M. Hatzaki

On Cyclonic Tracks over the Eastern Mediterranean

Abstract In this study, an updated and extended climatology of cyclonic tracks affecting the eastern Mediterranean region is presented, in order to better understand the Mediterranean climate and its changes. This climatology includes intermonthly variations, classification of tracks according to their origin domain, dynamic and kinematic characteristics, and trend analysis. The dataset used is the 1962–2001, 2.5° × 2.5°, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). The identification and tracking of the cyclones was performed with the aid of the Melbourne University algorithm. It was verified that considerable intermonthly variations of track density occur in the eastern Mediterranean, consistent with previous studies for the entire Mediterranean, while further interesting new features have been revealed. The classification of the tracks according to their origin domain reveals that the vast majority originate within the examined area itself, mainly in the Cyprus...

The Impact of the Eastern Mediterranean Teleconnection Pattern on the Mediterranean Climate

Abstract The objective of this study is to investigate the impact of the eastern Mediterranean teleconnection pattern (EMP) on the present and future climate of the eastern Mediterranean during winter. For the present climate, daily precipitation and maximum and minimum surface temperature station data are employed for the period of 1958–2003. For the future climate, datasets of the same parameters are derived from the Hadley Centre Regional Climatic Model (HadRM3P) for the period of 2070–2100, using two Intergovernmental Panel on Climate Change (IPCC) emission scenarios for the evolvement of the future atmospheric concentrations of greenhouse gases. The investigation of the impact was based on the regularized canonical correlation analysis (RCCA), while qualitative estimations were performed for each phase of the pattern. It was found that the pattern indeed affects the mean winter patterns of temperature, precipitation, and their extreme events with inverse impacts between the two phases. More specifica...

Indoor air quality assessment in the air traffic control tower of the Athens Airport, Greece

In this study, an assessment of indoor air quality (IAQ) and thermal comfort in the Athens Traffic Control Tower (ATCT) offices of Hellinicon building complex, which is mechanically ventilated, is presented. Measurements of PM10, PM2.5, TVOCs and CO2 concentrations were performed during three experimental cycles, while the Thom Discomfort Index was calculated to describe the employees’ feeling of discomfort. The aim of the first cycle was to identify the IAQ status, the second to investigate the effectiveness of certain measures taken, and the third to continuously monitor and control IAQ. During the first two cycles, daily spot measurements of TVOCs and CO2 were performed at various indoor locations and at the respective outdoor air intake positions, in addition with mean 24-h spot measurements of indoor PM10 and PM2.5. Results revealed that pollution levels vary according to the occupancy and the kind of activity. Following that, an automated system (IMAS) was designed and employed to continuously monitor indoor and outdoor CO2, TVOCs, temperature and relative humidity. The ultimate scope was to control the IAQ and offer acceptable comfort conditions to the employees, whose work is of special nature and extremely demanding. Intervention scenarios were formulated and applied to the system to improve indoor conditions, when and where necessary. Regarding the third cycle, 1-year measurements collected from the system to examine its effectiveness. While it was shown that discomfort may be attributed to co-existence of unsatisfactory thermal comfort conditions and IAQ, usually the sole predominant factor of discomfort feeling is thermal comfort.

Seasonal Aspects of an Objective Climatology of Anticyclones Affecting the Mediterranean

AbstractAn objective climatology of anticyclones over the greater Mediterranean region is presented based on the Interim ECMWF Re-Analysis (ERA-Interim) for a 34-yr period (1979–2012) and the Melbourne University automatic identification and tracking algorithm. The scheme’s robustness and reliability for the transient extratropical propagation of anticyclones, with the appropriate choices of parameter settings, has been established and the results obtained here present new research perspectives on anticyclonic activity affecting the Mediterranean. Properties of Mediterranean anticyclones, such as frequency, generation and dissipation, movement, scale, and depth are investigated. The highest frequency of anticyclones is found over continental areas, while the highest maritime frequency occurs over closed basins exhibiting also maxima of anticyclogenesis. There is a significant seasonality in system density and anticyclogenesis maxima, this being associated with the seasonal variations of the larger-scale a...

