The estimation of atmospheric boundary layer height (ABLH) during a full diurnal cycle using ground-based remote sensing instruments is one of the key challenges in atmospheric science. Most of these instruments such as the lidar, the microwave radiometer (MWR), the radar, and the sodar measure one of the physical parameters, i.e., temperature, aerosol concentration, wind speed, and heat flux, within the Atmospheric Boundary Layer (ABL). All these instruments, while performing well under specific atmospheric conditions, are limited in others. Thus, an estimate of the ABLH based on the lidar return signal alone is quite good under convective conditions, where there is a clear interface between a well-mixed concentration of aerosols in the mixing layer (ML) and the free troposphere (FT). In contrast, in night-time conditions, when the convective ML recedes and a stable boundary layer (SBL) develops near the surface of the Earth, the lidar backscattered signal is usually insufficient to resolve the SBL. Similarly, a MWR is limited by its poor range resolution. In this context, a MWR-ceilometer combination is proposed. Temperature-inversion retrievals from the MWR, containing the approximate height range where the SBL is located, roughly guide the Kalman Filter based ABLH estimation algorithm for the lidar return signal, hence resulting in acceptably accurate estimates of the ABLH. The proposed approach is applied to collocated ceilometer-MWR instruments under the simple ”clear-atmosphere” cases. Radiosonde data, whenever available, is used as a reference or ”physical truth”.

Peer Reviewed