Cirque glaciers found on the Colorado Front Range, USA are sensitive to climate change and are important for water supply and the delivery of water downstream. These glaciers are shrinking at a rapid rate in response ...Cirque glaciers found on the Colorado Front Range, USA are sensitive to climate change and are important for water supply and the delivery of water downstream. These glaciers are shrinking at a rapid rate in response to the global climate change, and thus it is important to track and analyze them. One of the ways to monitor these glaciers is by using multispectral satellite imagery (Landsat imagery). In this article, the feasibility of tracking glacial area via Landsat satellites has been discussed and the trend of 13 glaciers in the Colorado Front Range Region has been analyzed from 1993 to 2021. In this period, the total glacial area across 13 glaciers in the Colorado Front Range Region has decreased by 63.6%, and a significant correlation (p-value p < 0.05) found with the annual global average temperature indicates that the retraction of glaciers is likely a response to the global warming.展开更多
An atypical occlusion process that occurred in North China on 14 July 2011 is studied based on both observations and a real-data Weather Research and Forecasting (WRF) model simulation. The results show that this at...An atypical occlusion process that occurred in North China on 14 July 2011 is studied based on both observations and a real-data Weather Research and Forecasting (WRF) model simulation. The results show that this atypical occlusion process was significantly different from the traditional, synoptic-scale occlusion process that occurs within extratropical cyclones. It was caused by the merger of two cold-type mesoscale fronts. One of the fronts developed from the gust front of convective storms, while the other was a sea-breeze front. As the two fronts moved towards each other, the warm air between them was squeezed and separated from the surface. An atypical occluded front was formed when the two fronts merged, with the warm air forced aloft. This kind of occlusion is termed a "merger" process, different from the well-known "catch-up" and "wrap-up" processes. Moreover, local convection was found to be enhanced during the merger process, with severe convective weather produced in the merger area.展开更多
The daily 1°× 1° data of the Aviation (AVN) model, the black body temperature (TBB) data of cloud top, and cloud images by geostationary meteorological satellite (GMS) are used to identify a dew-p...The daily 1°× 1° data of the Aviation (AVN) model, the black body temperature (TBB) data of cloud top, and cloud images by geostationary meteorological satellite (GMS) are used to identify a dew-point front near the periphery of the western Pacific subtropical high (WPSH). The results clearly demonstrate the existence of the dew-point front, and its thermodynamic and dynamic structural characteristics are analyzed in detail. The dew-point front is a transitional belt between the moist southwest monsoon flow and the dry adiabatic sinking flow near the WPSH, manifested by a large horizontal moisture gradient in the mid-lower troposphere and conjugated with the mei-yu front to form a predominant double-front structure associated with intense rainfall in the mei-yu period. The mei-yu front is located between 30° and 35°N, vertically extends from the ground level to the upper level and shifts northward. The dew-point front is to the south of the mei-yu front and lies up against the periphery of the WPSH. Generally, it is located between 850 hPa and 500 hPa. On the dew-point front side, the southwesterly prevails at the lower level and the northeasterly at the upper level; this wind distribution is different from that on the mei-yu front side. Vertical ascending motion exists between the two fronts, and there are descending motions on the north side of the mei^yu front and on the south side of the dew-point front~ which form a secondary circulation. The dynamics of the double fronts also have some interesting features. At the lower level, positive vertical vorticity and obvious convergence between the two fronts are clearly identified. At the mid-lower level, negative local change of the divergence (corresponding to increasing convergence) is often embedded in the two fronts or against the mei-yu front. Most cloud clusters occur between the two fronts and propagate down stream in a wave-like manner.展开更多