On the Dynamics of Mediterranean Explosive Cyclogenesis

In this study, a first attempt is made to examine the mechanisms contributing to the explosive cyclogenesis in the Mediterranean basin during the cold period of the year. Surface explosive cyclones and their vertical characteristics were defined with the aid of the University of Melbourne Cyclone Tracking and Vertical Tracing Software, using the 6-hourly ERA-40 datasets at the resolution of 1° × 1° for a 40-year period (1962–2001), separately for the western (WM), central (CM) and eastern Mediterranean (EM). Composite anomalies of various thermodynamic parameters verified the strong baroclinic character of the phenomenon and the decisive role of the upper level dynamics during the time of explosive cyclogenesis. Moreover, an interesting differentiation characterizes the low level thermodynamic structure of the WM and mainly CM cases in relation to the EM ones, since explosive cyclogenesis in the former areas seem to occur as cold low – level air warms from below, penetrating the Mediterranean from NW, while in the EM cold and high – PV upper level air moves over areas of warm and moist low level environment. Nevertheless, a synergy of the lower and the upper levels is implied for all parts of the Mediterranean basin with different relative importance.

Climate Impact Assessments

This chapter highlights key climate impacts, hazards and vulnerabilities and associated indicators that have been used to assess current (recent) climate impacts at each of the case-study sites. The aim is to illustrate some of the wide range of information available from individual case studies and highlight common themes that are evident across multiple case-study locations. This is used to demonstrate linkages and sensitivities between the specific climate impacts of relevance for each case-study type (urban, rural and coastal) and the key climate hazards and biogeophysical and social vulnerabilities representing the underlying drivers and site conditions. For some impacts, there are clear, direct links with climate events, such as heat stress and flooding, while for others, such as energy supply and demand, the causal relationships are more indirect, via a cascade of climate, social and economic influences. Water availability and extreme temperatures are common drivers of current climate impacts across all case studies, including, for example, freshwater supply and heat stress for urban populations; irrigation capacity and growing season length for agricultural regions; and saltwater intrusion of aquifers and tourist visitor numbers at coastal locations. At some individual case-study locations, specific impacts, hazards and/or vulnerabilities are observed, such as peri-urban fires in Greater Athens, infrastructure vulnerability to coastal flooding in Alexandria, groundwater levels in Tel Hadya and vector-borne diseases in the Gulf of Oran. Throughout this chapter, evidence of current climate impacts, hazards and vulnerabilities from each of the case studies is detailed and assessed relative to other case studies. This provides a foundation for considering the wider perspective of the Mediterranean region as a whole, and for providing a context from which to assess consequences of future climate projections and consider suitable adaptation options.

Assessment of climate change extremes over the Eastern Mediterranean and Middle East region using the Hadley Centre PRECIS Regional Climate Model

Regional-scale climate projections based on the Hadley Centre PRECIS climate model have been used to assess future changes of rainfall and temperature extremes in the Eastern Mediterranean and Middle East region (EMME). Model output was evaluated by comparison with stations located in the western part of the study region. The area of interest is particularly vulnerable to extreme climate events such as droughts and heat waves. Extreme climate indices were calculated for three future 30-year time slices and compared to the reference period (1961–1990). Overall, model projections for the different future time periods reveal a continual and gradual future warming trend while conditions characterised as exceptional hot summers during the control period are found to become “typical” by the end of the twenty-first century. In agreement with previous studies, our results point to a drying tendency in the study domain, and indicate a decline in annual precipitation by 5–30% by the end of the twenty-first century relative to the reference period. The model projects larger precipitation reductions in the northern EMME, while the number of days with heavy precipitation is expected to decrease in the high-elevation areas of the region.

