Ceilometers as planetary boundary layer detectors and a corrective tool for ECMWF and COSMO NWP models

Abstract

<p><strong>Abstract.</strong> The growing importance of the planetary boundary layer (PBL) height detection is apparent in various fields, from air pollution analysis to weather prediction. In recent years micro-lidars such as ceilometers have been recognized as an efficient tool for such measurements. Here, the daytime summer PBL height is measured by eight ceilometers throughout Israel, along with with radiosonde profiles, the global IFS model, and the regional COSMO model. The analysis focused on three PBL height evaluation methods: the bulk Richardson method, the parcel method, and the wavelet covariance transform method. The best agreement between the PBL heights derived from a single radiosonde site on 33 summer days was found by the adjacent ceilometer (mean error = 12 m, RMSE = 97 m). Spatial analysis of the PBL heights derived from the models on 13 days in reference to five ceilometer measurement sites revealed COSMO evaluations by the bulk Richardson method (COSMOR) produced the best results for both flat (mean error = 19 m, RMSE = 203 m) and elevated terrain (mean error = −6 m, RMSE = 251 m). To improve COSMOR results, a regression tool was assimilated based on the PBL height difference between COSMOR and ceilometers. The regression is based on the altitude and distance from the shoreline for eight ceilometer sites.</p>

Performance Evaluation of High-Resolution Simulations with COSMO over South Italy

“…In any case, as stated also in [7], the combination of high-resolution COSMO data and ceilometer data provides a correct evolution of PBL height.…”

“…These results highlight that tuning COSMO for HPBL evaluation is still a challenging research area. In any case, as stated also in [7], the combination of high-resolution COSMO data and ceilometer data provides a correct evolution of PBL height.…”

“…In particular, for the summer, nocturnal wind speed results were underestimated. Uzan et al [7] tested the accuracy of planetary boundary layer (PBL) height estimations from COSMO, based on the bulk Richardson method over Israel, finding the model was characterized by good accuracy in both flat and elevated terrain. They concluded that a combination of ceilometers (devices that use a laser to determine the height of a cloud ceiling) and high-resolution model data enabled generation of a corrected spatial evolution of the daytime PBL height over Israel.…”