Impacts of the climate change on the precipitation regime on the island of Cyprus Michael Petrakis, Christos Giannakopoulos, Giannis Lemesios Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Athens, Greece 1. Introduction Cyprus lies at the eastern end of the Mediterranean Sea, hence it belongs in the Mediterranean climate zone and therefore, experiences mild winters and hot dry summers. Winters are mild, with some rain and snow on Troodos Mountains. In summer, the extension of the summer Asian Thermal Low is evident throughout the eastern Mediterranean in all seasonal circulation patterns associated with high temperatures and abundant sunshine. The average daytime temperature in winter ranges from 12 15 C. In summer, the average maximum temperature in coastal regions is 32 C. Further inland, the maximum temperature often reaches 40 C. Regarding precipitation, the annual total precipitation ranges from 190-300mm in the central part of Cyprus (from the north and the south) to 450-630mm in the western part of the country. Cyprus is among the most vulnerable regions to climate change, as it is expected to be relatively strongly affected by the projected warming and related changes. Therefore, it is likely to face increases in the frequency and intensity of droughts and hot weather conditions in the near future. Since the region is diverse and extreme climate conditions already common, the impacts may be disproportional. For the examination of near future climate conditions in Cyprus, the PRECIS regional climate model (RCM) has been employed as the main climate model. Except for PRECIS, additional RCMs of the ENSEMBLES EU project have also been used namely KNMI, CNRM, METO, C4I and MPI. The results of the models were used as an ensemble mean for testing and comparing the respective results of PRECIS. All simulations concerning future predictions of climate change in Cyprus are driven by the A1B emission scenario of the IPCC which provides a good mid-line scenario for carbon dioxide emissions and economic growth. Furthermore, the future period used for the simulations was the 2021-2050 and the control period was 1960-1990. The future period 2021-2050 has been chosen specifically for the needs of stakeholders and policy makers to assist their planning in the near future, instead of the end of the twenty-first century as frequently used in other climate impact studies. 2. Future projections for precipitation According to PRECIS model, along all northern coasts, especially Karpasia peninsula, are expected to receive less annual total precipitation in the future, than that estimated for the recent past 1961-1990 (Figure 2-1a). In all other parts of Cyprus, the annual total precipitation appears to have minor decreases or no changes at all. The only region with an increase in total annual precipitation, minor though (up to 5mm), is the area around Orites Forest, east of Paphos. On the other hand, in Figure 2-1b, the ENSEMBLE model mean presents a decrease in annual total precipitation all over Cyprus, with the highest one (about 100-120mm) located in Olympos mountain, in the central part of Troodos. 1
a. PRECIS model Figure 2-1: Changes in annual total precipitation between the future (2021-2050) and the control period (1961-1990). The spatial distributions of seasonal precipitation changes over Cyprus are presented in Figures 2-2 to 2-5. The modeled changes in precipitation exhibit a large spatial and temporal variability. Since most precipitation occurs in winter and autumn, the precipitation changes during these two seasons are very important for the study of droughts and associated water shortages. The winter total precipitation changes, derived from PRECIS output, are negative or zero all over Cyprus, with a minimum value of about -120mm in the peninsula of Karpasia (Figure 2-2a). A significant precipitation decrease is also evident in Ayia Napa, and in north and west coasts, such as Ayia Irini Forest and Akamas peninsula National Park. On the other hand, Orites Forest, in the west, and the continental area south from Nicosia do not present any winter precipitation changes. During 2