The baroclinic nonlinear stability of fronts in the ocean on a sloping continental shelf is studied, the model equations, called the frontal geostrophic model, developed by Cushman—Roisin et al.(1992) for describing ...The baroclinic nonlinear stability of fronts in the ocean on a sloping continental shelf is studied, the model equations, called the frontal geostrophic model, developed by Cushman—Roisin et al.(1992) for describing the dynamics of surface density fronts in the ocean are developed and the two—layer frontal geostrophic model for fronts on a sloping continental shelf is first obtained. The nonlinear stability criteria for the fronts on a sloping bottom are obtained by using Arnol’d (1965, 1969) variational principle and a prior estimate method. It is shown that our result is better than the former works. Key words Fronts in the ocean - Frontal geostrophic model - Nonlinear stability This Work was supported by “ the National Key Programme for Developing Basic Sciences” G199804901-1 and the National Natural Science Foundation of China “ Research Programme for Excellent State Key Laboratory” under Grant No. 49823002 and No. 49805002.展开更多
Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis w...Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis which is usually defined as an increasing of the scalar gradient. In this paper, the characteristic features of air flow with initial imbalance between the wind and the density fields are studied. Much attention is paid on the condition for the formation of discontinuity and its time scale. It is found that the initial distribution of density plays an important role in the formation of the discontinuity which happens in short time duration.展开更多
Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea (HES) were examined using the data collected from four airborne expendable bathythermo...Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea (HES) were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m(from the surface to 400 m deep) spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows : ( 1 ) multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; (2) springtime frontal eddy-like feature around Tsushima front; (3) year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and (4) multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.展开更多
During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmos- pheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristi...During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmos- pheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristics along the cruise are studied based on in-situ observation. The observations reveal that vertical distributions of the low-level wind field and air temperature field on both sides of the Subantarctic Front are very different. A stronger (weaker) vertical gradient is on the cold (warm) side, which demonstrates that the mid-latitude ocean-atmosphere interaction is active in the southeast Indian Ocean frontal region. A low-level jet is observed over the Subantarctic Front, with speed up to 14 m's-1. For the Antarctic polar front, low-level wind speed near the sea surface is greater than that aloft, in contrast with the situation of the Subantarctic Front. Comparing satellite remote sensing data and widely-used reanalysis datasets with our in-situ observations, differences of varying magnitudes are found. Air temperature from Atmospheric Infrared Sounder (AIRS) data has a limited difference. The European Center for Medium Range Weather Forecasts Interim Re-Analysis (ERA Interim) dataset is much more consistent with the observations than the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1 in the southeast Indian Ocean frontal region.展开更多
In order to study the characteristic features of the frontal motion over mountains, a frontal model is designed inthis paper. The analytical solution of the model with the assumption of semigeostrophic approximation a...In order to study the characteristic features of the frontal motion over mountains, a frontal model is designed inthis paper. The analytical solution of the model with the assumption of semigeostrophic approximation and no frichon is obtained and compared with numerical solution without the assumption. It assumes that the front is a free surface betWeen two nuid layers with different densihes. It also assumes that the mountain and the front are indefinitelylong. Therefore, the motion of such a front can be determined by the one-dimensional shallow water equationsystem. By making a series of experiments, we confirm the rule further that front can be retarded when climbing themountain and accelerated when going down the mountains. We also found some interesting characteristics of frontalstructure influenced by topography in addihon.展开更多
On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using t...On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using the thermodynamical equation and frontogenetical function. The results show that the outbreak of the severe storm is closely related to the local frontogenesis. In fact, the interaction between the shearing instability of the low-level jet (LLJ) and the topographic forcing generates an gravity-inertia wave as well as local frontogenesis (the ?rst front), which consequently induce the onset of the severe storm. From then on, owing to the horizontal and vertical advection of the potential temperature, the new frontogenesis (the second front) is formed to the northeast side of the severe storm, which initiates the second rain belt. Meanwhile, a two-front structure emerges over the southeastern part of Hubei province. Accompanied with the further intensi?cation of the convection, the rain droplets evaporation cooling strengthens the ?rst front and weakens the second front, resulting in single front structure over the southeastern part of Hubei province in the period of the strong convection.展开更多
