The atmospheric conditions over Europe and the Mediterranean, favoring snow events in Athens, Greece

International audienceThe 3-dimensional structure and the evolution of atmospheric circulation favoring snowfall in Athens are examined. The study refers to 61 snow events, which occurred during the period 1958?2001. For each one of the events, the patterns of MSL pressure, 850 hPa and 500 hPa air temperatures, 500 hPa geopotential height and 1000?500 hPa thickness are constructed for the European region, for the day before (D-1), the first day (D) and the day after the end of the event (END). A statistical methodology involving Factor Analysis and Cluster Analysis is applied to the above data sets and the 61 cases are finally classified into five clusters. These clusters are generally characterized by a north-easterly flow in the lower troposphere over the Athens area. This flow is associated with the presence of a low pressure system around Cyprus and an anticyclone over Europe. The position, the intensity and the trajectories of the surface and the upper air systems during D-1, D and END days are generally different among the five clusters

The main characteristics of atmospheric circulation associated with fog in Greece

The characteristics of the atmospheric circulation over Europe and the Mediterranean associated with the formation and the dissipation of fog in Greece are examined. The data used consists of: i) 3-hourly meteorological observations recorded at 16 meteorological stations in Greece and ii) daily (00:00 UTC) 2.5×2.5 grid point values of mean sea-level pressure, 500 hPa geopotential height, 850 hPa and 500 hPa air temperatures and 1000–500 hPa thickness over Europe for the period 1957–2002. 1055 fog events are extracted from the 3-hourly meteorological observations. A specific methodology scheme including S-mode Factor Analysis and k-means Cluster Analysis is applied to the grid point data sets for the first day of a fog event (D day), the day prior to D day (D-1 day) and the day that follows the last day of a fog event (END day) and the 1055 evolutions of the atmospheric circulation associated with fog events in Greece are classified into 10 clusters. The mean patterns of MSL Pressure, 850 hPa and 500 hPa air temperatures, 1000–500 hPa thickness and 500 hPa geopotential height show that in most of the clusters, the presence of anticyclonic conditions over the Balkans, a warm front passage, or a weak, humid southerly flow induced by the presence of a shallow depression over the western Mediterranean favor fog formation in Greece, while the dissipation of fog occurs when drier air masses are transferred over the Balkans. The main differences among the 10 clusters refer to the exact position, the intensity and the specific evolution of the surface and the upper air systems, the season of their predominance and the area of the Greek territory that mainly refer to

The influence of Indian summer monsoon on the climatic regime of Eastern Mediterranean

The objective of this study is to further investigate the ISM impact on the temperature and wind regime of the Eastern Mediterranean region, with the aid of multivariate statistics. For this purpose, the standardized Dynamic Indian Monsoon Index by Wang and Fan (1999) was used for a period of 44 years (1958-2001) along with ERA40 Reanalysis data, including monthly means of surface air temperature and wind at 850hPa with a horizontal resolution of 0.25° latitude x 0.25° longitude. Initially, the correlation maps of the seasonal anomalies of the two variables upon ISM index are computed and subsequently Empirical Orthogonal Function Analysis (EOF) is carried out on individual fields. Under this framework, correlation coefficients between the derived EOF amplitudes and ISM index are calculated and in order to validate the results from the first method, the EOF modes that exhibit high correlation coefficients are compared to the aforementioned correlation patterns. Our results verify that there is correlation between Indian monsoon and the etesian pattern over the Aegean Sea

Relationship between the Indian summer monsoon and the large-scale circulation variability over the Mediterranean

