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BACKGROUND AND AIM: In the LIFE ASTI project a forecasting system for estimating the urban heat island intensity (UHI) and defining high resolution heat health watch warning systems was developed i...

The spatial distribution, radiative forcing, and climatic effects of tropospheric ozone in China during summer were investigated by using the regional climate model RegCM4. The results revealed that the tropospheric ozone column concentration was high in East China, Central China, North China, and the Sichuan basin during summer. The increase in tropospheric ozone levels since the industrialization era produced clear-sky shortwave and clear-sky longwave radiative forcing of 0.18 and 0.71 W m–2, respectively, which increased the average surface air temperature by 0.06 K and the average precipitation by 0.22 mm day–1 over eastern China during summer. In addition, tropospheric ozone increased the land–sea thermal contrast, leading to an enhancement of East Asian summer monsoon circulation over southern China and a weakening over northern China. The notable increase in surface air temperature in northwestern China, East China, and North China could be attributed to the absorption of longwave radiation by ozone, negative cloud amount anomaly, and corresponding positive shortwave radiation anomaly. There was a substantial increase in precipitation in the middle and lower reaches of the Yangtze River. It was related to the enhanced upward motion and the increased water vapor brought by strengthened southerly winds in the lower troposphere.

This study aims at assessing the differences induced in the Global Horizontal Irradiance (GHI) predictions by the mesoscale atmospheric Weather Research and Forecasting (WRF) model when using different shortwave radiation. Model predictions are compared with GHI measurements at 12 stations of the Hellenic Network of Solar Energy (HNSE) for January, April, July and October 2013. The shortwave radiation schemes that were evaluated are: the Dudhia, the updated Rapid Radiative Transfer Model (RRTMG), the updated Goddard and the Goddard Fluid Dynamics Laboratory (GFDL) schemes. All schemes perform better under cloudless conditions due to limited ability of the WRF model to simulate cloudy conditions. The Dudhia scheme performs best with mean relative difference of 2.2 ± 15% for clear-skies, while the differences for the other schemes range between 5 and 12% with similar standard deviations. For all-skies, the model-derived hourly GHI is overestimated for all schemes (∼40–70%). For the daily averages, the model predictions are in better agreement with the measurements, mainly under all-sky conditions, with deviations of about half those of the hourly data and smaller standard deviations. There are strong indications that the differences of the model predictions from the measurements depend on the solar zenith angle and the amount of aerosols at each station.

Stratosphere-to-troposphere transport (STT) is an important natural source of tropospheric ozone, which can occasionally influence ground-level ozone concentrations relevant for air quality. Here, we analyse and evaluate the Copernicus Atmosphere Monitoring Service (CAMS) global and regional forecast systems during a deep STT event over Europe for the time period from 4 to 9 January 2017. The predominant synoptic condition is described by a deep upper level trough over eastern and central Europe, favouring the formation of tropopause folding events along the jet stream axis and therefore the intrusion of stratospheric ozone into the troposphere. Both global and regional CAMS forecast products reproduce the “hook-shaped” streamer of ozone-rich and dry air in the middle troposphere depicted from the observed satellite images of water vapour. The CAMS global model successfully reproduces the folding of the tropopause at various European sites, such as Trapani (Italy), where a deep folding down to 550 hPa is seen. The stratospheric ozone intrusions into the troposphere observed by WOUDC ozonesonde and IAGOS aircraft measurements are satisfactorily forecasted up to 3 days in advance by the CAMS global model in terms of both temporal and vertical features of ozone. The fractional gross error (FGE) of CAMS ozone day 1 forecast between 300 and 500 hPa is 0.13 over Prague, while over Frankfurt it is 0.04 and 0.19, highlighting the contribution of data assimilation, which in most cases improves the model performance. Finally, the meteorological and chemical forcing of CAMS global forecast system in the CAMS regional forecast systems is found to be beneficial for predicting the enhanced ozone concentrations in the middle troposphere during a deep STT event.

