The West African Monsoon (WAM) is characterized by strong decadal and multi-decadal variability and the impacts can be catastrophic for the local populations. One of the factors put forward to explain this variability...The West African Monsoon (WAM) is characterized by strong decadal and multi-decadal variability and the impacts can be catastrophic for the local populations. One of the factors put forward to explain this variability involves the role of atmospheric dynamics, linked in particular to the Saharan Heat Low (SHL). This article addresses this question by comparing the sets of preindustrial control and historical simulation data from climate models carried out in the framework of the CMIP5 project and observations data over the 20<sup>th</sup> century. Through multivariate statistical analyses, it was established that decadal modes of ocean variability and decadal variability of Saharan atmospheric dynamics significantly influence decadal variability of monsoon precipitation. These results also suggest the existence of external anthropogenic forcing, which is superimposed on the decadal natural variability inducing an intensification of the signal in the historical simulations compared to preindustrial control simulations. We have also shown that decadal rainfall variability in the Sahel, once the influence of oceanic modes has been eliminated, appears to be driven mainly by the activity of the Arabian Heat Low (AHL) in the central Sahel, and by the structure of the meridional temperature gradient over the inter-tropical Atlantic in the western Sahel.展开更多
Ocean response to atmospheric forcing in the CZ ocean model is analyzed.The results show that Nino 3 indexfrom the CZ ocean model driven by linear composite of biennial,ENSO and even annual time scale wind stressanoma...Ocean response to atmospheric forcing in the CZ ocean model is analyzed.The results show that Nino 3 indexfrom the CZ ocean model driven by linear composite of biennial,ENSO and even annual time scale wind stressanomalies is consistent well with composite of responding two or three components of observed Nino 3 index duringthe EI Nino period while the La Nina phenomena cannot be reproduced by the linear composite.It implies that linearresponse process for ocean response to atmospheric forcing is dominated during the EI Nino period while nonlinearresponse might be main process during the La Nina period.Simulated results also suggest that optimal response frequency of the CZ ocean model is the frequency lowerthan annual variability and ocean response to the atmospheric forcing with annual time scale can give rise to incorrectsignal-errors in the simulated SSTA field.展开更多
This study compares the seasonal and interannual-to-decadal variability in the strength and position of the Kuroshio Extension front(KEF)using high-resolution satellite-derived sea surface temperature(SST)and sea surf...This study compares the seasonal and interannual-to-decadal variability in the strength and position of the Kuroshio Extension front(KEF)using high-resolution satellite-derived sea surface temperature(SST)and sea surface height(SSH)data.Results show that the KEF strength has an obvious seasonal variation that is similar at different longitudes,with a stronger(weaker)KEF during the cold(warm)season.However,the seasonal variation in the KEF position is relatively weak and varies with longitude.In contrast,the low-frequency variation of the KEF position is more distinct than that of the KEF strength even though they are well correlated.On both seasonal and interannual-to-decadal time scales,the western part of the KEF(142°–144°E)has the greatest variability in strength,while the eastern part of the KEF(149°–155°E)has the greatest variability in position.In addition,the relationships between wind-forced Rossby waves and the low-frequency variability in the KEF strength and position are also discussed by using the statistical analysis methods and a wind-driven hindcast model.A positive(negative)North Pacific Oscillation(NPO)-like atmospheric forcing generates positive(negative)SSH anomalies over the central North Pacific.These oceanic signals then propagate westward as Rossby waves,reaching the KE region about three years later,favoring a strengthened(weakened)and northward(southward)-moving KEF.展开更多
As part of a joint effort to construct an atmospheric forcing dataset for China's Mainland with high spatiotemporal reso- lution, a new approach is proposed to construct gridded near-surface temperature, relative ...As part of a joint effort to construct an atmospheric forcing dataset for China's Mainland with high spatiotemporal reso- lution, a new approach is proposed to construct gridded near-surface temperature, relative humidity, wind speed and surface pressure with a resolution of 1 km× 1 km. The approach comprises two steps： （1） fit a partial thin-plate smoothing spline with orography and reanalysis data as explanatory variables to ground-based observations for estimating a trend surface; （2） apply a simple kriging procedure to the residual for trend surface correction. The proposed approach is applied to observations collected at approximately 700 stations over China's Mainland. The generated forcing fields are compared with the corresponding components of the National Centers for Environmental Predic- tion （NCEP） Climate Forecast System Reanalysis dataset and the Princeton meteorological forcing dataset. The comparison shows that, both within the station network and within the resolutions of the two gridded datasets, the interpolation errors of the proposed approach are markedly smaller than the two gridded datasets.展开更多
