Record low ozone at Mauna Loa observatory during winter 1994-1995: A consequence of chemical and dynamical synergism?

During two days in late December 1994, total ozone measured at the Mauna Loa Observatory on the island of Hawaii, dropped below 200 Dobson Units (DU) for the first time since ozone measurements began at this site over 30 years ago. Total ozone values this low have not previously occurred over populated areas except on rare occasions when the edges of the springtime Antarctic ozone hole temporarily pass over the southern tip of Argentina. The monthly total ozone average for January 1995 was 216 DU, about 14 % below the 1964-1981 baseline value. Ultraviolet radiation measured at Mauna Loa on clear days during this period increased inversely with ozone as expected, more than tripling in relative intensity at 295 MI. The normal annual minimum in total ozone occurs in winter at Mauna Loa; however, some winters experience considerably lower values than others. This was the case during the winter of 1994-1995. Although the general decline in global ozone, which began about 1980 and also appears in the Mauna Loa record, may he related to chemical ozone depletion, the unusually low values during some winters at Mauna Loa appear to be related to ozone transport from the tropics, and the timing of phase transitions of the QBO. This analysis provides an accurate method of forecasting low-ozone, high-UV winters in Hawaii.