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Richard B. Rood, Dale J. Allen, Wayman E. Baker, David J. Lamich, and Jack A. Kaye

Abstract

Analysis of atmospheric data by assimilation of height and wind measurements into a general circulation model is routine in tropospheric analysis and numerical weather prediction. A stratospheric assimilation system has been developed at NASA/Goddard Space Flight Center. This unique system generates wind data that is consistent with the geopotential height (and temperature) field and the primitive equations in the general circulation model. These wind fields should offer a significant improvement over the geostrophic analysis normally used in the stratosphere.

This paper reports the first known calculations to use data from an assimilation to calculate constituent transport in the stratosphere. Nitric acid (NHO3) during the LIMS period is studied. While there are still significant discrepancies between the calculated and observed HNO3, there are some remarkable successes. Particularly, the high-latitude time variance of the HNO3 is accurately captured. These studies suggest that data from an assimilation process offers tremendous potential for studying stratospheric dynamics, constituent transport, and chemistry.

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Stephen D. Steenrod, Richard B. Rood, David J. Lamich, Joan E. Rosenfield, and Ravi C. Govindaraju

Abstract

Using a stratospheric-tropospheric data assimilation system, referred to as STRATAN, a minor sudden stratospheric warming that occurred in January 1989 is investigated. The event had a maximum influence on the stratospheric circulation near 2 hPa. The zonal mean circulation reversed briefly in the polar region as the temperature increased 34 K in 3 days. The cause of the warming is shown to be the rapid development and subsequent movement of a warm anomaly, which initially developed in the midlatitudes. The development of the warm anomaly is caused by adiabatic descent, and the dissipation by radiative cooling. A brief comparison with the NMC analysis and temperature sounding data is also presented.

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