NAM, NAO and SAM

Figure number: Figure 3.33 From the IPCC Working Group I Contribution to the Sixth Assessment Report: Chapter 3

Description:

Model evaluation of NAM, NAO and SAM in boreal winter. Regression of Mean Sea Level Pressure (MSLP) anomalies (in hPa) onto the normalized principal component (PC) of the leading mode of variability obtained from empirical orthogonal decomposition of the boreal winter (Dec.-Feb.) MSLP poleward of 20ºN for the observed Northern Annular Mode (NAM, a), over 20ºN-80°N, 90°W-40°E for the North Atlantic Oscillation as shown by the black sector (NAO, b), and poleward of 20ºS for the Southern Annular Mode (SAM, c) for the JRA-55 reanalysis. Cross marks indicate regions where the anomalies are not significant at the 10% level based on t-test. The period used to calculate the NAO/NAM is 1958-2014 but 1979-2014 for the SAM. (d-f) Same but for the multi-model ensemble (MME) mean from CMIP6 historical simulations. Models are weighted in compositing to account for differences in their respective ensemble size. Diagonal lines stand for regions where less than 80% of the runs agree in sign. (g-i) Taylor diagram summarizing the representation of the modes in models and observations following Lee et al. (2019) for CMIP5 (light blue) and CMIP6 (red) historical runs. The reference pattern is taken from JRA-55 (a-c). The ratio of standard deviation (radial distance), spatial correlation (radial angle) and resulting root-mean- squared-errors (solid isolines) are given for individual ensemble members (crosses) and for other observational products (ERA5 and NOAA 20CRv3, black dots). Coloured dots stand for weighted multi-model mean statistics for CMIP5 (blue) and CMIP6 (light red) as well as for AMIP simulations from CMIP6 (orange). (j-l) Histograms of the trends built from all individual ensemble members and all the models (brown bars). Vertical lines in black show all the observational estimates. The orange, light-red, and light blue lines indicate the weighted multi-model mean of CMIP6 AMIP, CMIP6 and CMIP5 historical simulations, respectively.

Author list:

• Phillips, A.: NCAR, USA; asphilli@ucar.edu
• Kosaka, Y.: University of Tokyo, Japan
• Cassou, C.: CNRS-Cerfacs, France
• Karmouche, S.: University of Bremen, Germany
• Bock, L.: DLR, Germany
• Kazeroni, R.: DLR, Germany

ESMValTool Branch:

• ESMValTool-AR6-OriginalCode-FinalFigures: ar6_chapter_3

ESMValCore Branch:

• ESMValCore-AR6-OriginalCode-FinalFigures: fix_cmip6_models_newcore

Recipe & diagnostics:

Recipe used: recipes/ipccwg1ar6ch3/recipe_ipccwg1ar6ch3_modes.yml

Diagnostic used: diag_scripts/ipccwg1ar6ch3_modes/nam_nao_sam.ncl

Expected image path:

• recipe_ipccwg1ar6ch3_modes_YYYYMMDD_HHMMSS/plots/nam_nao_sam/nam_nao_sam/nam_nao_sam.png

Software description:

• ESMValTool environment file: IPCC_environments/esmvaltool_ar6_yu_conda_environment.yml
• pip file: IPCC_environments/esmvaltool_ar6_yu_pip_environment.txt

Hardware description:

Machine used: avocado.atmos.rcast.u-tokyo.ac.jp