The annual and diurnal behavior of the temperature differences in urban areas is important to predict the possible impacts of the future land-use development on climate change and air pollution in heavily populated areas. The behavior of the temperature as well as wind spatio-temporal differences in turn is strongly interconnected with the turbulent and radiative fluxes variability. A 3-year dataset from three automated micrometeorological stations run by the Regional Agency for Environment Protection of Lazio and located in and around the city of Rome is used. The distribution of the urban heat island intensity for the whole period of measurements peaks at 1 °C, but higher values are frequently registered especially referring to differences with the coastal site also due to the sea-breeze cooling effects. The city is generally drier and characterized by winds of lower intensity reaching their maximum 1 h later with the respect to the sub-urban/coastal sites during the afternoon. The micrometeorological data are also analyzed to estimate some key parameter characteristic of the terrain, which represents the main forcing in the numerical models for UHI estimates, such as the albedo, aerodynamics and atmospheric turbulence parameters.

The short–term prediction of near surface ozone levels is very important due to the negative impacts of ozone on human health, climate and vegetation. The objective of this paper is to develop and test an analytical model that could be applied to predict next day's maximum ozone concentration for the first time in Tirana, Albania, where ozone's monitoring has been recently started. The relationship of the daily maximum hourly ozone values with meteorological variables, including near surface air temperature and relative humidity and with air pollution variables like the persistency of ozone levels and its seasonal variation is examined. The data analysis reveals that the pollution persistency and the near surface air temperature are the factors that mainly affect the peak ozone levels. Multiple linear regression analysis has been performed to establish the relationship between the above mentioned parameters and peak ozone concentration. The agreement between observed and predicted daily maximum hourly ozone values is very good, with a correlation coefficient (R) of 0.87. The model slightly under–predicts the ozone concentration while no significant mispredictions are observed. Additionally, the model’s ability to predict the exceedances of a specific ozone limit value is examined. The model successfully predicts the exceedances of 105 μg m −3 , a value that corresponds to the 75 th percentile, in the 86% of the cases applied.

This paper provides a comprehensive overview of the actual knowledge on the atmospheric pollution sources, transport, transformation and levels in the East Mediterranean. It focuses both on the background atmosphere and on the similarities and differences between the urban areas that exhibited important urbanization the past years: the two megacities Istanbul, Cairo and the Athens extended area. Ground-based observations are combined with satellite data and atmospheric modeling. The overall evaluation pointed out that long and regional range transport of natural and anthropogenic pollution sources have about similar importance with local sources for the background air pollution levels in the area.

Modern European cities are characterized by high particulate matter (PM) concentrations. Unfortunately, the number of stations monitoring air pollution, especially PM, is never sufficient for the overall representation of the problem. In the present work, an inexpensive outdoor passive sampler (based on an indoor passive sampler) was developed and assembled in an effort to provide the means to extend current PM monitoring networks. The uncertainty of the sampler was tested in vitro and in vivo. Twenty such outdoor passive samplers were assembled and installed at specific locations in the Greater Thessaloniki Area and measurements of PM were carried out. The results were in good agreement with the official monitoring stations. In addition, they revealed the aggravated air quality in the center of the city and in the west suburbs.

During the summer of 2007 several Greek regions suffered periods of extreme heat, with midday temperatures of over 40 degrees C on several consecutive days. High temperatures were also recorded on the east coast of central Greece, where a complex sea breeze circulation system frequently develops. The more intense events occurred at the end of June and July. The highest temperatures were observed on 26 June and 25 July, while the sea breeze developed only on 25 July. Meteorological data collected at two sites-a coastal urban location and an inland suburban site that is not reached by the sea breeze flow-as well as pollution data collected at the urban site, were analysed in order to investigate the relationship between sea breeze development and the prevailing environmental conditions during these two heat wave events. The analysis revealed that sea breeze development affects temperature and pollution levels at the shoreline significantly, causing a decrease of approximately 4 degrees C from the maximum temperature value and an increase of approximately 30% in peak PM10 levels. Additionally, several stress indices were calculated in order to assess heat comfort conditions at the two sites. It was found that nocturnal comfort levels are determined mainly by the urban heat island effect, the intensity of which reaches up to 8 degrees C, while the applied indices do not demonstrate any significant daytime thermal stress relief due to sea breeze development.

