Abstract
Abstract. The 2008 Antarctic ozone hole was one of the largest and most long-lived in recent years. Predictions of the ozone hole were made in near-real time (NRT) and hindcast mode with the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The forecasts were carried out both with and without assimilation of satellite observations from multiple instruments to provide more realistic initial conditions. Three different chemistry schemes were applied for the description of stratospheric ozone chemistry: (i) a linearization of the ozone chemistry, (ii) the stratospheric chemical mechanism of the Model of Ozone and Related Chemical Tracers, version 3, (MOZART-3) and (iii) the relaxation to climatology as implemented in the Transport Model, version 5, (TM5). The IFS uses the latter two schemes by means of a two-way coupled system. Without assimilation, the forecasts showed model-specific shortcomings in predicting start time, extent and duration of the ozone hole. The assimilation of satellite observations from the Microwave Limb Sounder (MLS), the Ozone Monitoring Instrument (OMI), the Solar Backscattering Ultraviolet radiometer (SBUV-2) and the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) led to a significant improvement of the forecasts when compared with total columns and vertical profiles from ozone sondes. The combined assimilation of observations from multiple instruments helped to overcome limitations of the ultraviolet (UV) sensors at low solar elevation over Antarctica. The assimilation of data from MLS was crucial to obtain a good agreement with the observed ozone profiles both in the polar stratosphere and troposphere. The ozone analyses by the three model configurations were very similar despite the different underlying chemistry schemes. Using ozone analyses as initial conditions had a very beneficial but variable effect on the predictability of the ozone hole over 15 days. The initialized forecasts with the MOZART-3 chemistry produced the best predictions of the increasing ozone hole whereas the linear scheme showed the best results during the ozonehole closure.
Highlights
The paper presents forecasts of the ozone hole over Antarctica in 2008, which were made with and without assimilation of ozone retrieval products from multiple sensors to provide ozone initial conditions, and which used different chemistry schemes of varying complexity.The ozone hole in 2008 was large and long-lasting
The Integrated Forecast System (IFS) used (i) a linearized scheme, which is a further development of the scheme by Cariolle and Deque (1986), (ii) a full chemistry scheme implemented in the Chemical Transport Model (CTM) MOZART-3 and (iii) a climatological approach, which is the relaxation to the ozone climatology as implemented in the CTM TM5
The focus was put on the impact of three different ways to describe stratospheric ozone chemistry and on the characteristics of satellite observations from Microwave Limb Sounder (MLS), Ozone Monitoring Instrument (OMI), SCIAMACHY and SBUV-2 in the region of interest
Summary
The paper presents forecasts of the ozone hole over Antarctica in 2008, which were made with and without assimilation of ozone retrieval products from multiple sensors to provide ozone initial conditions, and which used different chemistry schemes of varying complexity. In addition to evaluating the quality of the ozone assimilation and chemistry, this paper investigates the time span over which the initialization with ozone analyses improves the forecast for each chemical scheme. This “chemical predictability” of ozone has to be distinguished from the “meteorological predictability” of the underlying dynamical processes. While the dynamical processes determine the spatial patterns of the ozone fields, the biases of the simulated ozone concentrations are caused by the accumulation of chemical biases and of biases due to errors in the resolved-scale and sub-scale transport processes (van Noije et al, 2004; Rind et al, 2007) If these biases are corrected by using ozone analyses as initial conditions, the effect might be longlasting because of the long-lasting impact of ozone anomalies mentioned above.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
