Qz. Geng et M. Sugi, Variability of the North Atlantic cyclone activity in winter analyzed fromNCEP-NCAR reanalysis data, J CLIMATE, 14(18), 2001, pp. 3863-3873
Principal component analysis is applied to the cyclone density over the Nor
th Atlantic in winter analyzed with an objective cyclone identification and
tracking algorithm by using the 6-h National Centers for Environmental Pre
diction reanalysis data from 1958 to 1998. Regressions of the cyclone densi
ty, deepening rate, moving speed, and central pressure gradient with the fi
rst principal component show that the cyclone activity over the northern No
rth Atlantic exhibits a significant intensifying trend along with a decadal
timescale oscillation in winter during the past 40 yr. All these variables
vary consistently with larger (smaller) cyclone density corresponding to s
tronger (weaker) cyclone intensity, faster (slower) moving speed, and stron
ger (weaker) deepening rate.
Analysis shows that the variations of the cyclone activity over the North A
tlantic are closely related to the changes of large-scale baroclinicity at
the lower troposphere and the North Atlantic oscillation. The relationships
with the change of the North Atlantic SST are also discussed.