Global existence of weak and strong solutions to the quasi-hydrostatic primitive equations is studied in this paper. This model, that derives from the full non-hydrostatic model for geophysical fluid dynamics in the z...Global existence of weak and strong solutions to the quasi-hydrostatic primitive equations is studied in this paper. This model, that derives from the full non-hydrostatic model for geophysical fluid dynamics in the zero-limit of the aspect ratio, is more realistic than the classical hydrostatic model, since the traditional approximation that consists in neglecting a part of the Coriolis force is relaxed. After justifying the derivation of the model, the authors provide a rigorous proof of global existence of weak solutions, and well-posedness for strong solutions in dimension three.展开更多
To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is...To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is developed. Numerical computation of the annually cyclic circulation fields is performed. The results of the annual mean zonal currents and deep to abyssal western boundary currents in the equatorial Pacific Ocean are reported. The North Equatorial Current,the North Equatorial Countercurrent, the South Equatorial Current and the Equatorial Undercurrent are fairly well simulated. The model well reproduces the northward flowing abyssal western boundary current.From the model results a lower deep western boundary current east of the Bismarck-Solomon-New Hebrides Island chain at depths around 2 000 m has been found. The model results also show that the currents in the equatorial Pacific Ocean have multi-layer structures both in zonal currents and western boundary currents, indicating that the global ocean overturning thermohaline circulation appears of multi-layer pattern.展开更多
Based on the observational data in summer,the variations of intraseasonal oscillation(ISO)of the daily rainfall over the lower reaches of the Yangtze River valley(LYRV)were studied by using the non-integer spectrum an...Based on the observational data in summer,the variations of intraseasonal oscillation(ISO)of the daily rainfall over the lower reaches of the Yangtze River valley(LYRV)were studied by using the non-integer spectrum analysis.The NCEP/NCAR reanalysis data for the period of 1979―2005 were analyzed by principal oscillation pattern analysis(POP)to investigate the spatial and temporal characteristics of principal ISO patterns of the global circulation.The relationships of these ISO patterns to the rainfall ISO and the heavy precipitation process over LYRV were also discussed.It is found that the rainfall over LYRV in May―August is mainly of periodic oscillations of 10―20,20―30 and 60―70 days,and the interannual variation of the intensity of its 20―30-day oscillation has a strongly positive correlation with the number of the heavy precipitation process.Two modes(POP1,POP2)are revealed by POP for the 20―30-day oscillation of the global 850 hPa geopotential height.One is a circumglobal telecon-nection wave train in the middle latitude of the Southern Hemisphere(SCGT)with an eastward propagation,and the other is the southward propagation pattern in the tropical western Pacific(TWP).The POP modes explain 7.72%and 7.66%of the variance,respectively.These two principal ISO patterns are closely linked to the low frequency rainfall and heavy precipitation process over LYRV,in which the probability for the heavy precipitation process over LYRV is 54.9%and 60.4%for the positive phase of the imaginary part of POP1 and real part of POP2,respectively.Furthermore,the models of the global atmospheric circulation for the 20―30-day oscillation in association with or without the heavy pre-cipitation process over LYRV during the Northern Hemisphere summer are set up by means of the composite analysis method.Most of the heavy precipitation processes over LYRV appear in Phase 4 of SCGT or Phase 6 of TWP.When the positive phases of 20―30-day oscillations for the rainfall over LYRV are associated with(without)the heavy precipitation process,a strong westerly stream appears(disappears)from the Arabian Sea via India and Bay of Bengal(BOB)to southern China and LYRV for the global 850 hPa filtered wind field during Phase 4 of SCGT.This situation is favorable(unfavorable)for the forming of the heavy precipitation process over LYRV.Similarly,a strong(weak)western wind belt forms from India through BOB to southern China and LYRV and the subtropical northwestern Pacific and central and eastern equatorial Pacific during Phase 6 of TWP for the cases with(without)the heavy precipitation process.The evolutions of these ISO patterns related to the 20―30-day oscillation are excited by either the interaction of extratropical circulation in both hemispheres or the heat source forcing in Asia monsoon domain and internal interaction of circulation in East Asia.These two global circulation models might therefore provide valuable information for the extended-range forecast of the heavy precipitation process over LYRV during the 10―30 days.展开更多
