Storms and Ocean

The theme Storms and Ocean will focus on the ability of the SR-ESMs to realistically represent the surface energy budget over the tropical ocean, as well as atmosphere-ocean coupling.

It will do so by studying the role of high-frequency coupling, upper ocean and atmospheric boundary layer processes in the tropics, and assumptions related to ocean and atmosphere discretisation and vertical mixing, so as to optimise existing or develop/propose new representations. Particular attention will be given to air-sea interaction across fine scale oceanic features and during intense tropical cyclones. Extensive use will be made of data from three field studies over the tropical Atlantic: EUREC4A in the trade-winds, BOW- TIE/TOOC and buoy measurements in the Intertropical Convergence Zone (ITCZ) region, and within the project Benguela Niños: Physical processes and long-period variability (BANINO) in the Eastern Boundary Current region, as well as 10 years of data collected to observe upper ocean mixing and satellite observations.

This theme will explore how resolving convective storms, ocean mesoscale eddies, and air-sea interaction on these scales influences the development of tropical SST anomalies; how this influences the mean climate (ITCZ biases), variability (diurnal to inter-annual), global teleconnections, and extremes; and how this alters the simulation of climate change. There will be a specific focus on the tropical Atlantic (where model biases are large with implications for high impact events), including the effects on the West African Monsoon, and the intensity, number and spatial distribution of Atlantic Hurricanes.


Work Package 6

Development Phase

Objectives

WP6 evaluates SR-ESM with a focus on ocean-atmosphere interactions in the tropical Atlantic region and to develop recommendations for model improvements in the representation of the ocean mixed layer and the planetary boundary layer and to provide user-oriented evaluation tools.

Further Description

In the development phase of S&O, WP6 will evaluate the SR-ESMs from an ocean perspective, focusing on tropical air-sea fluxes and including global metrics for ocean circulation and the Inter-tropical convergence zone (ITCZ). The ITCZ is a key feature linking tropical SST and precipitation, monsoons and the global atmospheric circulation. WP6 will also evaluate and improve the representation and interactions of the ocean mixed-layer and the planetary boundary layer. It is not guaranteed that the schemes developed at 10 km to
100 km grid scales represent mixing in the ocean and lower atmosphere well in storm resolving simulations. This is because current parametrisations make implicit assumptions about the resolved length and timescales that may be satisfied in coarser resolution ESMs, but not in SR-ESMs. Using the emerging database of mixing events in the tropical Atlantic, existing ocean mixing parametrisations will be evaluated with their underlying assumptions reconsidered, and the resulting near-field and far-field impacts of suggested changes quantified (in the S&O Application phase, WP7). This development work will focus on the tropical Atlantic because of the vast amount of relevant in situ data that has been collected there over the last ten years and continue to be collected. The wider tropical Atlantic region is also an ideal laboratory for studying land-ocean-atmosphere interactions, which have been linked to particularly longstanding climate model biases. WP6 will also explore innovative methods to assess the relevance of storm resolving scales for Earth-system processes (carbon) and fisheries applications (Task 6.5).

Lead Beneficiary: UCPH

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Work Package 7

Application Phase

Objectives

WP7 assess the importance of resolving storm-scales for simulating tropical climate and its response to climate change, as well as for Earth System modelling and marine ecosystem applications.

Further Description

In the application phase of S&O, WP7 will assess the importance of resolving air-sea interactions on mesoscales for climate, with a focus on tropical climate and its global impacts, and on identifying out of sample behaviour compared to current ESMs. This will include the dominant patterns of tropical climate variability, key global teleconnections, the West African Monsoon (WAM), and Atlantic hurricanes. There will also be an effort to assess the importance of further developing storm resolving ESMs, by continuing the development and evaluation of improved representation of turbulent mixing in the ocean and planetary boundary layers. The Knowledge Coproduction activities of WP7 will focus on applying innovative approaches to estimate global ocean primary productivity and then global climate impacts on fisheries with a regional focus on the Atlantic African regions. A hackathon will be held to explore how outputs of the storm resolving simulations can be used to assess the importance of these scales for climate change assessment, including key issues related to the Paris Climate Accord (e.g., passive uptake of heat and anthropogenic carbon). There will also be work on evaluating the refined ocean mixed layer and planetary boundary representation in coupled model context.

Lead Beneficiary: UiB

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