Composite Regression Analysis of the 8 Phases of the MJO

By: Zachary Handlos

Introduction

MJO – What is it? 8 phases of MJO Convective phases vs. suppressed phases

MJ 1971 – origins of oscillationMJ 1994 – Brief History of Research (ie: observational work, Super Clusters, Monsoons, etc...)

Wheeler and Hendon (2004)

Performed EOF analysis of combined fields (OLR, zonal wind at 850 hPa and 200 hPa) Subtracted out as much seasonal, annual variability as possible (ie: ENSO, etc...) RMM1 and RMM2 = EOF1 and EOF2

Explain MJO propagation over space RMM1 – enhanced convection over Maritime Continent RMM 2 – enhanced convection over the Pacific

Goal of This Project:

Understand WH (2004) statistical methods by recreating some of their work Show the significance of the RMM1 and RMM2 EOF's and their relationship to the MJO, forecasting the MJOFor this presentation, results regarding the composite regression analysis of OLR data considered

Composite Regression Analysis

ESRL (NCEP) interpolated OLR data (2.5 deg resolution, daily for May-June)Subtracted out meanRegressed OLR onto RMM 1 and RMM2Call the regression vectors r1 and r2

Composite Regression Analysis

Calculate the value of the OLR regression slope values as a combination of RMM1, RMM2:

r = r1-i*r2

OLR = Re{r*exp(i*[(9*π/8)+(j*(π/4))])]} where

j = phase (1-8)

i = sqrt(-1)

Wait Zak...what are you doing here?

Wheeler and Hendon (2004) phase space diagram Represent MJO phases with combined RMM value

Multiply r by the second term on the RHS of previous equation to composite regression into the 8 phasesWant the real part of equation

My Results vs. Wheeler and Hendon (2004)

Used complex, combined RMM regression vector and composite based on earlier algorithm

WH (2004) composite OLR (and wind) anomalies based on results from phase space diagram (Fig. 7 in paper)

Time Frame analyzed: 1990-2004 (Me) 1974-2003 (WH 2004)

Future Work (Current Research)Focus: ISCCP cloud regimes (Rossow et al, 2005)Currently looking at the shape of latent heating profiles, calculating shapes using only precipitation and surface convergence in the ITCZIdea: Look at evolution of latent heating profiles, clouds within MJO phases (and SCC's)Statistical Analysis methods such as composite analysis, EOF analysis, even spectral analysis could be useful

References Madden, R. A. and P. R. Julian, 1971: Detection of a 40-50-day oscillation in the zonal wind in the tropical

Pacific. J. Atmos. Sci., 28:702–708.

Madden, R. A. and P. R. Julian, 1972: Description of global scale circulation cells in the Tropics with a 40-50-day period. J. Atmos. Sci., 29:1109–1123.

Madden, R. A. and P. R. Julian, 1994: Observations of the 40–50-day tropical oscillation—A review. Mon. Wea. Rev., 122:814–837.

Tromeur, E., and W.B. Rossow, 2010: Interaction of tropical deep convection with the large-scale circulation in the MJO. J. Climate, 23, 1837-1853, doi:10.1175/202009JCLI3240.1

Wheeler, Matthew C., Harry H. Hendon, 2004: An All-Season Real-Time Multivariate MJO Index: Development of an Index for Monitoring and Prediction. Mon. Wea. Rev., 132, 1917–1932.