Science

Goals

The scientific goals for the ACE mission include:

  1. Understanding the chemical and dynamical processes that control the distribution of ozone in the stratosphere and upper troposphere, particularly in the Arctic
  2. Exploring the relationship between atmospheric chemistry and climate change
  3. Studying the effects of biomass burning on the free troposphere
  4. Measuring aerosols and clouds to reduce the uncertainties in their effects on the global energy balance

Results

The first release of ACE-FTS data was introduced in a special issue of the journal Geophysical Research Letters [Bernath et al., 2005]. Version 1.0 of the ACE-FTS level 2 data consists of the results for sunsets from February to October 2004, and was intended primarily for validation exercises [Walker et al., 2005]. Validation of the data has involved comparisons to multiple other instruments [Fussen et al., 2005; Jin et al., 2005; Mahieu et al., 2005; McHugh et al., 2005; and Petelina et al., 2005] but preliminary scientific studies based on these data have also been carried out.

The range of scientific studies using this data, includes investigating the current levels of stratospheric water vapor [Nassar et al., 2005a] and trends of many important halogenated molecules [Rinsland et al., 2005a] through comparison with the previous ATMOS measurements. ACE-FTS measurements have been used to determine latitudinal distributions of CO [Clerbaux et al., 2005] and properties such as the phases, densities, and size distributions of high-altitude cloud and aerosol particles in the tropics [Eremenko et al., 2005a]. Some other studies include the detection of the first infrared spectra of polar mesospheric clouds (PMCs), which prove to be small ice particles as expected [Eremenko et al., 2005b] and the first ever measurements of CFC-113 and HCFC-142b from space [Dufour et al, 2005]. The data include measurements both inside and outside the strong Arctic vortex in 2004 [Nassar et al., 2005b] in which we observed a major enhancement of stratospheric NO and NO2 levels in the vortex [Rinsland et al., 2005b]. The large NOx enhancements observed were compared with model simulations to assess the feasibility of their creation by aurorae or solar proton events [Semeniuk et al., 2005].

In two papers, stratospheric chlorine [Nassar et al., 2006a] and stratospheric fluorine [Nassar et al., 2006b] budgets have been found for the February 2004 to January 2005 time period. The partitioning and evolution of chlorine-containing species in the Arctic polar vortex in winter-spring 2004/2005 was investigated using ACE-FTS HCl, ClONO2 and ClO measurements [Dufour et al., 2006]. Satellite data including profiles from ACE-FTS and ACE-MAESTRO were used with a chemical transport model to quantify ozone loss in 2004/2005 Arctic winter [Singleton et al., 2007]. ACE data has also been used in the 2006 World Meterological Organization's Ozone Report.

A description of the ACE-MAESTRO instrument has been published along with performance data and preliminary results [McElroy et al., 2007]. Initial comparisons of ACE-MAESTRO ozone and NO2 to balloon and other satellite data has been done [Kar et al., 2007], and further comparisons are underway as part of the ACE Validation exercise. An independent retrieval of temperature and pressure profiles from the ACE-MAESTRO O2 A- and B-bands has recently been demonstrated [Nowlan et al., 2007].

Measurements taken by the ACE-FTS have increased the number of chemical species retrieved from space: first measurements of upper tropospheric and lower stratospheric methanol profiles have been found within biomass burning plumes [Dufour et al., 2006]. Also, first tropospheric retrievals of C2H4, C3H6O, H2CO and PAN have been done by infrared occultation from space [Coheur et al., 2007]. Discovery of elevated mixing ratios from upper tropospheric CO, C2H6, HCN and C2H2 have been found from biomass burning emissions and transport [Rinsland et al., 2005].

Global distributions have been determined for several chemical species based on ACE-FTS data, namely carbonyl sulfide (OCS) [Barkley et al., 2008; Rinsland et al., 2008], carbon tetrachloride (CCl4) [Allen et al., 2009], formic acid (HCOOH) [Abad et al., 2009], and carbonyl chlorofluoride (COClF) [Fu et al., 2009]. Also, seasonal cycles of upper tropospheric formaldehyde (HCHO) have been observed on a near-global scale [Dufour et al., 2009]. A long-term trend of CH4 in the lower stratosphere has been estimated for the 1985-2008 time period [Rinsland et al., 2009]. The tropical tape recorder effect has been observed in HCN using results from ACE-FTS and MLS [Pumphrey et al., 2008].

Level 2 Version 2.2 + updates has been validated for all the baseline species of the ACE-FTS. Validated species include: O3 [Dupuy et al., 2009]; H2O [Carleer et al., 2008]; CO [Clerbaux et al., 2008]; CH4 [De Mazière et al., 2008]; NO2 & NO [Kerzenmacher et al., 2008]; HCl, HF, CCl3F & CCl2F2 [Mahieu et al., 2008]; N2O [Strong et al., 2008]; HNO3, ClONO2 & N2O5 [Wolff et al., 2008]; temperature & pressure [Sica et al., 2008]. Feasibility of a CO2 retrieval from the ACE-FTS spectra has been investigated [Foucher et al. 2009].

Development is underway for new versions of the Level 2 data for both ACE-FTS and ACE-MAESTRO and these will provide an even better picture of chemical abundances over the current versions. Investigations are being done to determine if stratospheric winds can be retrieved from the ACE-FTS data. Also, research is being done on temperature trends in the middle atmosphere and on pyroconvection and its effects on stratospheric ozone and temperature.