From May 2003 through April 2005 a field experiment is being carried out
at the terrain of KNMI in De Bilt. The objectives of the experiments are to
study the representativeness of the current operational air temperature
measurements site and to explore the possibility of using present-day parallel
measurements to correct for inhomogeneities, caused by changes in the
surroundings and a relocation of the thermometer screen in 1951. At five
locations, including the operational location, temperature and wind speed
are measured at a height of 1.5 m every minute, using identical instruments.
The temperature differences between the sites are studied in connection
with wind speed differences and operationally measured weather variables.
The experiment is part of the KNMI-program 'Hisklim' (HIStorical
CLIMate). The measurements can be followed real time at the KNMIintranet
The present interim report presents the results of the first phase of the experiment
(May 2003–April 2004). The report is meant to serve as a basis
for deciding upon the optimal future location of the current operational
temperature site. A Final report will be published at the end of the experiment.
T Brandsma. Parallel air temperature measurements at the KNMI-terrain in De Bilt (the Netherlands) May 2003 - April 2005