Diversity of Tropical Intraseasonal Oscillation

The large-scale atmospheric circulation in the tropical region strongly fluctuates on a timescale of a few months. Such tropical intraseasonal “oscillation” (ISO) is dominated by the Madden-Julian Oscillation (MJO) phenomenon between November-April and the Boreal Summer Intraseasonal Oscillation (BSISO) phenomenon between June-October. The MJO typically elicits patterns of enhanced rainfall (and deep clouds) that evolve eastward while BSISO produces northeastward migrating intense rainfall patterns. Both phenomena greatly impact weather and climate worldwide. Recent observations have revealed that events associated with MJO/BSISO are quite diverse, differing strikingly in structure, propagation, lifecycle, and global impacts. Characterization and understanding of ISO diversities and their climate variations are crucial for realistic modeling and skillful prediction of global atmospheric variations. However, to date, they are largely unknown. Thus, this research aims to reveal the distinctive forms of ISO diversity and its impacts on extreme weather events, and to understand the fundamental processes governing the diversity and its decadal variability and future change. Results from this research can shed new light on tropical dynamics and monsoons as well as improve weather and climate forecasting for regions of over 1 billion people impacted by ISO. The researcher plans to host an international workshop to galvanize community interests in ISO. He will mentor a post-doctoral research scientist and train a graduate student. The specific research objectives are to: (a) detect and characterize a full range of ISO diversity in their initiation, propagation, structure, amplification/decay, and impacts, (b) elucidate the mechanisms responsible for generation of the diversified ISO behavior, (c) reveal global and regional sources of ISO decadal variability, and (d) quantify how the ISO diversity responds to anthropogenic forcing. To address these objectives, the researcher will employ a strategy of combining process- and dynamics-oriented diagnostics, theoretical analyses, and modeling. Results from this work may lead to a new conceptual framework for understanding ISO complexity and a new avenue to unravel root causes of ISO decadal variability and its future change. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.