Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

Abstract

We investigate the area-averaged sensible heat flux (Q H ) obtained with a scintillometer along a 3.1-km path length over the city centre of Łódź, Central Poland. The annual cycle of Q H peaks in June but is lower by the middle of summer. In winter, due to a large amount of anthropogenic heat input, Q H remains positive all day long, with positive nighttime fluxes also found during months with frequent cold advection, e.g., June 2010. In the diurnal cycle of this flux, several features specific to urban areas are seen: the peak shifts 1-2 h after noon, the heat flux turns from positive to negative 1-2 h after sunset. In Łódź Q H was observed during inflow from the north and north-west, i.e. from the city centre. As this area is mostly covered with impervious materials, most of the heat exchanged between the ground and the overlying air is in the form of sensible heat flux. Under the conditions of inflow from the east and south-east, the maximum heat flux is approximately 100 W m −2 lower than during the inflow from the city centre, since more vegetation exists to the east and south-east of the scintillometer path. Cold and warm advection are found to be a vital factor in the observed heat-flux variability in the centre of Łódź.

Computational Fluid Dynamics Simulation of High-Resolution Spatial Distribution of Sensible Heat Fluxes in Building-Congested Area

“…LCV's simulated Q h closely resembled prior research findings [49,50]. LCV similarly simulated the temperature measured at the flux tower.…”

Characterizing the State of the Urban Surface Layer Using Radon‐222

“…While numerous studies of urban landscapes have already been conducted (Bassett et al, 2016;Podstawczyńska, 2016;Theeuwes et al, 2017; see also reviews by Arnfield, 2003;Lietzke et al, 2015;Roth, 2000), compared to other global environment types, urban observations are still quite limited (Grimmond et al, 2016). Specifically, more detailed information is required about the urban water and carbon budgets, as well as mixing and pollution concentrations within the urban canopy layer (UCL), the zone of human occupation (Christen, 2014;Grimmond et al, 2016;Memon et al, 2009;Mills et al, 2010;Mirzaei & Haghighat, 2010;Nelson et al, 2007;Nicolini et al, 2013;Zieliński et al, 2018). Fortuniak et al (2006) highlighted the need to analyze urban influences within specific weather categories, due to large variability associated with transient meteorological phenomena.…”

Łódzkie badania klimatu miasta

“…Since 2006, the EC system has been extended to measure the turbulent CO2 flux (Pawlak et al 2011), and from 2013 also the CH4 flux (Pawlak, Fortuniak 2016). In 2009-2012, studies on the intensity of turbulence and sensible heat flux over the city centre were carried out on a three-kilometre path using a scintillometer (Zieliński et al 2013(Zieliński et al , 2017(Zieliński et al , 2018. The turbulence characteristics were also analyzed based on several years of EC data from two towers (Fortuniak et al 2013;Fortuniak, Pawlak 2015).…”