Methodology

- TS is surface ("skin") temperature and is used in lieu of sea surface temperatures (SSTs), TAS is 2m air temperature and is equivalent to TREFHT.
- PR is total precipitation and is equivalent to CESM variables PRECC+PRECL, PSL is sea level pressure, and SNOWDP is snow depth.
- The annual cycle is removed prior to every calculation by subtracting the long-term monthly means. Exceptions: The annual cycle is not removed for mean and standard deviation spatial maps.
- Area-averages are always based on cosine of latitude weighting.
- The following calculations used detrended data: standard deviations, nino3.4 spectra, and ENSO spatial composites.
- For visual clarity, the Y-axis
*may*differ amongst individual panels on a particular plot. - For more information on observational datasets and climate indices, see the Climate Data Guide.

AMO (Atlantic Multidecadal Oscillation) |
Monthly index timeseries defined as North Atlantic (0:60°N, 80°W:0°E) SST snomalies minus global (60°S:60°N) SST anomalies. Pattern created by regressing global SST anomalies onto index timeseries and smoothing with a 9-point spatial filter. Low pass-filtered timeseries (black curve) is based on a a 61-month running mean. Based on Trenberth, K. E., and D. J. Shea, 2006: Atlantic hurricanes and natural variability in 2005, Geophys. Res. Lett., 33, L12704, doi:10.1029/2006GL026894. |

PDO (Pacific Decadal Oscillation) |
Monthly index timeseries defined as the leading principal component (PC) of North Pacific (20:70°N, 110°E:100°W) area-weighted SST* anomalies, where SST* denotes that the global mean SST has been removed at each timestep. Pattern created by regressing global SST anomalies onto normalized PC timeseries. Low pass-filtered timeseries (black curve) is based on a a 61-month running mean. See Deser, C., M. A. Alexander, S. -P. Xie, and A. S. Phillips, 2010: Sea surface temperature variability: patterns and mechanisms. Ann. Rev. Mar. Sci., 2010.2, 115-143, doi:10.1146/annurev-marine-120408-151453. Also see Mantua, N. J., S. R. Hare, Y. Zhang, J. M. Wallace, and R. Francis, 1997: A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Amer. Met. Soc., 1069-1079. |

ENSO Spatial Composites |
The normalized December nino3.4 timeseries is used to composite all years greater than 1 standard deviation (El Niño) and all years less that -1 standard deviation (La Niña). The December nino3.4 timeseries is based on the December values of the monthly nino3.4 time series smoothed with a 3-point binomial filter. See Deser, C., A. S. Phillips, R. A. Tomas, Y. Okumura, M. A. Alexander, A. Capotondi, J. D. Scott, Y. -O. Kwon, and M. Ohba, 2012: ENSO and Pacific Decadal Variability in Community Climate System Model Version 4. J. Climate, 25, 2622-2651, doi: 10.1175/JCLI-D-11-00301.1. The red/blue shading on the Nino3.4 time series denotes positive/negative departures from the best-fit linear trend line. |

NAM (Northern Annular Mode) |
Seasonal/annual PSL averages are formed, square root of the cosine of the latitude weighting is applied, and then the leading EOF and associated principal component (PC) timeseries are computed over 20:90°N, 0:360°E. Pattern created by regressing global PSL anomalies onto normalized PC timeseries. Based on Hurrell, J. W., and C. Deser, 2009: North Atlantic climate variability: The role of the North Atlantic Oscillation. J. Mar. Syst., 78, 28-41, doi:10.1016/j.jmarsys.2008.11.026. Also see Thompson, D. W. J., and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13, 1000-1016. |

NAO (North Atlantic Oscillation) |
Seasonal/annual PSL averages are formed, square root of the cosine of latitude weighting is applied, and then the leading EOF and associated principal component (PC) timeseries are computed over 20:80°N, 90°W:40°E. Pattern created by regressing global PSL anomalies onto normalized PC timeseries. Based on Hurrell, J. W. and C. Deser, 2009: North Atlantic climate variability: The role of the North Atlantic Oscillation. J. Mar. Syst., 78, 28-41, doi:10.1016/j.jmarsys.2008.11.026. |

SAM/PSA1/PSA2 (Southern Annular Mode, Pacific South American Patterns 1/2) |
Seasonal/annual PSL averages are formed, square root of the cosine of latitude weighting is applied, and then the 1st (SAM), 2nd (PSA1) and 3rd (PSA2) EOFs and associated principal component (PC) timeseries are computed over 20:90°S, 0:360°E. Patterns created by regressing global PSL anomalies onto normalized PC timeseries. SAM calculation based on Thompson, D. W. J. and J.M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13, 1000-1016. |

PNA/NPO (Pacific North American Pattern, North Pacific Oscillation) |
Seasonal/annual PSL averages are formed, the square root of the cosine of the latitude weighting is applied, and then the 1st (PNA) and 2nd (NPO) EOFs and associated principal component (PC) timeseries are computed over 20:85°N, 120°E:120°W. Patterns created by regressing global PSL anomalies onto normalized PC timeseries. |

Atmospheric Mode SST Regressions |
SST anomalies are regressed upon the normalized atmospheric mode timeseries. |

Global Average Running Trends |
N-year running trends are computed by calculating the linear trend over the N-year interval beginning at each successive timestep. For instance, for a global timeseries that runs from 1970-2012, the 8yr running trend value for January 1970 is the linear trend during January 1970 - December 1977, and the value for January 2005 is the linear trend during January 2005 - December 2012. |

Metrics Table |
Area-weighted pattern correlations and rms differences are calculated between observations and each model simulation (regridded to match observational grid) for 11 climate metrics. The Total Score column shows the average of the 11 pattern correlations (Z-transformed) and rms differences. |

Power Spectra |
The best-fit first-order Markov red noise spectrum (red curve) and its 95% (blue curve) and 99% (green curve) confidence bounds are shown on each panel. Top X-axis shows the period (in years), and the bottom X-axis shows the frequency (cycles/mo). If calculated, the observational spectrum is overlaid in gray on each model spectrum. The spectra are displayed in variance-conserving form. |

Climatological Zonal Averages |
Climatological means are zonally averaged over the globe. |

NPI (North Pacific Index) |
Winter (December-March) average PSL anomalies area-averaged over 30°:65°N, 160°E:140°W. Based on Trenberth, K. E. and J. W. Hurrell, 1994: Decadal atmosphere-ocean variations in the Pacific, Climate Dynamics, 9, 303-319. |

Additional Indices |
Area-averaged anomalies as specified in the plot title. Red/blue shading denotes positive/negative departures from the best-fit linear trend line. |

Created Thu Dec 18 15:17:23 MST 2014

CVDP Version 3.3.1