The signature of ENSO in global temperature and precipitation fields derived from the microwave sounding unit
- Univ. of Washington, Seattle, WA (United States)
Global temperature anomalies associated with El Nino-Southern Oscillation (ENSO) are investigated, making use of a 13-year record of gridded temperature and precipitation data from the microwave sounding unit (MSU). The warm phase of the ENSO cycle during this period was characterized by an overall warming of the tropical troposphere, superimposed upon a distinctive equatorially symmetric dumbbell-shaped pattern straddling the equator near 140 deg W, accompanied by negative anomalies along the equator over the western Pacific. By means of singular value decomposition (SVD) analysis it is shown that this pattern fluctuated in phase with the displacements of convective activity over the equatorial Pacific, as reflected in the anomalies in outgoing longwave radiation (OLR) and MSU precipitation fields. Fluctuations in mean tropical tropospheric temperature lagged the OLR anomalies and the related temperature pattern by about 3 months. The same dumbbell-shaped pattern was evident, with reversed polarity, in the lower stratosphere, together with the zonally symmetric signature of the quasi-biennial oscillation. The dumbbell-shaped temperature pattern is related to the off-equatorial upper-tropospheric gyres that have been identified in previous studies. It can be interpreted as the dynamical response to shifts in the distribution of diabatic heating in the equatorial belt. It resembles the linear response to an equatorial heat source, but its major centers of action are shifted slightly eastward. It is detectable in SVD analysis for each season, but appears to be best organized around March, the season in which the equatorial cold tongue is weakest and precipitation anomalies associated with the ENSO cycle impact the equatorial dry zone most strongly.
- OSTI ID:
- 53431
- Journal Information:
- Journal of Climate, Vol. 7, Issue 11; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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