North Pacific Mesoscale Coupled Air-Ocean Simulations Compared with Observations

• Main Authors: Koracin, Darko, Cerovecki, Ivana, Vellore, Ramesh, Mejia, John, Hatchett, Benjamin, McCord, Travis, McLean, Julie, Dorman, Clive
• Other Authors: United States. Department of Energy., United States. Department of Energy. Office of Science.
• Format: Report
• Language: English
• Published: Desert Research Institute 2013
• Subjects: 54 Environmental Sciences Regional Climate Modeling; Air Sea Interaction; Coupling Atmospheric And Ocean Models; Kuroshio Current; Cold Air Outbreak; North Pacific; Regional Climate Modeling; Pacific; aleutian low; Siberia
• Online Access: http://digital.library.unt.edu/ark:/67531/metadc830185/

Executive summary The main objective of the study was to investigate atmospheric and ocean interaction processes in the western Pacific and, in particular, effects of significant ocean heat loss in the Kuroshio and Kuroshio Extension regions on the lower and upper atmosphere. It is yet to be determined how significant are these processes are on climate scales. The understanding of these processes led us also to development of the methodology of coupling the Weather and Research Forecasting model with the Parallel Ocean Program model for western Pacific regional weather and climate simulations. We tested NCAR-developed research software Coupler 7 for coupling of the WRF and POP models and assessed its usability for regional-scale applications. We completed test simulations using the Coupler 7 framework, but implemented a standard WRF model code with options for both one- and two-way mode coupling. This type of coupling will allow us to seamlessly incorporate new WRF updates and versions in the future. We also performed a long-term WRF simulation (15 years) covering the entire North Pacific as well as high-resolution simulations of a case study which included extreme ocean heat losses in the Kuroshio and Kuroshio Extension regions. Since the extreme ocean heat loss occurs during winter cold air outbreaks (CAO), we simulated and analyzed a case study of a severe CAO event in January 2000 in detail. We found that the ocean heat loss induced by CAOs is amplified by additional advection from mesocyclones forming on the southern part of the Japan Sea. Large scale synoptic patterns with anomalously strong anticyclone over Siberia and Mongolia, deep Aleutian Low, and the Pacific subtropical ridge are a crucial setup for the CAO. It was found that the onset of the CAO is related to the breaking of atmospheric Rossby waves and vertical transport of vorticity that facilitates meridional advection. The study also indicates that intrinsic parameterization of the surface fluxes within the WRF model needs more evaluation and analysis.