Simulating the extratropical response to the Madden-Julian Oscillation Hai Lin RPN-A, Environment Canada International S2S Conference, College Park February 10-13, 2014

Introduction MJO Global impact (boreal winter): NAO (Lin et al 2009); PNA (Mori and Watanabe 2008) AO (L’Heureux and Higgins 2008) Canadian temperature (Lin and Brunet 2010) Canadian precipitation (Lin et al 2010) Atmospheric response to MJO forcing: Matthews et al. (2004) Lin et al. (2010) Seo and Son (2012) To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

Outlines Introduction Numerical experiments: Summary Dependence on heating location Nonlinearity Dependence on initial condition Summary To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

Correlation when PC2 leads PC1 by 2 pentads: 0.66 Lin et al. (2010)

Normalized Z500 regression to PC2 Lin et al. (2010)

Model and experiment Primitive equation AGCM (Hall 2000) – similar configuration of model forcing as the Marshall-Molteni model, but not Q-G. T31, 10 levels Time-independent forcing to maintain the winter climate Linear integration, winter basic state

Thermal forcing Exp1 forcing Exp2 forcing Lin et al. (2010)

Z500 response Exp1 Exp2 Lin et al. (2010)

Why the response to a dipole heating is the strongest ? Linear integration, winter basic state with a single center heating source Heating at different longitudes along the equator from 60E to 150W at a 10 degree interval, 16 experiments Z500 response at day 10 To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

80E Day 10 Z500 linear response Similar pattern for heating 60-100E 110E 150E Similar pattern for heating 120-150W

Questions: Are the responses to opposite signs of MJO forcing mirror images? (nonlinearity) Which response is less sensitive to initial condition and background flow? with less spread? How does the response depend on extratropical jet initial condition? To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

Nonlinearity 3 sets of experiments: 1) Control 2) +MJO forcing From 360 different initial conditions 30-day nonlinear integrations To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

Thermal forcing +MJO thermal forcing Exp1 forcing Exp2 forcing Lin et al. (2010)

Nonlinearity Z500 response To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO

spread To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO +MJO response has less spread, less sensitive to initial condition

EOF of 360 Z500 day 6-10 responses to the same +MJO Downstream shift To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO Downstream shift Intensify

Dependence on initial condition U200 Jet intensifies To assess the contribution of moisture and convections to LFV, especially the MJO. Does tropical intraseasonal variability (TIV) exist in a dry model? Global view of the intraseasonal variability. Implication to the MJO Jet moves southward

Summary There is significant nonlinearity in response in mean response and spread Response to –MJO is more sensitive to initial condition (when the heating is over central Pacific) Response sensitive to the strength and position of East Asian jet Implication to subseasonal forecasting: MJO phase and jet initial condition