In this paper we study the strong and weak property of travelling wave front solutions for a class of degenerate parabolic equations. How the strong and weak property changes under the effects of wave speed and reacti...In this paper we study the strong and weak property of travelling wave front solutions for a class of degenerate parabolic equations. How the strong and weak property changes under the effects of wave speed and reaction diffusion terms are showed.展开更多
AIM:To evaluate the efficacy and safety of paclitaxelnedaplatin combination as a front-line regimen in Chinese patients with metastatic esophageal squamous cell carcinoma(ESCC).METHODS:A two-center,open-label,single-a...AIM:To evaluate the efficacy and safety of paclitaxelnedaplatin combination as a front-line regimen in Chinese patients with metastatic esophageal squamous cell carcinoma(ESCC).METHODS:A two-center,open-label,single-arm phaseⅡstudy was designed.Thirty-nine patients were enrolled and included in the intention-to-treat analysis of efficacy and adverse events.Patients received 175mg/m2of paclitaxel over a 3 h infusion on 1 d,followed by nedaplatin 80 mg/m2in a 1 h infusion on 2 d every3 wk until the documented disease progression,unac-ceptable toxicity or patient’s refusal.RESULTS:Of the 36 patients assessable for efficacy,there were 2 patients(5.1%)with complete response and 16 patients(41.0%)with partial response,giving an overall response rate of 46.1%.The median progression-free survival and median overall survival for all patients were 7.1 mo(95%CI:4.6-9.7)and 12.4 mo(95%CI:9.5-15.3),respectively.Toxicities were moderate and manageable.Grade 3/4 toxicities included neutropenia(15.4%),nausea(10.3%),anemia(7.7%),thrombocytopenia(5.1%),vomiting(5.1%)and neutropenia fever(2.6%).CONCLUSION:The combination of paclitaxel and nedaplatin is active and well tolerated as a first-line therapy for patients with metastatic ESCC.展开更多
In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with stro...In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with strong horizontal gradient, a deep-convective cloud tower band, a passageway transporting warm and moist air flow from the summer monsoon surge in the mid and low levels to the south of the mei-yu front, and a migrating synoptic scale trough to the north of the mei-yu front, which transports cold and dry air southward in the mid and upper levels. The maintenance of the mei-yu front is realized by: (1) is a positive feedback between the moist physical process enhancing frontogenesis and the development of the strong convective system in front of the mei-yu front; (2) the sustaining system to the north of the mei-yu front which is a migrating synoptic scale trough transporting cold and dry air to the mei-yu front and positive vorticity to the mesoscale system in front of the mei-yu front.展开更多
Two predominant currents, the warm Kuroshio Current and the cold Oyashio Current, meet in the North- west Pacific Ocean. The dynamics of physical oceanographic structures in this region, including frontal zones and me...Two predominant currents, the warm Kuroshio Current and the cold Oyashio Current, meet in the North- west Pacific Ocean. The dynamics of physical oceanographic structures in this region, including frontal zones and meandering eddies, result in a highly productive habitat that serves as a favorable feeding ground for various commercially important species. Neon flying squid, Ommastrephes bartramii, is an im- portant oceanic squid, which is widely distributed in the North Pacific Ocean. Based on the catch data col- lected by Chinese squid jigging fleets and relevant environmental data, including sea surface temperature (SST) and fronts (represented by gradients of SST and thermocline) during 1998-2009, the variations of oceanic fronts and their influence on the fishing grounds of O. bartramii were evaluated, and the differ- ences in distribution of fishing grounds of O. bartramii in 2000 and 2002 were compared by describing the differences in vertical temperature between 0-300 m. It was found that the preferred horizontal tem- perature gradient of SST for O. bartramii tended to be centered at 0.01-0.02~C/nm, which attracted nearly 80% of the total fishing effort, and the preferred horizontal temperature gradients at the 50 m and 105 m layers were mainly located at 0.01-0.03~C/nm, which accounted for more than 70% of the total fishing effort during August-October. The preferred vertical temperature gradient within the 0-50 m layer for O. bartramii tended to be centered at 0.15-0.25~C/m during August and September and at 0.10-0.15~C/m in October, implying that the mixed surface layer was distributed at depths of 0-50 m. It was concluded that the vertical temperature gradient was more important than the horizontal temperature gradient in playing a role in forming the fishing ground. The results improved our understanding of the spatial dynamics of the 0. bartramii fishery.展开更多
