While NCDC’s Dr. Thomas Peterson tries to ignore UHI, from Hans Von Storch at Die Klimazwiebel (h/t to Jos de Laat) we learn that many other people are actively measuring it. WUWT reader may remember my “do it yourself UHI kit” for vehicles…now there’s one for a bike:
It is long known that in cities there may be a significant climatic effect due to urbanization – thus in cities we have the interesting and challenging task of determining at least three significant drivers for change, if not more, namely the effect of the local modification of the environment as well as the local manifestation of global change due to greenhouse gases (plus, possibly other global factors). Unfortunately, systematic studies about the determination and separation of these effects – in principle a detection and attribution task – have not been done often. At least, I am not aware of such efforts; indeed even studies only on the size and distribution of the urban heat island effect (UHI) are not done often; in Hamburg, a first study was only published in the last few years – before that one could hear that in a maritime climatic environment as Hamburg, the effect would be negligible. It is not.
Now, an innovative study is about to be published – see the manuscript here: Measurement and statistical modeling of the urban heat island of the city of Utrecht (the Netherlands) by Theo Brandsm and Dirk Wolters from KNMI. The trick was, to do the year long observations by bike, as described in this abstract:
Mobile temperature and humidity measurements have been performed along a 14 km transect through the city of Utrecht (311,000 inhabitants) in the period March 2006 – January 2009. The measurements took place on a bicycle during commuter tra c and resulted in 106 nighttime profiles (before sunrise) and 77 daytime (afternoon) profiles. It is shown how the intensity of the urban heat island depends on wind direction, cloudiness and wind speed. Statistical models are constructed that relate the mean and maximum nighttime urban heat island intensity profiles to area-averaged sky-view factors and land use combined at both the micro and local scale. Sky-view factors are estimated from a 0:5 x 0:5 m surface elevation database and land use is obtained from a 25 x 25 m land use database. The models are calibrated using the mobile measurements and provide estimates of the spatial distribution of the mean and maximum nighttime urban heat island intensity in Utrecht. Both models explain more than 75% of the variance. A separate non-linear model is introduced that relates the temperature differences between the warmest and coolest part of the transects to wind speed and cloudiness.
Brandsma, T. and D. Wolters, Measurement and statistical modeling of
the urban heat island of the city of Utrecht (the Netherlands)
Journal of Applied Meteorology and Climatology, 2012, 51, 1046-1060.
I put a couple of the figures side by side to give you an idea of what was discovered: