Abstract
Abstract. The occurrence of events with increased and decreased integrated water vapor (IWV) at the Arctic site Ny-Ålesund, their relation to cloud properties, and the surface cloud radiative effect (CRE) is investigated. For this study, we used almost 2.5 years (from June 2016 to October 2018) of ground-based cloud observations processed with the Cloudnet algorithm, IWV from a microwave radiometer (MWR), long-term radiosonde observations, and backward trajectories FLEXTRA. Moist and dry anomalies were found to be associated with North Atlantic flows and air transport within the Arctic region, respectively. The amount of water vapor is often correlated to cloud occurrence, presence of cloud liquid water, and liquid water path (LWP) and ice water path (IWP). In turn, changes in the cloud properties cause differences in surface CRE. During dry anomalies, in autumn, winter, and spring, the mean net surface CRE was lower by 2–37 W m−2 with respect to normal conditions, while in summer the cloud-related surface cooling was reduced by 49 W m−2. In contrast, under moist conditions in summer the mean net surface CRE becomes more negative by 25 W m−2, while in other seasons the mean net surface CRE was increased by 5–37 W m−2. Trends in the occurrence of dry and moist anomalies were analyzed based on a 25-year radiosonde database. Dry anomalies have become less frequent, with rates for different seasons ranging from −12.8 % per decade to −4 % per decade, while the occurrence of moist events has increased at rates from 2.8 % per decade to 6.4 % per decade.
Highlights
It is well known that during the past three decades the Arctic climate has been drastically changing
A number of studies have shown that positive and negative anomalies in integrated water vapor (IWV) often result from horizontal transport of air masses from mid-latitudes and Arctic latitudes, respectively (Maturilli and Kayser, 2017a; Dahlke and Maturilli, 2017; Mewes and Jacobi, 2019; Wu, 2017)
For each 6-hourly period we found a FLEXTRA back trajectory with time when it reaches Ny-Ålesund corresponding to the beginning of the 6-hourly period
Summary
It is well known that during the past three decades the Arctic climate has been drastically changing. In the period from 1998 to 2012, the temperature increase in the Arctic was persistent and in contrast to the “hiatus” in global warming discussed in a number of studies (Wei et al, 2016; Huang et al, 2017). Even though only IWV is considered in this study, cloud formation and development depend on a number of other factors such as aerosol load and chemical composition (Baustian et al, 2012; Murray et al, 2012; Wex et al, 2019), dynamics (Korolev and Field, 2008; Schmidt et al, 2014), influence of surface layer (Morrison et al, 2012) and local orographic effects (Houze, 2012), and other processes.
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