Study of Extreme Changes of the Present Climate in the Cyprus Region: brief report for the PRECIS team at the Hadley Centre

Transcript

1 Study of Extreme Changes of the Present Climate in the Cyprus Region: brief report for the PRECIS team at the Hadley Centre The Study of Extreme Changes of the Present Climate in the Cyprus Region (acronym: CLIMA I) investigated the variations of the present climate in Cyprus for the period with emphasis on the extremes. Clima I combined computer modelling simulations of the PRECIS Regional Climate Model (RCM) (dynamical downscaling of the large-scale ERA-40 ECMWF meteorological data) with instrumental observations and statistical analysis. The use of the PRECIS RCM provides results of high spatial resolution (25 x 25 km) and therefore more detailed information of atmospheric parameters in the local level (model domain: figure 1). In addition, the simulation produces time-series of meteorological data long enough for statistical analysis for the study of the climate extremes during the recent past. Moreover, the comparison of the results from the experiment with the observations (from the Meteorological Service of Cyprus (MSC) and other data sources) allows the validation of the PRECIS model to reproduce the recent/present climate and quantify the uncertainties related to prediction of the future climate. The most important results from this project were: A. The PRECIS model simulation of the large-scale characteristics of the S.E. Europe and Eastern Mediterranean climate showed that: - The model exhibits realistically the climatological (30-year means) features of Temperature (figure 2). The Relative Humidity is also simulated realistically while its variation during is generally very small. - For the region of Cyprus, the model produces a positive trend of the temperature (0.7 ο C) during The decade presents the larger deviation relative to the whole period of study. - The standard deviation of the mean temperature in the area of study increases steadily from towards , indicative of a small rise in the degree of variability of the mean climate. B. The detailed comparison of the model results with the observations of the Meteorological Service of Cyprus (the Maximum and Minimum temperatures) in different stations in Cyprus showed the following: - The model reproduces well the seasonal evolution at all stations (figure 3). - In Nicosia the model also reproduces very well the quantitative features (absolute values) of the Maximum and Minimum Temperatures (figure 4). The precipitation is underestimated from the model although the time evolution is simulated satisfactorily (figure 5)

2 - The long-term variations of the Maximum and Minimum Temperatures are reproduced very well from the model, for all station in Cyprus (for example, figure 6 for Nicosia). C. The study of the extreme weather phenomena in Nicosia with the use of the indices showed that: - The very hot days (maximum temperature > 37 ο C) and the tropical nights (minimum temperature > 25 ο C), the heat-waves conditions, show a positive overall tendency during and an increase in the decade (figure 7). - The very hot and very cold days last longer in the more recent years compared to the initial ones. - An increase is also simulated for the intense rainfalls and the rainfall events that take place during one only day. - A weak (but non-negligible) inverse relationship was identified between the indices of intense rainfall and short duration and the Southern Oscillation - El Niño index (SOI). Therefore, the simulation of the climate during the recent past over the region of Cyprus has reproduced satisfactorily the large-scale qualitative characteristics as well as quantitative aspects of the temporal evolution, especially of temperature in Nicosia during In addition, the study of the extreme weather phenomena for that period in Nicosia revealed an increasing tendency of occurrence and duration of heat-wave conditions during the day and night. Panos Hadjinicolaou eng.hp@fit.ac.cy Acknowledgements This work was funded by the Experienced Expatriate Programme of the Research Promotion Foundation, Cyprus. The author is grateful to the PRECIS team at the Hadley Centre, UK and especially David Hein, David Hussel, Wilfran Moufouma-Okia and Simon Wilson. Special thanks to Silas Michaelides and Kyriakos Theofilou (Director) of the Meteorological Service of Cyprus for the observational data. The indices of extremes were calculated with the RClimdex software, courtesy Zhang and Yang, Climate Research Branch, Met. Service, Canada. MODEL DETAILS

3 The ERA-40 Lateral Boundary Conditions (LBC) are the drivers of the simulation and are produced from the original European Centre for Medium-range Weather Forecasts (ECMWF) ERA-40 meteorological analyses. Hadley Centre (David Hein, personal communication) has prepared a part of the ERA-40 dataset for a broad region of S.E. Europe (with corner coordinates -15 ο W, 55 ο E, 55 ο N, 20 ο S). The ERA-40 LBC are available every 6 hours and during the simulation are informing the PRECIS model for the observed meteorological conditions. The model then adjusts its own meteorological field (produced by its own physics at 0.22 o x 0.22 o horizontal resolution) to the ERA-40 information. Figure 1: a) Overall PRECIS domain b) Cyprus is represented in the model by 14 grid boxes of 25 x 25 km. The black dot indicates Nicosia (grid C4). The brightness of the green colour in every grid depends on the height. Figure 2: climatology from the PRECIS model (ERA-40 downscaling) for S.E. Europe

4 Figure 3: Monthly mean time-series of Maximum Daily Temperature from the PRECIS model and observation from the Meteorological Service of Cyprus for the stations of Nicosia ( ), Prodromos ( ), Larnaca ( ) and Pafos ( ). The model values have been adjusted to account for the height difference of the respective grid box with the real in every station.

5 . Figure 4: Biases of Maximum Temperature (PRECIS MSC) for the stations of Nicosia, Prodromos, Larnaca and Pafos.

6 Figure 5: Monthly time-series of total precipitation for Nicosia from the PRECIS model and the MSC observations (mm/month)

7 Figure 6: Deseasonalised monthly time-series of the maximum Temperature from the PRECIS model and the MSC observations for Nicosia, Prodromos, Larnaca and Pafos.

8 Figure 7: Yearly time-series of Indices of Extremes for Nicosia from the PRECIS model for : Frost Days (FD0, when Tmin < 0 o C), Ice Days (ID0 when Tmax < 0 o C), Summer Days (SU37, when Tmax > 37 o C) and Tropical Nights (TR25, when Tmin > 25 o C). Calculated with the RClimdex package (Zhang and Yang, Climate Research Branch, Met. Service, Canada).