The objective of this study is to model the mean and seasonal mass transportof the Pacific to Indian O-cean throughflow using variable-grid global Ocean General CirculationModel (OGCM) with fine grid (1°/6) cover...The objective of this study is to model the mean and seasonal mass transportof the Pacific to Indian O-cean throughflow using variable-grid global Ocean General CirculationModel (OGCM) with fine grid (1°/6) covering the area from 20°S to 60°N and from 98°E to 156°E.The computations show that Indonesian Throughflow (ITF) mass transport, computed as a sum ofthrough-strait transport, has maximum transport in Sept. (17. 5Sv) and minimum transport in Jan. (9.5Sv). The annual mean ITF transport amounts to 14. 5Sv. Twenty-two percent of this transport passesthrough Lombok Strait. Sixty-five percent of this transport passes through Timor Passage.Semi-annual variability is apparent in Lombok and Ombai Straits while annual variability is apparentin Timor Passage.展开更多
Nonpoint source pollution from agriculture is the main source of nitrogen and phosphorus in the stream systems of the Corn Belt region in the Midwestern US.The eastern part of this region is comprised of the Ohio-Tenn...Nonpoint source pollution from agriculture is the main source of nitrogen and phosphorus in the stream systems of the Corn Belt region in the Midwestern US.The eastern part of this region is comprised of the Ohio-Tennessee River Basin(OTRB),which is considered a key contributing area for water pollution and the Northern Gulf of Mexico hypoxic zone.A point of crucial importance in this basin is therefore how intensive corn-based cropping systems for food and fuel production can be sustainable and coexist with a healthy water environment,not only under existing climate but also under climate change conditions in the future.To address this issue,a OTRB integrated modeling system has been built with a greatly refined 12-digit subbasin structure based on the Soil and Water Assessment Tool(SWAT)water quality model,which is capable of estimating landscape and in-stream water and pollutant yields in response to a wide array of alternative cropping and/or management strategies and climatic conditions.The effects of three agricultural management scenarios on crop production and pollutant loads exported from the crop land of the OTRB to streams and rivers were evaluated:(1)expansion of continuous corn across the entire basin,(2)adoption of no-till on all corn and soybean fields in the region,(3)implementation of a winter cover crop within the baseline rotations.The effects of each management scenario were evaluated both for current climate and projected mid-century(2046-2065)climates from seven global circulation models(GCMs).In both present and future climates each management scenario resulted in reduced erosion and nutrient loadings to surface water bodies compared to the baseline agricultural management,with cover crops causing the highest water pollution reduction.Corn and soybean yields in the region were negligibly influenced from the agricultural management scenarios.On the other hand,both water quality and crop yield numbers under climate change deviated considerably for all seven GCMs compared to the baseline climate.Future climates from all GCMs led to decreased corn and soybean yields by up to 20%on a mean annual basis,while water quality alterations were either positive or negative depending on the GCM.The study highlights the loss of productivity in the eastern Corn Belt under climate change,the need to consider a range of GCMs when assessing impacts of climate change,and the value of SWAT as a tool to analyze the effects of climate change on parameters of interest at the basin scale.展开更多
基金supported by the ANR (No. ANR-06-BLAN0306-01)the National Science Foundation (No.NSF-DMS-0906440) and the Research Fund of Indiana University
文摘Global existence of weak and strong solutions to the quasi-hydrostatic primitive equations is studied in this paper. This model, that derives from the full non-hydrostatic model for geophysical fluid dynamics in the zero-limit of the aspect ratio, is more realistic than the classical hydrostatic model, since the traditional approximation that consists in neglecting a part of the Coriolis force is relaxed. After justifying the derivation of the model, the authors provide a rigorous proof of global existence of weak solutions, and well-posedness for strong solutions in dimension three.
基金This study is supported by the National Natural Sci-ence Foundation of China under contract No.40136010the Major State Basic Research Program of China under contract No.G1999043808the Youth Fund of National“863”Project of China under contract No.2002AA639350.
文摘To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is developed. Numerical computation of the annually cyclic circulation fields is performed. The results of the annual mean zonal currents and deep to abyssal western boundary currents in the equatorial Pacific Ocean are reported. The North Equatorial Current,the North Equatorial Countercurrent, the South Equatorial Current and the Equatorial Undercurrent are fairly well simulated. The model well reproduces the northward flowing abyssal western boundary current.From the model results a lower deep western boundary current east of the Bismarck-Solomon-New Hebrides Island chain at depths around 2 000 m has been found. The model results also show that the currents in the equatorial Pacific Ocean have multi-layer structures both in zonal currents and western boundary currents, indicating that the global ocean overturning thermohaline circulation appears of multi-layer pattern.
