(top) Seasonal range of precipitation centroid vs atmospheric heat transport at the equator (AHT) in individual CMIP preindustrial models (dashed colored lines with filled dots on each end), the model ensemble mean (thick purple line and filled dots), and the observations (thick black line and filled dots). The seasonal range is twice the amplitude of the annual harmonic of each variable and the slope of the line is the regression coefficient of the monthly data. The models are color coded by their annual average P_{Cent} with the color scale given by the color bar to the right. (bottom) As at top, but for precipitation centroid vs interhemispheric contrast of tropical SST.

(top) Seasonal range of precipitation centroid vs atmospheric heat transport at the equator (AHT) in individual CMIP preindustrial models (dashed colored lines with filled dots on each end), the model ensemble mean (thick purple line and filled dots), and the observations (thick black line and filled dots). The seasonal range is twice the amplitude of the annual harmonic of each variable and the slope of the line is the regression coefficient of the monthly data. The models are color coded by their annual average P_{Cent} with the color scale given by the color bar to the right. (bottom) As at top, but for precipitation centroid vs interhemispheric contrast of tropical SST.

## I next discuss the relationships amongst the regular extremes and the annual mean of P

Seasonal amplitude (amplitude of yearly harmonic) and you can regression coefficients away from rain centroid, AHT, and you may ?SST on findings plus CMIP3 preindustrial models. New 95% depend on constraints was listed after each worthy of and are usually examined from the latest interannual give on observations, intermodel give in the models, and suspicion on regression coefficients.

We note that the intermodel spread of the annual mean P_{Cent} and AHT are significantly correlated with each other with a regression coefficient of ?0.79 and a slope that is statistically indistinguishable from the ensemble mean seasonal relationship between P_{Cent} and AHT. This result suggests that the same physics that determine the seasonal migration of the ITCZ location and AHT (associated with meridional shifts in the Hadley cell) also govern the intermodel spread of ITCZ location in the annual mean. _{Penny} and AHT between the different models and the observations, the robust relationship between P_{Penny} and AHT allows one to predict P_{Cent} from AHT (or vice versa) with the same relationship holding for the seasonal problem and for the annual mean intermodel spread problem.

## EQ

Histograms of the monthly mean P_{Cent} over the last 150 years of the simulations are shown in Fig. 7. The P_{Cent} distribution in each model is bimodal; P_{Penny} is most often found in one of the two solstitial extremes (Lindzen and Hou 1988) and is rarely found in the vicinity of the annual average. By construction, the annual average is the average of the northernmost and southernmost extent shown by the shaded dots in Fig. 7 (and defined as the annual mean plus or minus the seasonal amplitude). Therefore, in order to shift the annual average P_{Penny} northward, the ITCZ must either migrate farther into (or stay longer in) the Northern Hemisphere in the boreal summer or migrate less far into (or spend less time in) the Southern Hemisphere during the austral summer. The models with an anomalous (relative to the ensemble average) northward annual mean P_{Penny} (the models Match vs Tinder shown in red toward the top of the figure) tend to have a P_{Cent} that migrates farther north in the boreal summer. In contrast, the models with a southward annual mean P_{Penny} (the models shown in blue toward the bottom of the figure) tend to have a P_{Penny} that migrates less far north in the boreal summer. Similarly, the magnitude of the southward migration of the ITCZ during the austral winter is largest in the models with an annual mean ITCZ location south of the ensemble average (blue dots) and smallest in the models with an annual mean ITCZ location north of the ensemble mean (red dots). _{Penny} and AHT in section 4.