H. Debacker et al., POTENTIAL FOR METEOROLOGICAL BIAS IN LIDAR OZONE DATA SETS RESULTING FROM THE RESTRICTED FREQUENCY OF MEASUREMENT DUE TO CLOUD COVER, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 99(D1), 1994, pp. 1395-1401
Lidar-based ozone data sets may be meteorologically biased since the m
easurements are performed in the absence of precipitation and fog and
the vertical profiles are truncated at the cloud base. This problem wa
s studied for the routine ozone lidar facility at Bilthoven, Netherlan
ds (52 degrees 07'N, 5 degrees 12'E). We used the long-term data recor
d of balloon soundings at Uccle, Belgium (50 degrees 48'N, 4 degrees 2
1'E) between 1969 and 1992 to examine the average ozone concentrations
as a function of altitude and season at different amounts of cloud co
ver. Since Uccle and Bilthoven are only 160 km apart and to a large ex
tent have the same climatology, the Uccle data are assumed to be repre
sentative of the atmospheric conditions at Bilthoven. The data set of
ozone profiles was arranged into several subsets according to increasi
ng amounts of cloud cover. When compared to the total set, the subset
for clear sky conditions showed significantly lower ozone partial pres
sures (absolute differences down to -2.37 mPa and percentage differenc
es down to -43.6%) around the tropopause in spring and early summer an
d higher values (up to +1.10 mPa and +39.2%) in the lower troposphere
in summer. These phenomena are explained by differences in the average
origin of air masses and photochemical ozone production. The results
have led to the definition of the monitoring strategy for the troposph
eric ozone lidar facility at Bilthoven such that a meteorological bias
in the set of ozone profiles is avoided.