Observations of Local Meteorological Variability under Large-Scale Circulation Patterns over Athens, Greece

• Main Authors: Christos H. Halios, Helena A. Flocas, Costas G. Helmis, Dimosthenis N. Asimakopoulos, Panagiotis G. Mouschouras
• Format: Article
• Language: English
• Published: MDPI AG 2018-01-01
• Series: Atmosphere
• Subjects: synoptic circulation patterns; mesoscale flows; geometric structures; recirculation
• Online Access: http://www.mdpi.com/2073-4433/9/1/25

Linking synoptic circulation patterns to specific environmental problems is of significance in the Eastern Mediterranean region, which is characterized by increased seasonal climatic variability and a wealth of distinct weather patterns. This study aims to discuss the links between synoptic scale circulation, intra-day variability and sub-hourly temperature changes over Athens. Diurnal cycles of surface atmospheric variability were examined by applying Principal Component Analysis and Integral Quantities Analysis to a four months data set with surface meteorological elements. Sub-hourly temperature changes were identified by applying a simple linear technique. Principal Components, Integral Quantities and temperature change rates (geometric structures) were related with synoptic circulation categories. It was found that the presence of a Closed Low over the area results in intense along-mountain flows, whilst, after the passage of a trough, when a strong northwesterly flow is established over the area, surface recirculation flows develop. On 64% of the days, geometric structures were observed in the hourly temperature time-series, and they were found to occur across all synoptic situations. Cliff—ramps was the most common geometric structure, and step changes were found to be related with recirculation flows.