AMS Forum: Climate Change Manifested by Changes in Weather


Bridging the gap between weather and climate

Greg Holland, NCAR, Boulder, CO; and J. Hurrell and Y. H. Kuo

We report on aspects of a major effort to examine the influences of 2-way scale interactions on tropical modes, including tropical cyclones. The NCAR Advanced Research Weather and forecasting model (ARW) has been adapted to a tropical channel mode and utilized with relocatable internal grids that are fully 2-way interactive with the larger scales. Configurations include a 36 km channel domain, with 12 and 4 km nests over the entire Maritime Continent region, which enables us to examine the upscale impact of resolvable convection on tropical modes and in particular the MJO. A moveable 4 km nest enables detailed investigations of the development and extratropical transformation of tropical cyclones and the upscale capacity enables analysis of their influence on larger scale circulations. A major data set has been developed covering the period 1996-2005 using the channel model embedded in NCEP/NCAR reanalysis on the meridional boundaries and forced by specified SST.

We first show that the major features of all tropical modes are well simulated. We next examine two major features of this experiment: the development of MJO modes associated with the lead up to the 1997-1998 El Nino; and the climatology of tropical cyclone genesis from easterly waves over the North Atlantic and eastern North Pacific. This will include a detailed case study of each and an examination of the associated 2-way scale interactions. This analysis provides a basis for further experimentation in support of THORPEX programs and in particular the downstream Rossby-mode energy dispersion from poleward moving typhoons in the PARC experiment. A brief summary of these plans will also be presented.


Session 3, THORPEX Special Session: Impacts of Processes over the Tropical Pacific and Indian Oceans on Mid-Latitude Weather and Predictability
Wednesday, 17 January 2007, 1:30 PM-5:15 PM, 214A

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