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Droughts over Hawaii and the U.S-affiliated Pacific Islands: a framework to understand processes and feedbacks, assess predictability and reduce uncertainties.

Undoubtedly, the phase and intensity of El Niño-Southern Oscillation (ENSO) exert
detectable imprints on the onset, severity and maintenance of droughts over Hawaii and the
U.S. affiliated Pacific Islands (USAPI). However, apart from ENSO characteristics, local
air-sea interactions, remotely forced teleconnections, phase and intensity of other natural
modes of variability [Pacific Meridional Mode (PMM) and/or Pacific decadal variability],
are also expected to contribute to observed drought characteristics. Observations show
occurrences of unprecedented persistence beyond ENSO timescales implying factors other
than ENSO are involved, and until now, no studies have attempted to explain the processes
and feedbacks that led to such drought persistence. Only as of May 2019, USAPI drought
information has been included in the U.S. Drought Monitor (USDM). In consultation with
local stakeholders, there is a need in the Insular Pacific to identify precursors to
monitor and predict the severity and persistence of droughts. Thus, we will devise a
framework with a focus on understanding processes and feedbacks, assessing causality
and reliably quantify uncertainties in their prediction.

Our overarching goal is to work towards the development of a Drought Early Warning
System (DEWS) in the Pacific and contribute to the Drought Task Force. To accomplish
this goal, our objectives are: (i) based on specific stakeholder-relevant thresholds, study
characteristics of severe and prolonged droughts from a multitude of observations and
reanalysis products; (ii) assess the predictability of drought life cycle, and develop a robust
system for drought monitoring; and (iii) work closely with various regional stakeholders and
National Integrated Drought Information System (NIDIS), and link the research results to
improve drought prediction. Three inter-linked tasks will be carried out, and they are: (1)
assess the role of multi-scale climate modes of variability, remote teleconnections in
conjunction with ENSO in determining droughts and their persistence, and study processes
and feedbacks; (2) apply skill metrics in the suite of hindcasts and real-time forecasts
performed with NMME models, and devise methods to reliably quantify uncertainties; and
(3) seek frequent feedbacks from stakeholders and NIDIS, and develop a process-based
monitoring system for drought life cycle (onset, amplification, persistence and withdrawal).
Our proposed research targets the MAPP competition “Characterizing and Anticipating
U.S. Droughts’ Complex Interactions” and specifically, the competition identified research
topics – “Identify the array of complex interactions that lead to US droughts, focusing on
key processes and feedbacks, explain why extreme or prolonged droughts occurs”, and
“Examine the predictability of US droughts considering the intervening processes and their
multi-scale evolution, focusing on identifying precursor mechanisms, methodologies for
prediction, with an overall reduction of uncertainties”. Project deliverables will enhance
USDM efforts for the USAPI through the development of a Drought Early Warning
System (DEWS) in the Pacific focused on the tropical Pacific. We will also contribute to
the Drought Task Force by sharing the developed approaches and metrics.

Award Announcement:

Climate Risk Area: Water Resources

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