Evaluation of climate model simulations of boundary layers in the Southern hemisphere

• Main Author: Lekoloane, Lesetja Ephraim
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2022
• Subjects: Climate Model Simulations; Climate Modelling; Southern Hemispheric boundary layers; Marion Island
• Online Access: https://hdl.handle.net/10539/36969

A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2022 There is a constant need to improve the simulations of weather and climate across different timescales. In this study we evaluate the simulations of Southern Hemispheric boundary layers by a variable-resolution global atmospheric model named the conformal-cubic atmospheric model (CCAM). To do the evaluation, we firstly determine a climatology of present-day ABL attributes from atmospheric soundings at three weather stations located in the high-latitudes (Syowa), mid-latitudes (Marion Island), and subtropical continent (Irene). We then proceed to evaluate how the CCAM simulates attributes of the ABL climatology over the three locations. Observational radiosonde data indicates that there persistently exists a temperature inversion over Irene at 00h00 UTC, throughout all the months of the year. It was found that this inversion is more intense during the autumn and winter seasons, while it is not as pronounced during the spring and summer seasons. Stability analysis over Marion Island indicated that the nearsurface atmosphere is neutrally stratified during all the seasons at 12h00 UTC. The radiosonde data over Syowa also indicated the presence of surface-based inversion at 00h00 UTC for all the months of the year. The surface-based inversion was also observed for 12h00 during all the months except the summer months, May, October and November. It was also found that monthly variability within the different seasons are prominently observed during the transitional seasons of autumn and spring, especially for thermodynamic variables. An interesting feature which was also observed over Irene and Syowa throughout all the seasons is a bulge in relative humidity above the surface. For Irene this is true for all the months of the year at 12h00 UTC, while for Syowa this bulge is observed for both 00h00 UTC and 12h00 UTC for all the months of the year. ...