The kinetic energy budget of tropical plumes and ENSO in NMC and ECMWF analyses /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Online Access: | Link to OAKTrust copy |
| Abstract: | The regional eddy kinetic energy (EKE) budget primarily at 200 mb is calculated over the tropical eastern Pacific Ocean to identify and quantify the physical processes related to the evolution of tropical plumes. In addition, energy processes in the wavenumber domain are investigated to quantify scale interactions within the tropical band between 2.5° and 20°N around the globe. Energetics are based on daily operational analyses prepared by ECMWF and NMC. Comparisons between the resultant analyses provide an estimate of the reliability and uncertainty of tropical kinetic energy computations. March 1983 and 1984 are examined to test sensitivity to differing general circulation regimes. The main physical difference in maintaining the area-averaged EKE over the eastern Pacific Ocean between March 1983 (ENSO period) and March 1984 (non-ENSO period) is that ENSO is dominated by flux convergence of eddy potential energy and non-ENSO is dominated by flux convergence of EKE. Anticyclonic systems over the eastern Pacific Ocean strengthen during ENSO, causing influxes of kinetic energy into the domain to weaken. The main change to the regional EKE budget during most of the 8 tropical plumes examined is an increase of EKE flux across the northern boundary, indicating the importance of tropical and mid-latitude interactions. Locally within the plume, the primary contribution to the increase of EKE is due mainly to potential energy fluxes by cross-contour flow. Plumes are generally barotropically and baroclinically stable in both NMC and ECMWF analyses. During March 1983 and March 1984, the tropical wave systems are driven mainly by flux convergence of EKE from wavenumbers 1 to 8. Differences between March 1984 and March 1983 are observed mainly in the extra-long waves for all the physical process terms. During active plume periods fluxes shift more to the synoptic scale and wave-wave interactions transfer EKE to the synoptic scale, as well. Disparities between different plumes and between different analyses leave some doubt as to the normal role of long waves in plume formation and the actual magnitude and direction of baroclinic and barotropic processes. Comparisons of ECMWF and NMC wind fields show that 10 ms^-1 discrepancies are common in synoptically active periods. Uncertainties in processes result and interpretation of the residuals, which become larger during plume events, also becomes a major uncertainty. With these exceptions the two model analyses confirm the major processes. Finally, the comparisons of the results from the ECMWF and NMC analyses show general agreement in the main features, even though there exist some differences in amplitudes locally, in certain waves, and, particularly, in the baroclinic terms. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Meteorology." |
| Physical Description: | xiii, 182 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |