The interdecadal circumglobal teleconnection （ID-CGT） pattern is the dominant circulation mode over the NH during boreal summer on the interdecadal time scale. Its temporal evolution is synchronous with that of the ...The interdecadal circumglobal teleconnection （ID-CGT） pattern is the dominant circulation mode over the NH during boreal summer on the interdecadal time scale. Its temporal evolution is synchronous with that of the Atlantic Multidecadal Oscillation （AMO）. In this study, through analyzing the results of sensitivity experiments using five AGCMs driven by specified AMO-related SST anomalies （SSTAs） in the North Atlantic, the authors investigate whether the ID-CGT is excited by the AMO. Two out of the five models simulate the barotropic stationary wave pattern located along the westerly jet, suggesting that the ID-CGT pattern should be excited, at least partially, by the AMO- related SSTAs. Model results suggest that the ID-CGT pattern plays a role in linking the AMO and NH summer land SAT perturbations on the interdecadal time scale.展开更多
A 30-year hindcast was performed using version 4.1 of the IAP AGCM（IAP AGCM4.1）, and its potential predictability of the MJO was then evaluated. The results showed that the potential predictability of the MJO is 13 ...A 30-year hindcast was performed using version 4.1 of the IAP AGCM（IAP AGCM4.1）, and its potential predictability of the MJO was then evaluated. The results showed that the potential predictability of the MJO is 13 and 24 days, evaluated using the signal-to-error ratio method based on a single member and the ensemble mean, respectively. However, the MJO prediction skill is only9 and 10 days using the two methods mentioned above. It was further found that the potential predictability and prediction skill depend on the MJO amplitude in the initial conditions. Prediction initiated from conditions with a strong MJO amplitude tends to be more skillful. Together with the results of other measures, the current MJO prediction ability of IAP AGCM4.1 is around 10 days, which is much lower than other climate prediction systems. Furthermore, the smaller difference between the MJO predictability and prediction skill evaluated by a single member and the ensemble mean methods could be ascribed to the relatively smaller size of the ensemble member of the model.Therefore, considerable effort should be made to improve MJO prediction in IAP AGCM4.1 through application of a reasonable model initialization and ensemble forecast strategy.展开更多
This study evaluates the performance of the Grid-point Atmospheric Model of IAP LASG,version 3(GAMIL3),in simulating the Madden–Julian Oscillation(MJO),based on the CMIP6(phase 6 of the Coupled Model Intercomparison ...This study evaluates the performance of the Grid-point Atmospheric Model of IAP LASG,version 3(GAMIL3),in simulating the Madden–Julian Oscillation(MJO),based on the CMIP6(phase 6 of the Coupled Model Intercomparison Project)AMIP(Atmospheric Model Intercomparison Project)simulation.Results show that GAMIL3 reasonably captures the main features of the MJO,such as the eastward-propagating signal in the MJO frequency band,the symmetric and asymmetric structures of the MJO,several convectively coupled equatorial waves,and the MJO life cycle.However,GAMIL3 underestimates the MJO amplitude,especially for outgoing longwave radiation,as do most CMIP5 models,and simulates slow eastward propagation.展开更多
Spring is the critical period for atmospheric circulation transition from winter to summer. The spring water cycle is very im- portant to agriculture in planting crop and the initial growth of crop. Note that there wa...Spring is the critical period for atmospheric circulation transition from winter to summer. The spring water cycle is very im- portant to agriculture in planting crop and the initial growth of crop. Note that there was a significant abrupt decadal change in the water budget increase during early spring over eastern China in the late 1970s. Studied here are the decadal variations of water budgets over the key regions and the associated change of water cycle over East Asia and atmospheric circulation over Asia-West Pacific region in early spring, using the observed （OBS） precipitation, the ECMWF （ERA） and NCEP/NCAR rea- nalysis （NRA）, and the Mantua＇s Pacific decadal oscillation index （PDOI）. The water budget increments from March to April exhibited a sharp decrease over the key region around Huaihe River basin （HHR） （111°-120°E; 31°-36°N） after year 1978. Before 1977 the water vapor flux through south boundary of the HHR region increased greatly during March to April by 1.52 mm d^-1 in ERA and 1.88 mm d^-1 in NRA. Concurrently the moisture convergence and precipitation over the region also in- creased greatly. The increment for the moisture convergence was 1.11 mmd^-1 in ERA and 1.22 mm d^-1 in NRA, and for the precipitation was 1.05 mm d^-1 in