As Earth’s climate warms, droughts may become more frequent and more intense, and the repercussions for agriculture and industry could be severe. Improving drought monitoring and prediction methods is vital to drought mitigation and response, and satellite monitoring may hold the key to more effective forecasting. Here Sun et al. use case studies of two major droughts—in Texas in 2011 and in the central Great Plains in 2012—to identify a proxy for drought origins.
To do this, the researchers looked at satellite observations of solar-induced chlorophyll fluorescence (SIF). As chlorophyll transitions from an excited to a nonexcited state, it emits a faint red light—a sign that photosynthesis is taking place in bacteria, algae, and plants. In other words, drought-affected regions emit less chlorophyll fluorescence. The team analyzed SIF measurements from the Global Ozone Monitoring Experiment-2 aboard the European MetOp-A weather satellite to assess its ability to monitor drought.
They tested the potential value with case studies of two different kinds of drought; the Texas drought was the result of below-normal rainfall for an entire year, whereas the Great Plains drought was caused by a combination of abnormally warm temperatures in winter/spring that drove evapotranspiration—a process that removes moisture from the soil and prompts drought conditions—and reduced rainfall that exacerbated the soil moisture deficit.
For both events, the researchers found a consistency between satellite measurements of below-normal SIF and the intensity of the drought as specified in U.S. Drought Monitor maps. Despite having different triggers, the SIF data accurately reflected root zone soil moisture in both events, thus providing an accurate depiction of agricultural drought. These results are strong evidence that SIF anomalies bear the potential to aid in assessing drought conditions. (Journal of Geophysical Research: Biogeosciences, doi:10.1002/2015JG003150, 2015)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2016), Satellites track chlorophyll fluorescence to monitor drought, Eos, 97, doi:10.1029/2016EO044961. Published on 3 February 2016.