Low‐ozone pockets observed by EOS‐MLS

Abstract

Earth Observing System (EOS) Microwave Limb Sounder (MLS) observations of ozone are analyzed along with meteorological data from the Met Office using a new automated algorithm to detect low‐ozone pockets (LOPs) in stratospheric anticyclones. The algorithm is illustrated with a case study, and all LOPs identified in over 3 years of MLS data are shown. Daily averaged LOP ozone mixing ratios are 5–30% lower than ozone mixing ratios located directly outside a LOP. In the middle stratosphere, near 50° latitude and the Date Line, large LOPs are identified on over 60% of Northern Hemisphere (NH) winter and 50% of Southern Hemisphere (SH) spring days. This suggests that a LOP is present in the Aleutian and Australian anticyclones nearly all the time during these seasons. Ozone reductions in the heart of the LOPs are typically about 20% (10%) in the NH (SH). Thus the LOP contribution to seasonal ozone loss in the anticyclones is estimated at up to ∼12% in NH winter and ∼5% in SH spring. Average total column ozone loss from individual LOPs is estimated at ∼3–6%.