基金Supported by the Program for the Fundamental Research of China Meteorological Administration(Grant No.200726)
文摘Based on the observational data in summer,the variations of intraseasonal oscillation(ISO)of the daily rainfall over the lower reaches of the Yangtze River valley(LYRV)were studied by using the non-integer spectrum analysis.The NCEP/NCAR reanalysis data for the period of 1979―2005 were analyzed by principal oscillation pattern analysis(POP)to investigate the spatial and temporal characteristics of principal ISO patterns of the global circulation.The relationships of these ISO patterns to the rainfall ISO and the heavy precipitation process over LYRV were also discussed.It is found that the rainfall over LYRV in May―August is mainly of periodic oscillations of 10―20,20―30 and 60―70 days,and the interannual variation of the intensity of its 20―30-day oscillation has a strongly positive correlation with the number of the heavy precipitation process.Two modes(POP1,POP2)are revealed by POP for the 20―30-day oscillation of the global 850 hPa geopotential height.One is a circumglobal telecon-nection wave train in the middle latitude of the Southern Hemisphere(SCGT)with an eastward propagation,and the other is the southward propagation pattern in the tropical western Pacific(TWP).The POP modes explain 7.72%and 7.66%of the variance,respectively.These two principal ISO patterns are closely linked to the low frequency rainfall and heavy precipitation process over LYRV,in which the probability for the heavy precipitation process over LYRV is 54.9%and 60.4%for the positive phase of the imaginary part of POP1 and real part of POP2,respectively.Furthermore,the models of the global atmospheric circulation for the 20―30-day oscillation in association with or without the heavy pre-cipitation process over LYRV during the Northern Hemisphere summer are set up by means of the composite analysis method.Most of the heavy precipitation processes over LYRV appear in Phase 4 of SCGT or Phase 6 of TWP.When the positive phases of 20―30-day oscillations for the rainfall over LYRV are associated with(without)the heavy precipitation process,a strong westerly stream appears(disappears)from the Arabian Sea via India and Bay of Bengal(BOB)to southern China and LYRV for the global 850 hPa filtered wind field during Phase 4 of SCGT.This situation is favorable(unfavorable)for the forming of the heavy precipitation process over LYRV.Similarly,a strong(weak)western wind belt forms from India through BOB to southern China and LYRV and the subtropical northwestern Pacific and central and eastern equatorial Pacific during Phase 6 of TWP for the cases with(without)the heavy precipitation process.The evolutions of these ISO patterns related to the 20―30-day oscillation are excited by either the interaction of extratropical circulation in both hemispheres or the heat source forcing in Asia monsoon domain and internal interaction of circulation in East Asia.These two global circulation models might therefore provide valuable information for the extended-range forecast of the heavy precipitation process over LYRV during the 10―30 days.
文摘The objective of this study is to model the mean and seasonal mass transportof the Pacific to Indian O-cean throughflow using variable-grid global Ocean General CirculationModel (OGCM) with fine grid (1°/6) covering the area from 20°S to 60°N and from 98°E to 156°E.The computations show that Indonesian Throughflow (ITF) mass transport, computed as a sum ofthrough-strait transport, has maximum transport in Sept. (17. 5Sv) and minimum transport in Jan. (9.5Sv). The annual mean ITF transport amounts to 14. 5Sv. Twenty-two percent of this transport passesthrough Lombok Strait. Sixty-five percent of this transport passes through Timor Passage.Semi-annual variability is apparent in Lombok and Ombai Straits while annual variability is apparentin Timor Passage.
基金This research was partially funded by the National Science Foundation,Award No.DEB1010259,Understanding Land Use Decisions&Watershed Scale Interactions:Water Quality in the Mississippi River Basin&Hypoxic Conditions in the Gulf of Mexicoby the U.S.Department of Agriculture,National Institute of Food and Agriculture,Award No.20116800230190,Climate Change,Mitigation,and Adaptation In Corn-Based Cropping Systems.
文摘Nonpoint source pollution from agriculture is the main source of nitrogen and phosphorus in the stream systems of the Corn Belt region in the Midwestern US.The eastern part of this region is comprised of the Ohio-Tennessee River Basin(OTRB),which is considered a key contributing area for water pollution and the Northern Gulf of Mexico hypoxic zone.A point of crucial importance in this basin is therefore how intensive corn-based cropping systems for food and fuel production can be sustainable and coexist with a healthy water environment,not only under existing climate but also under climate change conditions in the future.To address this issue,a OTRB integrated modeling system has been built with a greatly refined 12-digit subbasin structure based on the Soil and Water Assessment Tool(SWAT)water quality model,which is capable of estimating landscape and in-stream water and pollutant yields in response to a wide array of alternative cropping and/or management strategies and climatic conditions.The effects of three agricultural management scenarios on crop production and pollutant loads exported from the crop land of the OTRB to streams and rivers were evaluated:(1)expansion of continuous corn across the entire basin,(2)adoption of no-till on all corn and soybean fields in the region,(3)implementation of a winter cover crop within the baseline rotations.The effects of each management scenario were evaluated both for current climate and projected mid-century(2046-2065)climates from seven global circulation models(GCMs).In both present and future climates each management scenario resulted in reduced erosion and nutrient loadings to surface water bodies compared to the baseline agricultural management,with cover crops causing the highest water pollution reduction.Corn and soybean yields in the region were negligibly influenced from the agricultural management scenarios.On the other hand,both water quality and crop yield numbers under climate change deviated considerably for all seven GCMs compared to the baseline climate.Future climates from all GCMs led to decreased corn and soybean yields by up to 20%on a mean annual basis,while water quality alterations were either positive or negative depending on the GCM.The study highlights the loss of productivity in the eastern Corn Belt under climate change,the need to consider a range of GCMs when assessing impacts of climate change,and the value of SWAT as a tool to analyze the effects of climate change on parameters of interest at the basin scale.
