Abstract
The storage heat flux (ΔQS) is the net flow of heat stored within a volume that may include the air, trees, buildings and ground. Given the difficulty of measurement of this important and large flux in urban areas, we explore the use of Earth Observation (EO) data. EO surface temperatures are used with ground-based meteorological forcing, urban morphology, land cover and land use information to estimate spatial variations of ΔQS in urban areas using the Element Surface Temperature Method (ESTM). First, we evaluate ESTM for four “simpler” surfaces. These have good agreement with observed values. ESTM coupled to SUEWS (an urban land surface model) is applied to three European cities (Basel, Heraklion, London), allowing EO data to enhance the exploration of the spatial variability in ΔQS. The impervious surfaces (paved and buildings) contribute most to ΔQS. Building wall area seems to explain variation of ΔQS most consistently. As the paved fraction increases up to 0.4, there is a clear increase in ΔQS. With a larger paved fraction, the fraction of buildings and wall area is lower which reduces the high values of ΔQS.
Highlights
The storage heat flux (ΔQS) is the net flow of heat stored within a volume that includes the air, trees, buildings and ground
Given the difficulty of measuring storage heat flux in complex urban areas, we evaluate the performance of Element Surface Temperature Method (ESTM) for individual components of the urban environment
The best performance is for the grass (mean absolute error (MAE) = 5 W m−2)
Summary
The storage heat flux (ΔQS) is the net flow of heat stored within a volume that includes the air, trees, buildings and ground. The net heat stored in the canopy is a relatively large fraction of the net all-wave radiation (Q*) compared to other environments (Nunez and Oke 1977; Grimmond and Oke 1999). It can account for more than half the daytime net all-wave radiation (Oke et al 1999) and be two to ten times larger than for simple planar surfaces (e.g. soil). The wellknown nocturnal urban heat island (UHI) is caused by the release of stored heat and enhanced by anthropogenic heat (QF). Combined with reduced radiative cooling (or enhanced radiative trapping), the storage heat flux is a major contributor (Oke and Cleugh 1987). Combined with reduced radiative cooling (or enhanced radiative trapping), the storage heat flux is a major contributor (Oke and Cleugh 1987). Oliphant et al (2018) demonstrate
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