Measurements of Pollution in the Troposphere
Merritt Deeter (Project Leader)
John Gille (MOPITT Principal Investigator)
Shu-Peng (Ben) Ho
MOPITT Operational Production of Carbon Monoxide Data
The daily operational processing of Measurement Of Pollution In The Troposphere (MOPITT) instrument raw counts into the final retrieved geophysical products, delivery of products to NASA for free public access, and user education and support, constitutes a major service to the scientific community. MOPITT is also unique in providing the community with the longest continuous validated global CO data product. Scientific results have been presented worldwide at numerous scientific meetings and show a documented strong presence on the Internet. MOPITT data distribution, publications, literature citations, and conference presentations are all showing strong upward trends, indicating mounting demand and scientific interest.
Development of new data processing software for the next product release, 'Version 4,' has just been completed. Major features of the new retrieval algorithm include: (1) a new forward model with improved description of the MOPITT gas correlation cells and applicability to a wider range of CO mixing ratios; (2) a new description of the retrieval a priori surface emissivity; (3) a new seasonally and geographically variable CO retrieval a priori; and (4) the use of an assumed log-normal variability for CO volume mixing ratio. The new product also includes more extensive diagnostics, including the retrieval averaging kernels.
Activities during FY08
Algorithm Development and Product Evaluation
The development of a substantially improved retrieval algorithm for processing the next major MOPITT data product ('Version 4') was recently finalized. Associated activities completed in FY08 included (1) enhancement of the operational radiative transfer model to reflect actual in-orbit instrumental parameters and to better handle extremely polluted atmospheres and (2) determination of appropriate radiance bias correction factors. Product evaluation activities included analysis of V4 results at validation sites where aircraft in-situ profiles and surface measurements are available throughout the mission (since 2000). Overall, validation results indicate very small retrieval biases at all levels and demonstrate significantly weaker long-term drift than was observed in the current MOPITT Version 3 Product.
Long-term goals for the MOPITT Team include the incorporation of MOPITT's near-infrared measurements (i.e., 'solar channels') to provide additional information with respect to the CO total column measurement. Neither the current MOPITT Version 3 product nor the upcoming Version 4 products exploit these measurements because of challenges in understanding apparent instrument noise specific to these channels. During FY08, however, MOPITT retrievals based on these measurements were demonstrated for the first time, and clearly indicate the promise of combined thermal-infrared/near-infrared (TIR/NIR) CO retrievals for future products. Figure 1 presents global monthly-mean CO total column retrievals based solely on MOPITT NIR measurements during March, 2006. Regions of biomass burning in Equatorial Africa as well as anthropogenic emissions in China (principally from fossil fuel burning) are both clearly evident in the figure. Compared to current retrievals based purely on TIR measurements, the new NIR retrieval product is more sensitive to CO in the boundary layer and therefore should be much more capable of identifying sources at the surface.
Reference: "CO retrievals based on MOPITT near-infrared observations," by M. N. Deeter, D. P. Edwards, J. C. Gille, and James R. Drummond, submitted to J. Geophys. Res.
Field Campaign Support
The NCAR MOPITT Team produced and provided near real-time imagery and CO data products to support the ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) field campaign during Spring and Summer phases in FY08. Analyses of these data are ongoing.
Plans for FY09
Production and Release of V4
Operational processing of the MOPITT Version 4 product will begin in early FY09. The acquisition of new linux servers should allow processing of the entire MOPITT mission within several months, however the prerequisite task of porting all of the associated software to the new hardware may itself take several months. This process has begun. In preparation for the release of the new product, a new User's Guide is being drafted. Also, as the official release date approaches (possibly around the end of 2008), the new product will be publicized within the community. This effort will include a presentation at the Fall AGU meeting.
Version 5 Development
As operational processing of the Version 4 product becomes routine, initial steps to define and develop the Version 5 product will begin. While preliminary, current objectives for V5 development include the incorporation of MOPITT's solar channels and an evaluation of alternative sources for meteorological data.
Continued Analysis of Operational MOPITT Products
The MOPITT Science Team will continue to evaluate operational products both in the context of traditional validation (e.g., using available in-situ data from aircraft and ground-based spectroscopic measurements) and in comparison to models.