The Scandinavian(SCA)pattern is an important climate signal in regulating the variability of summer extreme precipitation(SEP)over the eastern slopes of the Tibetan Plateau(ESTP).There is a strong negative correlation...The Scandinavian(SCA)pattern is an important climate signal in regulating the variability of summer extreme precipitation(SEP)over the eastern slopes of the Tibetan Plateau(ESTP).There is a strong negative correlation between the SCA pattern and SEP over the ESTP,with a correlation coefficient of-0.57.Moisture budget analysis showed that the dynamic component anomalies of both the zonal and vertical moisture advection induced by the SCA pattern play the dominant roles in extreme precipitation variability over the ESTP.These anomalies are solely linked to variations in zonal wind and vertical velocity.The anomalies of the SCA pattern propagate downstream through Rossby waves,leading to the formation of cyclonic circulations over northern East Asia and the Iranian Plateau.The westerlies on the southern side of these cyclonic circulations play a crucial role in influencing the development of significant anomalous westerlies over the ESTP.The anomalous westerlies bring climatologically moist air from the Tibetan Plateau(TP)to the ESTP,resulting in positive zonal moisture advection anomalies over the area.Furthermore,these anomalous westerlies transport climatologically warm air from the TP to the ESTP,leading to significant warm advection anomalies and vertical upward motion anomalies over the ESTP.The upward motion carries lower-tropospheric moisture upward,resulting in positive vertical moisture advection anomalies over the ESTP.The combination of these positive zonal and vertical moisture advection anomalies eventually leads to excessive SEP.展开更多
The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are exp...The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are explored based on daily meteorological data contained in the Daily Surface Climate Dataset for China (V3.0) during the period 1960–2012. Results show that winter snowfall in the YHRB exhibits consistent anomalies over the whole region for the interannual variation during 1960–2012. Further analysis suggests that winter snowfall anomalies in the YHRB are closely linked to the anomalous wintertime SCAND activity. When there is more winter snowfall in the YHRB, SCAND is usually in a positive phase, accompanied by a strengthened Urals blocking high and East Asian trough, which is conducive to strengthened cold-air activity, intensified vertical motions, and more water vapor transport in the YHRB. In contrast, less winter snowfall in the YHRB usually happens in the negative phase of SCAND. Our results provide useful information to better understand the relevant mechanism responsible for anomalous winter snowfall in this area.展开更多
Understanding the interannual variability of wintertime marine cold air outbreak(MCAO)frequency is essential,as such events play a key role in shaping air-sea interactions,driving deep ocean convection,and influencing...Understanding the interannual variability of wintertime marine cold air outbreak(MCAO)frequency is essential,as such events play a key role in shaping air-sea interactions,driving deep ocean convection,and influencing regional climate variability.This study analyzes the two leading modes of the wintertime MCAO variability over the high latitudes of the North Atlantic on interannual timescales and their relation to large-scale teleconnection patterns and the oceanic mixed layer depth(MLD).The first mode is a meridional dipole pattern,reflecting the out-of-phase variations of the MCAO frequency between the northwestern and the subtropical North Atlantic.It is strongly tied to the seasonal mean North Atlantic Oscillation/Arctic Oscillation and the associated zonal temperature advection at around55°N from northeastern Canada towards the North Atlantic.The second mode is a zonal dipole pattern,reflecting the out-of-phase variations of the MCAO frequency between the Nordic Seas and the western North Atlantic,and is strongly tied to the Scandinavian pattern and the associated meridional temperature advection from the Arctic via Fram Strait.Though these associations are observed between the seasonal MCAO frequency and the seasonal mean teleconnection patterns,they also feature a good relationship on the daily timescale.This establishes a bridge between the annual frequency of synoptic MCAO events and the seasonal mean circulation and teleconnections.Both modes are associated with significant oceanic heat loss,lowering the SST.Accordingly,the positive phase of the EOF1 mode corresponds to a local deepening of the mixed layer over southern Greenland.In contrast,the positive phase of the EOF2 mode not only causes a deepening of the mixed layer in the Nordic Seas but also affects the depth of the mixed layer over southern Greenland through transport by oceanic currents.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U20A2097,U2442210 and 42175042)Natural Science Foundation of Sichuan Province(Grant No.2024NSFTD0017)。
