# Presentation: 887015

## Figure 1   Comparison of the observed (CMAP, Xie and Arkin 1997) and AM2.0 GOGA simulated precipitation climatologies for July-September season. Top panels are for AM2 simulation, bottom panels for observations. Left (right) panels show the precipitation (standard deviation of precipitation) in unit of mm/month. Also plotted in panel (a) is the vertically integrated moisture flux.

- AM2

**Figure 1**   Comparison of the observed (CMAP, Xie and Arkin 1997) and AM2.0 GOGA simulated precipitation climatologies for July-September season. Top panels are for AM2 simulation, bottom panels for observations. Left (right) panels show the precipitation (standard deviation of precipitation) in unit of mm/month. Also plotted in panel (a) is the vertically integrated moisture flux.

- AM2

- CMAP

- CMAP

## EOF1

- EOF2

- R=0.62

- R=0.61

- CRU

- AM2

**Figure 2**   Comparison of the observed (left column) and AM2 simulated (right column) precipitation EOFs (dimensional pattern in unit of mm/month). The observations are based on CRU land precipitation data. Top panels show the patterns of the first EOF and middle panels the second EOF of African land precipitation. The amplitudes of the EOFs are associated with 1 standard deviation of the corresponding principal components. The percentage indicates the variance explained by the corresponding EOF. Bottom panels compare the normalized time series of the observed and modeled principal components for each EOF and the correlation coefficient between the modeled and observed time series is indicated.

## Figure 3 Annual cycle of the zonally averaged (between 12°E and 34°E), monthly mean precipitation (contours, unit is mm/day) and net radiative budget (shading, unit is W/m2) at the top of the atmosphere. (a) is calculated based on the CMAP precipitation data and ERBE radiation observations; (b) is calculated based on the ensemble mean GOGA simulations by AM2.0.

**Figure 3 **Annual cycle of the zonally averaged (between 12°E and 34°E), monthly mean precipitation (contours, unit is mm/day) and net radiative budget (shading, unit is W/m2) at the top of the atmosphere. (a) is calculated based on the CMAP precipitation data and ERBE radiation observations; (b) is calculated based on the ensemble mean GOGA simulations by AM2.0.

## Figure 4   Modeled by AM21 (a) and AM20 (b), and observed (b) time mean (from 1958 through 1994) JAS zonal wind averaged between 20°W and 40°E over the tropical Africa. Panel (b) is computed based on ECMWF reanalysis data. 

**Figure 4**   Modeled by AM21 (a) and AM20 (b), and observed (b) time mean (from 1958 through 1994) JAS zonal wind averaged between 20°W and 40°E over the tropical Africa. Panel (b) is computed based on ECMWF reanalysis data.

## Figure 5   Similar to Figure 3 but for modeled (a) and observed (b) latitude-height cross-section of streamlines for v and - fields along 5°E. 

**Figure 5 **  Similar to Figure 3 but for modeled (a) and observed (b) latitude-height cross-section of streamlines for v and - fields along 5°E.

## Section 4

**Figure 6**   The JAS SRI (in mm/month) from GHCN station data (gray bars), the simulations of GOGA (panel a, solid line), G03’s NSSIP1 (panel a, dashed line), and GOGA2.1 (panel c, solid line).

## Figure 7   The linear JAS precipitation trend from 1950 to 2000 (in mm/month/50years) calculated from CRU-TS_2.1 land precipitation data (a), model output of GOGA (b), TOGA (c) and IPGA (d) experiments. 

**Figure 7**   The linear JAS precipitation trend from 1950 to 2000 (in mm/month/50years) calculated from CRU-TS_2.1 land precipitation data (a), model output of GOGA (b), TOGA (c) and IPGA (d) experiments.

## Figure 8   The comparison of summer circulation trend between the GOGA simulations and the ECMWF reanalysis. Top (bottom) panels are the trend in the zonal wind (vertical pressure velocity ) averaged between 20°W and 40°E during 1958 to 1994. Left (right) panels are for the AM2 simulation (ECMWF reanalysis). The background shadings are the corresponding climatological fields.

## A   I

**Figure 9**   Trajectory of the 20th century SST evolution (with years marked) plotted in the space spanned by SST indices A-I and I. 11-year running mean has been applied for the purpose of clarity. The slant solid lines indicate the sensitivity of SRI estimated from linear regression using observed time series (CRU-TS_2.1 precipitation data and HadISST data). The slant dashed lines are the counterpart estimated from GOGA2.1 simulated time series. Average of 20th century has been removed for this demonstration.

