Enhanced Tropospheric Ozone and the Arabian Anti-Cyclone (or the “Middle east ozone maximum?”)

John Worden1, Jane Liu2, Dylan Jones2, Kevin Bowman1, Helen Worden3, Ming Luo1, and JPL/TES team1

1 JPL / Caltech

2 U. of Toronto

3 NCAR

Background on Middle East Ozone Maximum

The GEOS-CHEM model predicts that ozone amounts in the upper troposphere during the summer are highest over the middle east relative to the rest of the globe.

Enhanced ozone due to summer time Arabian anti-cyclone which gathers ozone and ozone pre-cursors. Subsidence of Ozone also plays a role

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H. Worden et al. In Preperation

Enhanced Ozone Over Middle East Significant Green House Gas

Li et al., 2001

Monthly Mean O3 in GEOS-CHEM at ~350 hPa, ~8 km May 2005 June 2005 July 2005

Aug 2005 Sept 2005 Oct 2005

The ozone maximum is confined to a narrow altitude layer in the upper troposphere, where TES is most sensitive Ozone accumulation is seasonal, peaking during June-August

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What do satellite observations show?

SAGE II UV/visible solar occultation ozone at 7km (July 1985-1994)

TES Ozone 460 hPa July 2006

High ozone over NE Africa and Mediterranean and some enhanced ozone over middle east

Also high ozone over Central Asia and E. China

Kar et al., 2002

As with GEOS-CHEM….. TES Observations show this feature is seasonal with a peak in July

June July 2006 August

And is persistent year to year

July 2007

Upper Tropospheric Ozone in NE Africa and S.W. Russia is about 95 - 110 PPB as compared to 65-85 PPB at other longitudes

TES observations sensitive to these regions 0.5 < DOFS < 0.7 in Upper Troposphere Random Error < 5 PPB

Observed ozone spatial variations are statistically significant

Ozone spatial variations not due too a priori bias

TES Estimate TES estimate w/ fixed constraint vector

Ozone variations have low bias error in regions of interest

bias differences larger at higher latitudes where sensitivity is low

Conclusions• TES observes summertime enhanced upper tropospheric ozone over

NE Africa, the Mediterranean, and Central Asia.

• TES ozone observations are consistent with SAGE data and the observed spatial variability is statistically significant

• Spatial distribution of TES observed ozone is different from the GEOS-CHEM model in that ozone does not peak over the Middle East

• However, …the seasonality of the distribution and lack of ozone pre-cursors under regions of enhanced ozone suggests the Arabian anti-cyclone is driving the observed ozone spatial distribution (more on this from Dylan!)