Athens

Energy flux parametrization as an opportunity to get Urban Heat Island insights: The case of Athens, Greece (Thermopolis 2009 Campaign)

 Science of The Total Environment, Vol.  542(Pt A) , 136-143,  (2016).
doi:10.1016/j.scitotenv.2015.10.056
 
 
Energy flux parametrization as an opportunity to get Urban Heat Island insights: The case of Athens, Greece (Thermopolis 2009 Campaign).
 
                                    G. Loupa, S. Rapsomanikis, A. Trepekli, K. Kourtidis

 
 

Abstract.Energy flux parameterization was effected for the city of Athens, Greece, by utilizing two approaches, the Local- Scale UrbanMeteorological Parameterization Scheme(LUMPS) and the Bulk Approach (BA). In situ acquired data are used to validate the algorithms of these schemes and derive coefficients applicable to the study area. Model results from these corrected algorithms are compared with literature results for coefficients applicable to other cities and their varying construction materials. Asphalt and concrete surfaces, canyons and anthropogenic heat releases were found to be the key characteristics of the city center that sustain the elevated surface and air temperatures, under hot, sunny and dryweather, during theMediterranean summer. A relationship between storage heat flux plus anthropogenic energy flux and temperatures (surface and lower atmosphere) is presented, that results in understanding of the interplay between temperatures, anthropogenic energy releases and the city characteristics under the Urban Heat Island conditions.

 
 
 
 

A study of the hourly variability of the urban heat island effect in the Greater Athens Area during summer

 Science of The Total Environment (2015) 517C:162-177.
doi:10.1016/j.scitotenv.2015.02.062
 
A study of the hourly variability of the urban heat island effect in the Greater Athens Area during summer
 
K Kourtidis · A.K. Georgoulias · S Rapsomanikis · V Amiridis · I Keramitsoglou · H Hooyberghs · B Maiheu · D Melas
 
 
ABSTRACT: Measurements of air temperature and humidity in the urban canopy layer during July 2009 in 26 sites in Athens, Greece, allowed for the mapping of the hourly spatiotemporal evolution of the urban heat island (UHI) effect. City districts neighboring to the mountains to the east were the hottest during the afternoon, while being among the coolest during the early morning hours. While during the early morning some coastal sites were the hottest, the warm air plume slowly moved to the densely urbanized center of the city until 14:00-15:00, moving then further west, to the Elefsis industrial area in the afternoon. Results from the UrbClim model agree fairly well with the observations. Satellite-derived land surface temperature (LST) data from AATSR, ASTER, AVHRR and MODIS, for pixels corresponding to ground stations measuring Tair, showed that LST can be up to 5K lower than the respective Tair during nighttime, while it can be up to 15K higher during the rest of the day. Generally, LST during late afternoon as acquired from AATSR is very near to Tair for all stations and all days, i.e., the AATSR LST afternoon retrieval can be used as a very good approximation of Tair. The hourly evolution of the spatial Tair distribution was almost the same during days with NE Etesian flow as in days with sea breeze circulation, indicating that the mean wind flow was not the main factor controlling the diurnal UHI evolution, although it influenced the temperatures attained. No unambiguous observation of the urban moisture excess (UME) phenomenon could be made.

Vertical Energy and Momentum Fluxes in the Centre of Athens, Greece During a Heatwave Period (Thermopolis 2009 Campaign)

Boundary-Layer Meteorology, (2014)                                                                                                            doi:10.1007/s10546-014-9979-2                                                                                                                  link:http://link.springer.com/article/10.1007%2Fs10546-014-9979-2 

Vertical Energy and Momentum Fluxes in the Centre of Athens, Greece During a Heatwave Period (Thermopolis 2009 Campaign)

                            

                              S. Rapsomanikis • A. Trepekli • G. Loupa • C. Polyzou

Abstract. The atmospheric energy budget in the centre of Athens, Greece was determined during the Thermopolis 2009 campaign in order to investigate the development of the urban heat island. Heatwaves during summer are a common occurrence in this large conurbation. Micrometeorological data from a tower were acquired in a densely built central district, and net all-wave radiation, sensible heat, latent heat and momentum flux densities were derived by the eddy-covariance method and also estimated usingMonin–Obukhov similarity relationships. Under the prevailing hot and dry conditions, sensible heat-flux density was on average five times larger than the latent heat-flux density. The anthropogenic contribution to the energy budget was also determined on the basis of the acquired data.

