Warm Conveyor Belts in Idealized Moist Baroclinic Wave Simulations
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| Veröffentlicht in: | Journal of the Atmospheric Sciences vol. 70, no. 2 (Feb 2013), p. 627 |
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American Meteorological Society
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| Abstract: | This idealized modeling study of moist baroclinic waves addresses the formation of moist ascending airstreams, so-called warm conveyor belts (WCBs), their characteristics, and their significance for the downstream flow evolution. Baroclinic wave simulations are performed on the f plane, growing from a finite-amplitude upper-level potential vorticity (PV) perturbation on a zonally uniform jet stream. This nonmodal approach allows for dispersive upstream and downstream development and for studying WCBs in the primary cyclone and the downstream cyclone. A saturation adjustment scheme is used as the only difference between the dry and moist simulations, which are systematically compared using a cyclone-tracking algorithm, with an eddy kinetic energy budget analysis, and from a PV perspective. Using trajectories and a selection criterion of maximum ascent, forward- and rearward-sloping WCBs in the moist simulation are identified. No WCB is identified in the dry simulation. Forward-sloping WCBs originate in the warm sector, move into the frontal fracture region, and ascend over the bent-back front, where maximum latent heating occurs in this simulation. The outflow of these WCBs is located at altitudes with prevailing zonal winds; they hence flow anticyclonically (“forward”) into the downstream ridge. In case of a slightly weaker ascent, WCBs curve cyclonically (“rearward”) above the cyclone center. A detailed analysis of the PV evolution along the WCBs reveals PV production in the lower troposphere and destruction in the upper troposphere. Consequently, WCBs transport low-PV air into their outflow region, which contributes to the formation of distinct negative PV anomalies. They, in turn, affect the downstream flow and enhance downstream cyclogenesis. |
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| ISSN: | 0022-4928 1520-0469 0095-9634 |
| DOI: | 10.1175/JAS-D-12-0147.1 |
| Quelle: | Science Database |