MICHAEL A. ALEXANDER, ILEANA BLADE, MATTHEW NEWMAN, JOHN R. LANZANTE AND NGAR-CHEUNG LAU, JAMES D. SCOTT Mike Groenke (Atmospheric Sciences Major)

El Nino-Southern Oscillation (ENSO)  Tropical Pacific region  Associated sea surface temperature (SST) anomalies  Warm=El Nino…Cold=La Nina  ENSO events drive ocean SST anomalies around globe  “Atmospheric bridge” because connects the world’s oceans

Better explanation  UStFvz8 UStFvz8

 Q-net: net surface heat flux  We=entrainment heat flux  Vek=Ekman transport

Wait, why do we care?  Essential for prediction of SSTs in tropical Atlantic  Contributes to leading patterns of SSTs on many times scales around globe  Tests ability to simulate global atmospheric response to ENSO  Separate between atmospheric forcing and ocean feedbacks  Influence on marine ecosystems

ENSO Really Matters

Questions that remain  Ocean-atmosphere interactions via changes in solar radiation, precipitation, and boundary layer processes.  Indian Ocean response to ENSO  Feedback from SST anomalies beyond equatorial East Pacific

Purpose of this study  Review of how well we understand the “atmospheric bridge”  Present new data/observations  Focus on Pacific North America (PNA) region

Modeling Used  3 major models were used  “Control model”  “MLM” or mixed layer model  “NP-MLM” or North Pacific mixed layer model  NCEP-NCAR re-analysis project data also used

Methods  Look at observations from past  Interpret data and form hypotheses and assumptions  Run models and look for reproduction of observed data  Interpret results

Main Focus  Global precipitation influences from ENSO  Related SST anomalies on different times scales around the globe  Relationship between SST and SLP

Effects On Global Precip  Changes in jet stream speeds from ENSO  Anomalous clockwise flow=higher precip

ENSO Felt Around the World  North Pacific  Opposite sign of ENSO  Pacific Decadal Oscillation influenced by tropical and extra-tropical forcing  Far north near “sub arctic front” not correlated SST Anomalies

Current Example

ENSO Felt Around the World  Tropical Atlantic: Warm waters just north of equatorial Atlantic found with El Nino in spring after ENSO peak Southern Atlantic only weak links plus 3-6 months lag time  Indian Ocean Warms with El Nino Lag time of 3-6 months, but earlier than Atlantic Often during summer/fall also

Relationship in SLP & SST’s  Stronger Aleutian low (by 9mb) during Nino vs. Nina  Causes increased westerlies in north Pacific  Advects cold air into northern waters and warm air along west coast of North America  Consistent with previous SST map  Model differences likely due to error and missing ocean dynamics

Check out the pressure! ObservedMLM Simulation

Shaded areas indicated a 95% statistical significance in difference between taking local coupling effects into account or not

Other ENSO Induced Effects  MLD (Mixed Layer Depth) The depth at which the temperature is 1 degree C cooler than the surface  Salinity  Reemergence of SST anomalies Fades during summer, but effects next winter

Summary  Atmospheric response to changes in SST’s due to ENSO influences conditions across the rest of the globe  This connection is called the “Atmospheric Bridge”  Clear link in ENSO SST anomalies and other anomalies in Northern Pacific, north tropical Atlantic, and Indian Oceans  Atmospheric response affects SLP and jet stream patterns across the globe including deep trough near Alaska

Summary (cont’d)  Other impacts include effects on MLD, salinity, and the reemergence of anomalies during the following year  Changes in net heat flux are the leading driver of SST anomalies in the ENSO region  Ocean-air coupling modifies effects on pressure fields in the North Pacific

My Thoughts  Good review of impacts from El Nino/La Nina events  Too many assumptions that reader knows extremely technical processes  Further research in this field could improve seasonal forecasting  Lacked significant mention of effects from climate change