A213-0006
Forecasting the 2019/20 NH winter low column ozone with the NASA GEOS model

Wednesday, 16 December 2020
Poster
Lawrence Coy1, K. Emma Knowland2, Christoph Keller3, Krzysztof Wargan4 and Steven Pawson3, (1)Science Systems and Applications, Inc., Lanham, MD, United States, (2)Universities Space Research Association Columbia, Columbia, MD, United States, (3)NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, MD, United States, (4)Goddard Space Flight Center, Greenbelt, MD, United States
Abstract:
Low column ozone associated with a strong polar vortex characterized the 2019/20 NH winter and early spring. With column ozone far below the ozone column climatology, ozone forecasting during 2019/20 required a more sophisticated approach than climate-based tendencies. Here we compare, daily, near-real-time 5-day forecasts from two systems: the GEOS-FP (Goddard Earth Observing System - Forward Processing) and GEOS-CF (Composition Forecast). While GEOS-FP provides climate based ozone tendencies, GEOS-CF base ozone tendencies on a full tropospheric and stratospheric chemical model, GEOS-Chem (v12). Results show that the 5-day forecasted NH polar column ozone vary greatly between the two systems during 2019/20 with the GEOS-CF polar ozone column agreeing more strongly with ozone observation-based analyses. Specifically, during January-May 2020, the GEOS-FP 5-day column ozone forecasts were biased high by over 8 Dobson Units (DU) while the corresponding GEOS-Chem based GEOS-CF forecasts were biased by less than 2 DU. Thus the GEOS-CF system may prove especially useful in situations when vortex containment and chemistry drive stratospheric ozone far from climatology.
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