Integration of the Climate Impact Assessments with Future Projections

Climate projections are essential in order to extend the case-study impacts and vulnerability assessments to encompass future climate change. Thus climate-model based indicators for the future (to 2050 and for the A1B emissions scenario) are presented for the climate and atmosphere theme (including indices of temperature and precipitation extreme events), together with biogeophysical and socioeconomic indicators encompassing the other case-study themes. For the latter, the specific examples presented here include peri-urban fires, air pollution, human health risks, energy demand, alien marine species and tourism (attractiveness and socio-economic consequences). The primary source of information about future climate is the set of global and regional model simulations performed as part of CIRCE. These have the main novel characteristic of incorporating a realistic representation of the Mediterranean Sea including coupling between sea and atmosphere. These projections are inevitably subject to uncertainties relating to unpredictability, model structural uncertainty and value uncertainty. These uncertainties are addressed by taking a multi-model approach, but problems remain, for example, due to a systematic cold bias in the CIRCE models. In the context of the case-study integrated assessments, there are also uncertainties ‘downstream’ of climate modeling and the construction of climate change projections – largely relating to the modeling of impacts. In addition, there are uncertainties associated with all socio-economic projections used in the case studies – such as population projections. Thus there are uncertainties inherent to all stages of the integrated assessments and it is important to consider all these aspects in the context of adaptation decision making.

Identification of the development mechanisms of an explosive cyclone in the central Mediterranean with the aid of the MSG satellite images

The development mechanisms of an explosive cyclone over Central Mediterranean are examined, by relating the cloud patterns in the infrared, water vapour and visible channels of the Meteosat Second Generation (MSG) satellite images, to the surface-upper air operational analyses and thermodynamic parameters, including potential and geostrophic vorticity analyses, potential and equivalent potential temperature, static stability and thermal heat fluxes. The specific case study derived from an updated climatology of Mediterranean explosive cyclones for the 2002-2010 period, being performed with the aid of the University of Melbourne Cyclone Tracking scheme (MS algorithm) and ERA-INTERIM datasets. It was found that during the ordinary cyclogenesis the increased mid-upper level relative humidity over Northern Algeria along with the enhanced moisture gradient in the area between Portugal and Spain; indicate the existence of a jet -streak, with the dry zone to be located on the cold side of the jet axis. The descent of the dry air is more pronounced within the left exit region of the jet streak in the poleward portion of an upper confluence zone. Six hours later, the eastward movement of the cloud pattern in the Northern African coasts significantly resembles the structure of a baroclinic leaf, being related to the early stages of surface frontogenesis, due to the deformation process within a strong wind field. During the time of rapid deepening, when the surface cyclone propagated from the Northern African coasts towards the area of Sicily - Gulf of Taranto, the development is characterised by the transition from the baroclinic leaf structure to the comma cloud one and finally the formation of a bent-back occlusion.

Assessing the Sensitivity of COSMO/GR Atmospheric Model to Effectively Simulate the Influence of Diabatic Heating on Eastern Mediterranean Explosive Cyclogenesis Under Different Parameterizations of the Model Physics

Mediterranean explosive cyclogenesis is the result of the interaction between upper level baroclinic and low level diabatic processes. This interaction presents significant differences in specific Mediterranean sub-areas and in different cases of rapid deepening, especially regarding the evolution of the diabatic processes. In this study, the regional atmospheric model COSMO-GR is used for the evaluation of the spatial and temporal variations of low level diabatic heating in a case of explosive cyclogenesis in the north Aegean Sea. Model runs were performed for a series of different values of the model parameter sea roughness, which has proved to significantly affect the simulation of the diabatic processes. It was found that smaller values of the above parameter compared to the default parameterization, lead to significant enhancement of the model calculated surface turbulent fluxes and the respective surface deepening rates during the explosive deepening period and thus to lower minimum pressures, which are closer to ERA-Interim reanalysis values. Moreover, the intrusion of the diabatic heating in the middle troposphere due to latent heat release was also examined, demonstrating the necessity for the determination of the most suitable parameterization of the model physics.