The persistence barrier of sea surface temperature anomalies （SSTAs） in the North Pacific was investigated and compared with the ENSO spring persistence barrier. The results show that SSTAs in the central western No...The persistence barrier of sea surface temperature anomalies （SSTAs） in the North Pacific was investigated and compared with the ENSO spring persistence barrier. The results show that SSTAs in the central western North Pacific （CWNP） have a persistence barrier in summer： the persistence of SSTAs in the CWNP shows a significant decline in summer regardless of the starting month. Mechanisms of the summer persistence barrier in the CWNP are different from those of the spring persistence barrier of SSTAs in the central and eastern equatorial Pacific. The phase locking of SSTAs to the annual cycle does not explain the CWNP summer persistence barrier. Remote ENSO forcing has little linear influence on the CWNP summer persistence barrier, compared with local upper-ocean process and atmospheric forcing in the North Pacific. Starting in wintertime, SSTAs extend down to the deep winter mixed layer then become sequestered beneath the shallow summer mixed layer, which is decoupled from the surface layer. Thus, wintertime SSTAs do not persist through the following summer. Starting in summertime, persistence of summer SSTAs until autumn can be explained by the atmospheric forcing through a positive SSTAs-cloud/radiation feedback mechanism because the shallow summertime mixed layer is decoupled from the temperature anomalies at depth, then the following autumnwinter-spring, SSTAs persist. Thus, summer SSTAs in the CWNP have a long persistence, showing a significant decline in the following summer. In this way, SSTAs in the CWNP show a persistence barrier in summer regardless of the starting month.展开更多
The Florida Current （FC） largely fills the Straits of Florida and is variable on a broad spectrum of time and space scales. Some portions of the variability are due to variable forcing by tides, winds, heating/cooli...The Florida Current （FC） largely fills the Straits of Florida and is variable on a broad spectrum of time and space scales. Some portions of the variability are due to variable forcing by tides, winds, heating/cooling, and throughflow; other portions are due to intrinsic instabilities of the FC. To predict, as well as to better understand this complex regime, a nowcast/forecast system （East Florida Shelf Information System （EFSIS）） has been implemented and assessed （http：//efsis. rsmas. miami. edu）. EFSIS is based on an implementation of the Princeton Ocean Model （POM） with mesoscale-admitting resolution on a curvilinear grid. It is forced by a mesoscale numerical weather prediction system （called Eta） run operationally by the National Centers for Environmental Prediction （NCEP）, eight tidal constituents from a global tidal model, and lateral boundary conditions from an operational global ocean prediction model, i.e., the Navy Coastal Ocean Model （NCOM）. Real-time observations of coastal sea level, coastal sea surface temperature, coastal HF radar-derived surface current maps, and FC volume transport are used to verify and validate EFSIS. EFSIS is part of an evolving strategy for real-time predictive coastal ocean modeling methodology, and for fostering the understanding of the variability of the regime on several time and space scales. Here, some of the verification and validation results are provided, as well as diagnostic analyses of dynamical processes. The central point is that an example is provided of a ＇scientific revolution＇ in progress that combines real-time observations and numerical circulation models to yield a credible sequence of synoptic views of coastal ocean circulation for the first time.展开更多
The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern O...The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern Oscillation(ENSO).The present study evaluates and compares simulations of the SPQ-ENSO relationship by 20 climate models from CMIP6 and their corresponding 20 previous models from CMIP5.It is found that 16 of the20 pairs of models are able to consistently reproduce the spatial pattern of the SPQ.In terms of simulating the SPQ-ENSO relationship,9 of the 16 CMIP6 models show significant improvement over their previous CMIP5 models.The multi-model ensemble(MME) of these 16 CMIP6 models simulates the SPQ-ENSO connection more realistically than the CMIP5 MME.Further analysis shows that the performance of the model simulations in reproducing the SPQ-ENSO relationship is strongly dependent on their ability to simulate the SPQ-related surface air-sea coupling processes over the southwestern and southeastern South Pacific,as well as the response of the SPQ-related equatorial subsurface ocean temperature anomalies.The improvement of the CMIP6 models in simulating these two processes is responsible for the improved performance of the CMIP6 models over their CMIP5 counterparts in simulating the SPQ-ENSO relationship.展开更多
Near-surface wind speed(NSWS),a determinant of wind energy,is influenced by both natural and anthropogenic factors.However,the specific impacts of volcanic eruptions on NSWS,remain unexplored.Our simulations spanning ...Near-surface wind speed(NSWS),a determinant of wind energy,is influenced by both natural and anthropogenic factors.However,the specific impacts of volcanic eruptions on NSWS,remain unexplored.Our simulations spanning the last millennium reveal a consistent 2-year global NSWS reduction following 10 major historical eruptions.This equates to an NSWS decrease of approximately two inter-annual standard deviations from AD 851 to 1849.This reduction is linked to the weakening of subtropical descending air and a decrease in downward momentum flux,triggered by volcanic aerosol forcing.The 1815 Tambora eruption,one of the most powerful in recent history,led to a~9.2%reduction in global wind power density in the subsequent 2 years.Our research fills a knowledge gap,establishes a theoretical foundation for empirical studies,and highlights the potential wind energy risks linked to large atmospheric aerosol injections,including volcanic eruptions,nuclear warfare,and climate intervention.展开更多
