NSFGEO-NERC Equatorial Line Observations

Overview: Modern management of extreme weather events crucially depends on weather forecasts reliable for extended time periods. Much of the predictability of global weather patterns lays within the intraseasonal variability of the tropical circulation and in particular the Madden-Julian Oscillation (MJO). The Maritime Continent (MC) is arguably the most important region in the global weather and climate system, in terms of forcing global atmospheric variability on sub-seasonal to decadal time scales, and is the core region for the MJO. However, the multi-scale interactions of the atmosphere, ocean and land surfaces in the MC region are sparsely observed, poorly understood and badly represented in our models, leading to systematic errors in extended range forecasts. In this project, the interactions within atmospheric equatorial convectively coupled Kelvin waves
(CCKWs), the leading modes of eastward moving convection on time scales between several days and three weeks, will be investigated. CCKWs and other equatorial waves form the "building blocks" of the active phase of MJO. The main effort will be to organize and execute the Equatorial Line Observations (ELO) field campaign during the winter of 2018/2019 - as a component of the International Years of the Maritime Continent (YMC) program. Based on collected in-situ data as well as other observational, remote sensing and modelling datasets, the key physical mechanisms responsible for multi-scale interactions associated with the propagating atmospheric convection over the Maritime Continent will be analysed. To this end, a novel Lagrangian approach in the analysis of propagating events will be employed to study the interaction between tropical waves and the local atmospheric and oceanic environment, in particular over the MC region.

Intellectual Merit: The project involves state-of-the-art theoretical and observational research at the frontiers of atmospheric physics, physical oceanography and air-sea interactions. A major part of the project is dedicated to the collection and analysis of unique in-situ data - fundamental to an improved understanding of the interaction between the MJO and MC. As a result of this project - the physical, dynamical and thermodynamical mechanisms responsible for the blocking and favouring propagation of atmospheric convection across the MC region will be identified. This will allow full exploitation of the predictability of weather patterns that govern circulation in the tropics.

Broader Impacts: The identification of physical mechanisms governing extreme precipitation events will benefit inhabitants of the MC region. Improved reliability of weather and climate forecasts will benefit the policy-makers, strategic planners, insurance industry and food security industries who use these predictions for decision making. Collaboration between scientists from the USA, Europe and Indonesia will contribute to research diversity and capacity building among all the involved institutions with great benefit for the early career researchers involved in this project.

Due to the integral nature of the MC, the Madden-Julian Oscillation (MJO) and convectively coupled Kelvin waves (CCKWs) within the global weather and climate system, this work will significantly impact the field of atmospheric science and forecasting on scales ranging from the short-term process level understanding to climate prediction. Weather forecasters will benefit through scientific advances made in understanding and modelling the interactions of convection with atmospheric dynamics and ocean thermodynamics and their impact on severe and hazardous weather. This will feed into improved measures of uncertainty in weather forecasts.
Beyond the advances to weather models, an improved understanding of the MJO and its propagation through the MC will lead to better constraints in the confidence of global medium-range forecasts (up to 15 days) at the UK Met Office, the European Centre for Medium Range Weather Forecasts, and other national meteorological agencies. The MC is a critical region for the El Nino-Southern Oscillation (ENSO) which is the major source of climate predictability on seasonal to inter-annual time scales; hence improved understanding of MC processes will feed into ENSO prediction and analysis of biases in ENSO forecasts.
Academic researchers in climate science, meteorology and oceanography will benefit from the advances described above. The ocean observations will also include elements of biogeochemistry, so our results will benefit those working on fisheries management, carbon sequestration and ecosystem modelling. ELO will benefit the International Indian Ocean Expedition 2 (IIOE-2), by improving understanding of ocean-atmosphere coupling in the Indian Ocean region. Scientists in the developing countries of the MC region will benefit by learning how to operate radiosondes and take surface flux measurements, and how to deploy, operate and pilot Seagliders. The PDRA working on ELO will gain valuable skills in state-of-the-art numerical modelling, and observational meteorology and oceanography, data processing and analysis.