Atmosphere Boundary Layer Height (ABLH) Determination under Multiple-Layer Conditions Using Micro-Pulse Lidar

Abstract

Accurate estimation of the atmospheric boundary layer height (ABLH) is critically important and it mainly relies on the detection of the vertical profiles of atmosphere variables (temperature, humidity,’ and horizontal wind speed) or aerosols. Aerosol Lidar is a powerful remote sensing instrument frequently used to retrieve ABLH through the detection of the vertical distribution of aerosol concentration. A challenge is that cloud, residual layer (RL), and local signal structure seriously interfere with the lidar measurement of ABLH. A new objective technique presenting as giving a top limiter altitude is introduced to reduce the interference of RL and cloud layer on ABLH determination. Cloud layers are identified by looking for the rapid increase and sharp attenuation of the signal combined with the relative increase in the signal. The cloud layers weather overlay are classified or are decoupled from the ABL by analyzing the continuity of the signal below the cloud base. For cloud layer capping of the ABL, the limiter is determined to be the altitude where a positive signal gradient first occurs above the cloud upper edge. For a cloud that is decoupled from the ABL, the cloud base is considered to be the altitude limiter. For RL in the morning, the altitude limiter is the greatest positive gradient altitude below the RL top. The ABLH will be determined below the top limiter altitude using Haar wavelet (HM) and the curve fitting method (CFM). Besides, the interference of local signal noise is eliminated through consideration of the temporal continuity. While comparing the lidar-determined ABLH by HM (or CFM) and nearby radiosonde measurements of the ABLH, a reasonable concordance is found with a correlation coefficient of 0.94 (or 0.96) and 0.79 (or 0.74), presenting a mean of the relative absolute differences with respect to radiosonde measurements of 10.5% (or 12.3%) and 22.3% (or 17.2%) for cloud-free and cloudy situations, respectively. The diurnal variations in the ABLH determined from HM and CFM on four selected cases show good agreement with a mean correlation coefficient higher than 0.99 and a mean absolute bias of 0.22 km. Also, the determined diurnal ABLH are consistent with surface turbulent kinetic energy (TKE) combined with the time-height distribution of the equivalent potential temperature.

A Review of Techniques for Diagnosing the Atmospheric Boundary Layer Height (ABLH) Using Aerosol Lidar Data

“…Dang et al [56] defined an objective upper limiter altitude to reduce the interference of RL and cloud layer on daytime MLH retrieval. The top limiter altitude is determined according to the cloud location, whether the cloud is outside or within the ABL is classified through judging if the strongest signal gradient below the cloud base is lower than a preset threshold.…”

“…The robustness of the technique is based on utilizing the whole backscatter profile rather than the profile surrounding the top of ML [51]. Relatively, the FIT is less sensitivity to local signal structures than the methods directly based on the gradient [55,56]. However, the method is more suitable when ABL with structures that match the particular idealized profile.…”

“…Ceilometer can be regarded as a small lidar while it has a lower range gate than lidar. In recent years, several classical methodologies have been improved, meanwhile, some new ideas or algorithms have been proposed and developed by incorporating some advanced techniques such as image edge detection [52], cluster analysis [53], and layer tracking [54] [56]). The methodologies include several traditional algorithms, some improved versions of them, as well as some new aspects developed in recent years, which are introduced in Section 2, Section 3, and Section 4.…”

Variability of the Boundary Layer Over an Urban Continental Site Based on 10 Years of Active Remote Sensing Observations in Warsaw

“…Each of these approaches has its limitations regarding the measurement range and accuracy, spatial and temporal resolution, and weather conditions (clouds, fog, and precipitation). The ABLH measurement range and accuracy issues were solved to a large extent with the development of the light detection and ranging technology, e.g., by using next-generation high-power lidars [25][26][27] or low-power lidars and ceilometers [28][29][30][31]. The latter are recognized worldwide as efficient and affordable ground-based instruments for profiling of the atmosphere [32].…”

“…Most of the studies reported in the literature focus on ABLH retrieval during the daytime and for fair-weather conditions [24,28,34,[37][38][39][40] while retrievals during complex weather situations, as well as during the sunrise/sunset and at nighttime, have been performed less often [27,29,31,46]. The most complex boundary layer and aerosol conditions often form at night, which is regarded as an important part of the diurnal changes within the ABL, and thus the nocturnal boundary layer should not be excluded from the ABLH statistical analysis.…”