Lisbon Urban Heat Island Updated: New Highlights about the Relationships between Thermal Patterns and Wind Regimes

Abstract

Urban growth implies significant modifications in the urban climate. To understand the influence of the city of Lisbon on the urban boundary layer, a mesoscale meteorological network was installed in 2004. The main goals of the present study are to update the results of the research published in 2007 and to bring more precise information about the relationship between the Urban Heat Island (UHI) and the regional and local wind systems. The highest frequencies of the UHI were found in the city centre (Restauradores). In the green park of Monsanto, the highest frequency occurred between −2 and 0°C. During the summer, the effect of the breezes was observed in Belém, lowering the temperature. The “strong” UHI (intensity >4°C) occurred more often during the summer, with median values of 2°C by night and 1.8°C by day. The highest frequencies of UHI occurred for winds between 2 and 6 m/s and were not associated with atmospheric calm, as pointed out in the literature. Winds above 8 m/s inhibit the occurrence of strong UHI in Lisbon. Summer nighttime strong UHI should be further investigated, due to the heat stress consequences on the population and probable increase of energy consumption.

Lisbon heat island statistical study (2004-2012)

“…7). Data source: CliMa-CeG-ULisboa the relationship between UHii and wind has been studied and verified recently by Lopes et al (2013). the plots of UHii versus wind speed show an expected reduction of UHi intensity when wind exceeds 4 m/s ( fig.…”

“…One very interesting feature in figure 7 is the fact that, in summer, high UHii begins quite early in the afternoon, which can be explained by the wind regime in the city (alcoforado, 1987;Lopes et al, 2013). in the summer mornings, there are frequently e and se breezes from the tagus estuary that veer to the s and sW by midday or later, bringing cooler air into the river-site city centre, sometimes up to res (andrade, 2003) and in summer cause a negative heat island from 9:00h to 12:00h (or later).…”

“…this is explained in the summer by sea-breeze situations, bringing fresher air to the down-town area and in winter by the occurrence of foggy situations. the relationship between UHi and wind direction is not so clear and is discussed in Lopes et al (2013).…”

Urban Heat Island and Park Cool Island Intensities in the Coastal City of Aracaju, North-Eastern Brazil

“…To reach the ∆Tu (group) -r (group) of the UHI, we need to minimize the microclimatic influences of each station so that the local influence prevails. Some studies have used a group of stations to calculate UHI intensity instead of using only one station that represents the urban area and another that represents the rural area [3][4][5].…”

“…By using daily data between 1972 and 1991, Morris et al [5] showed, among other results, that the variation in the amount of clouds from 0 to 8 octas had very little influence on Melbourne UHI when the mean wind was ≥5 ms −1 . By using daily data between 2004 and 2012, Lopes et al [3] and Alcoforado et al [4] reported that low wind speeds were not associated with the highest Lisbon UHI intensities. In Aracaju, using the approaches discussed above, some studies pointed to higher heating in the central areas (up to 7.5 • C) in relation to the peri-urban areas and green spaces, which suggests that UHI intensities are equally significant [10][11][12].…”