Soil moisture data RIGHT: University of Manchester researchers also collected samples from Austria BELOW: Greek and Spanish soil samples after a lab drought event, as part of the University of Manchester research Both images: Océane Nicolitch events, he noticed that there were variations in the severity of the heat being predicted. Maraun says, “There were regions where the climate change signal for these very rare events was much stronger than in the mean climate, and other regions where the climate change signal had actually dampened for these extreme events. I started wondering what could be the cause of these variations. There’s a lot of research on how soil moisture conditions can amplify how heat events change compared with the mean climate. So, I thought maybe that was relevant here.” Maraun’s hunch was correct. As he investigated further, he discovered that soil did indeed alter the severity of the heat waves, but only under certain conditions. According to the research, the soil moisture only influenced the heat event when it was in an intermediate state – not too wet or too dry. This is because in very wet and very dry conditions, soil moisture is unaffected by the temperature, he notes. In rainy northern latitudes, for example, wet soil remains wet no matter how hot it gets. Very arid soils, which are already parched of moisture, remain in the same state despite the heat changes. However, soils that contain intermediate levels of soil moisture can The role of soil moisture in climate change Many of the efforts to understand the relationship between climate and soil are focused on soil moisture, which scientists now realize plays a key role in global climate. In fact, since 2010 the European Space Agency (ESA) has made soil moisture one of the “essential climate variables” that it monitors via its constellation of satellites as part of its Climate Change Initiative (CCI). “The important role of soil moisture for the environment and climate system is well known,” says Clément Albergel, who oversees the soil moisture project for the CCI. “Soil moisture influences hydrological and agricultural processes, runoff generation, drought development and many other processes. It also impacts the climate system through atmospheric feedback. Soil moisture is a source of water for evapotranspiration over the continents (through the soil-plant-atmosphere continuum) and is involved in both the water and energy cycles.” This reciprocal relationship between soil moisture and climate was investigated in a recent joint research project conducted by the UK’s University of Reading and Austria’s Graz University. The study showed how variations in soil moisture can amplify or reduce the effect of heat wave events. Lead researcher professor Douglas Maraun, head of the regional climate research group at the University of Graz’s Wegener Center for Climate and Global Change, kicked off the research using climate modeling to predict future extreme heat events. As the models began to detect these 32 • www.meteorologicaltechnologyinternational.com • April 2025
Meteorological Technology International Meteorological Technology International April 2025: Page 32
