This paper examines the effect of the total solar eclipse of 29 March 2006 on meteorological variables across Greece. Integrated micrometeorological measurements were conducted at Kastelorizo, a small island within the path of totality, and other sites within the Greek domain, with various degrees of solar obscuration. The observations showed a dramatic reduction in the incoming global radiation and subsequent, pronounced changes in surface air temperature with the lowest temperature values occurring about 15 min after the full phase. The amplitude of the air temperature drop was not analogous to the obscuration percentage but was principally determined by the surrounding environment (mainly the sea influence), the background meteorological conditions and local cloudiness. Surface wind-speed decreased in most sites as a result of the cooling and stabilization of the atmospheric boundary layer. This perturbation provided a unique opportunity to apply a sensitivity analysis on the effect of the eclipse to the Weather Research and Forecast (WRF) numerical mesoscale meteorological model. Strong anomalies, not associated with a dynamic response, were simulated over land especially in surface air temperature. The simulated temperature drop pattern was consistent with the observations.

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The effect of the total solar eclipse of 29 March 2006 on meteorological variables in Greece

Integrated atmospheric measurements were made at two sites in the UK during the total solar eclipse of 11 August 1999. Sensitive high–resolution meteorological observations revealed dynamical atmospheric effects despite the presence of cloud. Short–term eclipse–related changes dominated over temperature, wind speed and wind directions associated with the synoptic conditions, and 35 min period gravity waves were detected in surface–pressure observations. Theoretical calculations for solar radiation changes were compared with observations made during the 97% partial eclipse in clear skies at Reading, Berkshire, and used to predict the radiative changes expected at Camborne, Cornwall, during totality. At Camborne, a vertical array of sensitive fine–wire thermometers was operated with a high–resolution sonic anemometer, logged at 5 Hz. Despite cloudy conditions, which reduced the eclipseinduced thermal perturbations, small temperature and wind changes were detected which were consistent with theory. The cold outflow from the umbra was unambiguously detected for the first time in cloudy conditions.

Meteorological effects of the eclipse of 11 August 1999 in cloudy and clear conditions

This paper provides the overview of an inte- grated, multi-disciplinary effort to study the effects of the 29 March 2006 total solar eclipse on the environment, with special focus on the atmosphere. The eclipse has been visible over the Eastern Mediterranean, and on this occasion several research and academic institutes organised co-ordinated ex- perimental campaigns, at different distances from eclipse to- tality and at various environments in terms of air quality. De- tailed results and findings are presented in a number of com- ponent scientific papers included in a Special Issue of Atmo- spheric Chemistry and Physics. The effects of the eclipse on meteorological parameters, though very clear, were shown to be controlled by local factors rather than the eclipse mag- nitudes, and the turbulence activity near surface was sup- pressed causing a decrease in the Planetary Boundary Layer. In addition to the above, the decrease in solar radiation has caused change to the photochemistry of the atmosphere, with night time chemistry dominating. The abrupt "switch off" of the sun, induced changes also in the ionosphere (140 up to 220 km) and the stratosphere. In the ionosphere, both photochemistry and dynamics resulted to changes in the re- flection heights and the electron concentrations. Among the most important scientific findings from the experiments un- dertaken has been the experimental proof of eclipse induced thermal fluctuations in the ozone layer (Gravity Waves), due to the supersonic movement of the moon's shadow, for the first time with simultaneous measurements at three altitudes namely the troposphere, the stratosphere and the ionosphere.

/pdf/the-total-solar-eclipse-of-march-2006-overview-3dantmcz8s.pdf

The Total Solar Eclipse of March 2006: overview

Meteorological changes during a solar eclipse

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.

/pdf/aerosol-lidar-observations-and-model-calculations-of-the-3unyloso5o.pdf

Aerosol Lidar observations and model calculations of the Planetary Boundary Layer evolution over Greece, during the March 2006 Total Solar Eclipse

Boundary-layer meteorologicalmeasurements were made before, during, and after theMay 10, 1994 partial (94%) solar eclipse over thedesert at the Atmospheric Profiler Research Facilityat White Sands Missile Range, New Mexico, U.S.A. A largenumber of sensors were located in the middle of theTularosa Basin to measure mean and turbulentquantities and the refractive index structureparameter (Cn2). This event permitted a rareopportunity to measure, examine, and document theeffects upon the atmospheric boundary layer of asudden cut-off and subsequent turn-on of the sun'sradiant energy. At the peak of the eclipse, whichoccurred for more than three hours, all of the heatexchange parameters were affected, the turbulentprocesses were diminished, and the refractive indexstructure parameter decreased dramatically. A time-heightdisplay from the FM-CW radar shows a Kelvin–Helmholtzwave that developed during theeclipse. The results of several analyses arepresented to document and characterize the eclipse-modifiedboundary layer.

D. Garvey

Papers

Solar eclipse effects observed in the planetary boundary layer over a desert