A new methodology is presented for the model estimation of an import-export pollution balance across country borders based on the classification of the synoptic scale atmospheric circulation. As an application, the transboundary transport of SO2 and NOx across the Greek borders is investigated for the year 1995. The annual total inflow-outflow fluxes were derived by weighting the model results with the annual relative frequency of the corresponding synoptic type appearance. The results of the new modelling method are similar to those following the day-by-day calculation of the inflow-outflow fluxes for the whole year 1995 using the same models. The advantage of the new methodology is that it is definitely less time-consuming than the day-by-day calculations. Hence, the proposed methodology can be employed as a practical tool for several applications requiring the implementation of complex models over longer time periods. © 2003 Elsevier Ltd. All rights reserved.

An attempt is made to examine the relationship of the surface circulation prevailing over Europe with the corresponding surface and 500 hPa over Greece by correlating Lamb weather types for western Europe and Hess and Brezowsky (HB) types for central Europe with those derived from a new classification scheme for the Greek area. It was found that it was difficult to formulate rules controlling the frequency distributions of the circulation types over the Greek area in relation to the circulation over western and central Europe. However, statistically significant correlation was found between certain types with high frequency, which is greater between Lamb and HB types with the surface circulation types over the Greek area, compared with 500 hPa circulation types. For the most correlated pairs, seasonal composites of mean sea-level pressure and 500 hPa geopotential height anomalies demonstrated that the formation of the circulation types over the Greek area depends on the extent, intensity of the anticyclonic or cyclonic centres, air mass characteristics, and stability profile in the lower troposphere over the regions examined, but especially over the central and eastern Mediterranean. Copyright © 2004 Royal Meteorological Society.

An attempt is made to examine rainfall variability over the Greek area in relation to 500 hPa atmospheric circulation. Daily precipitation series from 22 evenly distributed Greek stations have been used for the period 1958-2000, along with the classification scheme of daily circulation types at 500 hPa for the same period. The seasonal frequency and the trends of circulation types have been calculated. It was found that there is a general positive trend of anticyclonic circulation types and a negative one for cyclonic types. The seasonal trends of rainy days and the precipitation totals have also been calculated and analysed. A general decreasing tendency of winter rainfall is observed; the decreasing trend during autumn and spring is less significant. Concerning the frequency and intensity of rainfall per circulation type, a decreasing tendency becomes evident for the majority of the stations during winter, whereas there is an increasing tendency during autumn. A multiple regression-cross-validation model was developed using the seasonal frequency of circulation types as predictors and the seasonal rainfall totals as predictants. Only the winter modelled precipitation shows a good agreement with the observed precipitation, whereas for the other seasons the agreement is relatively poor. This could be caused by the influence of different factors that are not captured by the classification scheme used. The proposed model could serve as a circulation-based downscaling method that could be further applied to geopotential data available from general circulation models in order to study regional climatological consequences of future climate scenarios. Copyright © 2004 Royal Meteorological Society.