Using the 1979-2009 NCEP/NACR reanalysis data and precipitation records in East China, research is performed of the climatological features of low-frequency oscillation(LFO) in OLR over the Maritime Continent(MC) as w...Using the 1979-2009 NCEP/NACR reanalysis data and precipitation records in East China, research is performed of the climatological features of low-frequency oscillation(LFO) in OLR over the Maritime Continent(MC) as well as their associations with precipitation disturbance in the eastern part of China. Results suggest that in the MC there is significant climatological low-frequency oscillation(CLFO) in outgoing long-wave radiation(OLR), with the intraseasonal oscillation(30-60 days) being the strongest for April-September, and the MC acting as a high-value region of percentage contributions of low-frequency OLR variance. On the low-frequency time scale there occur four events of more intense active OLR during this time interval. In the January-April(May-August) phase, MC convection is relatively weak(vigorous). The CLFO makes pronounced eastward displacement at tropics, with phase propagation seen longitudinally, too. There occur low-frequency disturbance circulations similar to the EAP wavetrain or P-J teleconnection,starting from the MC via the South China Sea and the Philippines to the Yangtze valley of China. At different phases,the variation in the low-frequency circulations and heating fields shows that the rainfall disturbance in eastern China is likely to be under possible effects of the CLFO from the MC in April-September, and the low-frequency heating variation exhibits a meridional pattern as an EAP wavetrain or P-J teleconnection. As the OLR CLFO is in a peak(valley)phase the low-level divergence or convergence with the reversal at high levels over the MC is related to relatively feeble(robust) low frequency convection, thereby exciting an EAP or P-J wavetrain from the MC to the Sea of Japan. At the higher levels, the South-Asian high is eastward(westward) of normal due to effects of low-frequency cyclones(anticyclones), resulting in less(more) rainfall in the Jiangnan(areas in the middle and lower reaches of Yangtze and to the south of the river) and Hetao(the Great Bend of Yellow River) areas, and increased(decreased) rainfall in SW China,Qinghai Plateau and Gansu. At the conversion phases, low-frequency convection becomes more active in parts of the MC, consequently exciting low-frequency wavetrain of cyclones-anticyclones-cyclones at low levels, making the South-Asian high southward of the mean, so that strong convergent zones emerge in the upper and middle Yangtze basins and Jilin of NE China, responsible for plentiful precipitation there in sharp contrast to the rainfall over the band between the Yellow and Huaihe Rivers and the Yunnan-Guizhou Plateau. These results help understand in depth the climatological LFO characteristics and the phase-locked feature, thereby further improving our understanding of the causes of rainfall disturbances in different parts of the country.展开更多
The relationship between the intensity of the South China Sea summer monsoon （SCSSM） and the Nino3.4 index and anomalous atmospheric circulation patterns associated with a strong and weak SCSSM are investigated usin...The relationship between the intensity of the South China Sea summer monsoon （SCSSM） and the Nino3.4 index and anomalous atmospheric circulation patterns associated with a strong and weak SCSSM are investigated using the NCEP/NCAR reanalysis data, Extended Reconstructed Sea Surface Temperature （ERSST） data and Climate Prediction Center Merged Analysis of Precipitation （CMAP） data. The SCSSM is significantly positively correlated with the Nino3.4 index in the succeeding northern autumn and winter. In the strong minus weak SCSSM composite, a positive East Asia-Pacific teleconnection （EAP） pattern and a negative Europe-Asian-Pacific teleconnection （EUP） pattern appear in the 500 hPa height difference field; low-level cross-equatorial flows are strengthened over the Maritime Continent （MC） region; positive （negative） precipitation anomalies occur in the South China Sea and western north Pacific （MC）. A possible mechanism through which SCSSM affects ENSO is proposed. A strong （weak） SCSSM strengthens （weakens） cross-equatorial flows over the MC. The anomalous cross-equatorial flows cool （warm） the SST around the MC through enhanced （reduced） surface latent heat fluxes. The cooling （warming） further leads to suppressed （enhanced） convection over the MC, and causes the anomalous westerly （easterly） in the equatorial western Pacific, which favors the onset of E1 Nino （La Nina） through modulating the positive air-sea feedback process.展开更多
