On the roles of circulation and aerosols in the decline of mist and dense fog in Europe over the last 30 years 1KNMI, P. O. Box 201, 3730 AE De Bilt, The Netherlands
2LSCE/IPSL, Laboratoire CEA/CNRS/UVSQ, 91191 Gif-sur-Yvette Cedex, France
Received: 23 October 2009 – Published in Atmos. Chem. Phys. Discuss.: 12 November 2009 Abstract. Fog and mist are meteorological phenomena that have significant contributions
to temperature variations. Understanding and predicting them is also crucial
for transportation risk management. It has been shown that low visibility
phenomena over Europe have been declining over the past three decades. The
trends in mist and haze have been correlated to atmospheric aerosol trends.
However, dense fog has not received yet such focus. The goal of this paper is
to examine the roles of synoptic atmospheric circulation and aerosol content
on the trends of dense fog. We show that sulphur emission trends are
spatially correlated with visibility trends, with a maximum correlation when
visibility is between 1 km and 10 km. We find that atmospheric dynamics
overall contributes up to 40% of the variability of the frequency of fog
occurrences. This contribution is spatially variable and highly depends on
the topography and the season, with higher values in the winter. The observed
long-term circulation changes do not contribute much to the trends in low
visibility found in the data. This process is illustrated on three stations
(De Bilt, Zürich Airport and Potsdam) for which a long-term visibility data
and a thorough meteorological description are available. We conclude that to
properly represent fog in future climate simulations, it is necessary to
include realistic representations of aerosol emissions and chemistry, land
surface properties and atmospheric dynamics.
Revised: 26 April 2010 – Accepted: 07 May 2010 – Published: 19 May 2010
Citation: van Oldenborgh, G. J., Yiou, P., and Vautard, R.: On the roles of circulation and aerosols in the decline of mist and dense fog in Europe over the last 30 years, Atmos. Chem. Phys., 10, 4597-4609, doi:10.5194/acp-10-4597-2010, 2010.