New York Office Event, The University of Tokyo

The New York Meeting on Tropical Cyclones and Global Storm-Resolving Analysis

 

Date: February 5, 2024

Hybrid format with The University of Tokyo New York Office (https://utokyony.adm.u-tokyo.ac.jp/)

and the Zoom streaming.

 

Photo of the keynote speakers: Feb. 5, 2024, UTokyoNY office

 

 

 

This meeting is organized to interchange recent developments in tropical cyclone (TC) research, particularly focusing on future changes, evaluations, and management of the current risks due to TCs. For this purpose, we would like to enhance the research activities related to global storm-resolving models (or global km-scale models) to simulate better and project TCs and understand their changes. The meeting topics include, but are not solely focused on, analysis of tropical cyclones in global storm-resolving models, future changes in tropical cyclones, seasonal and sub-seasonal TC forecast, and hurricane risks in the future.　

 

This meeting is the New York Office event at The University of Tokyo and is a part of the three-day workshop. This event will be held in a hybrid format, allowing on-site participation at The University of Tokyo New York Office and online streaming via Zoom. The Zoom streaming will be available for viewing via recording after the event.

 

To participate online, please submit the form below to register by January 31, 2024.

Zoom information will be sent to the registered participants.

 

Registration for ONLINE participation

 

 

•    9:30-10:00 Masaki Satoh (AORI, The University of Tokyo, Japan): Global Storm-Resolving Modeling Approach for Better Understanding of Future Changes in Tropical Cyclones

•    10:00-10:30 Pier Luigi Vidale (National Centre for Atmospheric Science, Dept. of Meteorology, University of Reading, UK): Cyclones of Tropical Origin in a Resolution Hierarchy of Atmosphere-Only and Coupled GCMs

•    10:30-11:00 Adam Sobel (Columbia University, US): Uncertainties in Tropical Cyclone Risk

•    11:00-11:30 Suzana Camargo (Lamont-Doherty Earth Observatory, Columbia University, US): ENSO Diversity Impacts on Tropical Cyclone Activity CMIP6 Projections

•     11:30-12:00 Kevin Reed (Stony Brook, US): A Storyline Framework in CESM for Quantifying Climate Change Impacts on Hurricanes

 

 

Abstract of the presentations

Masaki Satoh (AORI, The University of Tokyo, Japan): Global Storm-Resolving Modeling Approach for Better Understanding of Future Changes in Tropical Cyclones

To better predict the future changes in tropical cyclones (TCs), we need to conduct global climate experiments using high-resolution models that can represent the internal structure of TCs. Global storm-resolving models (GSRMs) at the kilometer scale resolution and large ensemble experiments spanning several decades are required. For instance, Yoshida et al. (2017, GRL) conducted experiments over 5,000 years, but the model resolution was limited to 60 km. Conducting such long-term and large ensemble experiments with global storm-resolving models is challenging, but it is the ultimate goal. Previously, we have conducted 10-year time-slice experiments with a 14-km mesh global model with NICAM. The significant outcomes include understanding the mechanisms of TC changes, such as changes in TC size, TC seeds, and the relationship between convective mass flux and TC frequency. Ongoing activities with GSRMs at km-scale resolution include attempts to conduct a 30-year integration in nextGEMS and EERIE, which plans for experiments with a subset of the 100-year experiments. In Japan, ongoing efforts involve a 10-year 3.5-km mesh NICAM integration. This presentation will discuss strategies for future projections of TCs using GSRMs.

Pier Luigi Vidale (National Centre for Atmospheric Science, Dept. of Meteorology, University of Reading, UK): Cyclones of Tropical Origin in a Resolution Hierarchy of Atmosphere-Only and Coupled GCMs

Recent events, and ongoing research, have brought into sharp focus the dangers posed by Cyclones of Tropical Origin (CTOs) to the North-East United States (NEUS), as well as the British Isles and Western Europe (BIWE). North of 30N, events in the last ten years have been the most costly on record, causing loss of life and widespread severe damage: Ophelia totalled $70m in Ireland; Sandy alone totalled US$17bn in New York City; Henri and Ida in autumn 2021 caused $31-44bn in losses around New York State. More generally, and despite uncertainty due to decadal variability, there are indications that the number of CTOs reaching the midlatitudes has increased, consistent with projections of CTOs making landfall in BIWE, in the future. Future projections, despite uncertainties, highlight the increasing likelihood of a CTO landfall over BIWE/NEUS. Even if such events should be rare, the potential consequences are alarming; for instance, our homes and infrastructure are not designed to resist hurricane-intensity winds, nor the associated flooding. Although our weather-forecasting centres surveil tropical weather, our early-warning systems remain largely untested against CTOs.