The Maritime Continent（MC） is under influences of both the tropical Pacific and the Indian Ocean. Anomalous convective activities over the MC have significant impacts on the East Asian summer monsoon（EASM） and cli...The Maritime Continent（MC） is under influences of both the tropical Pacific and the Indian Ocean. Anomalous convective activities over the MC have significant impacts on the East Asian summer monsoon（EASM） and climate in China. In the present study, the variation in convective activity over the MC in boreal summer and its relationship to EASM anomalies are investigated based on regression analysis of NCEP–NCAR reanalysis and CMAP [Climate Prediction Center（CPC） Merged Analysis of Precipitation] data, with a focus on the impacts of ENSO and the Indian Ocean Dipole（IOD）. The most significant interannual variability of convective activity is found over 10°S–10°N, 95°–145°E, which can be roughly defined as the key area of the MC（hereafter, KMC）. Outgoing longwave radiation anomaly（OLRA） exhibits 3- to 7-yr periodicities over the KMC, and around 70% of the OLRA variance can be explained by the ENSO signal. However, distinct convection and precipitation anomalies still exist over this region after the ENSO and IOD signals are removed. Abnormally low precipitation always corresponds to positive OLRA over the KMC when negative diabatic heating anomalies and anomalous cooling of the atmospheric column lead to abnormal descending motion over this region. Correspondingly, abnormal divergence occurs in the lower troposphere while convergence occurs in the upper troposphere, triggering an East Asia–Pacific/Pacific–Japan（EAP/PJ）-like anomalous wave train that propagates northeastward and leads to a significant positive precipitation anomaly from the Yangtze River valley in China to the islands of Japan. This EAP/PJ-like wave pattern becomes even clearer after the removal of the ENSO signal and the combined effects of ENSO and IOD, suggesting that convective anomalies over the KMC have an important impact on EASM anomalies. The above results provide important clues for the prediction of EASM anomalies and associated summer precipitation anomalies in China.展开更多
The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convecti...The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convective branches shifted south of the equator over the MC during eastern Pacific(EP)El Nino winters,while it became relatively symmetric about the equator during La Ni?a winters.The impact of central Pacific(CP)El Ninos to MJO pattern,on the other hand,is not statistically significant.The cause of the distinctive MJO pattern evolutions is likely attributed to the ENSO-induced changes of the background moisture and vertical shear over the MC.Idealized numerical experiments with a 2.5-layer model were carried out,and the result revealed that the background moisture change played a dominant role.An observational diagnosis of column-integrated moist static energy(MSE)budgets was further conducted.The result indicated that the MJO pattern difference was attributed to the MSE tendency asymmetry in front of MJO convection between EP El Nino and La Ni?a,caused by the advection of the mean MSE by anomalous meridional wind.The difference in the MJO-scale anomalous meridional wind was ultimately controlled by the change of the background meridional moisture gradient associated with EP El Nino and La Ni?a.展开更多
The United Nations Convention on the Law of the Sea entitled the coastal States to naturally extend the continental shelf, which has caused more drastic disputes of maritime delimitation. This paper devotes to clarify...The United Nations Convention on the Law of the Sea entitled the coastal States to naturally extend the continental shelf, which has caused more drastic disputes of maritime delimitation. This paper devotes to clarifying the significant concept of natural prolongation through an effect method combing the legal principles and technical analysis. Firstly, the classic samples with respect of the development of geological features are traced. Based on these samples, the classification with a model is proposed in order to affirm the concept＇s significance under certain geomorphologic situations. Lastly, scientific analysis is used to present two potential prolongation situations and emphasize that all the technical analysis on maritime delimitation should be complied with international law and protect the common interest of all the mankind.展开更多
This paper documents that the principal mode of Pan-Asian monsoon summer precipitation experienced a prominent interdecadal shift around 1992/1993 in terms of spatial pattern and major driving factors. During 1979-19...This paper documents that the principal mode of Pan-Asian monsoon summer precipitation experienced a prominent interdecadal shift around 1992/1993 in terms of spatial pattern and major driving factors. During 1979-1992 （Period 1, P1）, Pan-Asian monsoon summer precipitation anomalies mainly display a meridional dipole pattern from north to south, whereas in the period 1993-2016 （Period 2, P2）, it shows a meridional tripole pattern instead. The summer precipitation in P1 is primarily associated with a combination of the developing phase （central-eastern Pacific type） and decaying phase （eastern Pacific type） of El Nino-Southem Oscillation （ENSO）; while in P2, it is mainly associated with the decaying phase of central-eastern-Pacific-type ENSO.展开更多
