The review is compiled based on the results of the operation of the total ozone (TO) monitoring system in the CIS and Baltic countries, functioning in the operational regime at the Central Aerological Observatory (CAO). The monitoring system uses the data from the national network of filter ozonometers, M-124 type under supervision of the Main Geophysical Observatory (MGO). The proper operation of the entire system is under an operational control from observations with the OMI satellite equipment (US NASA). Basic TO observation data for each month of the fourth quarter of 2009 and for the quarter and the year as a whole are generalized. The data on the development of the Spring Antarctic Ozone Anomaly are presented. The results of regular observations of the surface ozone in the Moscow region and in Kiev are considered.The basic results of observations for 1st to 3rd quarters of 2009 were described earlier [1-3]. When compiling the maps, the TO observation data at the Kiev network station, permanently overestimated throughout the year compared to the general TO field (built on the data from other stations and also from the OMI satellite equipment) were replaced by the data from the UkrNIGMI station, 30 km away from it. The difference of annual mean TO values between these two stations in 2009 amounted to 21 DU. The observation data from the Lvov, Odessa, Ashkhabad, Chardzhou, Aral Sea, Khanty-Mansisk, and Vladivostok stations were not used in the TO field analysis because of their low quality.In the fourth quarter of 2009, over the entire territory under control, the quarterly mean TO values were mainly close to multiyear mean values for the 1974-1984 period (Fig. 1a). Of exception were Nikolaevsk-on-Amur, where the quarterly mean TO value abnormally exceeded the multiyear mean and amounted to 9% or 3.2 SD, and the Tura and Guryev stations, where anomalous deficiencies of the quarterly mean TO values were observed: 12 and 9% or 3.3 and 4.0 SD, respectively. The least quarterly mean TO values of 254-265 DU were observed over the northern Russian regions. The maximum TO values were observed over the Okhotsk Sea coast, Sakhalin, Kamchatka, and Chuckchi Peninsula and amounted to 350-404 DU. The quarterly mean TO values over the rest of the territory under control were 265-350 DU.The table contains the data on anomalous deviations from normal of daily TO values, which were recorded at the ozonometric network stations in the fourth quarter of 2009.In October 2009, monthly mean TO values over most of the territory under control were close to multiyear means (Fig. 1b). They were 260-320 DU over most of the territory, and 320-365 DU over the Far East, Sakhalin, Chuckchi Peninsula, and Kamchatka. The anomalous deficiency of the monthly mean TO value was recorded at the Guryev station: it was 12% or 3.3 SD. The norm was maximally exceeded at the Yekaterinburg station (8% or 1.9 SD).In November, monthly mean TO values were also close to multiyear means over most of the territory under control (Fig. 1c). The reduced TO values...
