Urban energy exchanges monitoring from space

Nektarios Chrysoulakis,Fredrik Lindberg,Ben Crawford,Lucas Landier,Jean-Philippe Gastellu-Etchegorry,Zina Mitraka,Eberhard Parlow,Sue Grimmond,William Morrison,Mattia Marconcini,Stavros Stagakis,Christian Feigenwinter,Frans Olofson

doi:10.1038/s41598-018-29873-x

Abstract

One important challenge facing the urbanization and global environmental change community is to understand the relation between urban form, energy use and carbon emissions. Missing from the current literature are scientific assessments that evaluate the impacts of different urban spatial units on energy fluxes; yet, this type of analysis is needed by urban planners, who recognize that local scale zoning affects energy consumption and local climate. Satellite-based estimation of urban energy fluxes at neighbourhood scale is still a challenge. Here we show the potential of the current satellite missions to retrieve urban energy budget fluxes, supported by meteorological observations and evaluated by direct flux measurements. We found an agreement within 5% between satellite and in-situ derived net all-wave radiation; and identified that wall facet fraction and urban materials type are the most important parameters for estimating heat storage of the urban canopy. The satellite approaches were found to underestimate measured turbulent heat fluxes, with sensible heat flux being most sensitive to surface temperature variation (−64.1, +69.3 W m−2 for ±2 K perturbation). They also underestimate anthropogenic heat fluxes. However, reasonable spatial patterns are obtained for the latter allowing hot-spots to be identified, therefore supporting both urban planning and urban climate modelling.

Highlights

The Urban Energy Balance (UEB) needs to account for the 3D nature of cities, quantifying the fluxes into, out of and the storage change within the control volume (Fig. 1)
Both Earth system science and urban planning communities need spatially disaggregated UEB data at local scale[18,19,20] (neighbourhood, e.g., order (100 m × 100 m) or larger). Such information is practically impossible to derive for extensive areas by in-situ flux measurements and Earth Observation (EO)-based estimation of spatio-temporal patterns of different UEB components is challenging
We address this by investigating the potential of the current satellite missions to retrieve UEB fluxes at local scale, supported by meteorological observations

Summary

Introduction

The Urban Energy Balance (UEB) needs to account for the 3D nature of cities, quantifying the fluxes into, out of and the storage change within the control volume (Fig. 1). Recent studies[16,17] have investigated the potential of EO to derive turbulent heat fluxes and identify and analyse the associated uncertainties Both Earth system science and urban planning communities need spatially disaggregated UEB data at local scale[18,19,20] (neighbourhood, e.g., order (100 m × 100 m) or larger). The question arises whether EO can provide reliable estimates of UEB at the times of satellite acquisitions We address this by investigating the potential of the current satellite missions to retrieve UEB fluxes at local scale, supported by meteorological observations. Recognising the range of city forms, size and settings, we explored three locations: London (UK), Basel (Switzerland) and Heraklion (Greece)

Methods

Results

Conclusion