Interannual variability of the South Asian monsoon: From improved understanding to skillful predictions of extreme monsoon seasons
Understanding and predicting the interannual variability of the South Asian monsoon, the largest monsoon in the Earth's atmosphere, is both a priority and a long-standing challenge in climate science. Extreme monsoon seasons cause drought, floods, and other natural hazards affecting millions of people's lives and resulting in huge economic losses. Variability in monsoon strength has been associated with variability in either land surface properties or in Sea Surface Temperatures in tropical oceans. In this project, we shift focus to the role of large-scale circulations in both the tropics and the extra-tropics, to isolate large-scale patterns associated with strong or weak monsoon years, both in antecedent and monsoon months. This approach is motivated by a progressive shift in the theoretical understanding of large-scale monsoons, which highlights the potential influence of weather systems in the winter hemisphere on tropical monsoons and suggests the need for revisiting these mechanisms in the context of the interannual variability of the South Asian monsoon. Observations, which include most recent reanalysis- and satellite-based estimates of thermodynamical and dynamical parameters, are used extensively to characterize patterns associated with strong or weak monsoon seasons. Numerical experiments with comprehensive general circulation models (GCM) will be used to investigate the dynamics at play. Finally, the emerging antecedent relationships will be developed into statistical prediction schemes for monsoonal rainfall variability. Our goal is to advance the scientific understanding of the largest monsoon in the Earth's atmosphere, and most importantly to improve predictive skills of its year-to-year variability, with great societal impacts for the millions of people living in the socially vulnerable economies affected by the monsoon.
Towards the continuous monitoring of natural hazards from river floods and debris flows from seismic observations
The broad goal of this project is to work towards being able to continuously monitor flood and debris flow hazards using seismic observations. Our specific aims in Yr1 were to conduct primarily laboratory experiments in the Caltech Earth Surface Dynamics Laboratory (ESDL) to improve our mechanistic models of bedload and water-flow induced seismic noise. Yr2 goals are to extend our studies to debris flows, including field studies in the San Gabriels, and large-scale hillside flume experiments.