46
land cover/land use maps, satellite images (e.g., Google Earth
©
), and published tables of property values (e.g., Davenport terrain roughness lengths)”
(Stewart and Oke, 2012, pp. 1889–1890).
“Step 2: Define the thermal source area. The thermal source area for a temperature measurement is the total surface area «seen» by the sensor […].” (Stewart
and Oke, 2012, p. 1890) “Sources will include upwind buildings, the walls
and floor of an upwind street, and perhaps a branching network of more distant street canyons” (p. 1890).
“Quantifying the surface properties for field sites and source areas located
on or near the border of two (or more) zones is problematic. If the location of
the sensor can be moved, it should be placed where it samples from a single
LCZ. […]. If the location of the sensor cannot be moved, temperature data
retrieved from that site should be stratified first according to wind direction,
then to LCZ. […] A site with a split classification is less ideal for heat island
studies because changes in airflow and stability conditions interfere confuse
the relation between surface form/cover and air temperature. It is recommended that transitional areas be avoided when siting meteorological instruments” (Stewart and Oke, 2012, p. 1891).
“Step 3: Select the local climate zone. Metadata collected in Step 1 should lead
users to the best, not necessarily exact, match of their field sites with LCZ
classes. Metadata are unlikely to match perfectly with the surface property
values of one LCZ class. If the measured or estimated values align poorly
with those in the LCZ datasheets, the process of selecting a best-fit class
becomes one of interpolation rather than straight matching. Users should first
look to the surface cover fractions of the site to guide this process. If a suitable
match still cannot be found, users should acknowledge this fact and highlight
the main difference(s) between their site and its nearest equivalent LCZ”
(Stewart and Oke, 2012, p. 1891).
Stewart and Oke (2012) note that “updating LCZ designations is crucial for all
sites, particularly those used in long-term temperature studies” (p. 1893). They add
that “sites located on the edges of cities where urban growth and environmental
change are rapid, or in the cores of cities where land redevelopment and large-scale
greening projects are taking place, should be surveyed and classified annually. For
sites used in mobile or short-term stationary surveys, the frequency of updates is
dictated largely by day-to-day variations in weather and soil moisture […]” (p. 1893).
2.4 Exposure of Instruments
There are numerous possibilities for setting up urban climate stations, such as screen
level, on a roof, in a street canyon, which vary depending on the LCZs where they
are situated.
A primary survey of study area can document the presence of obstacles close to
the measurement site. The main discrepancies are caused by unnatural surfaces and
shading:
G. Baranka et al.
land cover/land use maps, satellite images (e.g., Google Earth
©
), and published tables of property values (e.g., Davenport terrain roughness lengths)”
(Stewart and Oke, 2012, pp. 1889–1890).
“Step 2: Define the thermal source area. The thermal source area for a temperature measurement is the total surface area «seen» by the sensor […].” (Stewart
and Oke, 2012, p. 1890) “Sources will include upwind buildings, the walls
and floor of an upwind street, and perhaps a branching network of more distant street canyons” (p. 1890).
“Quantifying the surface properties for field sites and source areas located
on or near the border of two (or more) zones is problematic. If the location of
the sensor can be moved, it should be placed where it samples from a single
LCZ. […]. If the location of the sensor cannot be moved, temperature data
retrieved from that site should be stratified first according to wind direction,
then to LCZ. […] A site with a split classification is less ideal for heat island
studies because changes in airflow and stability conditions interfere confuse
the relation between surface form/cover and air temperature. It is recommended that transitional areas be avoided when siting meteorological instruments” (Stewart and Oke, 2012, p. 1891).
“Step 3: Select the local climate zone. Metadata collected in Step 1 should lead
users to the best, not necessarily exact, match of their field sites with LCZ
classes. Metadata are unlikely to match perfectly with the surface property
values of one LCZ class. If the measured or estimated values align poorly
with those in the LCZ datasheets, the process of selecting a best-fit class
becomes one of interpolation rather than straight matching. Users should first
look to the surface cover fractions of the site to guide this process. If a suitable
match still cannot be found, users should acknowledge this fact and highlight
the main difference(s) between their site and its nearest equivalent LCZ”
(Stewart and Oke, 2012, p. 1891).
Stewart and Oke (2012) note that “updating LCZ designations is crucial for all
sites, particularly those used in long-term temperature studies” (p. 1893). They add
that “sites located on the edges of cities where urban growth and environmental
change are rapid, or in the cores of cities where land redevelopment and large-scale
greening projects are taking place, should be surveyed and classified annually. For
sites used in mobile or short-term stationary surveys, the frequency of updates is
dictated largely by day-to-day variations in weather and soil moisture […]” (p. 1893).
2.4 Exposure of Instruments
There are numerous possibilities for setting up urban climate stations, such as screen
level, on a roof, in a street canyon, which vary depending on the LCZs where they
are situated.
A primary survey of study area can document the presence of obstacles close to
the measurement site. The main discrepancies are caused by unnatural surfaces and
shading:
G. Baranka et al.