Dissertation submitted to the Faculty of Science, University of the Witwatersrand, for
completion of the Degree of' Master of Science / The atmospheric response of the Colorado State University Regional Atmospheric
Modelling System (RAMS) to sea-surface temperature anomaliesis investigated. A period
of four days was chosen from 21 to 24 January 1981, where focus was placed on the
development and dissipation of a tropical-temperate trough across Southern Africa.
Previous experimenting this mesoscalenumerical model have detemined the kinematic,
moisture, and thermodynamic nature of these synoptic features. The research in this
dissertation focuses specifically on the sensitivity of the numerical model's simulated
responses to positive sea-surface temperature anomalies. Three separate experiments were devised, in which positive anomalous temperatures were added to the ocean surface north of Madagascar (in the tropical Indian Ocean), at the region of the Agulhas Current retroflection, and along the tropical African west coast (in the Northern Benguela and Angola currents). The circulation aspects of each sensitivity test were investigated through the comparison of simulated variables such as vapour and cloud mixing ratios, temperature, streamlines and vertical velocity, with the same variables created by a control simulation.
The results indicate that for the first sensitivity test, (the Madagascar anomaly),
cyclogenesis was initiated over the area of modified sea temperatures which resulted in a
marginal decrease in continental precipitation. The second sensitivity test (over the
Agulhas retroflection) produced a much smaller simulated response to the addition of
anomalously warm sea temperatures than the tropical Indian Ocean anomaly. Instability
and precipitation values increased over the anomalously warm retroflection region, and
were slowly transferred along the westerly wave perturbation and the South African east
coast. The third sensitivity experiment showed a predominantly localised simulated
increase in precipitation over Gabon and the Congo, with the slow southward progression
of other simulated circulation differences taking place. The small perturbations in each of
the simulated meteorological responses are consistent with the expected climate response
to anomalously warm sea-surface temperatures in those areas. / AC 2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/24293 |
| Date | January 1996 |
| Creators | Crimp, Steven Jeffrey |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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