Hydrographic data, ADCP velocity and sea level anomaly derived from the satellite altimeter have been jointly analyzed in the southeast lndian Ocean. Results show the locations and orientations of the major oceanic fr...Hydrographic data, ADCP velocity and sea level anomaly derived from the satellite altimeter have been jointly analyzed in the southeast lndian Ocean. Results show the locations and orientations of the major oceanic fronts as well as the characteristics of the currents within these fronts in the area. Double subtropical fronts are observed in the section along 120°E, which conflicts with the frontal structure frequently observed before the North Subtropical Front (NSTF) and South Subtropical Front (SSTF) merge into a single STF between 110°-115°E. The Subantarctic Front (SAF), influenced by the out-of-phase double eddies, runs across 48°S three times between 120° and 127°E. The surface current within the SAF is strengthened up to 105.4 cm/s by the geostrophic effect of these eddies. Furthermore eddies may cause the strong current to split up into two branches within the SAF. The SAF and the primary polar front (PFI) can be identified individually in the ADCP data with a separation distance of about 0.3° at latitude between 140° and 145°E, although they cannot be identified separately in the low-resolution hydrographic data. The different thcrmohaline characteristics of Circumpolar Deep Water (CDW) and Modified Circumpolar Deep Water (MCDW) result in the formation of Southern Antarctic Circumpolar Current Front (SACCF) in the southeast Indian Ocean. It consistently turns northward along the east flank of the Kerguclen Plateau after it runs through the Princess Elizabeth Trough and turns southward sharply north of 60°S with a little seasonal variations. It is shown that the locations and orientations of the SAK the primary PF and SACCF in the ACC of the southeast Indian Ocean can be identified more precisely by the current distribution derived from ADCP data than by hydrographic data, because these fronts are usually accompanied by strong currents. However, the locations and orientations of the STF and the secondary PF are more difficult to be identified through current data, since these two fronts are usually not accompanied by any jet. The STF the and the secondary PF are usually confined in the first few hundred meters of the upper ocean and the latter is often determined by the northern terminus of 2 ℃ isothermal.展开更多
Monitoring of the South China Sea is always one of the focuses in the field of ocean engineering for its particular geographic position. The modal wave number tomography is proposed for monitoring the front and numeri...Monitoring of the South China Sea is always one of the focuses in the field of ocean engineering for its particular geographic position. The modal wave number tomography is proposed for monitoring the front and numerical simulation is performed for the front of the South China Sea. With the empirical orthonormal function (EOF) applied to reduce the parameter search space, the perturbation inversion method is used for inversing sound speed profiles. The 2-D ocean environment used for numerical simulation is selected from the ocean area, located in 20°N, 118°E~20°N, 125°E, near the Luzon Strait in the South China Sea. The ocean environment sound speed distribution in the ocean area under study is obtained from the assimilation of multi-source remote sensing data. The numerical simulation shows that the modal wave number tomography can inverse the average sound speed profile, therefore,it can be used to monitor ocean internal structures such as ocean fronts and eddies which affect sound speed distribution.展开更多
