Four‐dimensional variational assimilation of ozone profiles from the Microwave Limb Sounder on the Aura satellite

Abstract

[1] Ozone profiles from the Microwave Limb Sounder (MLS) onboard the Aura satellite of the NASA's Earth Observing System (EOS) were experimentally added to the European Centre for Medium-range Weather Forecasts (ECMWF) four-dimensional variational (4D-var) data assimilation system of version CY30R1, in which total ozone columns from Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY) onboard the Envisat satellite and partial profiles from the Solar Backscatter Ultraviolet (SBUV/2) instrument onboard the NOAA-16 satellite have been operationally assimilated. As shown by results for the autumn of 2005, additional constraints from MLS data significantly improved the agreement of the analyzed ozone fields with independent observations throughout most of the stratosphere, owing to the daily near-global coverage and good vertical resolution of MLS observations. The largest impacts were seen in the middle and lower stratosphere, where model deficiencies could not be effectively corrected by the operational observations without the additional information on the ozone vertical distribution provided by MLS. Even in the upper stratosphere, where ozone concentrations are mainly determined by rapid chemical processes, dense and vertically resolved MLS data helped reduce the biases related to model deficiencies. These improvements resulted in a more realistic and consistent description of spatial and temporal variations in stratospheric ozone, as demonstrated by cases in the dynamically and chemically active regions. However, combined assimilation of the often discrepant ozone observations might lead to underestimation of tropospheric ozone. In addition, model deficiencies induced large biases in the upper stratosphere in the medium-range (5-day) ozone forecasts.

Simultaneous assimilation of satellite NO<sub>2</sub>, O<sub>3</sub>, CO, and HNO<sub>3</sub> data for the analysis of tropospheric chemical composition and emissions

“…the retrieved profile minus the retrieval a-priori). The MLS O 3 data assimilation is very effective in removing the positive O 3 model bias in the UTLS because of its wide and dense coverage and good quality, as similarly shown by Jackson (2007) and Feng et al (2008). The global RMSE against MLS O 3 data is also reduced by TES O 3 data assimilation.…”

On the extraction of wind information from the assimilation of ozone profiles in Météo–France 4-D-Var operational NWP suite

“…This is because it provides more dense spatial coverage with its daily 3500 profiles, between 82 • N and 82 • S, while UARS MLS could only produce up to 1300 every day. In addition, Aura MLS ozone profiles are retrieved with a horizontal resolution of 165 km and a typical vertical resolution of about 2.7 km in the stratosphere (Froidevaux et al, 2006;Jackson, 2007;Stajner et al, 2008;Feng et al, 2008). Although Aura MLS observations contain useful information on ozone concentrations between 316 hPa and 0.1 hPa, only the data between 215.4 and 0.46 hPa are recommended for scientific research.…”

Analysis of a rapid increase of stratospheric ozone during late austral summer 2008 over Kerguelen (49.4° S, 70.3° E)

“…It provides 3500 profiles per day within the ±82 • latitudinal range. Aura/MLS ozone profiles are obtained from measurements of a 240-GHz radiometer and they are retrieved with a horizontal resolution of 165 km and a typical vertical resolution of about 2.7 km in the stratosphere Jackson, 2007;Stajner et al, 2008;Feng et al, 2008). Ozone profiles from Aura/MLS observations are retrieved from 316 hPa to less than 0.01 hPa.…”