Ambient aerosol concentrations have been implicated in human health effects, in visibility reduction in urban and regional areas, in acid deposition and in perturbing the Earth’s radiation balance. The main concern of the air quality managers is to achieve compliance to the established air quality standards (AQS). As AQS are exceeded in numerous sites worldwide, it is essential to reduce the emissions. Having decided which statistical distribution fits well to the PM10 parent distribution, it is feasible to estimate the reduction in emissions that is required in order to meet AQS. In this study, it is verified that the PM10 concentration distribution can be adequately simulated by lognormal distribution, a conclusion drawn by the calculation of several statistical indexes. The study area is the city of Volos in central Greece, which is experiencing an unpleasant situation concerning the levels of PM10 pollution. The probability density function of lognormal distribution is capable to predict the number of days when the European Union (EU) AQS for PM10 concentration are exceeded in Volos area. Furthermore, the minimum reduction in current emission sources of PM10 required in order to meet the air quality regulations that are established by the EU is calculated for the study area and is found to be ~33%. The results could be utilized as reference for air pollution control strategy.

Ozone air pollution is identified as one of the main threats bearing upon human health and ecosystems, with 25 000 deaths in 2005 attributed to surface ozone in Europe (IIASA 2013 TSAP Report #10). In addition, there is a concern that climate change could negate ozone pollution mitigation strategies, making them insufficient over the long run and jeopardising chances to meet the long term objective set by the European Union Directive of 2008 (Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008) (60 ppbv, daily maximum). This effect has been termed the ozone climate penalty. One way of assessing this climate penalty is by driving chemistry-transport models with future climate projections while holding the ozone precursor emissions constant (although the climate penalty may also be influenced by changes in emission of precursors). Here we present an analysis of the robustness of the climate penalty in Europe across time periods and scenarios by analysing the databases underlying 11 articles published on the topic since 2007, i.e. a total of 25 model projections. This substantial body of literature has never been explored to assess the uncertainty and robustness of the climate ozone penalty because of the use of different scenarios, time periods and ozone metrics. Despite the variability of model design and setup in this database of 25 model projection, the present meta-analysis demonstrates the significance and robustness of the impact of climate change on European surface ozone with a latitudinal gradient from a penalty bearing upon large parts of continental Europe and a benefit over the North Atlantic region of the domain. Future climate scenarios present a penalty for summertime (JJA) surface ozone by the end of the century (2071-2100) of at most 5 ppbv. Over European land surfaces, the 95% confidence interval of JJA ozone change is [0.44; 0.64] and [0.99; 1.50] ppbv for the 2041-2070 and 2071-2100 time windows, respectively.

The NOPEX two concentrated field efforts (CFEs) (June 1994 and April–July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes of latent and sensible heat, but these flux estimates are not directly comparable due to differences in temporal and spatial scales. The challenge here has been to overcome these difficulties so that the different estimates can be critically compared and evaluated in a systematical way. Five different approaches for the estimation of the regional flux of sensible and/or latent heat over the NOPEX area have been evaluated: (1) Direct aggregation — mixed layer evolution method, (2) Weighted averages of (a) aircraft measurements in the boundary layer and of (b) mast measurements, (3) Numerical models (a) ECOMAG — a distributed hydrological model and (b) MIUU — a mesoscale meteorological model. In general, good agreement was found between the regional estimates of the sensible heat flux, based on the mixed layer evolution method and land use weighted mast measurements. The aircraft measurements were found to be systematically smaller than the land use weighted mast estimates. For the latent heat flux good agreement was found between the regional latent heat flux derived from airplane measurements, land use weighted mast estimates, and the two mesoscale numerical models.

A statistical analysis of ozone and PM10 concentration levels in the area of Volos, a medium-sized Greek coastal city, was carried out for the period 2001-2003. The data analysis revealed that the Daily Maximum Hourly (DMH) value of ozone concentration reaches a maximum of 160 µg/m³ during summer; it is observed during afternoon hours and is associated usually with winds from southern directions. This is attributed to the impact of the sea breeze on pollution levels. Concerning PM10 concentration, it was found that its DMH values are quite high and that its Daily Average (DA) value exceeds the limit value of 50 µg/m³ for approximately 38% of the days. The daily cycle shows two maxima (morning-evening) and in these cases the wind is typically from north-northwest directions. The weekly and seasonal variance of DA values of PM10 concentration is not very significant.

Summarization: The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM10 whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p