# Presentation: 239448

## Signal to Noise for Global Modes of Subseasonal Atmospheric Variability  

- Signal to Noise for Global Modes of Subseasonal Atmospheric Variability

***	******	******     ******Edward  Berry***
***                   ******NOAA/NWS Dodge City, Kansas   ***
*** ******Klaus Weickmann***
***  ******NOAA/ESRL/PSD Boulder, Colorado ***

-       	    NOAA’s 32nd Climate Diagnostics and 			     Predictability Workshop
- 		          October 25, 2007

##         		              Overview 

-         		              **Overview **

**> A Global Synoptic Dynamic Model (GSDM)**

**> Signal to noise for the MJO and the GWO**

**   ****> Example of week 2 forecast application**

**> Conclusions and future work **

**> The MJO and the Global Wind Oscillation**

## 		        Background

**>  WB(2007) proposed a Global Synoptic Dynamic Model of                  ****	****subseasonal atmospheric variabilty (GSDM)**
**>  GSDM considers the interaction of 3 different time scales ****	****including the quasi-oscillatory MJO **
**>  Purpose of GSDM is to extend current thinking beyond the ****	****MJO; is there anything else?**
**>  The Global Wind Oscillation (GWO) represents a slow portion ****	****of the GSDM having a “mixture” of oscillatory and red ****	****noise processes (~6-10 day decay)**
**>  Purpose is to improve subseasonal forecasts, **
**	****including extreme events**
** **

**	****	****        ****Background**

## GLOBAL SYNOPTIC DYNAMIC MODEL (GSDM)

**GLOBAL SYNOPTIC DYNAMIC MODEL (GSDM)**
**Weickmann and Berry (2007): Each stage shows superposition of 3 time scales**

- Wave energy dispersion favors high
- impact weather across USA Plains

- Below normal temperatures possible
- across central and eastern USA

- High Impact weather event possible
- along USA west coast

- Heavy precipitation event possible
- Southwest USA

## H

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 1

- L

- L

- L

- L

- L

- L

- Slow Meridional Rossby Wave Dispersion Favored

- L

- L

- L

- L

- L

- L

**Indian Ocean**

**Maritime Continent**

**West Pacific**

**Western Hemisphere/Africa  **

## What is the Global Wind “Oscillation”?

**What is the Global Wind “Oscillation”?**

**Represents portion of GSDM linked with AAM variations due to:**
**Tropical Convection (implicitly)**
**Momentum Transports (eddy vs. HC/FC)**
**Torques (Mountain and friction)**
**Captures poleward propagation of zonal mean wind anomalies **
**Provides independent information on variations of the global circulation (a “semi-coherent form of climate noise”)**

-   MJO,                   ****F-****M

- Eddy vacillations, mountain torques, etc.

- AAM Spectrum

- AAM Tendency Spectrum

- RMM1 Spectrum

- MJO

- MJO, ~30 day

- 365-day segments; 1968-2006 for AAM and 1979-2006 for MJO

## #1

- “Global
- Wind
- Oscillation (GWO)”
- Define
- eight stages
- much like
- WH(2004)
- defined
- eight phases
- for the MJO
-  Focus will be on
- Apr-May-Jun “snr”; week 2
- prediction of trough over west
- USA late
- May 2007

- Angular momentum
- added to atmosphere

- Angular momentum
- removed fm atmosphere

- #2

## Poleward propagation of zonal mean zonal wind anomalies

-  produced by momentum transports linked to MJO and GWO

- 2

- 4

- 3

- 1

- 2

- 3

- 4

- 1

- E

- E

- E

- E

- E

- E

- E

- E

- E

- E

- W

- W

- W

- W

- W

**#1**

- W

**#2**

- Transport-induced
- momentum sources & sinks
- provide a link between the MJO and GWO, and are the primary forcing for the poleward
- movement of zonal wind anomalies.
- GSDM describes “subseasonal events” produced by interaction and feedbacks between the GWO and the MJO.

## 0.5

- 1.0

- 1.5

- 2.0

- 2.5

- 3.0

- 3.5

- 4.0

- L

- L

- H

- H

- H

- Fast Zonal Rossby Wave Dispersion Favored

- H

- L

- H

- L

- L

- H

- H

- L

- H

- H

- L

- H

- H

- L

- H

- H

- MJO?

## Statistical Basis for Week-2 Forecast Made 11 May 2007 

- Statistical Basis for Week-2 Forecast Made 11 May 2007

- 0.5

- 1.0

- 1.5

- 2.0

- 2.5

- 3.0

- 3.5

- 4.0

- ~0.3 sigma

**May 19**

## PDF for Apr-May-Jun Stage 2 vs. 4 Western USA 850 Temp

- Stage 2

- Stage 4

**~-****4**

**~4**

**~-2**

- P
- r
- o
- b
- a
- b
- i
- l
- i
- t
- y

- Standard Deviation

## How big are MJO signals/impactsduring DJF?

- How big are MJO signals/impactsduring DJF?

**Signal/Noise for 2 meter air temperature**
**Eight**** MJO Phases, DJF 1979-2006**
**Max ~+0.5 sigma => 67% prob > 0 anomaly**

## What is the synoptic evolution?

**Signal/Noise for ~250 mb streamfunction**
**Four MJO Phases, DJF 1979-2006**
**Max ~+0.8 sigma => 77% prob > 0 anomaly**

- 2

- 3

- 4

- 5

- L

- H

- L

- L

- H

- L

- H

- L

- H

- L

- H

- L

- H

- H

- H

- H

- H

## Summary and Future Plans

**Hypothesis: MJO and GWO are independently forced but significant interactions and feedbacks occur**
**Eight phase compositing used for MJO and GWO; allows nonlinear **
**assessment**
**MJO and GWO signal/noise: tropics ~0.6-0.8σ;  extratropics ~0.2-0.3****σ****   **
**Plan global, zonal and local composites for MJO and GWO, including**
**zonal and vertical mean AAM budget terms**
**Results will feed into rigorous daily monitoring and synoptic analysis**
**Should be part of forecast process that includes operational forecast models, linear models and calibration procedures ;  e.g., **
- _[http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/](http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/)_
- _[http://weatherclimatelink.blogspot.com](http://weatherclimatelink.blogspot.com/)_** **

## QUESTIONS?

**QUESTIONS?**