Abstract
Abstract. Accurate boundary layer structure and height are critical in the analysis of the features of air pollutants and local circulation. Although surface-based remote sensing instruments provide a high temporal resolution of the boundary layer structure, there are numerous uncertainties in terms of the accurate determination of the atmospheric boundary layer heights (ABLHs). In this study, an algorithm for an integrated system for ABLH estimation (ISABLE) was developed and applied to the vertical profile data obtained using a ceilometer and a microwave radiometer in Seoul city, Korea. A maximum of 19 ABLHs were estimated via the conventional time-variance, gradient, wavelet, and clustering methods using the backscatter coefficient from the ceilometer. Meanwhile, several stable boundary layer heights were extracted through near-surface inversion and environmental lapse rate methods using the potential temperature from the microwave radiometer. The ISABLE algorithm can find an optimal ABLH from post-processing, such as k-means clustering and density-based spatial clustering of applications with noise (DBSCAN) techniques. It was found that the ABLH determined using ISABLE exhibited more significant correlation coefficients and smaller mean bias and root mean square error between the radiosonde-derived ABLHs than those obtained using the most conventional methods. Clear skies exhibited higher daytime ABLH than cloudy skies, and the daily maximum ABLH was recorded in summer because of the more intense radiation. The ABLHs estimated by ISABLE are expected to contribute to the parameterization of vertical diffusion in the atmospheric boundary layer.
Highlights
The atmospheric boundary layer (ABL) is the lowest part of the troposphere, which is directly influenced by the surface of the earth (Garratt, 1994)
The mean atmospheric boundary layer heights (ABLHs) were determined as around 500 m, and outliers appeared above 1 km, which were identified as the residual layer (RL) or clouds (Fig. 8)
ABLHs were concentrated in the lower layer at night, and the interquartile range (IQR) values increased as the mixed layer (ML) developed after sunrise
Summary
The atmospheric boundary layer (ABL) is the lowest part of the troposphere, which is directly influenced by the surface of the earth (Garratt, 1994). The ABL is repeated in a daily cycle with a well-mixed layer (ML) or a convective boundary layer (CBL) in the daytime and a stable boundary layer (SBL) at nighttime. The former mixes air vertically via convection which results from surface heating or mechanical turbulence due to vertical wind shear, while the latter appears in the lower ABL, and a residual layer (RL) remains in the upper ABL without any external force. The ABL is confined as a single layer, which is consisted of a ML or a SBL to exclude its complexity
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