- A   I

- I

## Figure 10   Regression pattern of JAS SSTs against the observed SRI during 1903-2000. Both SSTs and SRI have been filtered by 5-year running mean before the regression. The hatched area are where the regression coefficients are not significantly different from zero based on Students’ t-test with the reduction of degrees of freedom due to serial correlation considered. Unit is 10-2K/std of SRI.

**Figure 10**   Regression pattern of JAS SSTs against the observed SRI during 1903-2000. Both SSTs and SRI have been filtered by 5-year running mean before the regression. The hatched area are where the regression coefficients are not significantly different from zero based on Students’ t-test with the reduction of degrees of freedom due to serial correlation considered. Unit is 10-2K/std of SRI.

## Figure 11   Responses to the Indian Ocean SST anomalies in Expt. IND MS. (a) precipitation; (b) vertically integrated moisture flux (arrows, in unit of Kg/ms) and its divergence (contours, in unit of g/m2s); (c) anomalous moisture flux due to changes in specific humidity (i.e.,            ) and the associated divergence; (d) similar to (c) but for the anomalous flux due to the change in winds (i.e.,          ).          

**Figure 11**   Responses to the Indian Ocean SST anomalies in Expt. IND MS. (a) precipitation; (b) vertically integrated moisture flux (arrows, in unit of Kg/ms) and its divergence (contours, in unit of g/m2s); (c) anomalous moisture flux due to changes in specific humidity (i.e.,            ) and the associated divergence; (d) similar to (c) but for the anomalous flux due to the change in winds (i.e.,          ).

## Figure 12   The circulation response to Indian ocean SST anomalies in Expt. IND MS. (a) 700hPa eddy streamfunction (contours) and divergent wind (arrows); (b) 200hPa eddy streamfunction (contours) and divergent wind (arrows); (c) longitude-height cross-section of the streamlines for u and and - fields averaged between equator and 15°N.

**Figure 12**   The circulation response to Indian ocean SST anomalies in Expt. IND MS. (a) 700hPa eddy streamfunction (contours) and divergent wind (arrows); (b) 200hPa eddy streamfunction (contours) and divergent wind (arrows); (c) longitude-height cross-section of the streamlines for u and and - fields averaged between equator and 15°N.

## Figure 13    The transient response of vertically integrated temperature (square, in Kelvin), specific humidity (open circle, in Kg/Kg) between surface and 300hPa and precipitation (filled circle, in mm/day) to the switch-on of Indian SST forcing. The initial 25 days are stretched to illustrate the initial phase of the adjustment. 

## Figure 14   Seasonal mean vertical diabatic heating profiles averaged over the Sahel region (10°W-40°E, 10°N-20°N). The solid lines are for the heating terms in the control experiment, and the dashed lines for the IND SST perturbation experiment. The departure of the perturbation experiment from the control is depicted by the color shading with different colors for different terms. Unit is K/day.

## Figure 15   The tropical African precipitation response (unit is mm/month) in (a) Expt. IND1K+ (warm phase); (b) Expt. IND1K (cold phase); (c) Expt. ATL1K+ (warm phase) and (d) Expt. ATL1K (cold phase). Unit is mm/month. Note the color scales are different between upper and lower panels.

## Figure 16    Same as Fig.10 but for the response to uniform Atlantic SST warming in Expt. ATL+1K.

## Table 1  Experiments setup

|  | Experiments |  | Similar Experiments in Literatures |
| --- | --- | --- | --- |
|  | nomenclature | description |  |
|  | GOGA | global SST 50-2000 | Giannini et al., 2003, NSIPP1; 
Hoerling et al., 2005, 5 AGCMs; Wang et al., 2003; Paeth and Hense, 2004 (ECHAM4 and HADAM2); Tippett, 2006, 7 AGCMs |
|  | GOGA2.1 | global SST 1870-2004
using AM2.1 | Same as GOGA |
|  | IND | SST regression pattern over Indian Ocean | Hoerling et al., 2005 |
|  | IND ±1K | Uniform ±1K over Indian ocean | Bader and Latif, 2003, 2005 |
|  | ATL ±1K | Uniform ±1K over Atlantic ocean |  |

- Idealized runs

- AMIP runs

## Table 2  Regression and correlation between SRI and N - I and I

| Cases of analysis | Sensitivity |  |
| --- | --- | --- |
|  | N - I  | I |
| OBS_cru | 39% | -11% |
| GOGA2.1 | 35% | -10% |
| NSIPP1 | 14.3% | -4.8% |
| CM2.1 | 20% | -12% |
| 1K_IND |  | -23% |
| 1K_ATL |  | 14% |

| Correlation |  |
| --- | --- |
| N - I | I |
| 0.87 | -0.62 |
| 0.76 | -0.54 |
| 0.88 | -0.78 |
| 0.63 | -0.78 |

- Table 2  Regression and correlation between SRI and N - I and I