Analyzing storm track variations using feature tracking

Storm tracks form an important component of the climate system because they are tightly related to local weather and climate, and the eddy heat, momentum, and moisture transport due to storm track disturbances act to force and maintain the general circulation. Previous studies on storm track variability tend to largely focus on variability of eddy variance and covariance statistics. Recently, with the availability of robust feature tracking routines, storm track variability in terms of variations in cyclone and trough frequency and intensity can be readily examined. In this study, we have applied a sophisticated feature tracking package to examine seasonal and inter-annual variability of the Northern Hemisphere storm tracks.

In this presentation, we will focus on the variability of the Pacific storm track. A recent study suggests that the mid-winter suppression of the Pacific storm track can be attributed to a similar suppression in the upstream Central Asia region due to enhanced static stability over that region during mid-winter. We have examined the storm track variability over the Pacific storm track and its upstream “source” region, and found that during winter months when the storm track is strong over the upstream region, the Pacific storm track is not stronger than average, suggesting that storm track activity in the upstream region cannot be the primary factor controlling Pacific storm track intensity.

In addition, we have used cyclone tracks to examine the seasonal cycle of explosive cyclogenesis over west Pacific. Our results suggest that in contrast to the mid-winter suppression in storm track activity, the frequency of explosive cyclogenesis is highest during mid-winter. Reasons that may contribute to this contrasting behavior will be discussed in the presentation.