Low Frequency Variation Of 10-30d Air Temperature And Its Relationship With The Ural Mountain Circulation And Low Latitude Area Convection In Winter In China

Abstract:In this paper, winter daily air temperature data of National Climate Center and the NCEP / NCAR global reanalysis data,the non-filtering method was applied to extract the low-frequency signals of 10-30 days from the air temperature and atmospheric circulation.The low-frequency air temperature in China from 1979 to 2011 during Feb and Jan and associated atmospheric circulations are analyzed,focusing on the influence of the Ural mountain circulation on the low frequency air temperature in winter in China.The results showed that: (1) The first mode of the national low-frequency air temperature shows the spatial distribution pattern of most of the cold (warm) in the whole country. The contribution of low frequency variance accounts for over 30% of the typical annual temperature of 10-30d. (2) The North Atlantic to the polar regions,the Ural Mountains and Lake Baikal have a significant correlation with the winter temperature anomalies in China. When the polar vortex is weak and the NAO is abnormal in the North Atlantic, the high pressure ridge in the Ural Mountains is stronger and the Baikal Lake is negative anomaly,which is favorable to the cold high pressure near the lake Baikal, which makes the winter temperature of China cold; (3) The low-frequency temperature is closely related to the Ural mountain circulation from December to February, and the relationship between them is the best when the circulation anomaly is about 15 days ahead of the Ural Mountains. The enhancement of the Ural mountain circulation is favorable to the high pressure ridge of the Ural Mountains and the high pressure of Siberia. The winter monsoon intensity of the Ural Mountains is strengthened,leading to low winter temperatures in China. (4) EOF analysis was carried out on the day-to-day long-wave radiation field from 12 to 2 months in winter. The anomalous anomalies near the equator of the Atlantic are positive anomalies, showing positive and negative positive signs. There are low frequency oscillations in the OLR of the Atlantic low latitudes. (5) The typical annual Atlantic jet is stronger than the average year and northerly. The turbulence of the Atlantic high-level jet through its south-facing shear vorticity and the convergence of the front of the rapid-flow exit area, the anomalous wave train to affect the Ural mountain area circulation anomaly and China's winter temperature. By Rossby wave source analysis, it is further confirmed that the jet anomaly can excite the anomalous wave source and propagate downstream, thus affecting the circulation anomaly in the Ural mountain area. (6) When the Atlantic Ocean low latitude OLR anomalies, the convection is unusually strong (suppressing)the Atlantic jet location northerly northerly (position west to south), causing vorticity,divergence anomaly, from the jet south, the exit front to the Ural mountain to stimulate +-+ (-+-), the strong easing of the East Asian winter monsoon (weak) and the intensification of the Siberian high pressure (weak), which may eventually lead to the winter of China. The temperature is low (high).