Aerosol Lidar observations and model calculations of the Planetary Boundary Layer evolution over Greece, during the March 2006 Total Solar Eclipse
1Institute for Space Applications and Remote Sensing, National Observatory of Athens, Athens 15236, Greece
2Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
3National Technical University of Athens, Athens 15780, Greece
4Institute for Environmental Research and Sustainable Development, National Observatory of Athens, 15236 Athens, Greece
5Laboratory of Climatology, University of Athens, Athens 15784, Greece
Abstract. An investigation of the Planetary Boundary Layer (PBL) height evolution over Greece, during the solar eclipse of 29 March 2006, is presented. Ground based observations were carried out using lidar detection and ranging devices and ground meteorological instruments, to estimate the height of the mixing layer (ML) before, during and after the solar eclipse in northern and southern parts of Greece exhibiting different sun obscuration. Data demonstrate that the solar eclipse has induced a decrease of the PBL height, indicating a suppression of turbulence activity similar to that during the sunset hours. The changes in PBL height were associated with a very shallow entrainment zone, indicating a significant weakening of the penetrative convection. Heat transfer was confined to a thinner layer above the ground. The thickness of the entrainment zone exhibited its minimum during the maximum of the eclipse, demonstrative of turbulence mechanisms suppression at that time. Model estimations of the PBL evolution were additionally conducted using the Comprehensive Air Quality Model with extensions (CAMx) coupled with the Weather Research and Forecasting model (WRF). Model-diagnosed PBL height decrease during the solar eclipse due to vertical transport decay, in agreement with the experimental findings; vertical profiles of atmospheric particles and gaseous species showed an important vertical mixing attenuation.