The influence of air mass circulation patterns on the urban heat island intensity and fire risk weather in Helsinki Testbed

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The influence of air mass circulation patterns on
the urban heat island intensity and fire risk
weather in Helsinki Testbed
Andrea Vajda, Achim Drebs
Finnish Meteorological Institute
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Motivation of the study
The availability of the high resolution ground
and low atmosphere observation allows the
detailed analyses of the urban heat island, soil
moisture and fire risk.
Objectives

• To evaluate the behavior of urban boundary layer
  in two circulation patterns
• To estimate the urban heat island intensity in
  HTB under the given circulation patterns
• To evaluate the spatial and temporal variation
  of soil moisture and its determining variables in
  HTB under the given circulation patterns

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Air mass circulation patterns used in this study
Northern circulation 2.8. - 8.8.2006
South-western circulation 6.7. - 16.7.2006
7.8.2006
10.7.2006
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Data used in the project

• ceilometers HTB (6 ?)
• air temperature (2 m) HTB, FMI, MCN
• precipitation gauges HTB, FMI
• radar observation
• soil moisture data FMI (1010 km2)
• forest fire index FMI (1010 km2)

Location of ceilometers and studied area
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Working process and outputs
Data collection
Urban heat island
Soil moisture and forest fire risk
Spatial distribution of heat island during the
two types of circulation
Spatial variation of temperature (11
km2) Spatial variation of precipitation (11
km2) Soil moisture maps (1010 km2) Fire index
maps (1010 km2)
How the studied air mass circulation types
influens the development of urban heat island and
forest fire variation?