The mean instantaneous runoff rate over a mesoscale region is considered to be the residue between the areal mean precipitation and the amount of water infiltrated into surface soil layer.A rainfall probability densit...The mean instantaneous runoff rate over a mesoscale region is considered to be the residue between the areal mean precipitation and the amount of water infiltrated into surface soil layer.A rainfall probability density function（PDF） derived from rainfall data in 1996 is used,in conjunction with the mathematic description and empirical expression of rain water infiltration physics,in order to accurately estimate the soil infiltration rate and distribution.A statistical-dynamic scheme of regional mean surface runoff is constructed.The runoff rate can be viewed as the difference between mean precipitation and infiltration on a regional basis,and the averaged infiltration can be treated independently over saturated and unsaturated areas.For the physics of land surface water cycle,infiltration is caused by a source of water supply associated with the properties of underlying surface.After rainfall,with part of the water transported into the soil surface layer,runoff occurs just due to the surplus from the water trapped by vegetation cover and soil infiltration.Hence,the key in calculating surface runoff lies dominantly in the estimation of water amount required for surface-layer soil.Thus,the expression for soil water flux is utilized to derive a formula for the infiltration.Similarly,from the PDF for soil moisture and precipitation,a formula of sub-grid regional mean runoff rate is obtained by considering heterogeneous soil water content and climatic rainfall forcing in 1996 as well as precipitation and soil data over the Yangtze delta region.Sensitivity experiments are also done to indentify affecting factors.Evidence suggests that the proposed scheme gives the runoff rates highly close to those from the Mosaic method,thereby demonstrating the high reliability and feasibility of the statistical-dynamic parameterization scheme.展开更多
By using Lorenz’s moist general circulation model, a nonlinear and dissipative system describing atmospheric motion has been obtained in approximation of Low Order.The multiple equilibria and the transformation betwe...By using Lorenz’s moist general circulation model, a nonlinear and dissipative system describing atmospheric motion has been obtained in approximation of Low Order.The multiple equilibria and the transformation between the flow patterns of winter and summer, the latitudinal oscillation of subtropical high by thermal forcing and nonlinear interaction of general circulation are studied in this paper.The results show that the transformation of flow patterns is a discontinuous leaping, and is a process of resetting new flow pattern by rapid exchange inflow field.In the corresponding dry model, we cannot find the latitudinal oscillation of the center of subtropical high.In the moist model, after the thermal effect of water vapor is drawn into the model, nonlinear interaction appears between flow and heating fields.This effect helps to bring about the latitudinal oscillation of subtropical high.展开更多
We havc found that tide-forming forces have an important triggering effect on the abnormal changes in the atmospheric mction. They are different from classical tide-forming forces. The atmospheric tides in the troposp...We havc found that tide-forming forces have an important triggering effect on the abnormal changes in the atmospheric mction. They are different from classical tide-forming forces. The atmospheric tides in the troposphere dcpend primarily upon the tide-forming forces at the time of astronomical singularities. There are three resonance areas, i. c., the areas close to 54.7°and 90°from the sublunar point at the time of astronomical singularities, and the ≤2°area of the sublunar point. The superposition of the resonance arcas of sevcral astronomical singularities may excite anomalies of the atmospheric circulation, including the adjustment and continual anomalies of the extra-long waves, the subtropical high and the blocking situation. It is hopcd that our research can make contributions to thc improvement of medium-range, monthly and seasonai numerical predictions.展开更多
文摘The West African Monsoon (WAM) is characterized by strong decadal and multi-decadal variability and the impacts can be catastrophic for the local populations. One of the factors put forward to explain this variability involves the role of atmospheric dynamics, linked in particular to the Saharan Heat Low (SHL). This article addresses this question by comparing the sets of preindustrial control and historical simulation data from climate models carried out in the framework of the CMIP5 project and observations data over the 20<sup>th</sup> century. Through multivariate statistical analyses, it was established that decadal modes of ocean variability and decadal variability of Saharan atmospheric dynamics significantly influence decadal variability of monsoon precipitation. These results also suggest the existence of external anthropogenic forcing, which is superimposed on the decadal natural variability inducing an intensification of the signal in the historical simulations compared to preindustrial control simulations. We have also shown that decadal rainfall variability in the Sahel, once the influence of oceanic modes has been eliminated, appears to be driven mainly by the activity of the Arabian Heat Low (AHL) in the central Sahel, and by the structure of the meridional temperature gradient over the inter-tropical Atlantic in the western Sahel.
