Evaluation of retrieval methods of daytime convective boundary layer height based on lidar data

et al. 2019

Remote Sensing

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The height of the atmospheric boundary layer (ABLH) or the mixing layer height (MLH) is a key parameter characterizing the planetary boundary layer, and the accurate estimation of that is critically important for boundary layer related studies, which include air quality forecasts and numerical weather prediction. Aerosol lidar is a powerful remote sensing instrument frequently used to retrieve the ABLH through detecting the vertical distributions of aerosol concentration. Presently available methods for ABLH determination from aerosol lidar are summarized in this review, including a lot of classical methodologies as well as some improved versions of them. Some new recently developed methods applying advanced techniques such as image edge detection, as well as some new methods based on multi-wavelength lidar systems, are also summarized. Although a lot of techniques have been proposed and have already given reasonable results in several studies, it is impossible to recommend a technique which is suitable in all atmospheric scenarios. More accurate instantaneous ABLH from robust techniques is required, which can be used to estimate or improve the boundary layer parameterization in the numerical model, or maybe possible to be assimilated into the weather and environment models to improve the simulation or forecast of weather and air quality in the future.

Section: Ideal Profile Fitting (Curve Fitting) (Fit)mentioning

confidence: 99%

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

Dang

et al. 2019

Remote Sensing

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“…The site is approximately 8.83 km from SACOL in a suburban-rural area of Lanzhou. Li [49] indicated that the Yuzhong L-band radiosonde allows for estimation of the SACOL ABLH because the two sites have similar underlying surfaces.…”

Section: Description Of Evaluation Datamentioning

confidence: 99%

“…An example of an NRB profile with the shape of a Haar wavelet and the profile of the covariance transform is shown as Figure 1; the determined ABLH is approximately 2000 m. The selection of ∆h is key to successfully determining the ABLH. Li [46,49] showed that an appropriate value of ∆h = 200∆z = 300 m (∆z is the vertical resolution of the NRB, which is 15 m) is suitable for HM over SACOL. The lidar data used in this study was collected from the same observation site, and the initial value of the parameter, ∆h, is valued as 300 m. lidar signal to isolate the spikes due to aerosol concentrations.…”

Section: Traditional Techniquesmentioning

confidence: 99%

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

Dang

et al. 2019

Remote Sensing

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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.

“…There are usually sharp gradients in the aerosol concentration through the entrainment zone at the top of the CBL. This characteristic can be used to retrieve the boundary layer height, and the use of lidar data for boundary layer retrieval has been described sufficiently in the literature [5,16,[18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Application of Convective Condensation Level Limiter in Convective Boundary Layer Height Retrieval Based on Lidar Data

et al. 2017

Atmosphere

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Abstract:Micro pulse lidar is a promising tool for retrieving the convective boundary layer height (CBLH), but its application has been hindered by sharp extinction of the signal in high humidity conditions, e.g., clouds. To remedy this, we developed an effective and simple limiter to obtain more accurate estimates of the CBLH. The limiter is based on the algorithm for the convective condensation level (CCL) and is aimed at limiting the vertical extent of the lidar backscatter profile used in lidar methods to search for the CBLH. Four lidar methods (i.e., the gradient method, the idealized backscatter method, and two forms of the wavelet covariance methods) are used to calculate the CBLH with (or without) the limiter added. Compared to the CBLH calculated by the parcel method from microwave radiometer temperature data, more accurate retrieval of the CBLH is carried out with the limiter applied in four cloudy cases.