winter, the ENSEMBLE model mean presents an almost reverse image from PRECIS (Figure 2-2b). In this case, the highest decreases, up to 70mm, are located in western areas, while the eastern and northern regions of the country are affected by a minor drought. In spring the strongest drying (10-15mm) is projected to occur along the northern coasts of Cyprus, particularly in Ayia Irini Forest and Karpasia peninsula, as PRECIS designates in Figure 2-3a. On the other hand, the southern coasts and especially the area around Limassol Salt Lake may become wetter in spring during the period 2021-2050, with a precipitation increase of up to 15mm. The ENSEMBLE model mean in Figure 2-3b depicts drier future spring conditions all over Cyprus, more prominent in western areas, and less so in eastern areas of the country. According to PRECIS, during summer, continental lowlands, higher elevation areas and parts of the northern coasts of Cyprus receive precipitation decreases of not more than 5mm (Figure 2-4a). On the contrary, a precipitation increase occurs in the southwestern areas, reaching 10mm in Limassol Salt Lake and Orites Forest (southwest from Troodos Mountains). According to the ENSEMBLE model mean (Figure 2-4b), summer total precipitation changes are negative everywhere in the country, reinforcing the fact that rainfall deficits and summer dryness are expected in the near future 2021-2050. The highest precipitation decrease (5mm) is located around the central part of Troodos. Similar to winter, the autumn total precipitation changes, derived from PRECIS output, are mainly negative all over Cyprus, with a minimum value of about -70mm in Karpasia peninsula (Figure 2-5a). Much smaller precipitation decreases are noted in all other parts of the country. However, a slight increase of autumn total precipitation, not exceeding 10mm, is expected in the near future regarding the areas east from Paphos (Orites Forest) and west from Ayia Napa. On the contrary to the other three seasons, the ENSEMBLE model mean gives a wetter projection of the near future (Figure 2-5b). All Cyprus appears to receive more autumn total precipitation in the future than in the recent past (1961-1990), with the largest increases (up to 20 mm) in the western part of the country, especially in the greater area of Paphos. The overall findings of the analysis regarding the potential near future changes in precipitation due to climate change on the island of Cyprus are summarized in Table 2-1. 3
a. PRECIS model a. PRECIS model Figure 2-2: Changes in winter total precipitation between the future (2021-2050) and the control period (1961-1990). Figure 2-3: Changes in spring total precipitation between the future (2021-2050) and the control period (1961-1990). 4
a. PRECIS model a. PRECIS model Figure 2-4: Changes in summer total precipitation between the future (2021-2050) and the control period (1961-1990). Figure 2-5: Changes in autumn total precipitation between the future (2021-2050) and the control period (1961-1990). 5
Table 2-1: Changes in precipitation in Cyprus, between control period (1961-1990) and near future period (2021-2050). WESTERN COASTAL SOUTHERN COASTAL EASTERN COASTAL CONTINENTAL LOWLAND HIGHER ELEVATION INDEX PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE PRa 0-40 -5-60 0-30 0-30 -5-85 PRDJF -15-40 -10-40 -10-30 -5-30 -10-55 PRMAM 5-15 7-15 3-7 1-10 1-15 PRJJA 5-1 6-1 0-1 -2-1 -2-5 PRSON -10 20-15 10 0 5-5 5-10 5 Note: PRa: Annual total precipitation PRJJA: Summer total precipitation PRDJF: Winter total precipitation PRSON: Autumn total precipitation PRMAM: Spring total precipitation 3. Future projections for extreme precipitation To examine future precipitation extremes two indicators were used namely annual max total rainfall over 1 day and over 3 days. These indicators show, indirectly, extreme precipitation events which may lead to flooding events. Concerning future changes of annual max total rainfall over 1 day, PRECIS projections (Figure 3-1a) show that a slight increase of about 2-4 mm is anticipated in western, inland and mountain regions. Additionally, southern and southeastern areas present an increase of about 1 mm in annual max total rainfall over 1 day. On the contrary, ENSEMBLE model mean projections (Figure 3-1b) show that in western areas no changes are expected while in southern, southeastern and inland regions a decrease of about 2 mm is anticipated. Also, mountain regions present a slight decrease of about 1 mm. As regards the annual maximum total precipitation over 3 days, the areas of Ayia Irini Forest and Karpasia peninsula are expected to be the regions with the largest changes in the near future (2021-2050), as calculated by PRECIS model output (Figure 3-2a). Changes in the annual maximum total precipitation over 3 days in all other parts of the island are not remarkable. The only exception in PRECIS pattern is the greater area of Ayia Napa, as well as some higher elevation areas that appear to have a slight increase (not more than 5mm) in annual maximum total precipitation over 3 days. The ENSEMBLE model mean shows in general a more spatially homogenous dry future regime with slight changes (Figure 3-2b). The overall findings of the analysis regarding the potential near future changes in extreme precipitation due to climate change on the island of Cyprus are summarized in Table 3-1. 6
