Richard Moore1, Olivia Martius2, Thomas Spengler2 & Huw Davies2 The Modulation of Tropopause-level Wave Breaking by the Madden Julian Oscillation Richard Moore1, Olivia Martius2, Thomas Spengler2 & Huw Davies2

Shading: anomaly from DJF average Motivation 250 hPa Wind Velocity 500 hPa Height Average MJO Phase Shading: anomaly from DJF average Quantitatively assess the behavior of wave breaking that accompanies the observed flow anomalies

Roadmap Ingredients of analysis Briefly outline the climatological response of WB to MJO forcing Combine climatological and case study viewpoints to gain further insight Simplify and summarize via a ‘Cartoon’ interpretation of observed evolution

Data & Methodology ERA-40 Re-Analysis Data for NH Winter from 1979-2002: Wave breaking (Wernli & Sprenger 2007; Martius et al. 2007) Surface cyclone frequency (Wernli et al. 2006) Atmospheric blocking frequency (Croci-Maspoli et al. 2007) 10 MJO Indices (Climate Prediction Center) Combine a climatological and case-study analysis of the response to MJO forcing

Extratropical Wave Breaking “The basic criterion for saying whether a wave of any kind is breaking is whether material contours and surfaces are being irreversibly deformed rather than simply undulating back and forth as is assumed in linear wave theory” McIntyre and Palmer 83

Synoptic Scale Rossby Wave Breaking stratosphere, high PV Explain isentropic PV charts Transition stratosphere troposphere 3D feature intrusion of stratospheric air also called PV streamer Irreversible deformation of contours formation of a cut-off Complete seclusion from stratospheric air body troposphere, low PV PV on 325K January 2007

‘Lifecycle’ Separation of Wave Breaking (WB) Events Thorncroft et al. 93 LC1, AC anticyclonic life-cycle in anti- cyclonic shear jet Dynamical Tropopause cyclonic life-cycle in cyclonic shear jet LC2, C LC1/LC2 wave breaking in ERA-40: Martius et al. 2007

Wave Breaking Frequency: 1979-2002 DJF Cyclonic (LC2) on 310 K Anticyclonic (LC1) on 330 K

Links to Severe Weather Floods in Algeria November 2001 strong convective activity along eastern flank PV on 320K SLP IR meteosat L formation of low pressure systems cyclonic windfield which can reach the surface For are real case Typical morphology associated typically with streamers Subsidence plus dry air from stratosphere within streamer and along western flak Reduced stability plus upgliding along isentropes => strong convection along eastern flank Wind field not only at upper-levels but extending down into the lower troposphere if strong anomaly wind on 850hPa precipitation

Links to Severe Weather Gondo October 2000 PV-streamer tropopause Alps sea Investigation of extreme precipitation events over 33 year time period based on the observation based high resolution precip climatology from Frei and Schaer Working hypothesis from the work of Massacand et al. sea wind field Massacand et al. 98, 01

Atmospheric Blocking A disruption in the midlatitude westerlies due to the presence of a quasi-stationary high pressure system Z - PV Anomaly Link Blocking and streamer can be expected Use blocking and streamer climatology to investigate that link Blocking as low pv anomalies Blocking Climatology TP

Shading: anomaly from DJF average Cyclonic WB on 310 K Cyclonic WB Anomalies Average for MJO Phase Shading: anomaly from DJF average MJO INDEX 3 (120E) MJO INDEX 7 (40W)

WB Anomalies: Overview Cyclonic WB on 310 K Statistically significant anomalies are prevalent Dynamical distinction between baroclinic lifecycles is instructive Strong anti-correlation, fairly rapid transition between anomalies of opposite sign Anticyclonic WB on 340 K

Outstanding Questions What is the relationship between the tropical convection and the observed jet – wave breaking anomalies? Might wave breaking be integral to the observed evolution?

Direct Impact of MJO Convection upper-level anticyclone: shifts jet to the north; local jet intensification January 16, 1993 Streamfunction Anomaly POS NEG Shading: Daily Mean OLR

Shading: instantaneous 250 hPa velocity Jet / WB Structure 12Z January 16, 1993 Predisposition to anticyclonic lifecycle Weak waveguide in central Pacific coincides with anticyclonic WB WB locally shifts jet north 2 PVU on 310 K 2 PVU on 330 K 2 PVU on 350 K Shading: instantaneous 250 hPa velocity + - + - 250 hPa Velocity Anticyclonic WB

Jet / WB Structure 12Z January 28, 1993 Cyclonic WB in west-central Pacific on northside of locally-enhanced jet baroclinic instability? + - 250 hPa Velocity Cyclonic WB

Jet / WB Structure: Index 7 (40W) 12Z February 5, 1993 Eastward extended, zonal jet – strong waveguide Southward shift over Asia – cyclonic lifecyle WB shifts jet southward - + - +

Shading: anomaly from DJF average WB and PNA-like signal 7 (40W) 3 (120E) 4 (140E) 6 (120W) 5 (160E) MJO Index: 500 hPa Height Cyclonic WB on 310 K Average MJO Phase Shading: anomaly from DJF average

Anticyclonic WB Anomalies Average for MJO Phase Shading: anomaly from DJF average MJO INDEX 3 (120E) MJO INDEX 7 (40W)

modulation of sub & extratropics Northward shifted jet over Asia Anticyclonic WB in central Pacific Double jet structure Enhanced blocking frequency in central Pacific

modulation of sub & extratropics Pattern shifts east Cyclonic WB ensues on northside of zonally, locally-strong jet Surface cyclone often co-located in time and space with cyclonic wave breaking event LC2 wave breaking leads to quick transition of PNA

modulation of sub & extratropics Single jet extended to the east, southward shift over Asia Cyclonic WB (surface cyclones) eastern Pacific in jet exit region Subsequent to this time, in absence of MJO convection the jet breaks down and retreats westward

Questions? http://www.met.reading.ac.uk/~pete/

based on 200 hPa velocity potential MJO Indices based on 200 hPa velocity potential http://www.cpc.noaa.gov/products/precip/CWlink/daily_mjo_index/mjo_index.html

Anticyclonic WB Anomalies Average for MJO Phase Shading: anomaly from DJF average MJO INDEX 3 (120E) MJO INDEX 7 (40W)

Shading: anomaly from DJF average LC1, AC instantaneous field Shading: anomaly from DJF average

Shading: anomaly from DJF average LC2, C instantaneous field Shading: anomaly from DJF average

MJO forcing changes jet strength, meridional & longitudinal location Jet Structure MJO forcing changes jet strength, meridional & longitudinal location 250 hPa Jet: + anomaly - anomaly

Surface Cyclone Frequency MJO Index 3 MJO Index 7 @ @ - anomaly + anomaly

What is the MJO? Dominant source of tropical intraseasonal variability Large-scale coupled patterns in deep convection & atmospheric circulation Characteristics: Zonal scale ~ 12-20K km Eastward propagation ~ 5 m/s Lifecycle ~ 48 days http://www.met.reading.ac.uk/~pete/

Wave Breaking Frequency: 1979-2002 DJF Cyclonic (LC2) on 310 K Anticyclonic (LC1) on 330 K