New Umkehr ozone profile retrieval algorithm optimized for climatological studies

We present a new Umkehr ozone profile retrieval algorithm (UMK04) that has been optimized for the study of monthly mean anomalies (MMA) to assess climate variability in multi‐year time series. Although the Umkehr technique is too noisy to monitor short‐term variability in atmospheric ozone, it is capable of monitoring long‐term changes in MMA with less then 5% uncertainty in the stratosphere, and with no influence from a priori information. By examining the information content of UMK04 we conclude that Umkehr data contain useful information about long‐term ozone trend down to the surface, provided the data are analyzed as column ozone amounts in 8‐layers, consisting of two ∼9.6 km layers in the lower atmosphere (253–1013, 63–253 hPa), five ∼4.8 km layers (32–63, 16–32, 8–16, 4–8, 2–4 hPa) in the stratosphere, plus a broad top layer spanning from 0–4 hPa.