The heatwaves that affected Greece in July 1987 and July 1988 are considered in terms of (i) the relative strain index. For different types of activity, and (ii) the discomfort index. Hourly values of air temperature and humidity for Thessaloniki and Athens were used as the data base. Both indices show that in terms of physiological strain and general discomfort, Thessaloniki suffered a little more and a little longer than Athens. We conclude that the relative strain index is probably a useful tool in studies of the adverse effects of humid heatwaves on different sections of a population.

We examined the effect of the wind vector analyzed into its three components (direction, speed and persistence), on the circulation of pollen from different plant taxa prominent in the Thessaloniki area for a 4-year period (1996-1999). These plant taxa were Ambrosia spp., Artemisia spp., Chenopodiaceae, Corylus spp., Cupressaceae, Olea europaea, Pinaceae, Platanus spp., Poaceae, Populus spp., Quercus spp., and Urticaceae. Airborne pollen of Cupressaceae, Urticaceae, Quercus spp. and O. europaea make up approximately 70% of the total average annual pollen counts. The set of data that we worked with represented days without precipitation and time intervals during which winds blew from the same direction for at least 4 consecutive hours. We did this in order to study the effect of the different wind components independently of precipitation, and to avoid secondary effects produced by pollen resuspension phenomena. Factorial regression analysis among the summed bi-hourly pollen counts for each taxon and the values of wind speed and persistence per wind direction gave significant results in 22 cases (combinations of plant taxa and wind directions). The pollen concentrations of all taxa correlated significantly with at least one of the three wind components. In seven out of the 22 taxon-wind direction combinations, the pollen counts correlated positively with wind persistence, whereas this was the case for only two of the taxon-wind speed combinations. In seven cases, pollen counts correlated with the interaction effect of wind speed and persistence. This shows the importance of wind persistence in pollen transport, particularly when weak winds prevail for a considerable part of the year, as is the case for Thessaloniki. Medium/long-distance pollen transport was evidenced for Olea (NW, SW directions), Corylus (NW, SW), Poaceae (SW) and Populus (NW).

A pollen calendar has been constructed for the area of Thessaloniki and relationships between pollen transport and meteorological parameters have been assessed. Daily airborne pollen records were collected over a 15-year period (1987-2001), using a Burkard continuous volumetric pollen trap, located in the centre of the city. Sixteen allergenic pollen types were identified. Simultaneously, daily records of five main meteorological parameters (mean air temperature, relative humidity, rainfall, sunshine, wind speed) were made, and then correlated with fluctuations of the airborne pollen concentrations. For the first time in Greece, a pollen calendar has been constructed for 16 pollen types, from which it appears that 24.9% of the total pollen recorded belong to Cupressaceae, 20.8% to Quercus spp., 13.6% to Urticaceae, 9.1% to Oleaceae, 8.9% to Pinaceae, 6.3% to Poaceae, 5.4% to Platanaceae, 3.0% to Corylus spp., 2.5% to Chenopodiaceae and 1.4% to Populus spp. The percentages of Betula spp., Asteraceae (Artemisia spp. and Ambrosia spp.), Salix spp., Ulmaceae and Alnus spp. were each lower than 1%. A positive correlation between pollen transport and both mean temperature and sunshine was observed, whereas usually no correlation was found between pollen and relative humidity or rainfall. Finally, wind speed was generally found to have a significant positive correlation with the concentrations of 8 pollen types. For the first time in the area of Thessaloniki, and more generally in Greece, 15-year allergenic pollen records have been collected and meteorological parameters have been recorded. The airborne pollen concentration is strongly influenced by mean air temperature and sunshine duration. The highest concentrations of pollen grains are observed during spring (May).

Heatwaves, which occurred in both July 1987 and July 1988 in Greece, are considered from the point of view of human discomfort. Hourly values of dry bulb temperature and relative humidity at Thessaloniki, Larissa, and Athens were used to define various limits of discomfort defined by Terjung, Herrington, Thom, and Tromp. On both occasions the heatwave was most severe in Thessaloniki, although both Greek and British press reports concentrated on morbidity and mortality in Athens. Finally, the synoptic situation at the time of each episode is briefly described.

No abstract

The geographical distribution of heating degree-days (HDDs) in Greece is studied by means of special maps. HDDs are calculated by using daily thermal parameters (daily maximum and minimum air temperature) and then compared with an experimentally determined basic air temperature equal to 14°C, according to our estimations. These calculations are based on daily weather data of 40 meteorological stations of the Hellenic National Weather Service published in the Monthly Climatic Bulletin.The regionalization of the 40-point stations' data was achieved using the multiple regression analysis technique and a digital terrain model. For the statistical analysis, the calculated HDDs provide the dependent variables, and geographical data of latitude and longitude, elevation, nearest grid distance from the sea and the land/sea ratio were the independent variables. The resultant statistical correlation was very high.The final outcome of this study was the drawing up of 10 HDD maps, eight for the eight coldest months (October to May) in Greece, one for the entire cold period and one for the number of days demanding heating. The geographical distribution of HDDs is consistent with the great variety of Greek climates arising from the influence of the country's variable relief.The distribution of the HDDs presented in the maps shows that the calculated values were close to the measured ones, which confirms the accuracy of the statistical model used. Possible small deviations were deemed to be acceptable, as the net of the stations used is sparse and it is limited to the elevations below 700 m above sea level. The high accuracy of the HDD maps will be useful for various energy projects and other environmental applications.

No abstract

No abstract