Submitted for the CCSM3 Journal of Climate Special Issue
The largest and potentially most important ocean near surface biases are exam-ined in the Community Climate System Model coupled simulation of present day conditions. They are attributed to problems in the component models of the ocean, or atmosphere, or both. Troical biases in sea surface salinity...
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| Format: | Text |
| Language: | English |
| Published: |
2005
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.639.4542 http://www.cesm.ucar.edu/publications/jclim04/Papers/OWG1.pdf |
| Summary: | The largest and potentially most important ocean near surface biases are exam-ined in the Community Climate System Model coupled simulation of present day conditions. They are attributed to problems in the component models of the ocean, or atmosphere, or both. Troical biases in sea surface salinity (SSS) are associated with precipitation errors, with the most striking being a band of excess rainfall across the South Pacic at about 8S. Cooler than observed equatorial Pacic sea surface temperature (SST) is necessary to control a potentially catastrophic positive feedback, involving precipitation along the equator. The strength of the wind driven gyres and inter-basin exchange are in reasonable agreement with observations, de-spite the generally too strong near surface winds. However, the winds drive far too much transport through Drake Passage (>190 Sv), but with little eect on SST and SSS. Problems with the width, separation and location of western boundary currents and their extensions create large correlated SST and SSS biases in mid-latitudes. Ocean model deciencies are suspected, because similar signals are seen in uncoupled ocean solutions, but there is no evidence of serious remote impacts. The seasonal cycles of SST and winds in the equatorial Pacic are not well rep-resented and numerical experiments suggest that these problems are initiated by the coupling of either, or both wind components. The largest mean SST biases develop along the eastern boundaries of subtropical gyres, and the overall coupled model response is found to be linear. In the South Atlantic, surface currents advect the these biases most of the tropics. Signicant precipitation responses are found both in the north-west Indian Ocean, and locally where the net result is the loss of an identiable Atlantic Intertropical Convergence Zone, which can be regained by controlling the coastal temperatures and salinities. Biases o South America and Baja California are shown to signicantly degrade precipitation across the Pacic, subsurface ocean ... |
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