NOAA

Geophysical Fluid
Dynamics Laboratory

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CHiMES: Tropical cyclones and climate change

Introduction

In this study, we seek to answer the question of whether the statistics of fine-scale phenomena (e.g interannual variability in hurricane frequency and intensity) is predictable on the basis of free-running ESMs under time-varying forcing. The link between tropical cyclone frequencies and intensities and climate change is one of the hottest topics of current research: and besides the peer-reviewed literature, it is also the topic of a recent popular science bestseller: Storm World by Chris Mooney, in which GFDL and its scientists play starring roles. At GFDL, we have begun using high-resolution regional models to study the response of tropical storms to variations in the background climate state: these studies are limited by the technical problems of driving regional models from global data. We now propose to apply the extraordinary computational resources made available in the CHiMES project to study tropical storm statistics in a global high resolution model.

Conventional (hydrostatic) global high-resolution models created by progressively increasing resolution of current models show an enhanced ability to capture important features of intense tropical storms, such as the minimum central pressure and peak surface winds. These models are "conventional" because they use parameterized convention schemes as current low-resolution models. A further, fundamental advance, is achieved when we build a global non-hydrostatic model with explicit deep convection.

At GFDL, we have recently constructed and deployed a new atmospheric dynamical core on a cubed-sphere grid, This novel grid removes many scalability barriers associated with more conventional grids and provides a path forward to future platforms, where computations may be distributed across 10,000 or 100,000 processor cores. The Finite-Volumed Cubed-Sphere atmospheric dynamical core is used in the CHiMES project in both hydrostatic and non-hydrostatic modes.

Model configurations

We are currently running AMIP runs (coupled land-atmosphere runs forced by AMIP datasets providing ocean boundary conditions). Resolutions include C180 (55 km resolution) and C360 (28 km) resolution for the "conventional" runs, and C720 (14 km) resolution for the cloud-resolving runs.

Current status

A complete AMIP experiment (1980-2005) has been performed at C180 resolution. An ensemble of several such runs will be required for the complete study.

Individual years (1980, 2005) have been performed at C360. These runs evaluate the model's ability to distinguish between "strong" and "weak" Atlantic hurricance seasons.

Scatter plot of minimum central pressure against peak wind speeds. While maximum wind speeds are still underpredicted relative to observations, storms achieving minimum pressure below 900 hPa are seen at these resolutions. Click to enlarge.

Tropical storms in a C360 (28 km) model run. More images here, courtesy Prabhat of the LBL Viz Team.
GFDL only: see Ming Zhao's HiRAM page for links to output of runs.

emacs-muse-mode created by v. balaji (balaji@princeton.edu) in emacs using the emacs-muse mode.
last modified: 18 January 2010