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|Satellite observations help lessen the effects of heatwaves in urban area
|When heatwaves strike, it's far more difficult to cope with stifling temperatures in built-up areas than it is out in the countryside.
campaign has just been carried out to see if a spaceborne thermal infrared
sensor could help policy makers and town planners reduce the number of
casualties when temperatures soar. Over the last decade, heatwaves have claimed
an increasing number of casualties among the elderly â€“ particularly in southern
Europe. The heatwave that hit Europe in 2003, for instance, is estimated to have
caused more than 15 000 deaths in France alone, with about 70% of the
mortalities occurring in the over 75s. Prolonged periods of high temperatures
also put a strain on medical resources and place an additional financial cost to
society as a whole.
High densely built-up areas trap the heat, especially at night, causing what is called Urban Heat Islands (UHI) in which city centres can be up to 10Âº C warmer than surrounding rural areas. Another consequence of UHIs is that energy consumption rises with the increased use of air conditioners and refrigeration appliances. Whilst poor insulation keeps buildings hot in the summer, it also allows heat to escape in the winter months â€“ another factor associated with high-energy consumption and poor efficiency. With the social and financial costs that UHIs bring as well as climate-change issues in mind, many city councils have already adopted a range of energy efficiency policies to assess and monitor energy consumption.
ESA has recently launched a set of activities to aid decision and policy makers mitigate the effects of UHIs though appropriate alert systems, and in terms of reducing risk â€“ through improved urban planning. Within the framework of the proposed activities for the 'Reorientation of the Fuegosat Consolidation Phase', which falls under the Earth Watch element of ESA's Living Planet Programme, a high-resolution thermal infrared capability was recognised as necessary for Europe in the medium- to long-term.
In addition to the original fire-related application areas, infrared
observations have the potential to contribute to reducing the effects of UHIs.
To this end, an ESA project called Urban Heat Islands and Urban Thermography,
funded through the agencyâ€™s Data User Element (DUE), is currently the
an open and competitive tender, which will be initiated in September 2008 with
the participation of 10 European cities.
Madrid in Spain was chosen as
the test site for the campaign as it is one of the cities in Europe that suffers
many heatwaves with air temperatures sometimes reaching 50Âº C. More than 60
researchers from 14 different institutes gathered in Madrid to participate in
the two-week field campaign, which ended on 4 July. The intensive campaign,
organised in close cooperation with the Madrid City Council, involved multiple
satellites, airborne and field instruments.
The main instrument used during the campaign was the Airborne Hyperspectral
Scanner (AHS), which is an imaging line-scanner radiometer, installed on a
CASA-212 200 series aircraft owned by Spain's National Institute for Aerospace
Technology (INTA). The AHS has 80 spectral channels available in the visible,
shortwave infrared and thermal infrared. Thirty acquisition flight lines (15
flights in total) were obtained over Madrid with spatial resolutions varying
from 2.5 to 6.8 metres. Multiple field instrumentations operated by the partners
in the DESIREX 2008 campaign have provided extremely detailed ground
measurements, such as radiometric measurements used for calibration and
validation of parameters extracted from the AHS airborne sensor, measurements
for characterising the UHI, such as the air and radiometric temperatures in
different building terraces. Four cars carrying instrumentation followed the
flight paths and analysed the effect and the evolution of the UHI during the
"The city of Madrid will benefit greatly from the DESIREX-2008 campaign. The results will allow us to have detailed information on Urban Heat Islands for the delineation of these highly sensitive areas and their incorporation into more effective urban planning for heat wave mitigation," said JosÃ© Manuel Romero Cuadrado, Head of the Cartographic Department with the Madrid City Council. "The availability of information on urban climate should also help our city council to optimise an intelligent use of energy at the level of the city districts but also at building level."
The DESIREX-2008 activity was funded through ESA's Reorientation of the Fuegosat Consolidation Phase. Participants included Spanish teams from Universities in Valencia (UVEG), Madrid (UAM, UCM) and Vigo (UVIGO), along with national institutes (INTA, AEMET, CIEMAT, CECAF, AENA and LABEIN), French teams from the University of Strasbourg and the City Council of Madrid.