Since the early days of GCMs, Tropical-Cyclone-like vortices have been successfully simulated in the right domains and with credible seasonality, as well as inter annual variability, but the frequency/intensity relationship has only recently started to look realistic in GCMs with grid spacing of 20km or less. Rapid intensification also remains a challenge, even sub-10km, for many GCMs.

In this study, we show some new results from an ensemble of simulations, each lasting 34 years, with a grid spacing of ~10km. The most important improvement, compared to its 20 and 60km counterparts, is the ability to simulate the most intense phase of the lifecycle within the tropics. At the same time, careful identification of the point of extra-tropical transition shows that there are two maxima in the distribution of track densities: one in the tropics, for warm-core vortices, and one in the extra tropics, in regions where baroclinicity is able to re-initiate and sustain hurricane intensity cyclones, albeit with hybrid warm-cold core structures, or even full transitioned into cold-core cyclones. This new capability is crucially important for our ability to correctly predict the current and future risk posed by CTOs to countries in the extra-tropics, as it has been shown that the impact of each cyclone, upon landfall, depends significantly on its morphology.

Adam Sobel (Columbia University, US): Uncertainties in Tropical Cyclone Risk

I will give an overview of our group’s recent work on tropical cyclone risk, with an emphasis on projected future trends as well as, relatedly, assessment of the present anthropogenic signal. A theme that has emerged is that more research tends to increase our perception of the uncertainty, rather than decrease it. I will focus primarily on two sources of uncertainty: 1) global tropical cyclone frequency which to the best of our knowledge could either increase or decrease with warming, and 2) the pattern of sea surface temperature (SST) change, which strongly affects results for individual basins, but which is uncertain especially due to questions about the equatorial Pacific. I will briefly reflect on how we might deal with these uncertainties, and to what extent they are specific to TCs vs. broadly representative of the problem of climate risk.

Suzana Camargo (Lamont-Doherty Earth Observatory, Columbia University, US): ENSO Diversity Impacts on Tropical Cyclone Activity CMIP6 Projections

The El Niño-Southern Oscillation (ENSO) modulates tropical cyclone (TC) activity globally. Given that anthropogenic climate change can affect both ENSO and TCs, we explore if and how future projections of the ENSO-TC relationship could be affected by ENSO characteristics and biases in the CMIP6 models. In particular, we examine whether the ability of the CMIP6 models in reproducing ENSO diversity has an impact on their simulation of the ENSO-TC relationship. To this end, we analyze large-scale environmental fields that are typically associated with TC activity (e.g. vertical wind shear, potential intensity), as well as TC proxies, such as genesis indices and the ventilation index in the CMIP6 models. We consider 45 CMIP6 model historical simulations and 3 future scenarios (ssp245, ssp370, ssp585). We also include all ensembles available for each of the model simulations. ENSO diversity in the models is measured by the nonlinearity coefficient alpha described in Karamperidou et al. (2017) and is based on the models’ pre-industrial simulations. We classify the CMIP6 models into 3 groups, based on ENSO diversity: A (similar to observed), B (too weak diversity), and A+ (too strong diversity). ENSO composites of the large-scale environmental variables in the historical and future scenarios are constructed for the 3 groups. We show that models in the A+ group have very different future projections of the ENSO composites from the other two groups. While future projections of the ENSO modulation of TC proxies for models in groups A and B are very similar to those in historical simulations and observations, this is not the case for the A+ models, which show significant changes between future and historical patterns. Finally, we compare these results with those of CMIP5, to determine whether these relationships have changed since the previous generation of models.

Kevin Reed (Stony Brook, US): A Storyline Framework in CESM for Quantifying Climate Change Impacts on Hurricanes

Significant advances have been made in storyline frameworks to quantify climate change impacts on individual extreme events, including devastating hurricanes. Here we present the results of the storyline methodology for various individual North Atlantic hurricanes (e.g., Hurricane Irma and Hurricane Ian) using the Community Earth System Model (CESM). Furthermore, the implementation of the framework systematically throughout the 2020 hurricane season demonstrates the feasibility of such tools for operational applications more broadly.

 

 

 

The University of Tokyo, The New York Office (UTokyoNY)

 

ICCP-GSRA: International Core-to-Core Project on Global Storm Resolving Analysis

 

JSPS Core-to-Core Program