a. PRECIS a. PRECIS model Figure 3-1: Changes in annual maximum total precipitation over 1 day between the future (2021-2050) and the control period (1961-1990). Figure 3-2: Changes in annual maximum total precipitation over 3 days between the future (2021-2050) and the control period (1961-1990). 7
Table 3-1: Changes in indices of extreme precipitation (RX) in Cyprus. WESTERN COASTAL SOUTHERN COASTAL EASTERN COASTAL CONTINENTAL LOWLAND HIGHER ELEVATION INDEX PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE PRECIS ENSEMBLE RX1day (mm) RX3day (mm) 4 1 2-2 2-2 4-2 5-1 1 0-1 -3 4-1 2-1 3-2 4. Evaluation of the RCMs For the evaluation of the RCMs used for this study, climate time series were constructed with a view to compare the results of PRECIS and the ENSEMBLES RCMs with the observational data derived from 10 meteorological stations distributed throughout Cyprus. Time series of mean annual precipitation are presented in Figures 4-1 to 4-4, where it appears that most of the models demonstrate a good agreement with the observed values. The downward trend of all model outputs indicates a continuation of the decreasing precipitation amounts observed in Cyprus in the recent past. In some cases, the model data deviation from the average is large, since the models either underestimate or overestimate the observed values. Specifically, CNRM model follows better than all other models the observed data. C4I model goes also well with the observed values, despite its overestimation in almost all cases. MPI model presents very low values in continental areas and especially in higher elevation regions (Figures 4-3 to 4-4). 5. Conclusions The 1961-1990 precipitation patterns in Cyprus do not depend only upon the synoptic weather conditions but also on the pronounced topography, for example Troodos Mountains through which rivers supply the much needed water downstream. According to PRECIS model, the annual total precipitation ranges from 190-300mm in the central part of Cyprus (from the north and the south) to 450-630mm in the western part of the country. The dominance of local topography is also evident from the seasonal total precipitations. For example, winter total precipitation ranges from about 75mm in the lowlands of central Cyprus to 270mm in the western higher elevation areas, woodlands and wetlands. According to PRECIS, pronounced precipitation reduction is noticed in summer all over Cyprus, except from the greater area of Paphos, southwest from Troodos Mountains. Cyprus projected precipitation changes are quite variable among models. Winter drying will be modest in PRECIS with precipitation decreasing by 5-15mm but larger in the ENSMEBLEs model mean with precipitation decreases reaching 50mm in higher elevation areas. Throughout the year, Cyprus will not be affected by large changes according to PRECIS but according to the ENSEMBLES model mean reductions in precipitation may reach 60mm in southern coastal areas and 80 mm at higher elevation sites. Therefore, Cyprus precipitation patterns must be interpreted with caution, owing to the large temporal variability of rainfall and the inherent limitations of climate models to simulate accurately the hydrological cycle and the large variations of future projected changes among models. 8
Figure 4-1: Time series of mean annual precipitation, as derived from RCMs and observation data, in 3 coastal cities of Cyprus (Larnaca, Limassol, and Paphos). 9
Figure 4-2: Time series of mean annual precipitation, as derived from RCMs and observation data, in 2 continental lowland cities of Cyprus (Nicosia and Lefkara). 10
Figure 4-3: Time series of mean annual precipitation, as derived from RCMs and observation data, in 3 semi-mountainous areas of Cyprus (Stavros, Panagia, and Saittas). 11
Figure 4-4: Time series of mean annual precipitation, as derived from RCMs and observation data, in 2 mountainous areas of Cyprus (Amiantos and Prodromos). 12