Monitoring Depth of Shallow Atmospheric Boundary Layer to Complement LiDAR Measurements Affected by Partial Overlap

Abstract

Abstract:There is compelling evidence that the incomplete laser beam receiver field-of-view overlap (i.e., partial overlap) of ground-based vertically-pointing aerosol LiDAR restricts the observational range for detecting aerosol layer boundaries to a certain height above the LiDAR. This height varies from one to few hundreds of meters, depending on the transceiver geometry. The range, or height of full overlap, is defined as the minimum distance at which the laser beam is completely imaged onto the detector through the field stop in the receiver optics. Thus, the LiDAR signal below the height of full overlap remains erroneous. In effect, it is not possible to derive the atmospheric boundary layer (ABL) top (z i ) below the height of full overlap using lidar measurements alone. This problem makes determination of the nocturnal z i almost impossible, as the nocturnal z i is often lower than the minimum possible retrieved height due to incomplete overlap of lidar. Detailed studies of the nocturnal boundary layer or of variability of low z i would require changes in the LiDAR configuration such that a complete transceiver overlap could be achieved at a much lower height. Otherwise, improvements in the system configuration or deployment (e.g., scanning LiDAR) are needed. However, these improvements are challenging due to the instrument configuration and the need for Raman channel signal, eye-safe laser transmitter for scanning deployment, etc. This paper presents a brief review of some of the challenges and opportunities in overcoming the partial overlap of the LiDAR transceiver to determine z i below the height of full-overlap using complementary approaches to derive low z i . A comprehensive discussion focusing on four different techniques is presented. These are based on the combined (1) ceilometer and LiDAR; (2) tower-based trace gas (e.g., CO 2 ) concentration profiles and LiDAR measurements; (3) 222 Rn budget approach and LiDAR-derived results; and (4) encroachment model and LiDAR observations.

Forcing mechanisms governing diurnal, seasonal, and interannual variability in the boundary layer depths: Five years of continuous lidar observations over a suburban site near Paris

“…We investigate three key parameters of ABL diurnal cycle: daytime maximum z i denoted as z i Max , z i growth rate, and ABL growth duration. For instance, we choose z i Max for two main reasons: (1) previous studies using lidar measurements at SIRTA provided evidence that the z i Max coincide well with the elevated potential temperature ( θ ) inversion level obtained from the nearby radiosonde profiles at Trappes [e.g., Haeffelin et al ., ; Pal et al ., ] and (2), in general, on diurnal timescale, z i Max defines the “volume of the box” within which vertical mixing of trace gases and pollutants takes place [e.g., Yi et al ., ; Pal , ].…”

“…However, studies on the z i climatology based on multiyear lidar measurements have received little attention, partly for lack of continuous observations. In particular, routine, long‐term, and high‐resolution lidar‐derived z i time series were difficult to achieve until the very recent advancement in the automated lidar technology [e.g., De Tomasi and Perrone , ; van der Kamp and McKendry , ; Yang et al ., ; Lewis et al ., ; Ketterer et al ., ; Pal , ].…”

Evaluating the Governing Factors of Variability in Nocturnal Boundary Layer Height Based on Elastic Lidar in Wuhan

“…The overlap of the LiDAR system causes some difficulties in monitoring the shallow ABL, particularly the nocturnal boundary layer (NBL) [36]. The effect of incomplete overlap should be avoided to accurately estimate the ABLH by using a LiDAR system.…”

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

“…In order to reduce the impact of the overlap-affected range of the remote sensing measurements [65] and the middle-level clouds [53], the lower and the upper limit for the derived ABLH was defined. Within the blind region of the incomplete overlap range of each instrument, the received signal is extremely weak and dominated by noise, thus it is difficult to obtain a valid ABLH, except for particular conditions, such as very low clouds, fog, or smog (even then, the accuracy of the retrieval is low).…”