Implications of Urban Form and Topography in Thermal Conditions at Local
and Micro Scale in a Tropical Urban Area Located in a Valley
Abstract
Cities are the most sensitive and vulnerable places to climate
variability and change and weather-related extreme events given high
population density, with the aggravating factor that urban climate also
suffers modifications due to the widespread replacement of the natural
surface altering the local thermal conditions. The Aburrá Valley is a
narrow valley located at the tropical Andes in northern South America
with urban areas between 1300 and 2000 m.a.s.l, a population of
approximate 3.9 million people, and a comfortable climate relative to
standard indoor conditions. In this work, we examine observed weather
patterns in the local scale and the urban canopy layer (UCL) using data
from weather stations at sites with different surface features regarding
vegetation/non-impervious fractions and urban structure (Sky View Factor
SVF). UCL data is available from two data sources, the first one from a
field campaign using all-in-one weather sensors at the valley´s bottom,
and the second one from a low-cost sensor network with robust
temperature and humidity data as part of a local citizen science project
with measurements in a diverse altitude range. Results suggest that at
the local scale there exist different climate mean conditions due to
altitude, with significant weather variability depending on radiation
levels and rainfall occurrence, but at the same time, the urban effects
are evident since the lowest altitude stations do not necessarily
register the highest temperatures depending on the local
characteristics. UCL measurements show that, while the altitude defines
a background state, there are notable differences between places mainly
influenced by insolation changes due to vegetation around and above
sensors. Currently, the local population does not perceive thermal
stress as a risk factor because it is not difficult to find places with
appropriate thermal conditions when thermal discomfort arises. However,
this research is relevant considering the projected local surface
temperature increase due to climate change and the inexistence of
baseline studies assessing the thermal comfort in outdoors to support
local adaptation actions. The results of this study are useful for urban
planning and building design to improve thermal conditions, especially
in open spaces.