In this study the impact of the Indian summer monsoon on the large scale variability of the atmospheric circulation over the Mediterranean is investigated on an inter-annual time scale. Composite and correlation analysis results are presented, outlining different circulation patterns in the upper and lower troposphere for strong and weak monsoon years respectively. For this purpose ERA-40 Reanalysis monthly mean data at various isobaric levels together with the standardized All India Rainfall Index for boreal summer (June–July–August–September) of a 44- year period were employed. During strong monsoon years many atmospheric circulation systems appear strengthened over Eurasia, resembling a well-organized Rossby wave train over the area. In the upper troposphere a meridional shift of the jet streams over the examined area was also identified during extreme monsoon years. On the other hand, in the lower troposphere enhanced northerlies (Etesians) appear to dominate over Eastern Mediterranean along with intensified subsidence during strong monsoon years

On the link between Indian summer monsoon and the Etesian pattern over the Aegean Sea

The Indian summer monsoon (ISM) is a key factor influencing the eastern Mediterranean climate. During early summer period, the thermal low over Pakistan and northwestern India extends towards the Mediterranean through inner Iraq and Turkey. On the other hand, the Azores high expands eastwards and meets the Balkan high pressure system, forming one common system. Greece lies at the transitional zone between these two pressure systems, where persistent northeasterly wind currents form especially over the Aegean, known as the Etesians. The objective of this study is to investigate the interrelation between the ISM and the Etesian winds over the Aegean Sea during summer for an extended period of 44 years (1958-2001) with the aid of composite and correlation analyses and ERA 40 datasets. More specifically, the study will focus on the ISM activity during and prior to or after ‘Etesian episodes’ in order to determine the extent to which one system may lead another. The present analysis reveals that during enhanced monsoon years two upper level ridges prevail over the greater area of interest, one over western Europe and northern Africa, which is part of the Azores high and a second one over Pakistan region, Persian Gulf and Middle Asia, which extends to the west and connecting to the first one forms a slight trough over Eastern Mediterranean. At lower levels, an intensification of the thermal Asian low as well as of the high pressure system prevailing over western and central Europe is apparent. Concurring with this pattern in upper and lower troposphere, anomalously strong northerlies appear over the Aegean during periods with enhanced monsoon activity, as horizontal surface wind anomalies depict. In agreement with previous studies, mid-level subsidence during excess monsoon rainfall periods is found to be more intense over the Eastern Mediterranean, Iraq, Saudi Arabia and east of the Caspian Sea

The RISKMED project : philosophy, methods and products

This paper presents RISKMED, a project targeted to create an Early Warning System (EWS) in case of severe or extreme weather events in the central and eastern Mediterranean and specifically in southern Italy, northwestern Greece, Malta and Cyprus. As severe or extreme weather events are considered, cases when the values of some meteorological parameters (temperature, wind, precipitation) exceed certain thresholds, and/or a severe weather phenomenon (thunderstorm, snowfall) occurs. For an accurate weather forecast, selected meteorological models have been operated daily, based on a nesting strategy using two or three domains, providing detailed forecasts over the above mentioned areas. The forecast results are further exploited for the evaluation and prediction of human discomfort and fire weather indices. Finally, sea wave models have also been operating daily over the central and eastern Mediterranean Sea. In case a severe or extreme weather event is forecasted within the next 48 or 72 h for selected target areas (sub-regions defined by their morphological and population characteristics), the local authorities and the public are informed via a user-friendly graphic system, the so-called RISK MAP. On the web page of the Project (http://www.riskmed.net), additional information is provided about the real-time values of some meteorological parameters, the latest satellite picture and the time and space distribution of lightning during the last 24 h. The RISKMED project was financed by the EU and the Ministries of National Economy of Greece, Italy, Malta and Cyprus, in the frame of INTERREG IIIB/ARCHIMED programme.peer-reviewe

Operational forecasting of daily summer maximum and minimum temperatures in the Valencia Region

