‘HESS-BREZOWSKY’ ATMOSPHERIC CLASSIFICATION TYPES ASSOCIATED WITH NAO AND AO PHASES IN THE NORTHERN PART OF MOLDOVA

Abstract

The North Atlantic Oscillation (NAO) and that Artic (AO), respectively, are by considerable importance to make the short-time weather forecast (until three days), followed by those of middle range and long time (until two weeks). To analyzing the ‘Hess-Brezowsky’ weather patterns associated with the NAO and AO during 19 years (2000 to 2018), has highlighted some aspects over the weather kind in the north part of Moldova. The zonal air-masses’ movements such as northwestern and western, both of them into the anti-cyclonic and cyclonic regime, were deployed in a predominately positive phase of NAO and AO. In the case of NWA type, NAO was 0.17 and AO 0.60, and for WA, NAO was 0.12 and AO 0.71. From NWZ, the NAO shown values around of 0.03 and AO 0.08. Exceptionally, NAO was into a negative phase in the case of WZ, with a value of around -0.13. Instead, for WZ, the AO was positive, with a yearly average of 0.08. Such air-masses movements are associated with a mild weather pattern, especially during the wintertime. Then, over the southern part of Europe, it’s set up the ‘Omega’ ridge. In doing so, the amounts of the precipitations are low at the studied area’s level. By a more significant interest is the southwesterly air-masses movement into a cyclonic regime (SWZ) who shown values of NAO of -0.16 and 00.26 for AO. Also, negative values for NAO were in the case of TRM (Trough over Central Europe), with -0.04 and HNFZ (High over Scandinavia-Iceland, Trough over Central Europe), with -0.64. For the same synoptically contexts (TRM and HNFZ), the AO was of -0.23, respectively, -1.31. Associated with the negative phases of NAO and AO, the planetary waves have shown an undulatory tendency. In such a case, there are development areas with extreme weather. For the studied region, the negative phases of NAO and AO were associated with severe weather events, such as blizzards, storms, and floods.