文摘The Scandinavian(SCA)pattern is an important climate signal in regulating the variability of summer extreme precipitation(SEP)over the eastern slopes of the Tibetan Plateau(ESTP).There is a strong negative correlation between the SCA pattern and SEP over the ESTP,with a correlation coefficient of-0.57.Moisture budget analysis showed that the dynamic component anomalies of both the zonal and vertical moisture advection induced by the SCA pattern play the dominant roles in extreme precipitation variability over the ESTP.These anomalies are solely linked to variations in zonal wind and vertical velocity.The anomalies of the SCA pattern propagate downstream through Rossby waves,leading to the formation of cyclonic circulations over northern East Asia and the Iranian Plateau.The westerlies on the southern side of these cyclonic circulations play a crucial role in influencing the development of significant anomalous westerlies over the ESTP.The anomalous westerlies bring climatologically moist air from the Tibetan Plateau(TP)to the ESTP,resulting in positive zonal moisture advection anomalies over the area.Furthermore,these anomalous westerlies transport climatologically warm air from the TP to the ESTP,leading to significant warm advection anomalies and vertical upward motion anomalies over the ESTP.The upward motion carries lower-tropospheric moisture upward,resulting in positive vertical moisture advection anomalies over the ESTP.The combination of these positive zonal and vertical moisture advection anomalies eventually leads to excessive SEP.
基金jointly supported by jointly supported by the National Key Research and Development Program of China(Grant No.2016YFA0600702)the National Natural Science Foundation of China(Grant No.41625019)
文摘The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are explored based on daily meteorological data contained in the Daily Surface Climate Dataset for China (V3.0) during the period 1960–2012. Results show that winter snowfall in the YHRB exhibits consistent anomalies over the whole region for the interannual variation during 1960–2012. Further analysis suggests that winter snowfall anomalies in the YHRB are closely linked to the anomalous wintertime SCAND activity. When there is more winter snowfall in the YHRB, SCAND is usually in a positive phase, accompanied by a strengthened Urals blocking high and East Asian trough, which is conducive to strengthened cold-air activity, intensified vertical motions, and more water vapor transport in the YHRB. In contrast, less winter snowfall in the YHRB usually happens in the negative phase of SCAND. Our results provide useful information to better understand the relevant mechanism responsible for anomalous winter snowfall in this area.
基金Supported by the National Key Research and Development Program of China(2022YFE0106900)National Natural Science Foundation of China(42261134532)Research Council of Norway project ARCLINK(328938)。
文摘Understanding the interannual variability of wintertime marine cold air outbreak(MCAO)frequency is essential,as such events play a key role in shaping air-sea interactions,driving deep ocean convection,and influencing regional climate variability.This study analyzes the two leading modes of the wintertime MCAO variability over the high latitudes of the North Atlantic on interannual timescales and their relation to large-scale teleconnection patterns and the oceanic mixed layer depth(MLD).The first mode is a meridional dipole pattern,reflecting the out-of-phase variations of the MCAO frequency between the northwestern and the subtropical North Atlantic.It is strongly tied to the seasonal mean North Atlantic Oscillation/Arctic Oscillation and the associated zonal temperature advection at around55°N from northeastern Canada towards the North Atlantic.The second mode is a zonal dipole pattern,reflecting the out-of-phase variations of the MCAO frequency between the Nordic Seas and the western North Atlantic,and is strongly tied to the Scandinavian pattern and the associated meridional temperature advection from the Arctic via Fram Strait.Though these associations are observed between the seasonal MCAO frequency and the seasonal mean teleconnection patterns,they also feature a good relationship on the daily timescale.This establishes a bridge between the annual frequency of synoptic MCAO events and the seasonal mean circulation and teleconnections.Both modes are associated with significant oceanic heat loss,lowering the SST.Accordingly,the positive phase of the EOF1 mode corresponds to a local deepening of the mixed layer over southern Greenland.In contrast,the positive phase of the EOF2 mode not only causes a deepening of the mixed layer in the Nordic Seas but also affects the depth of the mixed layer over southern Greenland through transport by oceanic currents.
