Mixed-Layer Depth Determination in the Barcelona Coastal Area From Regular Lidar Measurements: Methods, Results and Limitations |
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Authors: | M Sicard C Pérez F Rocadenbosch J M Baldasano D García-Vizcaino |
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Institution: | (1) Dept. de TSC, Jordi Girona 1, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain;(2) LMA, Avda. Diagonal 647, Universitat Politècnica de Catalunya, planta 10, 08028 Barcelona, Spain |
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Abstract: | Regular aerosol backscatter measurements using an elastic-backscatter lidar were performed between May 2000 and December 2002
in Barcelona (Spain), within the framework of the European project EARLINET (European Aerosol Research Lidar Network). The
mixed-layer depth was one of the major parameters to be retrieved. Three derivative methods have been tested in this complex
coastal area using the range-squared-corrected lidar signal: (1) the minimum of its first derivative, (2) the minimum of its
second derivative, and (3) the minimum of the first derivative of its logarithm. The second method was found to give statistically
the best results when compared to radiosoundings, and was used to process the whole dataset. A number of 162 days and 660
profiles averaged over 30 min have been examined. Between 1000 and 1500 UTC, the mixed-layer depth oscillates between 300
and 1450 m in summer and between 390 and 1420 m in winter. The standard deviation for this portion of the day is 180 and 256
m, respectively, in summer and winter. In summer, low heights (mainly limited to 400–800 m) are associated with large mesoscale
compensatory subsidence over the sea and to the thermal internal boundary-layer formation. The strong coastal and orographic
influences and the climatological settling of Barcelona determine the complexity of the boundary-layer dynamics and the high
heterogeneity of the lidar signals. In many cases, single lidar analyses do not allow an unambiguous determination of the
mixed-layer depth. Two diurnal cycle measurements are discussed together with synoptic maps, backtrajectories and radiosoundings
in order to outline the complexity of the area and the limitations of the methods. |
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Keywords: | Coastal region Complex terrain Lidar profiles Mixed-layer depth Radiosoundings |
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