Contamination of the long-term temperature series of De Bilt (The Netherlands) by urban heat advection

A factor that complicates the assessment of cli-mate change and variability, is the neighborhood of (growing) cities to the locations of measuring sites. It is well known (Oke, 1974 and 1979; Landsberg, 1981) that cities develop Urban Heat Islands (UHIs). To cor-rect long-term temperature time series for the contri-bution of urban warming, it is important to understand the formation of UHIs and the extent to which heat is advected to measuring sites leeward.
In contrast to the magnitude of UHIs (the temperature difference between city centers and the background rural area, Tu-r,), the extent to which urban heat is advected to measuring sites leeward is not well known. The objective of the present paper is to study the latter phenomenon for the measuring site of De Bilt. Although the magnitude of the effect is about an order of magnitude smaller than Tu-r, it is of utmost importance for the detection of climate change and variability because it may contaminate the climate signal in long-term temperature records.