This study investigates the combined effect of the El Nino–Southern Oscillation(ENSO) and stratospheric quasi-biennial oscillation(QBO) on the Madden Julian Oscillation(MJO). The results show that the western Pacific...This study investigates the combined effect of the El Nino–Southern Oscillation(ENSO) and stratospheric quasi-biennial oscillation(QBO) on the Madden Julian Oscillation(MJO). The results show that the western Pacific MJO originating from the Indian Ocean during La Nina/QBO easterly years is stronger than that during El Nino years. This relation, however, disappears during La Nina/QBO westerly years. The reason is that ENSO and the QBO have different effects on each MJO event. For an El Nino year, there is only about one MJO event, and the QBO effect is small. During a La Nina/QBO easterly year, there are 1.7 MJO events, while during a La Nina/QBO westerly year, there are only 0.6 MJO events. El Nino can reinforce the MJO over the western Pacific because of the positive moisture advection of the El Nino mean state by MJO easterly wind anomalies. The QBO mainly affects the MJO over the Maritime Continent region by changing the high-cloud-controlled diurnal cycle;and the Maritime Continent barrier effect is enhanced during the QBO westerly phase because of the strong diurnal cycle. During El Nino years, even the MJO over the Maritime Continent is suppressed by the QBO westerly phase;the MJO can be reinforced over the western Pacific. During La Nina/QBO westerly years,the MJO over the Maritime Continent is suppressed because of the strong Maritime Continent diurnal cycle, and it is further suppressed over the western Pacific because of the lack of a reinforcement process.展开更多
基金Natural Science Foundation of China(41330425,41175062,40475028)Jiangsu PAPD ProjectJiangsu"Qinglan"Project for Activating Research Teams
文摘Using the 1979-2009 NCEP/NACR reanalysis data and precipitation records in East China, research is performed of the climatological features of low-frequency oscillation(LFO) in OLR over the Maritime Continent(MC) as well as their associations with precipitation disturbance in the eastern part of China. Results suggest that in the MC there is significant climatological low-frequency oscillation(CLFO) in outgoing long-wave radiation(OLR), with the intraseasonal oscillation(30-60 days) being the strongest for April-September, and the MC acting as a high-value region of percentage contributions of low-frequency OLR variance. On the low-frequency time scale there occur four events of more intense active OLR during this time interval. In the January-April(May-August) phase, MC convection is relatively weak(vigorous). The CLFO makes pronounced eastward displacement at tropics, with phase propagation seen longitudinally, too. There occur low-frequency disturbance circulations similar to the EAP wavetrain or P-J teleconnection,starting from the MC via the South China Sea and the Philippines to the Yangtze valley of China. At different phases,the variation in the low-frequency circulations and heating fields shows that the rainfall disturbance in eastern China is likely to be under possible effects of the CLFO from the MC in April-September, and the low-frequency heating variation exhibits a meridional pattern as an EAP wavetrain or P-J teleconnection. As the OLR CLFO is in a peak(valley)phase the low-level divergence or convergence with the reversal at high levels over the MC is related to relatively feeble(robust) low frequency convection, thereby exciting an EAP or P-J wavetrain from the MC to the Sea of Japan. At the higher levels, the South-Asian high is eastward(westward) of normal due to effects of low-frequency cyclones(anticyclones), resulting in less(more) rainfall in the Jiangnan(areas in the middle and lower reaches of Yangtze and to the south of the river) and Hetao(the Great Bend of Yellow River) areas, and increased(decreased) rainfall in SW China,Qinghai Plateau and Gansu. At the conversion phases, low-frequency convection becomes more active in parts of the MC, consequently exciting low-frequency wavetrain of cyclones-anticyclones-cyclones at low levels, making the South-Asian high southward of the mean, so that strong convergent zones emerge in the upper and middle Yangtze basins and Jilin of NE China, responsible for plentiful precipitation there in sharp contrast to the rainfall over the band between the Yellow and Huaihe Rivers and the Yunnan-Guizhou Plateau. These results help understand in depth the climatological LFO characteristics and the phase-locked feature, thereby further improving our understanding of the causes of rainfall disturbances in different parts of the country.