observation and 1.05 mm d^-1 in ERA. April was the time that the water budgets over HHR increased most rapidly before 1977. But after 1978 the water budgets decreased conversely from Mach to April. The water vapor flux increment through the south boundary was -0.03 mmd^-1 in ERA and 0.01 mm d^-1 in NRA, the moisture conver- gence increment was -0.91 mm d^-1 in ERA and -0.53 mm d^-1 in NRA, and precipitation increment was -0.08 mm d^-1 in ob- servation and -0.15 mm d^-1 in ERA. Further investigation has shown that the large-scale atmospheric circulation in the early spring has correspondingly changed significantly after the late 1970s. During March to April, the weakening of the trough over East Asia became significantly slower, and the strengthening of the ridge over the west China became significantly faster in the middle troposphere after the late 1970s. At the same time, in the lower troposphere, the strengthening and northward extending of the west pan of the subtropical high and the weakening of the trough over the southwest part of the Aleutian low in the early spring became slower, and the weakening of the main part of Asian high became slower, but the strengthening of its west part became faster. This significant decadal change of circulation caused a sharp decrease in the northward extending speed of wa- ter vapor transport, and in the water budgets increasing speed over the southeastern China during early spring after the late 1970s.展开更多
The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vib...The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vibration. In recent years, the effect of bump wall on the flow field around an airfoil has been investigated experimentally and as a result, it was observed that the bump wall is effective for the control of shock wave on the airfoil. In the transonic or supersonic flow field, a rapid expansion of moist air or steam gives rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation around a circular arc blade with or without a bump on the blade was investigated numerically. The results showed that the non-equilibrium condensation significantly reduced the flow field unsteadiness such as root mean of pressure oscillation and frequency compared to the case without the non-equilibrium condensation.展开更多
基金supported by the National Basic Research Program of China[grant number 2012CB955202]the National Natural Science Foundation of China[grant numbers 41005040 and 41023002]the R&D Special Fund for Public Welfare Industry(Meteorology)[grant number GYHY201506012]
文摘The interdecadal circumglobal teleconnection （ID-CGT） pattern is the dominant circulation mode over the NH during boreal summer on the interdecadal time scale. Its temporal evolution is synchronous with that of the Atlantic Multidecadal Oscillation （AMO）. In this study, through analyzing the results of sensitivity experiments using five AGCMs driven by specified AMO-related SST anomalies （SSTAs） in the North Atlantic, the authors investigate whether the ID-CGT is excited by the AMO. Two out of the five models simulate the barotropic stationary wave pattern located along the westerly jet, suggesting that the ID-CGT pattern should be excited, at least partially, by the AMO- related SSTAs. Model results suggest that the ID-CGT pattern plays a role in linking the AMO and NH summer land SAT perturbations on the interdecadal time scale.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA05110200]the Special Scientific Research Fund of the Meteorological Public Welfare Profession of China[grant number GYHY201406021]the National Natural Science Foundation of China[grant numbers 41575095,41175073,41575062,41520104008]
文摘A 30-year hindcast was performed using version 4.1 of the IAP AGCM（IAP AGCM4.1）, and its potential predictability of the MJO was then evaluated. The results showed that the potential predictability of the MJO is 13 and 24 days, evaluated using the signal-to-error ratio method based on a single member and the ensemble mean, respectively. However, the MJO prediction skill is only9 and 10 days using the two methods mentioned above. It was further found that the potential predictability and prediction skill depend on the MJO amplitude in the initial conditions. Prediction initiated from conditions with a strong MJO amplitude tends to be more skillful. Together with the results of other measures, the current MJO prediction ability of IAP AGCM4.1 is around 10 days, which is much lower than other climate prediction systems. Furthermore, the smaller difference between the MJO predictability and prediction skill evaluated by a single member and the ensemble mean methods could be ascribed to the relatively smaller size of the ensemble member of the model.Therefore, considerable effort should be made to improve MJO prediction in IAP AGCM4.1 through application of a reasonable model initialization and ensemble forecast strategy.