The conventional and intensive observational data of the China Heavy Rain Experiment and Study (CHeRES) are used to specially analyze the heavy rainfall process in the mei-yu front that occurred during 20-21 June 2002...The conventional and intensive observational data of the China Heavy Rain Experiment and Study (CHeRES) are used to specially analyze the heavy rainfall process in the mei-yu front that occurred during 20-21 June 2002, focusing on the meso-β system. A mesoscale convective system (MCS) formed in the warm-moist southwesterly to the south of the shear line over the Dabie Mountains and over the gorge between the Dabie and Jiuhua Mountains. The mei-yu front and shear line provide a favorable synoptic condition for the development of convection. The GPS observation indicates that the precipitable water increased obviously about 2-3 h earlier than the occurrence of rainfall and decreased after that. The abundant moisture transportation by southwesterly wind was favorable to the maintenance of convective instability and the accumulation of convective available potential energy (CAPE). Radar detection reveals that meso-β and -γ systems were very active in the MaCS. Several convection lines developed during the evolution of the MaCS, and these are associated with surface convergence lines. The boundary outflow of the convection line may have triggered another convection line. The convection line moved with the mesoscale surface convergence line, but the convective cells embedded in the convergence line propagated along the line. On the basis of the analyses of the intensive observation data, a multi-scale conceptual model of heavy rainfall in the mei-yu front for this particular case is proposed.展开更多
In summer, the Yellow Sea Cold Water Mass (YSCWM) is a stable water mass of low temperature lying at the bottom of the central Yellow Sea (YS). It is fringed by some typical tidal fronts, which separate deep, stra...In summer, the Yellow Sea Cold Water Mass (YSCWM) is a stable water mass of low temperature lying at the bottom of the central Yellow Sea (YS). It is fringed by some typical tidal fronts, which separate deep, stratified water on the offshore side from the well-mixed, shallow water on the inshore side. Three striking fronts--Subei Bank Front (SBF), Shandong Peninsula Front (SPF), and Mokpo Front (MKF; a front off the southwestern tip of the Korean Peninsula)--have been iden- tified by various studies from both satellite observations and model results. Tide plays an important role in the formation and maintenance of these fronts. However, it is still a matter of debate as to the roles these two kinds of mechanisms of upwelling and tidal mixing play, and how importance they are in the maintenance processes of the above three fronts. Basing a nested high-resolution model HYCOM (the Hybrid Coordinate Ocean Model), this study focuses on the different mechanisms of tidal effects on the thermal fronts in the YS in summertime. Through comparative experiments with and without tidal forcing, the results indicate that the MKF is mainly driven by tide-induced upwelling. For the SPF, tidal mixing is the dominant factor, when lower cold water is stirred upwards along the sloping topography of the western YS. Meanwhile, the combined effect of upwelling and tidal mixing is the main cause of the formation of the SBF. Diagnostic analysis of thermal balance shows that horizontal nonlinear advection induced by strong tidal currents also contributes to the thermal balance of frontal areas.展开更多
文摘Cirque glaciers found on the Colorado Front Range, USA are sensitive to climate change and are important for water supply and the delivery of water downstream. These glaciers are shrinking at a rapid rate in response to the global climate change, and thus it is important to track and analyze them. One of the ways to monitor these glaciers is by using multispectral satellite imagery (Landsat imagery). In this article, the feasibility of tracking glacial area via Landsat satellites has been discussed and the trend of 13 glaciers in the Colorado Front Range Region has been analyzed from 1993 to 2021. In this period, the total glacial area across 13 glaciers in the Colorado Front Range Region has decreased by 63.6%, and a significant correlation (p-value p < 0.05) found with the annual global average temperature indicates that the retraction of glaciers is likely a response to the global warming.
基金supported by the National Research Fund for Public Welfare (Grant No.GYHY200906011)the National Key Technology R&D Program of China (Grant No.2009BAC51B01)the National Fundamental 973 Research Program of China (Grant No.2013CB430100)
文摘An atypical occlusion process that occurred in North China on 14 July 2011 is studied based on both observations and a real-data Weather Research and Forecasting (WRF) model simulation. The results show that this atypical occlusion process was significantly different from the traditional, synoptic-scale occlusion process that occurs within extratropical cyclones. It was caused by the merger of two cold-type mesoscale fronts. One of the fronts developed from the gust front of convective storms, while the other was a sea-breeze front. As the two fronts moved towards each other, the warm air between them was squeezed and separated from the surface. An atypical occluded front was formed when the two fronts merged, with the warm air forced aloft. This kind of occlusion is termed a "merger" process, different from the well-known "catch-up" and "wrap-up" processes. Moreover, local convection was found to be enhanced during the merger process, with severe convective weather produced in the merger area.