基金National Science Foundation of China under contract (4067505440505019)China Meteorological Administration (CMATG2006L03)
文摘The relationship between the intensity of the South China Sea summer monsoon （SCSSM） and the Nino3.4 index and anomalous atmospheric circulation patterns associated with a strong and weak SCSSM are investigated using the NCEP/NCAR reanalysis data, Extended Reconstructed Sea Surface Temperature （ERSST） data and Climate Prediction Center Merged Analysis of Precipitation （CMAP） data. The SCSSM is significantly positively correlated with the Nino3.4 index in the succeeding northern autumn and winter. In the strong minus weak SCSSM composite, a positive East Asia-Pacific teleconnection （EAP） pattern and a negative Europe-Asian-Pacific teleconnection （EUP） pattern appear in the 500 hPa height difference field; low-level cross-equatorial flows are strengthened over the Maritime Continent （MC） region; positive （negative） precipitation anomalies occur in the South China Sea and western north Pacific （MC）. A possible mechanism through which SCSSM affects ENSO is proposed. A strong （weak） SCSSM strengthens （weakens） cross-equatorial flows over the MC. The anomalous cross-equatorial flows cool （warm） the SST around the MC through enhanced （reduced） surface latent heat fluxes. The cooling （warming） further leads to suppressed （enhanced） convection over the MC, and causes the anomalous westerly （easterly） in the equatorial western Pacific, which favors the onset of E1 Nino （La Nina） through modulating the positive air-sea feedback process.
基金National Natural Science Foundation of China(41330425)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406024)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The Maritime Continent（MC） is under influences of both the tropical Pacific and the Indian Ocean. Anomalous convective activities over the MC have significant impacts on the East Asian summer monsoon（EASM） and climate in China. In the present study, the variation in convective activity over the MC in boreal summer and its relationship to EASM anomalies are investigated based on regression analysis of NCEP–NCAR reanalysis and CMAP [Climate Prediction Center（CPC） Merged Analysis of Precipitation] data, with a focus on the impacts of ENSO and the Indian Ocean Dipole（IOD）. The most significant interannual variability of convective activity is found over 10°S–10°N, 95°–145°E, which can be roughly defined as the key area of the MC（hereafter, KMC）. Outgoing longwave radiation anomaly（OLRA） exhibits 3- to 7-yr periodicities over the KMC, and around 70% of the OLRA variance can be explained by the ENSO signal. However, distinct convection and precipitation anomalies still exist over this region after the ENSO and IOD signals are removed. Abnormally low precipitation always corresponds to positive OLRA over the KMC when negative diabatic heating anomalies and anomalous cooling of the atmospheric column lead to abnormal descending motion over this region. Correspondingly, abnormal divergence occurs in the lower troposphere while convergence occurs in the upper troposphere, triggering an East Asia–Pacific/Pacific–Japan（EAP/PJ）-like anomalous wave train that propagates northeastward and leads to a significant positive precipitation anomaly from the Yangtze River valley in China to the islands of Japan. This EAP/PJ-like wave pattern becomes even clearer after the removal of the ENSO signal and the combined effects of ENSO and IOD, suggesting that convective anomalies over the KMC have an important impact on EASM anomalies. The above results provide important clues for the prediction of EASM anomalies and associated summer precipitation anomalies in China.
