the first time to the authors' knowledge, wind profiler data to examine the possibility of accurate and continuous planetary boundary layer (PBL) height measurements on short temporal resolution (1- and 15-min averages, respectively). Determining the mixing in the PBL was one goal of a study of the spatial and diurnal variations of the PBL height over Maryland for July 2011, during NASA's Earth Venture mission DISCOVER-AQ. The PBL heights derived from ground-based lidars [at University of Maryland, Baltimore County (UMBC); 39.25°N, 76.70°W], a 915-MHz wind profiler, and radiosondes (at Beltsville, Maryland; 38.92°N, 77.02°W) were compared. Results from the comparison show an R2 = 0.89, 0.92, and 0.94 correlation between the radiosonde PBL heights and two lidars and wind profiler PBL heights, respectively. Accurate determination of the PBL height by applying the CWT to lidar and wind profilers will allow for improved air quality forecasting and understanding of regional pollution dynamics.

Comparison of aerosol lidar retrieval methods for boundary layer height detection using ceilometer aerosol backscatter data

“…As with previous studies (Brooks, 2003;Baars et al, 2008;Compton et al, 2013;Scarino et al, 2014), the dilation factor a affects the number of covariance wavelet transform coefficient (CWTC) local minimums. Larger values create a few large local minimums (Fig.…”

“…Out of the three methods tested in this study, it is suggested to employ the wavelet method in future studies, in particular for longterm seasonal and diurnal boundary layer studies and spatial analysis of the BL using multiple lidar aerosol backscatter measurements. A combination of the wavelet method BLH retrievals during clear skies and the cluster analysis method's ability to calculate cloud depth is also recommended for more robust BL studies to retrieve more information about the boundary layer under both conditions, as both the wavelet and cluster analysis methods were seen to perform well using various lidar instruments in studies such as Compton et al (2013), Scarino et al (2014), and Toledo et al (2014). Although not tested in this study, recent work by de Bruine et al (2016) and Poltera et al (2017) show promising results using an automated method which reduces incorrect detection of the BLH using graph theory.…”

“…Aerosol backscatter BLHs are derived with a covariance wavelet transform utilizing the Haar wavelet compound step function with multiple user-defined wavelet dilations (Cohn and Angevine, 2000;Davis et al, 2000;Brooks, 2003;Baars et al, 2008;Compton et al, 2013;Uzan et al, 2016). This method identifies the sharp aerosol backscatter gradient corresponding to the top of the BL by calculating the wavelet transform.…”

“…Apart from a few occasions (e.g., André and Mahrt, 1982;Berman et al, 1999;Day et al, 2010), NSL measurements are particularly uncommon since most radiosonde launches are performed during daytime ML hours. In recent years, remote-sensing techniques such as light detection and ranging (lidar), radio acoustic sounding systems (RASS), and sonic detection and ranging (sodar) systems have allowed for the continuous monitoring of the BL (Cohn and Angevine, 2000;Schäfer et al, 2011;Seibert et al, 2000;Emeis et al, 2004Emeis et al, , 2006Emeis et al, , 2012Eresmaa et al, 2006;Baars et al, 2008;McKendry et al, 2009;Muñoz and Undurraga, 2010;Haman et al, 2012;Milroy et al, 2012;Compton et al, 2013;Scarino et al, 2014;Wiegner and Gasteiger, 2015;Uzan et al, 2016). Ceilometers in particular offer a low-maintenance and low-cost solution to constantly monitoring the ML using aerosol backscatter while also facilitating the monitoring of the nocturnal stable layer, internal aerosol layers, and the nighttime residual layer (Haman et al, 2012Pandolfi et al, 2013;Peña et al, 2013).…”

New Results from the NOAA CREST Lidar Network (CLN) Observations in the US Eastcoast

“…CLN is comprised of lidar facilities at mainly 4 sites (campuses) supported by the NOAA CREST Center (see Fig.1 [5,6,7]. The high pulse powers allow the observation and quantification of multi-layer plumes; and the multiwavelength capacity enables us to classify aloft aerosol type (smoke or dust).…”