Extreme-temperature events have a great impact on human society. Thus, knowledge of summer temperatures can be very useful both for the general public and for organizations whose workers operate in the open. An accurate forecasting of summer maximum and minimum temperatures could help to predict heatwave conditions and permit the implementation of strategies aimed at minimizing the negative effects that high temperatures have on human health. The objective of this work is to evaluate the skill of the regional atmospheric and modelling system (RAMS) model in determining daily summer maximum and minimum temperatures in the Valencia Region. For this, we have used the real-time configuration of this model currently running at the Centro de Estudios Ambientales de Mediterráneo Foundation. This operational system is run twice a day, and both runs have a 3-day forecast range. To carry out the verification of the model in this work, the information generated by the system has been broken into individual simulation days for a specific daily run of the model. Moreover, we have analysed the summer forecast period from 1 June to 31 August for 2007, 2008, 2009 and 2010. The results indicate good agreement between observed and simulated maximum temperatures, with RMSE in general near 2 °C both for coastal and inland stations. For this parameter, the model shows a negative bias around −1.5 °C in the coast, while the opposite trend is observed inland. In addition, RAMS also shows good results in forecasting minimum temperatures for coastal locations, with bias lower than 1 °C and RMSE below 2 °C. However, the model presents some difficulties for this parameter inland, where bias higher than 3 °C and RMSE of about 4 °C have been found. Besides, there is little difference in both temperatures forecasted within the two daily RAMS cycles and that RAMS is very stable in maintaining the forecast performance at least for three forecast days

Patients with artificial joints: do they need antibiotic cover for dental treatment?

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.This study reviews whether patients with artificial joints need antibiotic cover for dental treatment. Generally in Australia the practice has developed of giving most patients with artificial joints antibiotic prophylaxis for a wide range of dental procedures. This is partly on anecdotal grounds, partly historical and partly for legal concerns. It has been encouraged by some guidelines. Scientifically, the risk and the benefit of each step in the process needs to be analysed. This review shows that the risk of an artificial joint becoming infected from a bacteraemia of oral origin is exceedingly low whereas the risk of an adverse reaction to the antibiotic prophylaxis is higher than the risk of infection. If all patients with artificial joints receive antibiotic prophylaxis then more will die from anaphylaxis than develop infections. Factors which balance the risk benefit are if the patient is seriously immunocompromised, if the joint prosthesis is failing or chronically inflamed and if the dental procedures, such as from extractions and deep periodontal scaling, produce high level bacteraemias. Recommendations to rationalize antibiotic prophylaxis for patients with artificial joints are presented.JF Scott, D Morgan, M Avent, S Graves and AN Gos

Prospective Study of Infection, Colonization and Carriage of Methicillin-Resistant Staphylococcus Aureus in an Outbreak Affecting 990 Patients

In the three years between November 1989 and October 1992, an outbreak of methicillin-resistantStaphylococcus aureus (MRSA) affected 990 patients at a university hospital. The distribution of patients with carriage, colonization or infection was investigated prospectively. Nosocomial acquisition was confirmed in at least 928 patients, 525 of whom were identified from clinical specimens as being infected (n=418) or colonized (n=107) by MRSA. An additional 403 patients were identified from screening specimens, of whom 58 subsequently became infected and 18 colonized. Screening of the nose, throat and perineum detected 98 % of all carriers. Of the 580 infections in 476 patients, surgical wound, urinary tract and skin infections accounted for 58 % of the infections. Of the 476 infected patients, death was attributable to MRSA infection in 13 %. Colonization with MRSA was found in 127 patients and 42 % of 165 colonized sites were the skin. Auto-infection from nasal carriage or cross-infection, probably via staff hands, seemed to be the most common mode of acquisition of MRSA infections

Should patients with hip joint prosthesis receive antibiotic prophylaxis before dental treatment?

The safety committee of the American Academy of Orthopedic Surgeons (AAOS) recommended in 2009 that clinicians should consider antibiotic prophylaxis for all patients with total joint replacement before any invasive procedure that may cause bacteremia. This has aroused confusion and anger among dentists asking for the evidence. The present review deals with different aspects of the rationale for this recommendation giving attention to views both in favor of and against it