文摘Ocean response to atmospheric forcing in the CZ ocean model is analyzed.The results show that Nino 3 indexfrom the CZ ocean model driven by linear composite of biennial,ENSO and even annual time scale wind stressanomalies is consistent well with composite of responding two or three components of observed Nino 3 index duringthe EI Nino period while the La Nina phenomena cannot be reproduced by the linear composite.It implies that linearresponse process for ocean response to atmospheric forcing is dominated during the EI Nino period while nonlinearresponse might be main process during the La Nina period.Simulated results also suggest that optimal response frequency of the CZ ocean model is the frequency lowerthan annual variability and ocean response to the atmospheric forcing with annual time scale can give rise to incorrectsignal-errors in the simulated SSTA field.
基金The National Natural Science Foundation of China under contract Nos 41975066,41605051 and 41406003the Open Research Fund of State Key Laboratory of Estuarine and Coastal Research under contract No.SKLEC-KF201707+1 种基金the High-Tech Innovation Think-Tank Youth Project under contract No.DXB-ZKQN-2016-019Jiangsu Provincial Natural Science Foundation under contract No.BK20130064。
文摘This study compares the seasonal and interannual-to-decadal variability in the strength and position of the Kuroshio Extension front(KEF)using high-resolution satellite-derived sea surface temperature(SST)and sea surface height(SSH)data.Results show that the KEF strength has an obvious seasonal variation that is similar at different longitudes,with a stronger(weaker)KEF during the cold(warm)season.However,the seasonal variation in the KEF position is relatively weak and varies with longitude.In contrast,the low-frequency variation of the KEF position is more distinct than that of the KEF strength even though they are well correlated.On both seasonal and interannual-to-decadal time scales,the western part of the KEF(142°–144°E)has the greatest variability in strength,while the eastern part of the KEF(149°–155°E)has the greatest variability in position.In addition,the relationships between wind-forced Rossby waves and the low-frequency variability in the KEF strength and position are also discussed by using the statistical analysis methods and a wind-driven hindcast model.A positive(negative)North Pacific Oscillation(NPO)-like atmospheric forcing generates positive(negative)SSH anomalies over the central North Pacific.These oceanic signals then propagate westward as Rossby waves,reaching the KE region about three years later,favoring a strengthened(weakened)and northward(southward)-moving KEF.
基金supported by the National Program on Key Basic Research Project of China (Grant Nos.2010CB951604 and 2010CB950703)the National Natural Science Foundation of China General Program (Grant Nos.40975062 and 40875062)+2 种基金R&D Special Fund for Nonprofit Industry (Grant No.Meteorology GYHY201206008)the Key Technologies Research and Development Program of China (Grant No.2013BAC05B04)the Fundamental Research Funds for the Central Universities (Grant No.2012LYB42)
文摘As part of a joint effort to construct an atmospheric forcing dataset for China's Mainland with high spatiotemporal reso- lution, a new approach is proposed to construct gridded near-surface temperature, relative humidity, wind speed and surface pressure with a resolution of 1 km× 1 km. The approach comprises two steps： （1） fit a partial thin-plate smoothing spline with orography and reanalysis data as explanatory variables to ground-based observations for estimating a trend surface; （2） apply a simple kriging procedure to the residual for trend surface correction. The proposed approach is applied to observations collected at approximately 700 stations over China's Mainland. The generated forcing fields are compared with the corresponding components of the National Centers for Environmental Predic- tion （NCEP） Climate Forecast System Reanalysis dataset and the Princeton meteorological forcing dataset. The comparison shows that, both within the station network and within the resolutions of the two gridded datasets, the interpolation errors of the proposed approach are markedly smaller than the two gridded datasets.
