Using the daily average outgoing longwave radiation and NCEP/NCAR reanalysis data in boreal summer(Mays to Octobers)from 1979 to 2007,the propagating characteristics of convection intraseasonal oscillations(ISOs)in th...Using the daily average outgoing longwave radiation and NCEP/NCAR reanalysis data in boreal summer(Mays to Octobers)from 1979 to 2007,the propagating characteristics of convection intraseasonal oscillations(ISOs)in the Asian-western Pacific(AWP)region and the relationship between tropical synoptic waves and ISOs are examined by means of finite-domain wavenumber-frequency energy spectrum analysis and lagged linear regression technique.The results are shown as follows.(1)The AWP ISOs propagate both eastward and westward,showing seasonality and regionality.The ISOs propagate eastward with a period of 30 to 60 days over equatorial regions in the whole AWP region,while the westward propagation occurs over 10 to 20°N western Pacific or in the late summers(August,September and October) with periods of 20 to 40 days.The ISOs eastward propagation mainly occurs in primary summers while the westward propagation enhances in late summers.(2)Deep ISO convections associate with westerly and cyclonic circulation anomalies that first form in the Indian Ocean,propagate eastward to the dateline in the Pacific and then turn northwestward.The ISOs convections show northwestward propagating characteristics in the western North Pacific.(3)The ISOs link with the tropical synoptic waves closely.Both convection signals,though with different spatio-temporal scale,enhance simutaneously in the northwestern Pacific,and the ISOs facilitate the forming of a cluster of tropical cyclones(TCs),while a cluster of TCs convection becomes one portion of the northwestward ISOs.展开更多
The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there...The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there are respectively two and one wave trains around the QXP during the onset of the South China Sea monsoon in strong and weak monsoon years.The locations and strength of the wave train propagation differ between the strong and weak monsoon years.Because diabatic heating of the QXP prevents the low-frequency oscillation,the wave train of interaction between the diabatic heating and the zonal wind MJO propagates along the west and east of the QXP in the strong monsoon years.The distribution of the wave train interaction between the diabatic heating and the zonal wind MJO traverses the QXP and coincides with the location of the southern and northern upper-level jet streams,showing that they are remarkably correlated.An interesting and notable phenomenon is that the interaction between diabatic heating and the zonal wind MJO over the QXP suddenly disappears during the monsoon onset in weak monsoon years.展开更多
Concerning a bounded sequence of finite energy weak solutions to the compressible Navier-Stokes-Poisson system (denoted by CNSP), which converges up to extraction of a subsequence, the limit system may not be the same...Concerning a bounded sequence of finite energy weak solutions to the compressible Navier-Stokes-Poisson system (denoted by CNSP), which converges up to extraction of a subsequence, the limit system may not be the same system. By introducing Young measures as in [6, 15], the authors deduce the system (HCNSP) which the limit functions must satisfy. Then they solve this system in a subclass where Young measures are convex combinations of Dirac measures, to give the information on the propagation of density-oscillations. The results for strong solutions to (CNSP) (see Corollary 6.1) are also obtained.展开更多
Using 32-yr National Centers for Environment Prediction-National Center for Atmospheric Research(NCEP-NCAR) reanalysis data,we investigated zonal propagation and circulation characteristics of the low-frequency circul...Using 32-yr National Centers for Environment Prediction-National Center for Atmospheric Research(NCEP-NCAR) reanalysis data,we investigated zonal propagation and circulation characteristics of the low-frequency circulation for the prevailing period over Eurasian mid-high latitude in boreal summer(May-August) in terms of empirical orthogonal function(EOF),linear regression,and phase analysis and so on.We found that the dominant periods of the low-frequency circulation are 10-30 days and it clearly shows meridional(southward) and zonal(westward) propagation features at the middle troposphere(500 hPa).The average zonal speed of the 10-30 days low-frequency oscillation(LFO) is about 9-10 longitudes per day.Further analysis shows that the southernmost part of the polar vortex in the northern hemisphere exhibits westward clockwise rotation in the eastern hemisphere in boreal summer.Also,the southernmost tips of 5400 and 5500 gpm contours,which indicate the site of the major trough in the eastern hemisphere,obviously move westwards.The southernmost tip of 5500 gpm contour line propagates westwards at the speed of about 9-10 longitudes per day,which is consistent with the mean zonal speed of the westward propagation of the low-frequency circulation.Moreover,the 10-30-day LFO-related cold air also shows west propagation feature with respect to LFO phases.The westward propagation of the LFO is the low-frequency-scale embodiment of the clockwise rotation of polar vortex.The cold air activities closely related to polar vortex or to ridge-trough system activities is the essential circulation of 10-30 days LFO circulation over the Eurasian mid-high latitude in boreal summer.展开更多