Keywords. Aerodynamic roughness length • Anthropogenic contributions • Eddy covariance • Energy budget • Monin–Obukhov similarity theory • Urban heat island

Numerical study of the urban heat island over Athens (Greece) with the WRF model

Atmospheric Environment,Volume 73, 103-111, (2013).

doi:10.1016/j.atmosenv.2013.02.055

Numerical study of the urban heat island over Athens (Greece) with the WRF model

T.M. Giannaros, D. Melas, I.A. Daglis, I. Keramitsoglou, K. Kourtidis.

Abstract. In this study, the Weather Research and Forecasting (WRF) model coupled with the Noah land surface model was tested over the city of Athens, Greece, during two selected days. Model results were compared against observations, revealing a satisfactory performance of the modeling system. According to the numerical simulation, the city of Athens exhibits higher air temperatures than its surroundings during the night (>4 °C), whereas the temperature contrast is less evident in early morning and mid-day hours. The minimum and maximum intensity of the canopy-layer heat island were found to occur in early morning and during the night, respectively. The simulations, in agreement with concurrent observations, showed that the intensity of the canopy-layer heat island has a typical diurnal cycle, characterized by high nighttime values, an abrupt decrease following sunrise, and an increase following sunset. The examination of the spatial patterns of the land surface temperature revealed the existence of a surface urban heat sink during the day. In the nighttime, the city surface temperature was found to be higher than its surroundings. Finally, a simple data assimilation algorithm for satellite-retrieved land surface temperature was evaluated. The ingestion of the land surface temperature data into the model resulted to a small reduction in the temperature bias, generally less than 0.2 °C, which was only evident during the first 4–5 h following the assimilation.

Assessment of the sources of the inorganic fraction of aerosol in a conurbation

International Journal of Environmental Analytical Chemistry, Vol. 90, (1) 64-83,(2010). doi:10.1080/03067310903168554

Assessment of the sources of the inorganic fraction of aerosol in a conurbation

E. T. Karageorgos and  S. Rapsomanikis

 

Abstract. Two intensive sampling campaigns for coarse (PM2.5–10) and fine (PM2.5) particulate matter were carried out in August 2003 and March 2004 in the multiimpacted centre of the Athens (Greece) conurbation. Receptor modelling by means of Positive Matrix Factorization was utilised in order to provide an insight to the poorly characterised sources of the chemically analysed inorganic fraction of the sampled aerosol mass. Using elemental concentrations, seven factors have been resolved for both fractions for August 2003. Combining elemental and ionic concentrations, nine factors were resolved in the coarse particulate matter and eight in the fine particulate matter for March 2004. The greatest contributors of primary origin are (re)suspended dust/soil and sea salt. Secondary aerosol contributions were resolved in the form of secondary sulphate, secondary nitrate as well as an aged sea salt factor which was characterised by the replacement of chloride with sulphate and, secondarily, nitrate. Furthermore, throughout sites and fractions, primary anthropogenic emissions were identified in a series of factors, including a Pb-rich profile, representing non-catalytic exhaust emissions, a Cu-Mo-Sb-rich profile representing brake emissions, a Zn-Ba-rich profile representing tyre-wear and heavy vehicle brakes, and, lastly, a V-Ni-rich factor representing industrial heavy oil-combustion. Local anthropogenic emissions predominated, outweighing long-range transport as it was suggested by the lack of direct relationship between changes in the wind speed and direction and species mass burdens, as well as factor contributions.
 

Chemical characterization of the inorganic fraction of aerosols and mechanisms of the neutralization of atmospheric acidity in Athens, Greece

Chemical characterization of the inorganic fraction of aerosols and mechanisms of the neutralization of atmospheric acidity in Athens, Greece

E. T. Karageorgos, S. Rapsomanikis, Atmos. Chem. Phys., 7, 3015-3033, (2007)