Sensitivity of modeled arctic mixed‐phase stratocumulus to cloud condensation and ice nuclei over regionally varying surface conditions

Abstract

[1] A two-moment microphysics scheme implemented in the polar version of the mesoscale model MM5 is used to simulate a mixed-phase stratocumulus deck observed during the Fall 2004 Mixed-Phase Arctic Cloud Experiment (MPACE). In situ aircraft instrumentation and remote sensors gathered extensive microphysical and radiative data that serve as a testbed for the model. Model results are reasonably similar to observations in terms of the liquid microphysical properties, while the ice microphysical properties are more significantly biased, especially the ice crystal concentration. Sensitivity tests examine the impact of increased cloud condensation and ice nucleus concentrations. Increasing the concentration of cloud condensation nuclei to values typical for polluted 'Arctic haze' conditions substantially reduces the mean droplet size, but has little impact on the downwelling longwave flux because the cloud already emits as a blackbody (except near the Arctic Ocean pack ice edge). However, the smaller droplet size does lead to a slight increase in liquid water path and more significant decrease ($50%) in the ice water path and snowfall rate due to reduced collision-coalescence and riming of snow by droplets. Increasing the ice nucleus concentration specified from MPACE observations by 1-2 orders of magnitude produces a substantial reduction in liquid water path and downwelling longwave flux at the surface over interior northern Alaska, but has less impact over the open ocean and coastal regions. However, a large discrepancy between the observed ice nucleus and ice crystal concentrations, leading to the underprediction of simulated crystal concentration, also suggests that additional ice initiation mechanisms (not included in current models) may have occurred in the real cloud layer.

Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study.

“…For example, extensive in situ observations have been performed in mixed-phase clouds (Hobbs and Rangno, 1998;Lawson et al, 2001;Korolev et al, 2003;McFarquhar and Cober, 2004;McFarquhar et al, 2007) as well as remote sensing observations by Shupe et al (2001), Intrieri et al (2002), Dong and Mace (2003) and Zuidema et al (2005). There have also been a number of modeling studies published in the last year through analysis of a couple of case studies of single-and multi-layer mixed-phase clouds during M-PACE (Morrison et al, 2008;Fridlind et al, 2007).…”

A satellite-based estimate of aerosol-cloud microphysical effects over the Arctic Ocean

“…Based on single or small cloud samples, others have observed decreased precipitation probability with increased aerosol concentrations in Arctic MPCs (Lance et al, 2011;Morrison et al, 2008). It is not entirely clear why the regional trends observed here appear to be opposite these smaller-scale in situ observations, but recent work indicates that aerosols might 15 influence ice content of the clouds, and thereby affect precipitation (Fu and Xue, 2017;Norgren et al, 2018;Zamora et al, 2017) and potentially CF.…”

Can Temperature Extremes in East Antarctica be Replicated from ERA Interim Reanalysis?

“…Fewer IN in clouds are present at low temperatures, and realistic simulations are possible for Antarctica (Guo et al, 2003). However, not surprisingly, early attention has focused more on the Arctic (Morrison et al, 2008), and little on the Antarctic. (5) The cloud impact on radiation may not be well simulated by the Polar WRF (Wilson et al, 2012).…”