The Vertical Stratification of Air Temperature in the Center of Athens

Abstract

The intraurban temperature variation in the center of Athens, Greece, was investigated in relation to urban geometry. This paper describes two main tasks: 1) Air temperature was recorded in the center of Athens and at the Meteorological Service Station at the University of Athens. Experimental data were collected through extensive monitoring at four different heights inside five different urban canyons in the center of Athens during the summer period. A measurement uncertainty analysis was carried out to estimate critical threshold values of air temperature below which differences were not significant. 2) The correlation between urbansuburban air temperature differences was assessed, using the geometrical characteristics of each urban street canyon. Urban-rural air temperature differences were considered to be not important if they were below the threshold value of 0.38C. It was concluded that the major factor controlling urban-suburban air temperature differences was the geometry of the urban area. Other factors were the orientation of the observational sites, the current weather conditions, and the inversion of air masses adjacent to the ground level. An increase in the value of aspect ratios leads to a decrease in the difference between air inside the canyons and at the suburban station. The air temperature profile in an open-space area was the most important defining factor for the stratification of the urban-rural air temperature differences.

Distribución termal intraurbana en las ciudades de Santiago y Valparaíso. Análisis comparativo de sus factores explicativos

“…En la ciudad de Santiago coinciden con el aeródromo Cerrillos y su cono de aproximación, el cual permite el ingreso de los vientos provenientes del sur oeste y del sector del piedmont de la ciudad, el que posee una mayor proporción de vegetación. Esto, entrega importantes indicios de que lo que señalan muchos autores respecto al viento, como MONTÁVEZ et al (2000), CUADRAT et al (2005), GEORGAKIS et al (2010, y VERÓN (2010), es correcto, y constata por otra parte, lo que NOWAK & MCPHERSON (1993), CHIESURA (2004), VILELA (2004) y ESCOBEDO et al (2008) entre otros, afirman en el caso de la vegetación. Ambas variables, son determinantes en la regulación de las temperaturas elevadas y contribuyen a la conformación de áreas frías al interior de la ciudad, lo que destaca la necesidad de incorporar mediciones de viento, teniendo en cuenta la condición de ciudad costera de Valparaíso y considerando algunos antecedentes para la ciudad de Santiago, los que permiten establecer que existe relación entre la dirección del viento y la distribución espacial de la temperatura atmosférica (ROMERO & OPAZO 2010).…”

“…Por el contrario, una isla de calor puede desaparecer e inclusive no formarse si las condiciones meteorológicas son desfavorables. Estados de tiempo frecuentes en otoño e invierno, como fuertes vientos y cielos cubiertos, dificultarían su formación debido a la reducción de la radiación solar que alcanza finalmente el suelo y a la mezcla de las masas de aire urbanas y rurales (GEORGAKIS et al 2010;SALAMANCA 2010;VERÓN 2010). No obstante, hay quienes relativizan la ocurrencia de las mismas, a una combinación más variada de factores, en donde por ejemplo la presencia de nubosidad podría perfectamente ser una condición favorable para su formación (RUIZ -FLAÑO et al 2008).…”

Observations of Local Meteorological Variability under Large-Scale Circulation Patterns over Athens, Greece

“…Parts which have a correlation coefficient >0.9 are selected and categorized under the specific structure; (c) The part of the time series that was just recognized as being part of the specific shape is deleted, and excluded from further analysis; (d) The procedure for the specific shape is completed after all parts with r > 0.9 have been selected; (e) The procedure begins for the next geometric shape. From this database, geometric structures with a well-defined range ∆T > 0.5 • C, well above the accuracy of the thermometer (0.1 + 0.005 T, where T is temperature [22]), have been selected and further processed.…”

Ilha De Calor Urbana Em Cidade De Pequeno Porte E a Influência De Variáveis Geourbanas

“…A maioria dos estudos de ilhas de calor urbanas foi realizada à noite (CHANG; GOH, 1999;MIHALAKAKOU et al, 2002;MONTÁVEZ;RODRÍGUEZ;JIMÉNEZ, 2000;SANTAMOURIS, 2007), relativamente, poucos estudos têm enfocado ilhas de calor diurnas (GEORGAKIS; SANTAMOURIS; KAISARLIS, 2010;SANTAMOURIS, 2007).…”