基金jointly supported by the National Key Research and Development Program of China grant number 2017YFA0603903the National Natural Science Foundation of China grant numbers 41622503 and 41775101。
文摘This study evaluates the performance of the Grid-point Atmospheric Model of IAP LASG,version 3(GAMIL3),in simulating the Madden–Julian Oscillation(MJO),based on the CMIP6(phase 6 of the Coupled Model Intercomparison Project)AMIP(Atmospheric Model Intercomparison Project)simulation.Results show that GAMIL3 reasonably captures the main features of the MJO,such as the eastward-propagating signal in the MJO frequency band,the symmetric and asymmetric structures of the MJO,several convectively coupled equatorial waves,and the MJO life cycle.However,GAMIL3 underestimates the MJO amplitude,especially for outgoing longwave radiation,as do most CMIP5 models,and simulates slow eastward propagation.
基金supported by Key Project for Integration and Ap-plicaion of Key Meteorological Technology (Grant No.CMAGJ2012Z08)Public Welfare Scientific Research Project (Meteorology) Foundation (Grant No.GYHY201106010)National Natural Science Foundation of China (Grant Nos.40821092,40810059005 and 41105097)
文摘Spring is the critical period for atmospheric circulation transition from winter to summer. The spring water cycle is very im- portant to agriculture in planting crop and the initial growth of crop. Note that there was a significant abrupt decadal change in the water budget increase during early spring over eastern China in the late 1970s. Studied here are the decadal variations of water budgets over the key regions and the associated change of water cycle over East Asia and atmospheric circulation over Asia-West Pacific region in early spring, using the observed （OBS） precipitation, the ECMWF （ERA） and NCEP/NCAR rea- nalysis （NRA）, and the Mantua＇s Pacific decadal oscillation index （PDOI）. The water budget increments from March to April exhibited a sharp decrease over the key region around Huaihe River basin （HHR） （111°-120°E; 31°-36°N） after year 1978. Before 1977 the water vapor flux through south boundary of the HHR region increased greatly during March to April by 1.52 mm d^-1 in ERA and 1.88 mm d^-1 in NRA. Concurrently the moisture convergence and precipitation over the region also in- creased greatly. The increment for the moisture convergence was 1.11 mmd^-1 in ERA and 1.22 mm d^-1 in NRA, and for the precipitation was 1.05 mm d^-1 in observation and 1.05 mm d^-1 in ERA. April was the time that the water budgets over HHR increased most rapidly before 1977. But after 1978 the water budgets decreased conversely from Mach to April. The water vapor flux increment through the south boundary was -0.03 mmd^-1 in ERA and 0.01 mm d^-1 in NRA, the moisture conver- gence increment was -0.91 mm d^-1 in ERA and -0.53 mm d^-1 in NRA, and precipitation increment was -0.08 mm d^-1 in ob- servation and -0.15 mm d^-1 in ERA. Further investigation has shown that the large-scale atmospheric circulation in the early spring has correspondingly changed significantly after the late 1970s. During March to April, the weakening of the trough over East Asia became significantly slower, and the strengthening of the ridge over the west China became significantly faster in the middle troposphere after the late 1970s. At the same time, in the lower troposphere, the strengthening and northward extending of the west pan of the subtropical high and the weakening of the trough over the southwest part of the Aleutian low in the early spring became slower, and the weakening of the main part of Asian high became slower, but the strengthening of its west part became faster. This significant decadal change of circulation caused a sharp decrease in the northward extending speed of wa- ter vapor transport, and in the water budgets increasing speed over the southeastern China during early spring after the late 1970s.
文摘The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vibration. In recent years, the effect of bump wall on the flow field around an airfoil has been investigated experimentally and as a result, it was observed that the bump wall is effective for the control of shock wave on the airfoil. In the transonic or supersonic flow field, a rapid expansion of moist air or steam gives rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation around a circular arc blade with or without a bump on the blade was investigated numerically. The results showed that the non-equilibrium condensation significantly reduced the flow field unsteadiness such as root mean of pressure oscillation and frequency compared to the case without the non-equilibrium condensation.
