Amanda Thandeka Masilela

In many social contexts, I often notice that we ask each other questions like: “What do you do?”, “What is your research about?”, or “Which department are you in?”. These are such common icebreakers. More often than not, when I describe what I do, the response is: “That sounds so cool!”.

For context, I am a Master’s student in the Ocean and Atmosphere Sciences discipline at the University of Cape Town, within the Oceanography Department. Our department is small and not very popular, as often it is assumed that we only study marine animals, which is not the case. In fact, oceanography is the study of the oceans and the ways in which their different components interact, including but not limited to the movement and composition of water, the plants and animals, the air above, and the geology below. This naturally branches into various themes such as climate sciences, physical oceanography, marine and atmospheric biogeochemistry, polar research, numerical modelling, and ocean statistics and machine learning. Our department is incredibly diverse in the research that we do, but what we all have in common is that we either focus on the ocean, the atmosphere, or their intersection. As for myself, my research focuses solely on the atmosphere.

For as long as I can remember, I’ve been fascinated by weather presenters. How do they know what the weather will be like tomorrow or for the next 10 days? How are they able to inform us that this year we will experience a dry season; that floods are coming; or that there is a cold front on its way? What is this cold front that they are talking about? I had so many questions, and I had no idea which field would bring about clarity. It is miraculous how I applied to major in Ocean and Atmosphere Science for my undergraduate degree, not really sure what it was, or how it would actually be the path to getting answers. I just wanted to learn about the ocean as it felt unique and the possibility of going on a research vessel one day sounded surreal (which I was lucky enough to experience in my Honours year). My journey in the Ocean and Atmosphere Sciences has been deeply rewarding, from answering questions that sparked my curiosity as a child, to empowering me to contribute meaningful research.

In a nutshell, my study is about tracing and quantifying the transport of moisture towards the Berg-Olifants and Breede-Gouritz Catchments in the southwestern South Africa (Fig. 1). Put simply, winds are the main driver of water vapor air masses (hereafter referred to as  “water parcels”) as they circulate and travel in the atmosphere in different phases of the water cycle. Water parcels are influenced by the warming of water bodies, which increase evaporation adding more water parcels in the atmosphere. Conversely, as air cools with decreasing temperature, the amount of water vapor also decreases. The rising of warm air and descending of cool air happens on a large scale in the atmosphere due to the presence of warm and cold sections of the ocean called currents. The warm currents and inland regions are the major contributors to water parcels that can potentially aid in cloud formation, enhancing weather systems, and fuelling the continuous water circulation in the atmosphere.

How exactly did we trace water parcels in the atmosphere? By utilising the numerical Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model executed with the high resolution ERA5 reanalysis dataset. The HYSPLIT model can track backward (or forward) in time estimating the water parcels pathways and help determine their origin before arriving at the study region. Part of the results revealed that moisture tracked back from the southwestern South Africa originates as distant as the south Australian region; the western, central, and eastern South Pacific and South Atlantic Oceans; the Agulhas Current region; and from the southern African continental region (Namibia, Botswana, southern Zimbabwe, and southern Mozambique). Although the Berg-Olifants Catchment is a winter rainfall region and the Breede-Gouritz Catchment is an all-year round rainfall region, they illustrated similar moisture source routes.

With focus on a historical long term, as carried out in this study, prolonged deficiency (excess) in moisture in the atmosphere can potentially lead to persistent droughts (floods). Moisture can be influenced by wind patterns, differences in temperature, and earth’s landscape (mountains and valleys), among other things. Resultantly, not all moisture parcels traced back from their source regions arrive at the study domain. Understanding where moisture is coming from and where it is propelled to can help forecasters better understand current climate conditions, consequently helping the society to be better informed and prepared when regions become drier or more humid than usual.

While I am not a weather presenter (which still seems like an incredibly cool career!), I take pride in knowing that the work I am involved in contributes to a better understanding of the atmosphere. This journey continues to inspire me every day, as my knowledge grows, my list of questions becomes endless. Who would’ve imagined that diving into something so unfamiliar could be so deeply fulfilling?!

Figure 1: Map of the southwestern South Africa highlighting the positions of the Berg-Olifants Catchment (black outline) and the Breede-Gouritz Catchment (grey outline). The shading illustrates the difference in height above ground in meters.