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A quantitative analysis on the relationship between atmospheric waves andpolar stratospheric clouds (PSCs) in the 2008 austral winter and the2007/2008 boreal winter is made using CALIPSO, COSMIC and Aura MLSobservation data and reanalysis data. A longitude-time section of thefrequency of PSC occurrence in the Southern Hemisphere indicates that PSCfrequency is not regionally uniform and that high PSC frequency regionspropagate eastward at different speeds from the background zonal wind. Thesefeatures suggest a significant influence of atmospheric waves on PSCbehavior. Next, three temperature thresholds for PSC existence arecalculated using HNO3 and H2O mixing ratios. Among the three, theTSTS (a threshold for super cooled ternary solution)-based estimates ofPSC frequency accord best with the observations in terms of the amount,spatial and temporal variation, in particular, for the latitude ranges of55° S–70° S and 55° N–85° N. Moreover, the effects of planetarywaves, synoptic-scale waves and gravity waves on PSC areal extent areseparately examined using the TSTS-based PSC estimates. The latituderange of 55° S–70° S is analyzed because the TSTS-based estimatesare not consistent with observations at higher latitudes (<75° S)above 18 km, and PSCs in lower latitudes are more important to the ozonedepletion because of the earlier arrival of solar radiation in spring. It isshown that nearly 100% of PSCs between 55° S and 70° S at altitudesof 16–24 km are formed by temperature modulation, which is influenced byplanetary waves during winter. Although the effects of synoptic-scale waveson PSCs are limited, around an altitude of 12 km more than 60% of thetotal PSC areal extent is formed by synoptic-scale waves. The effects ofgravity waves on PSC areal extent are not large in the latitude range of55° S–70° S. However, at higher latitudes, gravity waves act toincrease PSC areal extent at an altitude of 15 km by about 30% inSeptember. Similar analyses are performed for the Northern Hemisphere. It isshown that almost all PSCs observed in the Northern Hemisphere areattributable to low temperature anomalies associated with planetary waves

The effects of atmospheric waves on the amounts of polar stratospheric clouds