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

Remote Sensing

关键词: atmospheric boundary layer depth;    encroachment model;    lidar;    nocturnal boundary layer;    overlap factor;    trace gases;   

DOI  :  10.3390/rs6098468

来源: mdpi

【 摘 要 】

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., CO₂) concentration profiles and LiDAR measurements; (3) ²²²Rn budget approach and LiDAR-derived results; and (4) encroachment model and LiDAR observations.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland