Joint NOAA-NASA Development of a Data Assimilation System for Aerosol Reanalysis and Forecasting

Not only are atmospheric aerosols pivotal contributors to air pollution but through impact on atmospheric radiation and clouds they affect weather and climate. Because of complexity of origin and interactions with environment, modeling aerosol concentrations and quantification of their impact on climate and weather remain highly uncertain. Data assimilation constrains these uncertainties by correcting model errors and filling observation voids thus providing an estimate of the aerosol state that is uniform in space and time.

Here, we propose a joint NOAA-NASA partnership to develop a new global aerosol data assimilation system for reanalysis and forecasting. This partnership has a long and fruitful history of collaboration on atmospheric modeling and assimilation and the proposed work is its natural continuation.

The system will rely on the following components: NASA’s extension to Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosol parameterization that includes nitrates; assimilation of multi-channel Aerosol Optical Depth (AOD) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) satellites, and AErosol RObotic NETwork (AERONET) direct sun measurements; new Ensemble Kalman Filter (EnKF) methodology using a chemical model with stochastic perturbations to emissions, chemical backgrounds and parameters/tendencies. Computer codes will build upon those employed operationally at NCEP, starting with the current NEMS GFS Aerosol Component (NGAC) implementation and evolving into a system based on the FV3-GFS version with the enhanced GOCART and the GFS physical parameterizations. Aerosol data assimilation will be based on an extension of the meteorological Ensemble Kalman Filter (EnKF) for aerosols. Software development will be coordinated with the Joint Effort for Data assimilation Integration (JEDI) so that it adheres to the architecture and object oriented framework emerging from this initiative.

The proposed scope of work is as follows:
● Adapt NASA’s aerosol observation processing system and quality control for the
NOAA environment plus contributing interfaces to NOAA specific instruments.

● Develop ensemble perturbation strategies specific for aerosols and evaluate the
quality of the ensemble.

● Deploy a cycled aerosol data assimilation system at NOAA/ESRL/GSD in hindcast
mode.

● Perform a systematic evaluation of this hindcast system against NASA’s MERRA-2, ECMWF’s CAMSiRA (previously MACC), and independent in-situ and satellite observations and produce year-long reanalysis for 2016.

The proposal work addresses MAPP Program objective to develop a new DA-based approach to monitor atmospheric composition. It aims to provide tools to produce global scale aerosol reanalysis to study climate, its change and prediction. By virtue, it addresses NOAA goals to “advance understanding of Earth’s climate system and to foster the application of this knowledge to improve the resilience of our Nation and its partners”.