ON SHORT-TERM TOTAL-COLUMN-OZONE-FORECAST ERRORS

The accuracy of short-term. predicted total-column ozone amount, Omega , is reported to be 10-12 DU or about 3-4%. This result was achieved b y several authors independently using linear multiple regressions with different predictors. The operational procedure of the German Weather Service to predict Omega uses as predictors the ozone amount of the p receding day and temperatures at some pressure levels at the forecast day. The previous day ozone is the most informative predictor. It expl ains 30-55% of the variance. The reduction of variance, achieved total ly, varied from 64-83% with maximum values in spring (March-May) and m inimum values in November. Forecast errors of the predictors have in g eneral no substantial impact on the Omega forecast. On average, an err or of 1 K in T-55 = T-50(i) - T-500(i) causes an error of 3 DU in ozon e prediction. An error of 1 DU in Omega (i - 1) results in 0.3-0.6 DU forecast errors. The replacement of Omega (i - 1) by the climatologica l ozone amount is thus generally not critical. Errors in T-55(i) and ( T-200(i)-T-200(i - 1)) have about 8 and 4 times more weight, respectiv ely, than errors in Omega of the preceding day, when the parameters ar e related to K and DU. The limit of 20 DU maximum deviation, found for Omega forecast and diagnosis, is exceeded only for large errors of th e predictors, e.g. more than 5 K for T-55 and 7 K for T-200. Copyright (C) 1996 Elsevier Science Ltd