Quantifying Regional Measurement Requirements for ASCENDS

Author: Marikate Mountain, , Thomas Nehrkorn, Jennifer D. Hegarty, Ryan B. Aschbrenner, John M. Henderson and T. Scott Zaccheo
December 6, 2011
Poster presentation
AGU Fall Meeting 2011

Marikate E. Mountain; Janusz Eluszkiewicz; Thomas Nehrkorn; Jennifer D. Hegarty; Ryan Aschbrenner; John Henderson; Scott Zaccheo (2011) Quantifying Regional Measurement Requirements for ASCENDS. AGU Fall Meeting 2011.

Quantification of greenhouse gas fluxes at regional and local scales is required by the Kyoto protocol and potential follow-up agreements, and their accompanying implementation mechanisms (e.g., cap-and-trade schemes and treaty verification protocols). Dedicated satellite observations, such as those provided by the Greenhouse gases Observing Satellite (GOSAT), the upcoming Orbiting Carbon Observatory (OCO-2), and future active missions, particularly Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) and Advanced Space Carbon and Climate Observation of Planet Earth (A-SCOPE), are poised to play a central role in this endeavor. In order to prepare for the ASCENDS mission, we are applying the Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by meteorological fields from a customized version of the Weather Research and Forecasting (WRF) model to generate surface influence functions for ASCENDS observations. These “footprints” (or adjoint) express the sensitivity of observations to surface fluxes in the upwind source regions and thus enable the computation of a posteriori flux error reductions resulting from the inclusion of satellite observations (taking into account the vertical sensitivity and error characteristics of the latter). The overarching objective of this project is the specification of the measurement requirements for the ASCENDS mission, with a focus on policy-relevant regional scales.

Several features make WRF-STILT an attractive tool for regional analysis of satellite observations: 1) WRF meteorology is available at higher resolution than for global models and is thus more realistic, 2) The Lagrangian approach minimizes numerical diffusion present in Eulerian models, 3) The WRF-STILT coupling has been specifically designed to achieve good mass conservation characteristics, and 4) The receptor-oriented approach offers a relatively straightforward way to compute the adjoint of the transport model. These aspects allow the model to compute surface influences for satellite observations at high spatiotemporal resolution and to generate realistic flux error and flux estimates at policy-relevant scales. The main drawbacks of the Lagrangian approach to satellite simulations are inefficiency and storage requirements, but these obstacles can be overcome by taking advantage of modern computing resources (the current runs are being performed on the NASA Pleiades supercomputer).