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This work concerns an analysis of inter-basin and inter-layer exchanges in the component ocean part of the coupled ECHAM4/OPYC3
general circulation model, aimed at documenting the simulation of North Atlantic Deep Water (NADW) and related thermohaline
circulations in the Indian and Pacific Oceans. The modeled NADW is formed mainly in the Greenland– Iceland–Norwegian Seas
through a composite effect of deep convection and downward cross-isopycnal transport. The modeled deep-layer outflow of NADW
can reach 16 Sv near 30 °S in the South Atlantic, with the corresponding upper-layer return flow mainly coming from the “cold
water path” through Drake Passage. Less than 4 Sv of the Agulhas “leakage” water contributes to the replacement of NADW along
the “warm water path”. In the South Atlantic Ocean, the model shows that some intermediate isopycnal layers with potential
densities ranging between 27.0 and 27.5 are the major water source that compensate the NADW return flow and enhance the Circumpolar
Deep Water (CDW) flowing from the Atlantic into Indian Ocean. The modeled thermohaline circulations in the Indian and Pacific
Oceans indicate that the Indian Ocean may play the major role in converting deep water into intermediate water. About 16 Sv
of the CDW-originating deep water enters the Indian Ocean northward of 31 °S, of which more than 13 Sv “upwell” mainly near
the continental boundaries of Africa, South Asia and Australia through inter-layer exchanges and return to the Antarctic Circumpolar
Current (ACC) as intermediate-layer water. As a contrast, only 4 Sv of Pacific intermediate water is connected to “upwelling”
flow southward across 31 °S while the magnitude of northward deep flow across 31 °S in the Pacific Ocean is significantly
greater than that in the Indian Ocean. The model suggests that a large portion of the deep waters entering the Pacific Ocean
(about 14 Sv) “upwells” continually into some upper layers through the thermocline, and becomes the source of the Indonesian
throughflow. Uncertainties in these results may be related to the incomplete adjustment of the model’s isopycnal layers and
the sensitivity of the Indonesian throughflow to the model’s geography and topography.
Received: 12 August 1997/Accepted: 12 March 1998 相似文献
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Condensation heating of the Asian summer monsoon and the subtropical anticyclone in the Eastern Hemisphere 总被引:27,自引:0,他引:27
The effects of condensation heating on the formation of the subtropical anticyclone in the Eastern Hemisphere (EH) are studied
by means of theoretical analysis and numerical simulation. The complete vorticity equation is employed for the analysis. It
is found that, due to the vertical gradient of strong condensation heating, the distribution of cyclone and anticyclone in
the upper troposphere is out of phase with that in the middle and lower troposphere. This is confirmed by a series of numerical
experiments. The horizontal gradient of the condensation heating also affects the configuration of the subtropical anticyclone.
It is concluded that condensation heating is a key factor for the formation and location of the summer subtropical anticyclone
in the EH. The latent heating released by the Asian monsoon rainfall contributes to the formation of the 200 hPa South Asian
anticyclone on the western side of the heating center and the 500 hPa western Pacific subtropical anticyclone on the eastern
side of the center. Such configurations are modified to some extent by surface sensible heating and orography. The circulation
in mid-latitudes is also affected by the latent heating in the subtropical area through the propagation of Rossby waves.
Received: 10 September 1999 / Accepted: 5 June 2000 相似文献
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