Caribbean low-level jets and accompanying moisture fluxes in a global warming climate projected with CMIP3 multi-model ensemble and fine-mesh atmospheric general circulation models

摘要

This study used the third phase of the Coupled Model Intercomparison Project (CMIP3) multi-model ensemble (MME) and atmospheric general circulation models (AGCMs) with three horizontal resolutions, 20, 60, and 180 km, to investigate climate projections of the Caribbean low-level jet (CLLJ) and accompanying moisture fluxes. Future climate simulations were also performed with 60- and 180-km mesh AGCMs forced by four lower boundary conditions both to quantify uncertainty in the CLLJ projections and to determine the physical mechanism of change in the CLLJ. Changes among the CMIP3 MME models in projected CLLJ in the future climate were inconsistent in sign and statistically insignificant, whereas consistently among the models the easterly moisture flux accompanying the CLLJ significantly intensified. The AGCM simulations with three different horizontal resolutions demonstrated that the merits of dynamical downscaling for the CLLJ and moisture flux were limited for climate projections, although the high-horizontal resolution models improved reproducibility of the CLLJ and moisture flux in the present-day climate and can provide spatially detailed projections. Different projected sea surface temperatures (SSTs) as lower boundary conditions of the 60- and 180-km mesh single-AGCM simulations clearly affected changes in the CLLJ. Both the CMIP3 MME analysis and the 60- and 180-km mesh AGCM ensembles showed that large-scale SST patterns between the eastern tropical Pacific and the region from the Caribbean Sea to the western tropical Atlantic influenced changes in the CLLJ in the future climate, as seen in the present-day climate.