Characteristics of the ozone decline in the Northern polar and middle latitudes during the winter-spring

The total ozone decline during the past twenty years, especially strong dur ing the winter-spring season poleward from 50 degrees N, is well establishe d with known average trends of 5-7% per decade. This study presents a numbe r of additional characteristics such as ozone-mass deficiency (O3MD) from t he pre-1976 base average, and anal extent with negative deviations greater than similar to 2 and similar to 3 sigma. Gridded satellite data, combined with ground-based total ozone maps, permit calculations of daily and region al ozone deficiencies from the anthropogenically undisturbed average ozone levels of the 1960s and early 1970s. Then the quantity of the O3MD and the changes in surface area, with deficiencies larger than -10 and -15% are int egrated for the 1 January to 15 April period for each of the last 20 years, and compared. In addition, the polar vortex extent during the last 10 year s is determined using the PV at 475 degrees K. The quantity of the O3MD wit hin the sunlit part of the vortex is shown to contribute from similar to 15 to 35% of the overall ozone deficiency within the -10% contours over the a rea 35-90 degrees N. The ozone deficiency, integrated for the first 105 day s of each year, has increased dramatically from similar to 2,800Mt in the e arly 1980s to similar to 7,800Mt in the 1990s, exceeded 12,000 Mt in the wi nter-springs of 1993 and 1995. The latter quantity is comparable with the a verage O3MD over the same Southern latitudes in the last ten austral spring s. During the 1990s over the 35-90 degrees latitudes the average ozone defi ciency in the Southern hemisphere belt is less than over the Northern hemis phere belt by similar to 40%. It is known that the main ozone decline is ob served in the lower stratosphere and the ozone loss over the Arctic is very sensitive to decreasing stratospheric temperatures; negative 50 hPa monthl y anomalies greater than 4 degrees C have occurred during 7 of the springs in the last decade, thus possibly facilitating doubling the area with negat ive ozone deviations greater than -10% in the 1990s to similar to 5,000.10( 6)km(2), and nearly tripling the O3MD as stated above. The changes in total eddy heat fluxes as a proxy indicator of the longwave perturbations are po sitively correlated with the ozone deficiency in the 45-75 degrees N. The s trong anticorrelation between the ozone deficiency in the region >55 degree s N versus the 35-50 degrees N belt is discussed in relation to possible tr ansport of air masses with low ozone from the sub-tropics, which in some ye ars are the dominant reason for the observed ozone deficiency.