(top) Scatterplot of AHTEQ vs the mass overturning streamfunction at 500 hPa over the equator over the seasonal cycle in the observations. Each asterisk is a monthly average and the dashed line is the linear best fit. (bottom) Scatterplot of the location of the 0 mass overturning streamfunction ??=0 at 500 hPa vs AHTEQ (red asterisk and linear best fit dashed line) and PPenny vs AHTEQ (blue asterisk and linear best fit dashed line). The expected relationship between ??=0 and AHTEQ from Eq. (9) is shown by the dashed black line.
1) Model works utilized and strategy
We play with model returns of phase 3 of your Combined Design Intercomparison Enterprise (CMIP3) multimodel database (Meehl ainsi que al. 2007): a clothes out-of standard combined environment simulations from twenty-five other environment models that have been included in the brand new Intergovernmental Panel to your Weather Change’s Next Evaluation Statement. We become familiar with the brand new preindustrial (PI) simulations right here. When it comes to those simulations, greenhouse gasoline concentrations, aerosols, and http://datingranking.net/nl/thaicupid-overzicht you may solar power pressuring is fixed at preindustrial levels in addition to habits are running getting eight hundred years. The very last two decades of one’s PI simulations are accustomed to estimate climatological industries. The fresh sixteen models used in this study try listed in Table step one.
Activities included in this research in addition to their resolution. The newest lateral resolution is the latitudinal and you will longitudinal grid spacing or the spectral truncation. The newest vertical quality is the level of straight account.
The turbulent and radiative energy fluxes at the surface and TOA are provided as model output fields. This allows ?SWABS? and ?SHF? to be directly calculated from Eqs. (6) and (7). The ?OLR? is directly calculated and ?STORATMOS? is calculated from finite difference of the monthly averaged vertically integrated temperature and specific humidity fields; AHTEQ is then calculated from the residual of the other terms in Eq. (5).
We show the seasonal amplitude (given by half the length of the line) and the regression coefficient (given by the slope of the line) between PCent and AHTEQ for each CMIP3 ensemble member in the upper panel of Fig. 6. We define the seasonal amplitude of PCent and AHTEQ as the amplitude of the annual harmonic of each variable. The CMIP3 ensemble mean regression coefficient between PCent and AHTEQ is ?2.4° ± 0.4° PW ?1 (the slope of the thick black line) and is slightly smaller but statistically indistinguishable from the value of ?2.7° ± 0.6° PW ?1 found in the observations (the thick purple line). Table 2 lists the seasonal statistics of PPenny and AHTEQ in observations and the models. Seasonal variations in PCent and AHTEQ are significantly correlated with each other in all models with an ensemble average correlation coefficient of ?0.89. On average, the linear best fits in the models come closer to the origin than do the observations (thick black line in Fig. 6), conforming to our idealized expectation that when the precipitation is centered on the equator, the ascending branch of the Hadley cell will also be on the equator, resulting in zero cross-equatorial heat transport in the atmosphere. The relationship between PCent and AHTEQ over the seasonal cycle is fairly consistent from one model to the next (all the slopes in Fig. 6 are similar) and is similar to the relationship found in the observations. Cent and AHTEQ, mainly the mutual relationship among the tropical precipitation maximum, AHTEQ, and the location of the Hadley cell. The precipitation centroid lags the cross-equatorial atmospheric heat transport in the models by 29 days in the ensemble average (with a standard deviation of 6 days). This is in contrast to the observations where there is virtually no (<2 days) phase shift between PPenny and AHTEQ. We further discuss this result later in this section.