Abstract
Abstract. Low-level mixed-phase clouds have a substantial impact on the redistribution of radiative energy in the Arctic and are a potential driving factor in Arctic amplification. To better understand the complex processes around mixed-phase clouds, a combination of long-term measurements and high-resolution modeling able to resolve the relevant processes is essential. In this study, we show the general feasibility of the new high-resolution icosahedral nonhydrostatic large-eddy model (ICON-LEM) to capture the general structure, type and timing of mixed-phase clouds at the Arctic site Ny-Ålesund and its potential and limitations for further detailed research. To serve as a basic evaluation, the model is confronted with data streams of single instruments including a microwave radiometer and cloud radar and also with value-added products like the CloudNet classification. The analysis is based on a 11 d long time period with selected periods studied in more detail focusing on the representation of particular cloud processes, such as mixed-phase microphysics. In addition, targeted statistical evaluations against observational data sets are performed to assess (i) how well the vertical structure of the clouds is represented and (ii) how much information is added by higher horizontal resolutions. The results clearly demonstrate the advantage of high resolutions. In particular, with the highest horizontal model resolution of 75 m, the variability of the liquid water path can be well captured. By comparing neighboring grid cells for different subdomains, we also show the potential of the model to provide information on the representativity of single sites (such as Ny-Ålesund) for a larger domain.
Highlights
The Arctic is warming at a higher rate than the global mean: the increase in the near-surface air temperature in the Arctic is more than twice as large as the observed increase in global mean temperature (Serreze and Barry, 2011; Wendisch et al, 2017)
We presented the first simulations with the new ICON-LEM under Arctic conditions and over the complex terrain of Ny-Ålesund
By analyzing 11 d during the ACLOUD campaign, we showed the potential for more detailed studies focusing on the composition of mixed-phase clouds and the dominating microphysical processes
Summary
The Arctic is warming at a higher rate than the global mean: the increase in the near-surface air temperature in the Arctic is more than twice as large as the observed increase in global mean temperature (Serreze and Barry, 2011; Wendisch et al, 2017). The complex surroundings of Ny-Ålesund create their own need for high-resolution simulations that can capture the surface heterogeneities caused by the mixed surroundings of mountains, flat land, glaciers and the fjord These conditions mean that the conventional idealized way to run largeeddy simulations with periodic boundary conditions and homogeneous surfaces is not feasible (e.g., Klein et al, 2009; Ovchinnikov et al, 2014; Loewe et al, 2017). We investigate how suitable the default microphysics and especially the parameterizations of cloud condensation nuclei (CCN) and ice nuclei (IN) (Hande et al, 2016) are for the Arctic regime To investigate these questions, we picked an 11 d long time period (14 to 24 June 2017) during the ACLOUD and PASCAL campaigns (Wendisch et al, 2019), when, in addition to the ground-based observations, aircraft-based remote sensing and in situ observations were performed in the surroundings of Ny-Ålesund. – Can we use high-resolution simulations to evaluate the representativity of point measurements at complex locations (Sect. 5.3)?
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