Interannual variation of spring total ozone and winter planetary-scalewave activity in re-analyses data
Chiaki KOBAYASHI
Ozone Layer Monitoring Office, Atmospheric Environment Division,
Japan Meteorological Agency, Japan
chiaki.kobayashi@met.kishou.go.jp
INTRODUCTION
In the Northern Hemisphere, the stratospheric ozone is the most abundant in spring. The variability of ozone
transport in polar region and lower stratospheric temperature are correlated because they are both driven by
dynamical variability. The arctic polar lower stratospheric temperature in spring is primarily controlled byplanetary-scale waves in late winter (Newman et al., 2001). In this study, we validate the lag correlation between
spring total ozone in polar region and winter wave activity represented in each re-analysis data for monitoring ofthe spring ozone in polar region.
DATA AND ANALYSESThe column ozone data used here are obtained with the Ozone Monitoring Instrument (OMI) on Aura for 2005
and 2006, and the Total Ozone Mapping Spectrometer (TOMS) instruments using Version 8 of the TOMS
processing algorithm from 1979 to 2004. Monthly averages are calculated from daily original data.
The products of the following four reanalyses are used as the atmospheric datasets in this study.
*Japanese 25-year Reanalysis (JRA-25) [Onogi et al., 2007] and JCDAS (1979-2006)*ECMWF 40-year Reanalysis (ERA-40) [Uppala et al., 2004] (1979-2002)*NCEP/NCAR reanalysis [Kalnay et al., 1996] and CDAS1 (1979-2006).
*NCEP/DOE reanalysis [Kanamitsu et al., 2002] and CDAS2 (1979-2006)
In the JRA-25, ozone observations are not assimilated directly in the data assimilation system. Instead a3-dimensional daily ozone profile is separately produced in advance and provided to the forecast model. In theERA-40 project, retrievals from TOMS and SBUV instruments on various satellites are directly assimilated. InNCEP/NCAR and NCEP/DOE, zonally averaged seasonal climatological ozone are used in the radiation
computation.
Using these reanalyses, zonally averaged eddy heat flux is calculated to estimate the amount of planetary wave
activity propagating into the lower stratosphere. The eddy heat flux is the vertical component of EP-flux which
represents wave activities, and vertical component of residual circulation related to transport of ozone. The eddy
heat fluxes are calculated from those reanalyses datasets and we calculated monthly means for the period
1979-2006.
RESULTS
Year-to-year variation of observed total ozone over arctic polar region in March and eddy heat flux over
mid-latitude in late winter (Jan-Feb) which indicates tropospheric planetary wave activity are shown in Figure 1a.
The monthly mean eddy heat fluxes at 100hPa are calculated using JRA-25. The eddy heat flux in late winter arecorrelated well (r=0.63) with the total ozone in March. Simultaneous relation between observed total ozone andeddy heat flux are shown in Figure 1b. There is no significant correlation (r=-0.03) between these two elements.
The time lag correlation is larger than the simultaneous correlation. The strong lag correlation between total ozone

in March and eddy heat flux in late winter are confirmed in JRA-25.

Figure 1 Time series of eddy heat flux (solid line) over 45N-75N at 100hPa in Jan and Feb (a) andin Mar (b). Broken lines indicate total ozone over polar cap region in March.

Figure 2 Correlation of March total ozone (60N-90N, 1979-2006) and total eddy heat flux (a) andwave 1-3 component of eddy heat flux during Jan-Feb in JRA-25.

Figure 3 Correlation of March total ozone (60N-90N, 1979-2006) and wave 1-3 component of eddy
heat flux during Jan-Feb.
Same map as Fig.2b but for a) ERA40, b) NCEP/NCAR, c) NCEP/DOE.

To see the spatial distribution of the correlation in JRA-25, 28-year-average March total ozone over polar
region is correlated with each latitude and height of zonal mean eddy heat flux field in late winter represented inJRA-25. Figure 2a shows the correlation between March total ozone and total eddy heat flux in late winter andFigure 2b shows the correlation between March total ozone and eddy heat flux for waves 1-3 in late winter. The
maximum correlation is found at around 60N and 70hPa. The correlation of the polar ozone with the zonal mean
waves 1-3 eddy heat flux is slightly improved than the total eddy heat flux. The eddy heat flux time series and its
interannual variation are dominated by planetary-scale waves in stratosphere.
Figure 3 shows same correlation maps as Figure 2b, but by using other reanalyses. Large positive correlations
over polar lower stratosphere are commonly found in other reanalyses. However the maximum value ofcorrelation in ERA40 is greater than that of JRA-25, and the correlation in NCEP/NCAR and NCEP/DOE are lessthan that of JRA-25.Differences among correlation patterns may be due to the difference of ozone assimilation
method.
Figure 4 shows the year-to-year variation of waves 1-3 component of eddy heat flux in each reanalyses. Theinter-annual variation of eddy heat flux well matches among these reanalyses after 1992. However they do notmatch during 1979-1991. The correlations among the reanalyses are shown in table 1. The correlation between
JRA-25 and ERA40 is 0.82 and the correlation between JRA-25 and NCEP/NCAR is 0.97. The inter-annualvariation of eddy heat flux in JRA-25 well matches both ERA-40 and NCEP/NCAR.

Figure 4 Time series of eddy heat flux (45N-75N, wave 1-3) at 100hPa in Jan-Feb
Triangle: JRA-25, Square: ERA40, Cross: NCEP/NCAR, None: NCEP/DOE

Table 1. Correlation coefficient among the year-to-year variation of eddy heat flux at 100 hPa over
45N-75N in each reanalyses
ERA40
NCEP/NCAR
NCEP/DOE

JRA-25

ERA40

NCEP/NCAR

0.82
0.97
0.49

0.78
0.58

0.41

SUMMARY
The results are summarized as follows:
1) The variation of the lower stratospheric eddy heat flux in late winter in JRA-25 is correlated well with theobserved total ozone over arctic region in March.
2) These correlations were confirmed by 4 major reanalyses.
3) The inter-annual variation of eddy heat flux in JRA-25 well matches both ERA40 and NCEP/NCAR.
It is confirmed that the variation of total ozone over the polar region in spring can be diagnosed and/orpredicted by using the eddy heat flux of JRA-25 in winter, same as ERA40 and NCEP/NCAR.

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