Interannual variability in the NCEP reanalysis 1948-1999

We examine horizontally and vertically distributed climate fields in Northern Hemisphere NCEP reanalysis data (1948-1999) for joint modes of spatiotemporal variation. Our analysis is based on the "MTM-SVD" methodology to isolate significant spatially-coherent variability with narrowband, oscillatory character. Interannual tropospheric climate variability associated with the ENSO signal is identified in distinct quasibiennial (2-3 yr) and quasiquadrennial (4-6 yr) frequency bands, with evidence of evolution in amplitude over time. From this dataset, there is no clear evidence to support the existence of any other significant oscillatory signal in the troposphere.