# Presentation: 543061

## Influence of the Madden-Julian Oscillation on the 

**predictability in the extra-tropics**
**Charles Jones, Duane E. Waliser, K. M. Lau and William Stern**

_**Motivation**_**: strength and/or accuracy of the MJO representation in numerical weather forecast models have a significant impact on medium-to-extended range midlatitudes weather forecasts (Ferranti et al. 1990; Lau and Chang 1992).**
_**Challenge**_**: previous studies relied on NWP models with unrealistic representation of the MJO (weaker and faster).**
**What is the overall influence of MJO activity on weather predictability in the midlatitudes and subtropical regions (e.g. Americas)?**
**How does this influence depend on the MJO strength and phase? **
**Are seasonal variations in MJO activity important?**
**Does MJO variability (e.g. strength and phase) influence forecast skills of extreme precipitation events in the Americas?**

## Approach

- NASA Goddard Laboratory for the Atmospheres (GLA) GCM (Kalnay et al. (1983).
- GLA model performed very well with respect to MJO representation in AMIP study (Slingo et al. 1996; Sperber et al. (1996).
- Ten year control run with climatological SST version of the model.
- MJO events selected with extended empirical orthogonal function analysis (EEOF) of 30-90 day rainfall anomalies (32N-32S; 32.5E-92.5W).
- Candidate MJO events and Null cases were chosen from the amplitude time series of EEOF modes 1 and 2.
- Conducted a set of twin numerical predictability experiments:
- 		75 cases [(4 MJO phases + Null phase) * 15 events].
- Perturbation to initial conditions based  on scaled day-to-day root-mean-square from daily averaged values of the model’s four prognostic variables (u,v,T,q).
- For each alternative initial condition, model was integrated for 90 days.
- Waliser et al. 2002: Potential Predictability of the Madden-Julian Oscillation. *Bull. Am. Meteor. Soc *(in press).

## Observed and Model Canonical MJO 

## Initial Condition Selection

**Initial Condition Selection**

**Example: N.H. Winter - MJO**

**Notes:**
Statistical Models: Show some skill out to 10-20 days.
   (e.g. Waliser et al. 1999; Hendon et al. 2000; Wheeler et al.2000)
Dynamical Models:  For the most part only forecast
  skill studies with models that have poor ISO representation
    (e.g., Chen and Alpert, 198x; Lau and Chang 1996; 
       Jones et al. 2000; Hendon et al 2000)

Few/No MJO predictability studies with “good” MJO models.  

Thus the question remains?

## RAINFALL

**Composite filtered (30-90 days) rainfall anomalies for the 15 initial conditions selected to represent the four “phases” of the MJO as well as the null cases **
**Except in null case (lower left), the headings indicate the geographic region of the most intense MJO-related rainfall**

**RAINFALL**

## ACC is computed for each set of MJO phase and Null cases for lead times  = 1, 30 days

**Standardized Root-Mean-Square Error**

**Anomaly Correlation Coefficient**

**Fisher **
**Transform:**

- Subtract daily climatology: Z500, SF200, U850, Rain
- ACC is computed for each set of _MJO phase_ and _Null cases_ for lead times  = 1, 30 days
- _Domains_: N.H., S.H. and Tropics (Z500, SF200, U850); Indian/W. Pac., N. America and S. America (Rainfall)

**Test:**

-  = 1, 30 days

## ACC

**ACC**

## Northern Hemisphere 20N – 60N

**Northern Hemisphere 20********N – 60********N**

## RMS

**RMS**

## RMS

**RMS**

**ACC**

## ACC

**ACC**

## Slide 12

## Conclusions

- Results from _boreal winter_ predictability experiments (GLA) suggest that predictability is higher during MJO active phases than in quiescent periods. Agreement with NWP predictive studies (Ferranti et al. 1990; Lau and Chang 1992).
- Northern Hemisphere (20N – 60N):
- Enhanced (suppressed) convection in Indian Ocean (W. Pacific) suggests a gain of 1-3 days in useful skill relative to quiescent MJO.
- Tropical Region (20S – 20N):
- Slight increase in predictability of U850 when there is enhanced (suppressed) convection in W. Pacific (Indian ocean).
- Southern Hemisphere (60S – 20S):
- Moderate predictability increase in Z500 and U850 during C.PAC and Indian phases.
- Rainfall: no statistically significant differences between active MJO and quiescent periods.
- Caveats: model shortcomings in MJO representation. Fixed SST’s. Model contains too little variability over western Indian Ocean and southern maritime continent region.