基金projects of the National Natural Science Foundation of China(Grant Nos.40405007 , 40505009)the National Key Basic Research and Development Project of China(Grant No.2004CB418302) projects of Chinese Academy of Sciences (Nos.KZCX3-SW-225 and 2005r-2-16)
文摘The daily 1°× 1° data of the Aviation (AVN) model, the black body temperature (TBB) data of cloud top, and cloud images by geostationary meteorological satellite (GMS) are used to identify a dew-point front near the periphery of the western Pacific subtropical high (WPSH). The results clearly demonstrate the existence of the dew-point front, and its thermodynamic and dynamic structural characteristics are analyzed in detail. The dew-point front is a transitional belt between the moist southwest monsoon flow and the dry adiabatic sinking flow near the WPSH, manifested by a large horizontal moisture gradient in the mid-lower troposphere and conjugated with the mei-yu front to form a predominant double-front structure associated with intense rainfall in the mei-yu period. The mei-yu front is located between 30° and 35°N, vertically extends from the ground level to the upper level and shifts northward. The dew-point front is to the south of the mei-yu front and lies up against the periphery of the WPSH. Generally, it is located between 850 hPa and 500 hPa. On the dew-point front side, the southwesterly prevails at the lower level and the northeasterly at the upper level; this wind distribution is different from that on the mei-yu front side. Vertical ascending motion exists between the two fronts, and there are descending motions on the north side of the mei^yu front and on the south side of the dew-point front~ which form a secondary circulation. The dynamics of the double fronts also have some interesting features. At the lower level, positive vertical vorticity and obvious convergence between the two fronts are clearly identified. At the mid-lower level, negative local change of the divergence (corresponding to increasing convergence) is often embedded in the two fronts or against the mei-yu front. Most cloud clusters occur between the two fronts and propagate down stream in a wave-like manner.
基金the National Key Programme for Developing Basic Sciences"!G199804901-lthe National Natural Science Foundation of China" Re
文摘The baroclinic nonlinear stability of fronts in the ocean on a sloping continental shelf is studied, the model equations, called the frontal geostrophic model, developed by Cushman—Roisin et al.(1992) for describing the dynamics of surface density fronts in the ocean are developed and the two—layer frontal geostrophic model for fronts on a sloping continental shelf is first obtained. The nonlinear stability criteria for the fronts on a sloping bottom are obtained by using Arnol’d (1965, 1969) variational principle and a prior estimate method. It is shown that our result is better than the former works. Key words Fronts in the ocean - Frontal geostrophic model - Nonlinear stability This Work was supported by “ the National Key Programme for Developing Basic Sciences” G199804901-1 and the National Natural Science Foundation of China “ Research Programme for Excellent State Key Laboratory” under Grant No. 49823002 and No. 49805002.
文摘Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis which is usually defined as an increasing of the scalar gradient. In this paper, the characteristic features of air flow with initial imbalance between the wind and the density fields are studied. Much attention is paid on the condition for the formation of discontinuity and its time scale. It is found that the initial distribution of density plays an important role in the formation of the discontinuity which happens in short time duration.
基金The Naval Oceanographic Office,Office of Naval Research,and Naval Postgraduate School
文摘Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea (HES) were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m(from the surface to 400 m deep) spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows : ( 1 ) multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; (2) springtime frontal eddy-like feature around Tsushima front; (3) year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and (4) multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.
