Figure 1. ECMWF monthly mean height anomalies (1995-2004) show the wave train that emanates from convection near Indonesia, propagates energy poleward in the UTLS (panels e,f), then upward into the austral stratosphere (c,d a,b). This amplifies from August to October as zonal winds weaken during SH spring. Ozone-rich air is found in the ridge over the South Pacific. (cf. Hitchman and Rogal, 2009a,b; Rogal et al., 2010).

Figure 2. ENSO modulates the distribution of clouds in the Indian Ocean - Pacific Ocean region, with the center of change near Indonesia. This modulates the distribution of height anomalies in the Southern Hemisphere. Top: Annually averaged 500 hPa geopotential height anomalies (m) for a) El Nino minus La Nina, b) El Nino minus neutral, and c) La Nina minus neutral, with regions of statistical significance exceeding the 95% confidence level represented in color. d), e), f) same except for NOAA OLR anomalies (W per m2). Solid (dashed) contours indicate positive (negative) values. Note that in the Ross Sea area geopotential heights are anomalously high during El Nino and low during La Nina (Welhouse et al., 2016).

Figure 3. Some authors have explored dividing differences in the source region for planetary waves from different parts of the tropics. This schematic illustration shows typical wave trains associated with the (a) Indian Ocean Dipole (IOD) and (b) ENSO for JJA and (c) for the IOD and ENSO together for SON. This description is for positive phases of the IOD and El Nino. Typically opposite patterns occur during negative IOD and La Nina. Shaded blue (red) areas indicate regions of increased (decreased) tropical convection. Blue (red) contours indicate anomalously low (high) upper-level heights. The dashed lines trace prominent wave trains: gray for the Eastern Indian Ocean wave train, green for the Western Indian Ocean wave train, and orange for the Equatorial African wave train. The PNA and PSA wave trains are not marked but visible in (b) and (c) (Cai et al., 2011).

Figure 4. Total Ozone Mapping Spectrometer column ozone distribution for JJA and SON. Column ozone maximizes poleward of the Australian Subtropical Westerly Jet in the subsidence warm anomaly (cf. idealized linear model by Wirth, 1993). The *geographical location* of the ozone croissant and associated wave one structure is partly controlled by convection in Southeast Asia, since outflow in the UTLS creates the subtropical westerly jet that extends across the Pacific (Hitchman and Rogal, 2010).

Figure 5. Another significant contributor to the enhanced Pacific column ozone maximum during SON is the interaction of Indonesian UTLS outflow pulses with travelling wave two in the SH stratosphere. An outflow pulse will cause the wave two to stall, with an amplification of the wave two ridge nearest to Indonesia. An example is shown in this longitude-altitude section from the surface to the stratopause of eddy geopotential height at 22 degrees S on 24 August 2000, contour interval 50 (Hitchman and Rogal, 2009).

Figure 6. a) Latitude - altitude section at 95E on 24 August 2000 of ozone mixing ratio in ppmv. Stratospheric ozone is seen to maximize just poleward of the subtropical jet near the tropopause. b) Longitude - altitude section at 38S showing the coincidence of high ozone values (color, ppmv) and high geopotential height (contour interval 150 m), consistent with circulation of ozone poleward and downward around planetary anticyclones. Averaged over many such events, Indonesian outflow pulses preferentially amplify the nearest wave two height maximum, contributing to the column ozone maximum in the high latitude Pacific (Hitchman and Rogal, 2009).

Back to top of page

Under Construction: Collaboration with

• Takenari Kinoshita
  National Institute of Information and Communications Technology, Japan


• Prof. Kaoru Sato
  University of Tokyo, Japan

We are investigating changes in fluxes of Rossby wave Energy out of the tropics in the UTLS into the SH

The UTLS is a conduit whereby tropical convection can Influence the propagation of extratropical planetary wave Activity through the connecting westerly waveguide

Back to top of page