The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60°S in the upper stratosphere evident in many data assimilation products.
Bibliographical noteFunding Information:
C. I. G. was supported by the Israel Science Foundation (grant 1558/14). We thank those involved in model development at GSFC-GMAO and support by the NASA MAP program. High-performance computing resources were provided by the NASA Center for Climate Simulation (NCCS). The topographic variance data are in the supporting information. Correspondence and requests for model output should be addressed to C. I. G. (email:email@example.com.
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- Southern Ocean
- gravity waves
- stratospheric circulation