Comparison of mineral dust layers vertical structures modeled with CHIMERE-DUST and observed with the CALIOP lidar

摘要

[1] The fmal budget of dust remaining in the atmosphere or deposited on the surface depends directly on the emissions, boundary layer turbulence, stability in the troposphere, and clouds properties. The modeling of these processes remains uncertain and mineral dust long-range transport constitutes a major unknown. To improve this transport, it is crucial to improve modeling of altitudes and thicknesses of mineral dust layers. The spaceborne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) collects new information about the aerosol vertical distribution. Here we diagnose the lidar profile from the outputs of the transport model CHIMERS-DUST and we compare those with their observed counterparts. During the periods June to September 2006 and January to March 2007, the occurrences and structures of dust layers are estimated from the observed and modeled lidar signals. Accounting for the daytime and nighttime periods, the seasonal variability, and CALIPSO flight tracks, it is shown that the presence/absence of dust is correctly reproduced by the model in 70% of the 170,000 vertical profiles studied. The mineral dust horizontal distribution is quite correctly reproduced by the model, while the vertical one shows a vertical overspread which is more pronounced during winter (+100% compared to observations) than summer (+50%). The maximum value of the modeled lidar signal is underestimated with respect to the measured one by typically 30%. Multilayered dust situations are more frequent in the observations (30% of the total data set) than in the model (10%). Despite these errors, the model is able to catch the seasonal variations of the dust layers: the increases of the dust load and of the dust altitudes during summer and the northward shift of the maximum dust occurrence.