262
amending land-use and building development plans. These refer to climate-relevant
aspects only indirectly, e.g. the objective “to (4.) preserve or create environmental
conditions that will ensure a healthy environment, in particular with a view to housing,
work and leisure time ” (Building Code for Vienna, §1, para 2 Z4).
Protection of the urban climate has been embedded in the strategic and legal
tools to enable targeted measures for reducing the UHI effect.
9.3 UHI and the Urban Climate in Vienna – Status Quo
and Future Developments
Building up natural permeable surfaces is considered the main culprit in the development of Urban Heat Islands (Kuttler 2011 ). The UHI effect is further enhanced by
both a steady decrease and fragmentation of urban green spaces and the waste heat
produced by industrial processes, air conditioning and motor vehicles. Construction
developments also increase the surface roughness, slowing down wind speed in the
course. They prevent cold air fl ows generated in undeveloped “cold air production
sites” from entering the densely built-up city. Building developments in many cases
act as an additional blockade for cold air fl ows from undeveloped environs to
agglomeration areas. Generally speaking temperatures are expected to rise from the
periphery to the city centre (see Fig. 9.1 ).
The isothermal map highlights the Urban Heat Islands, the outlines of the builtup area, as well as the “hot spots”, such as sealed car parks or industrial areas, and
“cold spots”, such as parks, agricultural areas and bodies of water in Vienna.
Forecasts for climate development are subject to a certain amount of uncertainty.
From today’s point of view temperatures in Vienna are reckoned to increase. “The
2040ies in the eastern parts of Austria will likely see an increase in temperatures of
1.3–1.8 °C in winter, 1.8–2.5 °C in spring, 2.0–2.5 °C in summer and 2.5–.0 °C in
autumn, compared to the 1980s. Heat waves will be on the rise. Between 1961 and
1990 there were an average of 5.1 heat wave days per year (also known as “Kysely
days”), between 1976 and 2005 there were as many as 9.1 already, and the current
forecast for the period between 2010 and 2039 in the centre of Vienna is an average
17.7 Kysely days per year, the inner districts, because of the UHI effect, being more
affected by the heat stress than the periphery” (Vienna City Administration 2009,
196) (Fig. 9.3 ).
The Central Institute for Meteorology and Geodynamics in Vienna (ZAMG),
during the project “Focus I” (Zuvela-Aloise et al. 2013 ), calculated high-resolution,
climate simulations of future heat stress in Vienna and examined the effectiveness
of adaptation strategies in urban planning aimed at reducing heat stress in densely
populated areas. The simulation showed how to improve buildings and open spaces
by raising the amount of green and water surfaces, as well as the level of desealing,
and by exploiting the Albedo (refl ection coeffi cient) effect on surfaces and roofs.
D. Damyanovic et al.
amending land-use and building development plans. These refer to climate-relevant
aspects only indirectly, e.g. the objective “to (4.) preserve or create environmental
conditions that will ensure a healthy environment, in particular with a view to housing,
work and leisure time ” (Building Code for Vienna, §1, para 2 Z4).
Protection of the urban climate has been embedded in the strategic and legal
tools to enable targeted measures for reducing the UHI effect.
9.3 UHI and the Urban Climate in Vienna – Status Quo
and Future Developments
Building up natural permeable surfaces is considered the main culprit in the development of Urban Heat Islands (Kuttler 2011 ). The UHI effect is further enhanced by
both a steady decrease and fragmentation of urban green spaces and the waste heat
produced by industrial processes, air conditioning and motor vehicles. Construction
developments also increase the surface roughness, slowing down wind speed in the
course. They prevent cold air fl ows generated in undeveloped “cold air production
sites” from entering the densely built-up city. Building developments in many cases
act as an additional blockade for cold air fl ows from undeveloped environs to
agglomeration areas. Generally speaking temperatures are expected to rise from the
periphery to the city centre (see Fig. 9.1 ).
The isothermal map highlights the Urban Heat Islands, the outlines of the builtup area, as well as the “hot spots”, such as sealed car parks or industrial areas, and
“cold spots”, such as parks, agricultural areas and bodies of water in Vienna.
Forecasts for climate development are subject to a certain amount of uncertainty.
From today’s point of view temperatures in Vienna are reckoned to increase. “The
2040ies in the eastern parts of Austria will likely see an increase in temperatures of
1.3–1.8 °C in winter, 1.8–2.5 °C in spring, 2.0–2.5 °C in summer and 2.5–.0 °C in
autumn, compared to the 1980s. Heat waves will be on the rise. Between 1961 and
1990 there were an average of 5.1 heat wave days per year (also known as “Kysely
days”), between 1976 and 2005 there were as many as 9.1 already, and the current
forecast for the period between 2010 and 2039 in the centre of Vienna is an average
17.7 Kysely days per year, the inner districts, because of the UHI effect, being more
affected by the heat stress than the periphery” (Vienna City Administration 2009,
196) (Fig. 9.3 ).
The Central Institute for Meteorology and Geodynamics in Vienna (ZAMG),
during the project “Focus I” (Zuvela-Aloise et al. 2013 ), calculated high-resolution,
climate simulations of future heat stress in Vienna and examined the effectiveness
of adaptation strategies in urban planning aimed at reducing heat stress in densely
populated areas. The simulation showed how to improve buildings and open spaces
by raising the amount of green and water surfaces, as well as the level of desealing,
and by exploiting the Albedo (refl ection coeffi cient) effect on surfaces and roofs.
D. Damyanovic et al.