Modeling the summertime Arctic cloudy boundary layer

• Main Authors: Curry, J.A., Pinto, J.O., McInnes, K.L.
• Language: unknown
• Published: 2018
• Subjects: 54 ENVIRONMENTAL SCIENCES ;99 MATHEMATICS; COMPUTERS; INFORMATION SCIENCE; MANAGEMENT; LAW; MISCELLANEOUS; CLOUDS; RADIATION TRANSPORT; CHEMISTRY; CLIMATE MODELS; HUMIDITY; LAYERS; POLAR REGIONS; SENSITIVITY; TURBULENCE; COMPUTERIZED SIMULATION; WATER; RAIN; DOWNWELLING; Arctic
• Online Access: http://www.osti.gov/servlets/purl/263507; https://www.osti.gov/biblio/263507

Global climate models have particular difficulty in simulating the low-level clouds during the Arctic summer. Model problems are exacerbated in the polar regions by the complicated vertical structure of the Arctic boundary layer. The presence of multiple cloud layers, a humidity inversion above cloud top, and vertical fluxes in the cloud that are decoupled from the surface fluxes, identified in Curry et al. (1988), suggest that models containing sophisticated physical parameterizations would be required to accurately model this region. Accurate modeling of the vertical structure of multiple cloud layers in climate models is important for determination of the surface radiative fluxes. This study focuses on the problem of modeling the layered structure of the Arctic summertime boundary-layer clouds and in particular, the representation of the more complex boundary layer type consisting of a stable foggy surface layer surmounted by a cloud-topped mixed layer. A hierarchical modeling/diagnosis approach is used. A case study from the summertime Arctic Stratus Experiment is examined. A high-resolution, one-dimensional model of turbulence and radiation is tested against the observations and is then used in sensitivity studies to infer the optimal conditions for maintaining two separate layers in the Arctic summertime boundary layer. A three-dimensional mesoscale atmospheric model is then used to simulate the interaction of this cloud deck with the large-scale atmospheric dynamics. An assessment of the improvements needed to the parameterizations of the boundary layer, cloud microphysics, and radiation in the 3-D model is made.