基金National Basic Research Program of China(973 Program)(2009CB421503)Natural Science Foundation of China(41075073+2 种基金40775058)Tropical Marine&Meteorologic Science Foundation(201103)Natural Science Foundation of Guangxi(2010GXNSFA013010)
文摘Using the daily average outgoing longwave radiation and NCEP/NCAR reanalysis data in boreal summer(Mays to Octobers)from 1979 to 2007,the propagating characteristics of convection intraseasonal oscillations(ISOs)in the Asian-western Pacific(AWP)region and the relationship between tropical synoptic waves and ISOs are examined by means of finite-domain wavenumber-frequency energy spectrum analysis and lagged linear regression technique.The results are shown as follows.(1)The AWP ISOs propagate both eastward and westward,showing seasonality and regionality.The ISOs propagate eastward with a period of 30 to 60 days over equatorial regions in the whole AWP region,while the westward propagation occurs over 10 to 20°N western Pacific or in the late summers(August,September and October) with periods of 20 to 40 days.The ISOs eastward propagation mainly occurs in primary summers while the westward propagation enhances in late summers.(2)Deep ISO convections associate with westerly and cyclonic circulation anomalies that first form in the Indian Ocean,propagate eastward to the dateline in the Pacific and then turn northwestward.The ISOs convections show northwestward propagating characteristics in the western North Pacific.(3)The ISOs link with the tropical synoptic waves closely.Both convection signals,though with different spatio-temporal scale,enhance simutaneously in the northwestern Pacific,and the ISOs facilitate the forming of a cluster of tropical cyclones(TCs),while a cluster of TCs convection becomes one portion of the northwestward ISOs.
基金supported by National Basic Research Program of China (Grant No. 2007CB411506)National Natural Science Foundation of China (Grant No. 40875050)
文摘The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there are respectively two and one wave trains around the QXP during the onset of the South China Sea monsoon in strong and weak monsoon years.The locations and strength of the wave train propagation differ between the strong and weak monsoon years.Because diabatic heating of the QXP prevents the low-frequency oscillation,the wave train of interaction between the diabatic heating and the zonal wind MJO propagates along the west and east of the QXP in the strong monsoon years.The distribution of the wave train interaction between the diabatic heating and the zonal wind MJO traverses the QXP and coincides with the location of the southern and northern upper-level jet streams,showing that they are remarkably correlated.An interesting and notable phenomenon is that the interaction between diabatic heating and the zonal wind MJO over the QXP suddenly disappears during the monsoon onset in weak monsoon years.
基金the National Natural Science Foundation of China (No. 10531020)the Program of 985Innovation Engineering on Information in Xiamen University (2004–2007)the New Century ExcellentTalents in Xiamen University
文摘Concerning a bounded sequence of finite energy weak solutions to the compressible Navier-Stokes-Poisson system (denoted by CNSP), which converges up to extraction of a subsequence, the limit system may not be the same system. By introducing Young measures as in [6, 15], the authors deduce the system (HCNSP) which the limit functions must satisfy. Then they solve this system in a subclass where Young measures are convex combinations of Dirac measures, to give the information on the propagation of density-oscillations. The results for strong solutions to (CNSP) (see Corollary 6.1) are also obtained.
基金supported jointly by the National Natural Science Foundation of China(Grant Nos.40875052&41221064)the Calling Project of China(Grant Nos.GYHY200906017&GYHY201006020)the Basic Research Foundation of CAMS(Grant No.2010Z003)
文摘Using 32-yr National Centers for Environment Prediction-National Center for Atmospheric Research(NCEP-NCAR) reanalysis data,we investigated zonal propagation and circulation characteristics of the low-frequency circulation for the prevailing period over Eurasian mid-high latitude in boreal summer(May-August) in terms of empirical orthogonal function(EOF),linear regression,and phase analysis and so on.We found that the dominant periods of the low-frequency circulation are 10-30 days and it clearly shows meridional(southward) and zonal(westward) propagation features at the middle troposphere(500 hPa).The average zonal speed of the 10-30 days low-frequency oscillation(LFO) is about 9-10 longitudes per day.Further analysis shows that the southernmost part of the polar vortex in the northern hemisphere exhibits westward clockwise rotation in the eastern hemisphere in boreal summer.Also,the southernmost tips of 5400 and 5500 gpm contours,which indicate the site of the major trough in the eastern hemisphere,obviously move westwards.The southernmost tip of 5500 gpm contour line propagates westwards at the speed of about 9-10 longitudes per day,which is consistent with the mean zonal speed of the westward propagation of the low-frequency circulation.Moreover,the 10-30-day LFO-related cold air also shows west propagation feature with respect to LFO phases.The westward propagation of the LFO is the low-frequency-scale embodiment of the clockwise rotation of polar vortex.The cold air activities closely related to polar vortex or to ridge-trough system activities is the essential circulation of 10-30 days LFO circulation over the Eurasian mid-high latitude in boreal summer.
