Sensitivity of calculated odd nitrogen distributions to the diabatic wind fields

Abstract

Two‐dimensional and three‐dimensional model calculations are known to give stratospheric total odd nitrogen (NOy = N + NO + NO2 + 2 × N2O5 + HNO3 + HNO4 + ClONO2) mixing ratios which are significantly smaller than values inferred using measurements obtained from the limb infrared monitor of the stratosphere (LIMS) instrument. We examine NOy distributions calculated with two different advective transport fields, one derived from reported climatological data and one derived from LIMS T, O3, and H2O data. Specifically, it is of interest to see if the use of the advective fields derived from the LIMS data leads to a reconciliation of the inferred and calculated NOy distributions. Calculations with the advective field derived from climatological data show stronger poleward and downward motion in the winter season compared to the advective field derived from LIMS data. This leads to NOy mixing ratios in the lower stratosphere that are about 20% larger in the polar regions of both hemispheres and approximately 40% higher in the equatorial region for climatological transport fields compared to those derived from LIMS data. As a consequence, the NOy distributions calculated in the present model with the LIMS advective field show worse agreement with NOy values inferred from the LIMS measurements than similar results obtained with the climatological wind field. Ozone levels in the lower stratosphere calculated with the climatological wind field are smaller than those computed with the LIMS wind field, which is most likely an indirect chemical effect associated with the larger NOy values.