Northern Hemisphere Climatology and Interannual Variability of Storm Tracks in NCEP’s CFS Model

Timothy Paul Eichler,Francisco Alvarez,Jon Gottschalck

doi:10.1155/2015/720545

Abstract

Evaluating the climatology and interannual variability of storm tracks in climate models represents an excellent way to evaluate their ability to simulate synoptic-scale phenomena. We generate storm tracks from the National Center for Environmental Prediction (NCEP) Climate Forecast System (CFS) model for the northern hemisphere (NH) and compare them to storm tracks generated from NCEP’s reanalysis I data, the European Centre for Medium Range Prediction (ECMWF) ERA40 data, and CFS reanalysis data. To assess interannual variability, we analyze the impacts of El Niño, the North Atlantic Oscillation (NAO), and the Indian Ocean Dipole (IOD). We show that the CFS model is capable of simulating realistic storm tracks for frequency and intensity in the NH. The CFS storm tracks exhibit a reasonable response to El Niño and the NAO. However, it did not capture interannual variability for the IOD. Since one path by which storm tracks respond to external forcing is via Rossby waves due to anomalous heating, the CFS model may not be able to capture this effect especially since anomalous heating for the IOD is more local than El Niño. Our assessment is that the CFS model’s storm track response is sensitive to the strength of external forcing.

Highlights

With climate models consistently evolving to finer temporal and spatial resolution, it has become feasible to explore their ability to simulate synoptic-scale storms
Our study focuses on assessing the climatology and interannual variability of storm tracks from two long integrations of the National Center for Environmental Prediction (NCEP)
There is good general agreement, with active storm track areas located in the North Pacific and North Atlantic for all reanalysis and model datasets (Figures 1(a)–1(e))

Summary

Introduction

With climate models consistently evolving to finer temporal and spatial resolution, it has become feasible to explore their ability to simulate synoptic-scale storms. Lambert et al [11] used a Lagrangian approach to assess storm tracks in 13 models from the Atmospheric and Modeling Intercomparison Project (AMIP) They found large-scale agreement of storm events with storms generated from ECMWF (ERA) data, regional differences were noted (e.g., the models had difficulty simulating leemountain cyclogenesis). Graff and LaCasce [10] explored ENSO impacts by uniformly increasing sea-surface temperatures (SSTs) equatorward of 15∘ S in the NCAR Community Climate model version 3 and found an equatorward shift in storm tracks in the North Pacific, similar to Eichler and Higgins [21], Chang et al [20], and Lu et al. For the northern hemisphere, the NAO plays a significant role in altering storm tracks.

Data and Methodology

Results

Interannual Variability

Conclusions