The influence of anomalous atmospheric conditions at Ny-Ålesund on clouds and their radiative effect

• Main Authors: Nomokonova, Tatiana, Ebell, Kerstin, Löhnert, Ulrich, Maturilli, Marion, Ritter, Christoph
• Format: Text
• Language: English
• Published: 2019
• Subjects: Arctic; Ny-Ålesund; North Atlantic; Ny Ålesund
• Online Access: https://doi.org/10.5194/acp-2019-985; https://www.atmos-chem-phys-discuss.net/acp-2019-985/

This study analyses occurrence of events with increased and decreased integrated water vapor (IWV) and atmospheric temperature (T) at the Arctic site Ny-Ålesund and their relation to cloud properties and the surface cloud radiative effect (CRE). 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 and T from 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 circulations in the Arctic region, respectively. The amount of water vapor is often correlated with cloud occurrence, presence of cloud liquid water, liquid and ice water path (LWP and 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 occurrence of dry and moist anomalies were analyzed based on 25-year-radiosonde database. Dry anomalies become less frequent with rates for different seasons from −12.8 to −4 % per decade, while the occurrence of moist event increases at rates from 2.8 to 6.4 % per decade. Taking into account the relations between the anomaly types and cloud properties the trends might be related to an increase in cloud occurrence, LWP, and IWP. The change in cloud properties could, in turn, modulate the surface CRE and lead to stronger surface cooling and warming related to clouds in summer and other seasons, respectively.