**DRAFT
WGNE STANDARD DIAGNOSTICS OF VARIABILITY
DRAFT**

** **

**Tropospheric**

not stratospheric (SPARC), e.g. not QBO

- Atmospheric

not coupled system (AMWG)

except as response to specified SST

- Consisting of diagnostics which have been demonstrated

and which can be calculated by each group

(perhaps with code supplied)

- Should be ``stable''

i.e. not strongly influenced by natural variability

so meaningful from a single AMIP type realization

and ensembles are not required

- Should be representative but not exhaustive

- Should have examples from a single model before releasing list

Note: Some variance and eddy statistics are included in the

WGNE Standard Diagnostics of the Mean Climate

http://www-pcmdi.llnl.gov/amip/OUTPUT/WGNEDIAGS/wgnediags.html

**Intraseasonal Variability**

29-70 day bandpassed 200 hPa velocity potential, averaged 5N to 5S, Hovmöller (time vs longitude). Abscissa 0 to 360 longitude. Plot 1986, 1987, 1988 and other selected years, one year per plot.

Ex: Fig 1 of Innes and Gregory (1995) and Fig 1 of Reynolds et al. (1995).

**Madden-Julian Oscillation (MJO)**

1) Time series of daily zonal mean 10N-10S averaged 200hPa zonal wind and low-pass filtered

Ex: Fig 2, top panel of Slingo et al. (1999)

2) MJO index - (100 day running variance of 20-100 day band-pass filtered zonal averaged 10N-10S averaged 200hP zonal wind averaged 10N-10S.

Ex: Fig 3, solid line of Slingo et al. (1999)

**El Niño - Southern Oscillation (ENSO)**

Hovmöller (time vs longitude) diagram of monthly mean anomalies (relative to AMIP II period: 1979-1995) in the tropical Pacific, averaged between 5S and 5N for precipitation, OLR, and 850 mb zonal wind. Abscissa 100E to 80W. Plots can extend beyond the period providing the climatological averages from which the anamolies are computed.

Ex: Fig 3, Lo et al. (1995) and Fig 4 van den Dool et al. (1995).

**Blocking**

Blocking index as defined in D'Andrea et al. (1998)

1) DJF blocking frequency (%) as function of longitude

Ex: Fig 4 of D'Andrea et al. (1998)

2) Hovmöller diagram, DEC-DEC vs longitude

Ex: Fig 5 of D'Andrea et al. (1998)

Wavenumber-Frequency plots

Zonal wavenumber-frequency power spectra calculated from 6 hourly data (summed 15S to 15N) for antisymmetric and symmetric component of u at 850 and 200 mb, omega at 500 mb OLR and precip.

1) Raw power spectra

Ex: Fig 1 of Wheeler and Kiladis (1999)

2) Spectra with background removed

Ex: Fig 2 of Wheeler and Kiladis (1999)

**Histograms**

Averaged daily precipitation rate, for all grid points 10N-10S, 30N-60N land, 30N-60N ocean.

By classes

Ex: Fig 10 of Inness et al. (2001), except classes and regions differ.

**Seasonal Cycle**

Horizontal maps of climatological average monthly average amplitude (max-min)
and phase (Month of max, and Month of min) of Precip and T_{2m}.

Ex: Fig 3 of Yang and Slingo
(2001) which shows similar plot for Diurnal cycle.

Note: Phase is plotted using ``circular'' color table without contours,

i.e. 112 by bluegreenredpurple(blue)

**Diurnal Cycle**

Horizontal maps of climatological average amplitude and phase (local time of
max) of diurnal harmonic of precip and T_{2m}, calculated based on Fourier
analysis of climatological average of 3-hourly samples.

Ex: Fig 3 of Yang and
Slingo (2001).

Note: Phase is plotted using ``circular'' color table without contours,

i.e. 124 by bluegreenredpurple(blue)

Atmospheric Angular Momentum

Global average, monthly average vs time. (Defined as in WGNE Standard Diagnostics of Mean Climate, 2. Global Averages)

Ex: Fig 2 of Hide et al. (1997)

**Modes of Variability**

(1) Pacific sector (20-80N, 120E-90W) first and second EOF of monthly mean 500 mb height field during four winter months (Dec-Mar) and percent variance explained. (Plots of nondimensional normalized EOF multiplied by the square root of the corresponding EOF variance to obtain the dimensional standard deviation of 500 mb height field at each grid point associated with the EOF.

Ex: Figs 1 and 3 of Saravanan (1998)

(2) Atlantic sector (20-80N, 90W-30E) first and second EOF of monthly mean 500 mb height field during four winter months (Dec-Mar) and four summer months (Jun-Sep) and percent variance explained. (Plots of nondimensional normalized EOF multiplied by the square root of the corresponding EOF variance to obtain the dimensional standard deviation of 500 mb height field at each grid point associated with the EOF.

