Inna A. Megretskaia

Effects of the 2006 El Nino on tropospheric composition as revealed by data from the Tropospheric Emission Spectrometer (TES)

[1] The Tropospheric Emission Spectrometer (TES) is unique in providing multi-year coincident tropospheric profiles of CO, O 3 and H 2 O. TES data show large differences in these gases over Indonesia and the eastern Indian Ocean in October-December 2006 relative to 2005. In 2006, O 3 was higher by 15-30 ppb (30-75%) while CO was higher by >80 ppb in October and November, and by ∼25 ppb in December. These differences were caused by high fire emissions from Indonesia in 2006 associated with the lowest rainfall since 1997, reduced convection during the moderate El Nino, and reduced photochemical loss because of lower H 2 O. The persistence of the O 3 difference into December is consistent with higher NO x emissions from lightning in 2006. TES CO and O 3 enhancements in 2006 were larger than those observed during the weak El Nino of 2004.

Changes in ozone over Europe: Analysis of ozone measurements from sondes, regular aircraft (MOZAIC) and alpine surface sites

We use ozone observations from sondes, regular aircraft, and alpine surface sites in a self-consistent analysis to determine robust changes in the time evolution of ozone over Europe. The data are most coherent since 1998, with similar interannual variability and trends. Ozone has decreased slowly since 1998, with an annual mean trend of −0.15 ppb yr−1 at ∼3 km and the largest decrease in summer. There are some substantial differences between the sondes and other data, particularly in the early 1990s. The alpine and aircraft data show that ozone increased from late 1994 until 1998, but the sonde data do not. Time series of differences in ozone between pairs of locations reveal inconsistencies in various data sets. Differences as small as few ppb for 2-3 years lead to different trends for 1995-2008, when all data sets overlap. Sonde data from Hohenpeissenberg and in situ data from nearby Zugspitze show ozone increased by ∼1 ppb yr−1 during 1978-1989. We construct a mean alpine time series using data for Jungfraujoch, Zugspitze, and Sonnblick. Using Zugspitze data for 1978-1989, and the mean time series since 1990, we find that the ozone increased by 6.5-10 ppb in 1978-1989 and 2.5-4.5 ppb in the 1990s and decreased by 4 ppb in the 2000s in summer with no significant changes in other seasons. It is hard to reconcile all these changes with trends in emissions of ozone precursors, and in ozone in the lowermost stratosphere. We recommend data sets that are suitable for evaluation of model hindcasts.

A quantitative assessment of uncertainties affecting estimates of global mean OH derived from methyl chloroform observations

[1] We estimated the global abundance of OH for the years 1988–1994 by interpreting observations of methyl chloroform (MCF) from two networks using an inverse technique and a 3-D chemical transport model driven by assimilated meteorology. Our inversion approach optimized both the emissions of MCF and the abundance of OH. Because of an a priori overestimate of the latitudinal gradient of MCF concentration by the model in the standard setup, the inversion lowers global emissions and the global sink due to OH. Optimized emissions are about 10% lower than published inventories on average between 1988 and 1994, and the decrease in the sink suggested by the inversion implies an average lifetime for MCF (with respect to tropospheric OH) of about 6.9 years, 11–21% longer than the 5.7–6.2 years reported in previous optimization studies. Our results are driven by the need to match the observed latitudinal gradient of MCF while balancing the MCF budget. We find that these results depend on the a priori constraint placed on MCF emissions, the rate of interhemispheric mixing in the model, the interhemispheric distribution of OH assumed, and the model simulation of pollution events. Since these factors are highly uncertain, we believe that the level of understanding on global lifetimes of pollutants removed by OH is lower than might be implied by the narrow range of estimates for MCF lifetime in the literature.

Linking ArcView™ and XGobi: Insight behind the Front End

Abstract This article presents aspects of the implementation of a bidirectional link between the Geographic Information System (GIS) ArcView™ and the interactive dynamic statistical graphics program XGobi. We describe the main functionality of the link, the underlying remote procedure call (RPC) mechanism, and internal data structures, and discuss topics such as security, concurrency, and linked brushing. We think that these topics are of particular interest to software authors intending to link similar software packages, and software users learning about strengths (and weaknesses) of the implementation of our link.