# Presentation: 353493

## Evaluation of ENSO prediction and its impact on US surface climate using NCEP/CFS retrospective seasonal forecasts

- Augustin Vintzileos and Jae-Kyung E. Schemm

## Seasonal-to-Interannual Forecasting

- Emission: e.g., Tropical Pacific (ENSO)

- Reception: e.g., Extra-tropics

- Persistent (seasonal to interannual) surface forcing 
- Persistent tropical atmospheric forcing 
- Tele-connections to mid-latitudes result to the seasonal-to-interannual signal

## Outline: 

- _Outline:__ _

- Mean state and interannual variability in the tropical Pacific in boreal winter at 0-season lead time
- Mean state and interannual variability of surface variables over North America during boreal winter at 0-season lead time
- Tropical Extra-tropical teleconnections at 0-1 season lead times
- _Forecast Skill_

## The Tropical Pacific

## Nino 3.4 Forecast, Anomaly correlation skill

- I.C. from November

- I.C. from September

## Stratus 

- Simulated – Observed Temperature at lead=0s (initialized in November)

- Stratus

- Local thermo-dynamical effect? Impact from the eastern Pacific warming ?

## Simulated – Observed Temperature at lead=0s (initialized in November)

- Colder Cold tongue

## Oceanic Mixed Layer

## Simulated – Observed STDV of Temperature at lead=0s (initialized in November)

## Simulated – Observed Precipitation at lead=0s (initialized in November)

## Simulated – Observed Precipitation at lead=0s (initialized in November)

- Simulated – Observed STDV of Precipitation at lead=0s (initialized in November)

## Mean winter North American surface climate and its interannual variability 

## Slide 13

## Slide 14

## Biases

## Teleconnection patterns 

## Correlation of Nino 3.4 vs. all grid-points

- Correlation of Nino 3.4 *vs*. all grid-points

- Temperature

- Precipitation

## Seasonal Prediction of North American surface climate

## Anomaly Correlation Skill

- 0s

- 1s

- Temperature

- Precipitation

## Teleconnection patterns vs. forecast skill

- Temperature

- Precipitation

- Skill

- Pattern

## Conclusions

**CFS/NCEP is a tool which can provide skillful winter forecasts of T2m and precipitation over some areas of the US. Skillful forecasts of precipitation occur over the Southeast and Mid-Atlantic and for temperature in the Northwest. Good skill over these areas is directly related to the realistic representation of the impacts of ENSO and of good ENSO forecast at these lead times. **
**	****We documented a number of biases in the simulated North American climate. Simulated winter temperature variability is weaker than observed, suggesting too zonal a flow over the US. Alleviation of this problem will certainly allow for a better response of the large scale circulation to ENSO and thus improvement of the temperature forecast in the Northwest. A significant bias in simulated precipitation variability is its absence from the region of the northern Gulf of Mexico and its extension towards the Atlantic ocean. This is an area of skillful precipitation forecast and therefore it is highly possible that model improvements will increase forecast skill over the Southeast. Another significant bias of the model relevant to forecast of North American surface climate is the unrealistically strong variability in the central Pacific ITCZ and the implied spurious teleconnection patterns. Improvements on these biases will enhance the winter time forecast skill of CFS.**

## Future research:

- _Tropics:_
- Tuning of the parameterizations of atmospheric convection AND of the ocean mixed layer using the _**Coupled GCM**_ in order to improve simulation of the mean ITCZ and its variability

- _Extra-tropics:_
- Increasing the resolution of the AGCM may allow for better representation of the atmospheric flow and thus of the surface climate of North America during winter. As a consequence a better forecast skill is expected
- Spurious Lake-effects should be taken into consideration and corrected