基金supported by the 973 program(Grant No.2010CB950400)the Innovation Key Program(Grant No.KZCX2-YWQ11-02) of the Chinese Academy of Sciences+2 种基金the NSFC project(Grant Nos.41030961,41005042,and 41005049)the Fund of State Key Laboratory of Tropical Oceanography(South China Sea Institute of Oceanology,Chinese Academy of Sciences(LTO1101)the 973 program (Grant No.2012CB956000)
文摘The persistence barrier of sea surface temperature anomalies （SSTAs） in the North Pacific was investigated and compared with the ENSO spring persistence barrier. The results show that SSTAs in the central western North Pacific （CWNP） have a persistence barrier in summer： the persistence of SSTAs in the CWNP shows a significant decline in summer regardless of the starting month. Mechanisms of the summer persistence barrier in the CWNP are different from those of the spring persistence barrier of SSTAs in the central and eastern equatorial Pacific. The phase locking of SSTAs to the annual cycle does not explain the CWNP summer persistence barrier. Remote ENSO forcing has little linear influence on the CWNP summer persistence barrier, compared with local upper-ocean process and atmospheric forcing in the North Pacific. Starting in wintertime, SSTAs extend down to the deep winter mixed layer then become sequestered beneath the shallow summer mixed layer, which is decoupled from the surface layer. Thus, wintertime SSTAs do not persist through the following summer. Starting in summertime, persistence of summer SSTAs until autumn can be explained by the atmospheric forcing through a positive SSTAs-cloud/radiation feedback mechanism because the shallow summertime mixed layer is decoupled from the temperature anomalies at depth, then the following autumnwinter-spring, SSTAs persist. Thus, summer SSTAs in the CWNP have a long persistence, showing a significant decline in the following summer. In this way, SSTAs in the CWNP show a persistence barrier in summer regardless of the starting month.
文摘The Florida Current （FC） largely fills the Straits of Florida and is variable on a broad spectrum of time and space scales. Some portions of the variability are due to variable forcing by tides, winds, heating/cooling, and throughflow; other portions are due to intrinsic instabilities of the FC. To predict, as well as to better understand this complex regime, a nowcast/forecast system （East Florida Shelf Information System （EFSIS）） has been implemented and assessed （http：//efsis. rsmas. miami. edu）. EFSIS is based on an implementation of the Princeton Ocean Model （POM） with mesoscale-admitting resolution on a curvilinear grid. It is forced by a mesoscale numerical weather prediction system （called Eta） run operationally by the National Centers for Environmental Prediction （NCEP）, eight tidal constituents from a global tidal model, and lateral boundary conditions from an operational global ocean prediction model, i.e., the Navy Coastal Ocean Model （NCOM）. Real-time observations of coastal sea level, coastal sea surface temperature, coastal HF radar-derived surface current maps, and FC volume transport are used to verify and validate EFSIS. EFSIS is part of an evolving strategy for real-time predictive coastal ocean modeling methodology, and for fostering the understanding of the variability of the regime on several time and space scales. Here, some of the verification and validation results are provided, as well as diagnostic analyses of dynamical processes. The central point is that an example is provided of a ＇scientific revolution＇ in progress that combines real-time observations and numerical circulation models to yield a credible sequence of synoptic views of coastal ocean circulation for the first time.
基金This research was jointly supported by the National Natural Science Foundation of China[Grant number 41975070]the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences[Project number LTO1901].
文摘The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern Oscillation(ENSO).The present study evaluates and compares simulations of the SPQ-ENSO relationship by 20 climate models from CMIP6 and their corresponding 20 previous models from CMIP5.It is found that 16 of the20 pairs of models are able to consistently reproduce the spatial pattern of the SPQ.In terms of simulating the SPQ-ENSO relationship,9 of the 16 CMIP6 models show significant improvement over their previous CMIP5 models.The multi-model ensemble(MME) of these 16 CMIP6 models simulates the SPQ-ENSO connection more realistically than the CMIP5 MME.Further analysis shows that the performance of the model simulations in reproducing the SPQ-ENSO relationship is strongly dependent on their ability to simulate the SPQ-related surface air-sea coupling processes over the southwestern and southeastern South Pacific,as well as the response of the SPQ-related equatorial subsurface ocean temperature anomalies.The improvement of the CMIP6 models in simulating these two processes is responsible for the improved performance of the CMIP6 models over their CMIP5 counterparts in simulating the SPQ-ENSO relationship.
