Sensitivity of a meridional temperature gradient index to latitudinal domain

We compare two alternative definitions of the meridional surface temperatur e gradient (MTG) in the northern hemisphere. One focuses on equator-pole di fferences ((0 degrees-25 degrees N)-(65 degrees-90 degrees N)) and the othe r focuses on differences over midlatitudes ((30 degrees-35 degrees N)- (50 degrees-55 degrees N)). The MTG is sensitive to the choice of latitudes use d to define it, and these two MTGs show substantial differences in behavior on timescales from interannual to multidecadal. The equator-pole MTG is pl agued by missing data in the high-latitude belt, which affects its characte ristics over at least the early part of the data record. Because the missin g data are concentrated most heavily in the northernmost zones of the high- latitude belt, the variance of the equator-pole MTG is unduly high. This su ggests a need to weight the equator-pole MTG by data availability in each l atitude zone. The midlatitude-oriented MTG is more robust with respect to d ata availability and provides a measure of midlatitude circulation features .