Measuring the Effects of Urban Heat Island Mitigation Techniques in the Field: Application to the Case of Pavement-Watering in Paris

Martin Hendel (1) , Pierre Gutierrez (2) , Morgane Colombert (3) , Youssef Yd Diab (3) , Laurent Royon (4)

1 LIED (UMR_8236) - Laboratoire Interdisciplinaire des Energies de Demain
2 Dataiku
3 LAB'URBA - LAB'URBA
4 MSC - Matière et Systèmes Complexes

Urban heat island (UHI) countermeasures are of growing interest for cities. Field studies of their micro-climatic effects are scarce, yet are essential to properly evaluate their effectiveness and that of anti-UHI policies. The standard approach to determining their micro-climatic effects is to study the difference in measurements made at case and control stations. However, measurements conducted during a pavement-watering experiment in Paris, France reveal that this assumption is unfounded in the general case, making the approach ill-suited to its task. An alternative approach based on a two-sample t-test was developed. The Parisian pavement-watering field trial was used as a case study to test it and determine its feasibility. In the case of full-street-width watering, statistically significant daily effects were found. Watering was found to reduce maximum daily heat stress, while having smaller statistically significant UH-reducing effects. The greatest effects were reached during the day for all parameters with reductions of 0.79°C, 1.76°C and 1.03°C for air, mean radiant and UTCI-equivalent temperatures and a 4.1% increase in relative humidity. UHI-mitigation reached up to -0.22°C. The methodology developed is not specific to pavement-watering and recommendations for its improvement and its application to the field-evaluation of other UHI countermeasures are made.

Domaines: Physique [physics]; Ingénierie de l'environnement; Physique Atmosphérique et Océanique [physics.ao-ph]

Martin Hendel, Pierre Gutierrez, Morgane Colombert, Youssef Yd Diab, Laurent Royon. Measuring the Effects of Urban Heat Island Mitigation Techniques in the Field: Application to the Case of Pavement-Watering in Paris. Urban Climate, 2016, ⟨10.1016/j.uclim.2016.02.003⟩. ⟨hal-01113917v4⟩