ECMWF: Toward accurate representation of inland waters in Earth System Models

Inland waters (lakes, rivers, and reservoirs) are an important component of the earth system, and their presence in the landscape has a range of effects on weather and climate. For example, over mid-latitude regions, inland waters (notably lakes) help to foster mild micro-climate conditions by acting as thermal inertial bodies and, in turn, can influence air temperatures in some regions and precipitation patterns in others. Moreover, at high latitudes, lakes tend to freeze each winter, altering the albedo and thermal capacity of the region. Likewise, lakes affect the surface fluxes exchanged with the atmosphere which can influence snowfall downwind from a lake (e.g., near the North American Great Lakes). Lakes also influence the weather in temperate and tropical regions, and are even linked with high-impact events by contributing to the formation of convective cells (e.g., in Lake Victoria, East Africa).

To account for lake presence in Numerical Weather Prediction, ECMWF recently implemented a simple but effective lake model to represent the water temperature and ice cover of all the world’s major inland water bodies in their Integrated Forecasting System (IFS). The model currently uses a static dataset to represent the extent of the world’s lakes. However, satellite data show that the world’s surface water bodies are far from static, and that variations in water extent can be particularly extreme in some cases (Fig. 1). Moreover, recent studies have shown that between 1984 and 2015 almost 90,000 km2 of inland waters typically thought of as permanent have vanished from the Earth’s surface, linked to drought and human activities, including river diversion, or damming and unregulated withdrawal. Elsewhere, more than 180,000 km2 of new permanent bodies of water have formed due to, for example, new reservoirs being created in some regions and increased glacial melt in others leading to lake expansion. Furthermore, the representation of lakes in ECMWFs IFS have also assumed that lake colour is constant both in time and space. However, satellite data tell a different story (Fig. 2). Satellites show that lakes differ considerably in terms of their surface colour which can, importantly, influence the amount of heat absorbed in a lake or released to the atmosphere above (e.g., as darker water bodies absorb more heat), ultimately altering the surface energy fluxes. By not correctly mapping the geographic limits of lakes or adequately capturing across-lake variations in water colour, weather prediction can be considerably biased in some regions.

The overarching aim of this project is to advance lake representation in numerical weather prediction models by using new space observations and applying a unique combination of emerging and beyond state-of-the-art methodologies for simulating aquatic systems at a global scale. Ultimately, the PhD will explore a more dynamic representation of lakes in Earth System Models, specifically exploring the value-added of (i) dynamic lakes, where their spatial extent is allowed to vary in time, and (ii) temporally and spatially varying water colour. Moreover, the PhD will compare model outputs from ECMWF with new satellite data generated by the European Space Agency’s Climate Change Initiative Lakes project (https://climate.esa.int/en/projects/lakes/). Developing and testing this improved modelling chain has intrinsic value and represents a major step towards integrated Earth system modelling which includes comprehensive lake representation. This alignment of global simulations with other research fields will also constitute a breakthrough in the way inland waters have been approached so far, and will provide a unique opportunity to further explore the influence of climate change on the natural world.

Eligibility requirements: Applicants should hold or expect to gain a minimum of a 2:1 Bachelor Degree , Masters with Merit, or equivalent in meteorology, physics, mathematics or a closely related environmental or physical science. Due to restrictions on the funding this studentship is open only to citizens of ECMWF member states https://www.ecmwf.int/en/about/who-we-are/member-states .

How to apply: please click the link here to apply. Create an account and during the application process please select the PhD in Atmosphere, Oceans and Climate. Please quote reference GS22_004 in “Scholarship applied for” box. When you are prompted by the online application system to upload a research proposal, please omit this step as the project is already defined.