(3) Squared correlation (%) between tropical Atlantic SST and precipitation averaged over northern Nordeste Brazil (11-3S, 46-38W) for MAM season. (dashed contours where correlations are negative before squaring)

Ex: Fig 2 of Saravanan and Chang (2000)

(4) Southern Hemisphere (30-90S) first and second EOF of monthly mean 500 mb height field during four winter months (Jun-Sep) and percent variance explained. (Plots of nondimensional normalized EOF multiplied by the square root of the corresponding EOF variance to obtain the dimensional standard deviation of 500 mb height field at each grid point associated with the EOF.

Ex: Figs 8.3a and b of
Kiladis and Mo (1998) and

Figs 1 and 2 of Rogers and van Loon (1982)

REFERENCES

D'Andrea, F., S. Tibaldi, M. Blackburn, G. Boer, M. Déqué, M. R. Dix, B. Dugas, L.
Ferranti, T. Iwasaki, A. Kitoh, V. Pope, D. Randall, E. Roeckner, D. Straus, W. Stern, H.
van den Dool and D. Williamson, 1997: Northern Hemisphere Atmospheric Blocking as
simulated by 15 Atmospheric General Circulation Models in the period 1979-1988. *Clim.
Dynamics*, **14**, 385-407.

Hide, R., J. O. Dickey, S. L. Marcus, R. D. Rosen and D. A. Salstein, 1997: Atmospheric
angular momentum fluctuations during 1979-1988 simulated by global circulation models. *J.
Geophys. Res.*, **102**, 16,423-16,438.

Innes, P.M. and D. Gregory, 1995: Analysis of tropical intraseasonal variability in the
U.K. Met. Office Unified Model. *Proceedings of the First International AMIP Scientific
Conference*, WMO/TD-N0.732, 131-136.

Inness, P. M., J. M. Slingo, S. J. Woolnough, R. B. Neale and V. D. Pope, 2001:
Organization of tropical convection in a GCM with varying vertical resolution;
implications for the simulation of the Madden-Julian Oscillation. *Clim. Dynamics*, **17**,
777-794.

Kiladis and Mo, 1998: Interannual and Intraseasonal Variability in the Southern
Hemisphere. Chapter 8 of *Meteorology of the Southern Hemisphere*, Ed. D. J. Karoly
and D. G. Vincent. Meteorology Monographs, Vol. 27, No. 49, American Meteorological
Society, 307-336.

Lo, K.-w., A. D. Del Genio, 1995: Evaluation of the New Giss GCM. *Proceedings of the
First International AMIP Scientific Conference*, WMO/TD-N0.732, 283-288.

Reynolds, C., R. Gelaro and T. Murphree, 1995: Intraseasonal Variability in a 10-year
integration of the Navy operational global atmospheric prediction system. *Proceedings
of the First International AMIP Scientific Conference*, WMO/TD-N0.732, 143-148.

Rogers, J. C., and H. van Loon, 1982: Spatial Variability of Sea Level Pressure and 500
mb Height Anomalies over the Couthern Hemisphere. *Mon. Wea. Rev.*, **110**,
1375-1392.

Saravanan, R., 1998: Atmospheric Low-Frequency Variability and Its Relationship to
Midlatitude SST Variability: Studies Using the NCAR Climate System Model. *J. Climate*,
**11**, 1386-1404.

Saravanan, R., and P. Chang, 2000: Interaction between Tropical Atlantic Variability
and El Niño-Southern Oscillation. *J. Climate*, **13**, 2177-2194.

Slingo, J. M., D. P. Dowell, K. R. Sperber and F. Nortley, 1999: On the predictability
of the interannual behavior of the Madden-Julian oscillation and its relationship with El
Niño. *Quart. J. Roy. Meteor. Soc.*, **125**, 583-509.

van den Dool, H. M., S. Saha, J. Schemm and W. Ebisuzaki, 1995: A Multi-Year Climate
Run with the NCEP/NCAR Reanalysis Model. *Proceedings of the First International AMIP
Scientific Conference*, WMO/TD-N0.732, 289-294.

Wheeler, M. and G. N. Kiladis: 1999, Convectively coupled equatorial waves: analysis of
clouds and temperature in the wavenumber-frequency domain. *J. Atmos. Sci.*, 56,
374-399. Yang, G.-Y. and J. Slingo, 2001, The Diurnal Cycle in the Tropics, *Mon. Wea.
Rev.*, **129**, 784-801.