Abstract. Clouds are a key factor for the Arctic amplification of global warming, but
their actual appearance and distribution are still afflicted by large
uncertainty. On the Arctic-wide scale, large discrepancies are found between
the various reanalyses and satellite products, respectively. Although
ground-based observations by remote sensing are limited to point
measurements, they have the advantage of obtaining extended time series of
vertically resolved cloud properties. Here, we present a 25-year data record
of cloud base height measured by ceilometer at the Ny-Ålesund, Svalbard,
Arctic site. We explain the composition of the three sub-periods with
different instrumentation contributing to the data set, and show examples of
potential application areas. Linked to cyclonic activity, the cloud base
height provides essential information for the interpretation of the surface
radiation balance and contributes to the understanding of meteorological
processes. Furthermore, it is a useful auxiliary component for the analysis
of advanced technologies that provide insight into cloud microphysical
properties, like the cloud radar. The long-term time series also allows
derivation of an annual cycle of the cloud occurrence frequency, revealing
the more frequent cloud cover in summer and the lowest cloud cover amount in
April. However, as the use of different ceilometer instruments over the years
potentially imposed inhomogeneities onto the data record, any long-term trend
analysis should be avoided. The Ny-Ålesund cloud base height data from August 1992 to July 2017 are
provided in a high temporal resolution of 5 min (1 min) before (after)
July 1998, respectively, at the PANGAEA repository
(https://doi.org/10.1594/PANGAEA.880300).
Cloud Base Height and Effective Cloud Emissivity Retrieval with Ground-Based Infrared Interferometer
