The flow of urban heat in the centre of the Parisian conglomeration - Book 3: Thermal breezes

Map extract “Intensity of thermal breezes in the Parisian conglomeration” © Apur
Book 3: Thermal breezes
This, the third Apur study to deal with urban heat islands, is devoted to the subject of thermal breezes. It investigates the phenomenon of winds which arise during periods of heat waves, analyses their impact on the thermal comfort experienced by pedestrians and the possible links with atmospheric pollution.
Periods of atmospheric pollution are a recurring phenomenon in Paris. They often occur in contexts when the air is calm and pollution cannot be evacuated due to lack of wind. The absence of wind during heat waves in the heart of the Parisian conglomeration is also a recurring phenomenon. The territory is not protected from a situation where pollution and heat waves coincide.
When this situation arises, it is shown to be very unevenly spread over the Parisian territory. Even when the air is calm, certain zones are aired better than others because of the flow of local winds called “thermal breezes”,  which are the consequence of the Parisian topography and types of land occupation. Consequently certain districts are both hot and polluted, like for example the right bank in the centre of Paris. A trough effect can be observed where air pollution, coming from surrounding higher altitudes, stagnates. The high minerality of areas intensifying heat islands thus creates a vulnerable situation.
Conversely, on the slopes of the hills (Buttes-Chaumont, Belleville, Père Lachaise, Butte Montmartre, etc.), air circulates gently according to the steepness of the slope, this movement of air has a cooling effect which makes a heatwave more bearable during the night and pollution is moved around a little better than in the rest of Paris. The presence of green spaces on these hillsides seems to have the effect of accelerating breezes which reinforces the cooling sensation at night.   
This study is part of a series of 5 notebooks dedicated to urban heat islands in the heart of the Parisian conglomeration:


Documents to download

  • The flow of urban heat in the centre of the Parisian conglomeration - Book 3: Thermal breezes

    Format : pdf, 9.8 MB