The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina winters.In 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spr...The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina winters.In 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spring and is predicted to reach its mature phase in December 2022.Under such a significant global climate signal,whether the Eurasian Continent will experience a tough cold winter should not be assumed,despite the direct influence of mid-to high-latitude,large-scale atmospheric circulations upon frequent Eurasian cold extremes,whose teleconnection physically operates by favoring Arctic air invasions into Eurasia as a consequence of the reduction of the meridional background temperature gradient in the NH.In the 2022/23 winter,as indicated by the seasonal predictions from various climate models and statistical approaches developed at the Institute of Atmospheric Physics,abnormal warming will very likely cover most parts of Europe under the control of the North Atlantic Oscillation and the anomalous anticyclone near the Ural Mountains,despite the cooling effects of La Nina.At the same time,the possibility of frequent cold conditions in mid-latitude Asia is also recognized for this upcoming winter,in accordance with the tendency for cold air invasions to be triggered by the synergistic effect of a warm Arctic and a cold tropical Pacific on the hemispheric scale.However,how the future climate will evolve in the 2022/23 winter is still subject to some uncertainty,mostly in terms of unpredictable internal atmospheric variability.Consequently,the status of the mid-to high-latitude atmospheric circulation should be timely updated by medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction for the necessary date information and early warnings.展开更多
通过对近百年 El Nino/ L a Nina事件与北京气候相关性研究发现 ,El Nino/ L aNina事件与北京夏季 ( 6～ 8月 )降水、平均最高气温 ( 7月 )和冬季 ( 1月 )平均最低气温之间相互关系显著。 El Nino事件与夏季降水、冬季平均最低气温呈负...通过对近百年 El Nino/ L a Nina事件与北京气候相关性研究发现 ,El Nino/ L aNina事件与北京夏季 ( 6～ 8月 )降水、平均最高气温 ( 7月 )和冬季 ( 1月 )平均最低气温之间相互关系显著。 El Nino事件与夏季降水、冬季平均最低气温呈负相关 ,与夏季平均最高气温呈正相关 ,造成降水减少 ,气温年较差增大 ,大陆性增强的气候特点。L a Nina事件与夏季降水、冬季平均最低气温呈正相关 ,与夏季平均最高气温呈负相关 ,使降水增加 ,气温年较差减小 。展开更多
Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-...Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone(WNPC), which can in turn be attributed to the different sea surface temperature anomaly(SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance.SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Ni?a events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.展开更多
The curved surface of the maximum sea temperature anomaly (MSTA) was created from the JEDAC subsurface sea temperature anomaly data at the tropical Pacific between 1955 and 2000. It is quite similar to the depth distr...The curved surface of the maximum sea temperature anomaly (MSTA) was created from the JEDAC subsurface sea temperature anomaly data at the tropical Pacific between 1955 and 2000. It is quite similar to the depth distribution of the 20℃ isotherm, which is usually the replacement of thermocline. From the distribution and moving trajectory of positive or negative sea temperature anomalies (STA) on the curved surface we analyzed all the El Nino and La Nina events since the later 1960s. Based on the analyses we found that, using the subsurface warm pool as the beginning point, the warm or cold signal propagates initially eastward and upward along the equatorial curved surface of MSTA to the eastern Pacific and stays there several months and then to (urn north, usually moving westward near 10°N to western Pacific and finally propagates southward to return to warm pool to form an off-equator closed circuit. It takes about 2 to 4 years for the temperature anomaly to move around the cycle. If the STA of warm (cold) water is strong enough, there will be two successive El Nino (La Nina) events during the period of 2 to 4 years. Sometime, it becomes weak in motion due to the unsuitable oceanic or atmospheric condition. This kind process may not be considered as an El Nino ( La Nina) event, but the moving trajectory of warm (cold) water can still be recognized. Because of the alternate between warm and cold water around the circuits, the positive (negative) anomaly signal in equatorial western Pacific coexists with negative (positive) anomaly signal near 10°N in eastern Pacific before the outbreak of El Nino (La Nina) event. The signals move in the opposite directions. So it appears as El Nino (La Nina) in equator at 2-4 years intervals. The paper also analyzed several exceptional cases and discussed the effect and importance of oceanic circulation in the evolution of El Nino/ La Nina event.展开更多
基金supported by the Key Research Program of Frontier Sciences,CAS(Grant No.ZDBS-LY-DQC010)the National Natural Science Foundation of China(Grant No.42175045)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB42000000)。
文摘The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina winters.In 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spring and is predicted to reach its mature phase in December 2022.Under such a significant global climate signal,whether the Eurasian Continent will experience a tough cold winter should not be assumed,despite the direct influence of mid-to high-latitude,large-scale atmospheric circulations upon frequent Eurasian cold extremes,whose teleconnection physically operates by favoring Arctic air invasions into Eurasia as a consequence of the reduction of the meridional background temperature gradient in the NH.In the 2022/23 winter,as indicated by the seasonal predictions from various climate models and statistical approaches developed at the Institute of Atmospheric Physics,abnormal warming will very likely cover most parts of Europe under the control of the North Atlantic Oscillation and the anomalous anticyclone near the Ural Mountains,despite the cooling effects of La Nina.At the same time,the possibility of frequent cold conditions in mid-latitude Asia is also recognized for this upcoming winter,in accordance with the tendency for cold air invasions to be triggered by the synergistic effect of a warm Arctic and a cold tropical Pacific on the hemispheric scale.However,how the future climate will evolve in the 2022/23 winter is still subject to some uncertainty,mostly in terms of unpredictable internal atmospheric variability.Consequently,the status of the mid-to high-latitude atmospheric circulation should be timely updated by medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction for the necessary date information and early warnings.
基金The National Natural Science Foundation of China under contract Nos 41576029, 41976221 and 42030410the National Key Research and Development Program of China under contract No. 2019YFA0606702the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology。
文摘Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone(WNPC), which can in turn be attributed to the different sea surface temperature anomaly(SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance.SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Ni?a events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.
基金This work was supported by the National Natural Science Foundation of China under Grant No.40126002.
文摘The curved surface of the maximum sea temperature anomaly (MSTA) was created from the JEDAC subsurface sea temperature anomaly data at the tropical Pacific between 1955 and 2000. It is quite similar to the depth distribution of the 20℃ isotherm, which is usually the replacement of thermocline. From the distribution and moving trajectory of positive or negative sea temperature anomalies (STA) on the curved surface we analyzed all the El Nino and La Nina events since the later 1960s. Based on the analyses we found that, using the subsurface warm pool as the beginning point, the warm or cold signal propagates initially eastward and upward along the equatorial curved surface of MSTA to the eastern Pacific and stays there several months and then to (urn north, usually moving westward near 10°N to western Pacific and finally propagates southward to return to warm pool to form an off-equator closed circuit. It takes about 2 to 4 years for the temperature anomaly to move around the cycle. If the STA of warm (cold) water is strong enough, there will be two successive El Nino (La Nina) events during the period of 2 to 4 years. Sometime, it becomes weak in motion due to the unsuitable oceanic or atmospheric condition. This kind process may not be considered as an El Nino ( La Nina) event, but the moving trajectory of warm (cold) water can still be recognized. Because of the alternate between warm and cold water around the circuits, the positive (negative) anomaly signal in equatorial western Pacific coexists with negative (positive) anomaly signal near 10°N in eastern Pacific before the outbreak of El Nino (La Nina) event. The signals move in the opposite directions. So it appears as El Nino (La Nina) in equator at 2-4 years intervals. The paper also analyzed several exceptional cases and discussed the effect and importance of oceanic circulation in the evolution of El Nino/ La Nina event.