基金supported by Swedish Formas(2019-01520 and 2023-01648)the Natural Science Foundation of China(42488201 and 41975107)+2 种基金the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)supported by the Sven Lindqvists Forskningsstiftelse,Stiftelsen L€angmanska Kulturfonden(BA24-0484)StiftelsenÅforsk(24-707)and Adlerbertska Forskningsstiftelsen(AF2024-0069).
文摘Near-surface wind speed(NSWS),a determinant of wind energy,is influenced by both natural and anthropogenic factors.However,the specific impacts of volcanic eruptions on NSWS,remain unexplored.Our simulations spanning the last millennium reveal a consistent 2-year global NSWS reduction following 10 major historical eruptions.This equates to an NSWS decrease of approximately two inter-annual standard deviations from AD 851 to 1849.This reduction is linked to the weakening of subtropical descending air and a decrease in downward momentum flux,triggered by volcanic aerosol forcing.The 1815 Tambora eruption,one of the most powerful in recent history,led to a~9.2%reduction in global wind power density in the subsequent 2 years.Our research fills a knowledge gap,establishes a theoretical foundation for empirical studies,and highlights the potential wind energy risks linked to large atmospheric aerosol injections,including volcanic eruptions,nuclear warfare,and climate intervention.
基金Supported by the Natural Science Foundation of China under Grant No.40375035
文摘The mean instantaneous runoff rate over a mesoscale region is considered to be the residue between the areal mean precipitation and the amount of water infiltrated into surface soil layer.A rainfall probability density function（PDF） derived from rainfall data in 1996 is used,in conjunction with the mathematic description and empirical expression of rain water infiltration physics,in order to accurately estimate the soil infiltration rate and distribution.A statistical-dynamic scheme of regional mean surface runoff is constructed.The runoff rate can be viewed as the difference between mean precipitation and infiltration on a regional basis,and the averaged infiltration can be treated independently over saturated and unsaturated areas.For the physics of land surface water cycle,infiltration is caused by a source of water supply associated with the properties of underlying surface.After rainfall,with part of the water transported into the soil surface layer,runoff occurs just due to the surplus from the water trapped by vegetation cover and soil infiltration.Hence,the key in calculating surface runoff lies dominantly in the estimation of water amount required for surface-layer soil.Thus,the expression for soil water flux is utilized to derive a formula for the infiltration.Similarly,from the PDF for soil moisture and precipitation,a formula of sub-grid regional mean runoff rate is obtained by considering heterogeneous soil water content and climatic rainfall forcing in 1996 as well as precipitation and soil data over the Yangtze delta region.Sensitivity experiments are also done to indentify affecting factors.Evidence suggests that the proposed scheme gives the runoff rates highly close to those from the Mosaic method,thereby demonstrating the high reliability and feasibility of the statistical-dynamic parameterization scheme.
文摘By using Lorenz’s moist general circulation model, a nonlinear and dissipative system describing atmospheric motion has been obtained in approximation of Low Order.The multiple equilibria and the transformation between the flow patterns of winter and summer, the latitudinal oscillation of subtropical high by thermal forcing and nonlinear interaction of general circulation are studied in this paper.The results show that the transformation of flow patterns is a discontinuous leaping, and is a process of resetting new flow pattern by rapid exchange inflow field.In the corresponding dry model, we cannot find the latitudinal oscillation of the center of subtropical high.In the moist model, after the thermal effect of water vapor is drawn into the model, nonlinear interaction appears between flow and heating fields.This effect helps to bring about the latitudinal oscillation of subtropical high.
文摘We havc found that tide-forming forces have an important triggering effect on the abnormal changes in the atmospheric mction. They are different from classical tide-forming forces. The atmospheric tides in the troposphere dcpend primarily upon the tide-forming forces at the time of astronomical singularities. There are three resonance areas, i. c., the areas close to 54.7°and 90°from the sublunar point at the time of astronomical singularities, and the ≤2°area of the sublunar point. The superposition of the resonance arcas of sevcral astronomical singularities may excite anomalies of the atmospheric circulation, including the adjustment and continual anomalies of the extra-long waves, the subtropical high and the blocking situation. It is hopcd that our research can make contributions to thc improvement of medium-range, monthly and seasonai numerical predictions.