基金Supported by the National Natural Science Foundation of China(42088101 and 41875069)US National Science Foundation(AGS-2006553)+2 种基金US NOAA Grant(NA18OAR4310298)SOEST contribution number 11206IPRC contribution number 1494。
文摘The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convective branches shifted south of the equator over the MC during eastern Pacific(EP)El Nino winters,while it became relatively symmetric about the equator during La Ni?a winters.The impact of central Pacific(CP)El Ninos to MJO pattern,on the other hand,is not statistically significant.The cause of the distinctive MJO pattern evolutions is likely attributed to the ENSO-induced changes of the background moisture and vertical shear over the MC.Idealized numerical experiments with a 2.5-layer model were carried out,and the result revealed that the background moisture change played a dominant role.An observational diagnosis of column-integrated moist static energy(MSE)budgets was further conducted.The result indicated that the MJO pattern difference was attributed to the MSE tendency asymmetry in front of MJO convection between EP El Nino and La Ni?a,caused by the advection of the mean MSE by anomalous meridional wind.The difference in the MJO-scale anomalous meridional wind was ultimately controlled by the change of the background meridional moisture gradient associated with EP El Nino and La Ni?a.
基金The National Social Science Foundation of China under contract No.16CFX069China Postdoctoral Science Foundations under contract Nos 2015M581913 and 2016T90531the Fundamental Research Funds for the Central Universities
文摘The United Nations Convention on the Law of the Sea entitled the coastal States to naturally extend the continental shelf, which has caused more drastic disputes of maritime delimitation. This paper devotes to clarifying the significant concept of natural prolongation through an effect method combing the legal principles and technical analysis. Firstly, the classic samples with respect of the development of geological features are traced. Based on these samples, the classification with a model is proposed in order to affirm the concept＇s significance under certain geomorphologic situations. Lastly, scientific analysis is used to present two potential prolongation situations and emphasize that all the technical analysis on maritime delimitation should be complied with international law and protect the common interest of all the mankind.
基金supported by the National Natural Science Foundation of China[grant number 41505070]the Development Program of China[grant number 2016YFA0600703]the Chinese Academy of Sciences-Peking University Joint Research Program
文摘This paper documents that the principal mode of Pan-Asian monsoon summer precipitation experienced a prominent interdecadal shift around 1992/1993 in terms of spatial pattern and major driving factors. During 1979-1992 （Period 1, P1）, Pan-Asian monsoon summer precipitation anomalies mainly display a meridional dipole pattern from north to south, whereas in the period 1993-2016 （Period 2, P2）, it shows a meridional tripole pattern instead. The summer precipitation in P1 is primarily associated with a combination of the developing phase （central-eastern Pacific type） and decaying phase （eastern Pacific type） of El Nino-Southem Oscillation （ENSO）; while in P2, it is mainly associated with the decaying phase of central-eastern-Pacific-type ENSO.
基金supported by the National Natural Science Foundation of China [grant number 41420104002]the China National 973 Project [grant number 2015CB453200]+2 种基金the Public Science and Technology Research Funds Projects of the Ocean[grant number 201505013]the Natural Science Foundation of Jiangsu Province [grant numbers BK20150907 and 14KJA170002]the National Science Foundation of the US [grant number AGS-1540783]
文摘This study investigates the combined effect of the El Nino–Southern Oscillation(ENSO) and stratospheric quasi-biennial oscillation(QBO) on the Madden Julian Oscillation(MJO). The results show that the western Pacific MJO originating from the Indian Ocean during La Nina/QBO easterly years is stronger than that during El Nino years. This relation, however, disappears during La Nina/QBO westerly years. The reason is that ENSO and the QBO have different effects on each MJO event. For an El Nino year, there is only about one MJO event, and the QBO effect is small. During a La Nina/QBO easterly year, there are 1.7 MJO events, while during a La Nina/QBO westerly year, there are only 0.6 MJO events. El Nino can reinforce the MJO over the western Pacific because of the positive moisture advection of the El Nino mean state by MJO easterly wind anomalies. The QBO mainly affects the MJO over the Maritime Continent region by changing the high-cloud-controlled diurnal cycle;and the Maritime Continent barrier effect is enhanced during the QBO westerly phase because of the strong diurnal cycle. During El Nino years, even the MJO over the Maritime Continent is suppressed by the QBO westerly phase;the MJO can be reinforced over the western Pacific. During La Nina/QBO westerly years,the MJO over the Maritime Continent is suppressed because of the strong Maritime Continent diurnal cycle, and it is further suppressed over the western Pacific because of the lack of a reinforcement process.
