Revision of Heat wave in Paris- 2003 from Sat, 06/18/2011 - 16:26

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According to climate model for the 21st century, summer warming trends might increase the incidence, intensity and duration of heat waves, particularly in western and central Europe, the Mediterranean regions, and the western and southern regions of the United States, (Meehl and Tebaldi, 2004; Shar et al., 2004).

Heat waves are especially deadly in cities due to the alteration of their surfaces, a decrease of surface moisture available for evapotranspiration, changes in radiative fluxes and near surface flow, and production of anthropogenic heat and pollutants.

At night, while temperature may drop in rural areas, cities release the heat stored in the buildings, inducing a lack of relief and increasing the risk of heat stress and mortality for the more vulnerable population (the elderly, infants and people with chronic diseases).

In summer 2003, the western Europe experienced a heat wave of exceptional strength and duration, with a death toll exceeding 70 000 (Robine et al., 2008).The heat wave led to health crises in several countries and combined with drought to create a crop shortfall in Southern Europe. In August, the Paris metropolitan area encountered nine consecutive days with temperature reaching 38°C in daytime and increasing from 20°C to 25°C in nighttime at the peak of the heat wave, resulting in a 4,867 excess mortality.

Mortality in Paris due to heat wave in 2003

Air temperature and mortality graph of Paris in 2003

Mean diurnal cycles of land surface temperature

Paris-thermal map-2003

Mean diurnal cycles of land surface temperature, at an industrial site, in downtown Paris, and in an urban park, constructed from 50 NOAAAVHRR images (August 4 13,2003

Estimates of urban heat stress and vulnerability requires observations at high spatial resolution, which are best obtained from satellites thermal infrared imagery.

Thermal map of Paris @ various time

Figure 6 shows three maps of temperature thresholds and areas vulnerable to heat stress, delineated from the NOAA-AVHRR time series images. Using the land cover classification from the SPOT4 image and the Paris geographic database, those maps impart the displacement of heat stress and level of risk according to the occurrence and intensity of heat islands and thermal anomalies, surfaces properties (especially the albedo), water and vegetation, and building and population density.

Measures taken

The combined analysis of satellites thermal images and public health data of the Paris region, during the summer of 2003, confirms the importance of high minimum temperatures in the heat wave process and the subsequent heat stress and mortality. A summertime satellite surveillance system is being developed to monitor heat waves over the Paris Metropolitan area, and to inform the local public and authorities on extreme surface temperatures and potential heat stress. The use of satellite thermal remote sensing over cities is yet a trade-off between accuracy and efficiency. However, it should improve the current health alert systems, contribute to adaptation strategies and reduce the societal impacts of climate change.

Global Warming, Not Just Heat Wave