Speaker
Description
NASA’s Global Modeling and Assimilation Office is producing a new reanalysis of stratospheric composition by assimilating water vapor, hydrogen chloride, nitric acid, nitrous oxide, and ozone profiles from Aura Microwave Limb Sounder (MLS). Named M2-SCREAM (MERRA-2 Stratospheric Composition Reanalysis of Aura MLS), this product covers the period between late 2004 and the present. Global three-dimensional fields of the assimilated species alongside winds, temperature, geopotential height and potential vorticity are provided at a three-hourly frequency and 50-km horizontal resolution. The vertical resolution in the stratosphere ranges between 1 and 2 km. The reanalysis output agrees well with independent data owing to the assimilation of high-quality vertically resolved MLS observations. The high frequency and resolution of the M2-SCREAM fields as well as the length of the record afford an opportunity to use the reanalysis in detailed studies of constituent transport and chemistry at a broad range of spatial and temporal scales. In this presentation we will briefly discuss preliminary analyses of several rare and extreme events observed in the stratosphere in recent years: water vapor plume from the eruption of Hunga Tonga – Hunga Ha’apai, chemical and dynamical perturbation of the Southern Hemisphere stratosphere from pyrocumulonimbus injections following Australian wildfires of 2019/2020, and tracer transport during the exceptional Arctic winter of 2019/2020. In all cases we will highlight the utility of the reanalysis for these studies and the importance of global limb data from MLS in providing rich spatiotemporal information in the reanalysis tracer fields. We will also discuss challenges that extreme events pose for data assimilation and for the use of limb observations in general.
