Solar Eclipse Effects on Clear Days: Case of 11 August 1999, Turkey

Turkey was one of the perfect sites to watch the total solar eclipse on August 11, 1999. The total eclipse was observed across a diagonal path extending from Bartin (41.63oN, 32.33oE) on the Black Sea coast to Diyarbakir (37.55oN, 40.14oE) in southeastern Turkey. The weather was cloudless. Therefore, the eclipse effects were expected to be clearly observable. The cooling effect of total eclipses is observable in temperature and humidity records. It was suggested that the total eclipse can produce a local cyclonic (anticlockwise) rotation of the surface winds within the totality region and the strength of the wind decreases. In this study, we investigate some of these eclipse related effects using surface temperature and wind measured at the meteorological stations located along the totality path of the August 11, 1999 eclipse. Analysis results show a maximum temperature drop of 4oC and wind speed decrease of 6 m/s at the maximum time of the eclipse. It was seen that both temperature and wind speed drops increase with the increasing sea level height.  In two of the twelve selected  stations, an anti-cyclonic rotation of the wind direction within the umbral region was detected.