基金supported by the National Program on Key Basic Program,Research Program of China(973 Program,Grant nos.2010CB950304 and 2012CB955601)SOA Science Fund for Young Scholars(Grant no.2011244)+2 种基金the Chinese Polar Strategy Fund(Grant no.20072017)the Chinese Polar Investigation Fund(Grant no.CHINARE 2012-01-01)the International Cooperation Fund(Grant no.JD201002)
文摘During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmos- pheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristics along the cruise are studied based on in-situ observation. The observations reveal that vertical distributions of the low-level wind field and air temperature field on both sides of the Subantarctic Front are very different. A stronger (weaker) vertical gradient is on the cold (warm) side, which demonstrates that the mid-latitude ocean-atmosphere interaction is active in the southeast Indian Ocean frontal region. A low-level jet is observed over the Subantarctic Front, with speed up to 14 m's-1. For the Antarctic polar front, low-level wind speed near the sea surface is greater than that aloft, in contrast with the situation of the Subantarctic Front. Comparing satellite remote sensing data and widely-used reanalysis datasets with our in-situ observations, differences of varying magnitudes are found. Air temperature from Atmospheric Infrared Sounder (AIRS) data has a limited difference. The European Center for Medium Range Weather Forecasts Interim Re-Analysis (ERA Interim) dataset is much more consistent with the observations than the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1 in the southeast Indian Ocean frontal region.
文摘In order to study the characteristic features of the frontal motion over mountains, a frontal model is designed inthis paper. The analytical solution of the model with the assumption of semigeostrophic approximation and no frichon is obtained and compared with numerical solution without the assumption. It assumes that the front is a free surface betWeen two nuid layers with different densihes. It also assumes that the mountain and the front are indefinitelylong. Therefore, the motion of such a front can be determined by the one-dimensional shallow water equationsystem. By making a series of experiments, we confirm the rule further that front can be retarded when climbing themountain and accelerated when going down the mountains. We also found some interesting characteristics of frontalstructure influenced by topography in addihon.
基金the National Natural Science Foundation of China (Grant Nos. 40205009, 40175005, 40075011) the Nanjing University Postdoctoral Foundation,the State Key Basic Program (CHERES).
文摘On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using the thermodynamical equation and frontogenetical function. The results show that the outbreak of the severe storm is closely related to the local frontogenesis. In fact, the interaction between the shearing instability of the low-level jet (LLJ) and the topographic forcing generates an gravity-inertia wave as well as local frontogenesis (the ?rst front), which consequently induce the onset of the severe storm. From then on, owing to the horizontal and vertical advection of the potential temperature, the new frontogenesis (the second front) is formed to the northeast side of the severe storm, which initiates the second rain belt. Meanwhile, a two-front structure emerges over the southeastern part of Hubei province. Accompanied with the further intensi?cation of the convection, the rain droplets evaporation cooling strengthens the ?rst front and weakens the second front, resulting in single front structure over the southeastern part of Hubei province in the period of the strong convection.
文摘In this paper we study the strong and weak property of travelling wave front solutions for a class of degenerate parabolic equations. How the strong and weak property changes under the effects of wave speed and reaction diffusion terms are showed.
基金Supported by Natural Science Foundation of Anhui Province No.070413256XMedical Research Foundation of Anhui Provincial Health Department No.2010B001 and No.13zc012
文摘AIM:To evaluate the efficacy and safety of paclitaxelnedaplatin combination as a front-line regimen in Chinese patients with metastatic esophageal squamous cell carcinoma(ESCC).METHODS:A two-center,open-label,single-arm phaseⅡstudy was designed.Thirty-nine patients were enrolled and included in the intention-to-treat analysis of efficacy and adverse events.Patients received 175mg/m2of paclitaxel over a 3 h infusion on 1 d,followed by nedaplatin 80 mg/m2in a 1 h infusion on 2 d every3 wk until the documented disease progression,unac-ceptable toxicity or patient’s refusal.RESULTS:Of the 36 patients assessable for efficacy,there were 2 patients(5.1%)with complete response and 16 patients(41.0%)with partial response,giving an overall response rate of 46.1%.The median progression-free survival and median overall survival for all patients were 7.1 mo(95%CI:4.6-9.7)and 12.4 mo(95%CI:9.5-15.3),respectively.Toxicities were moderate and manageable.Grade 3/4 toxicities included neutropenia(15.4%),nausea(10.3%),anemia(7.7%),thrombocytopenia(5.1%),vomiting(5.1%)and neutropenia fever(2.6%).CONCLUSION:The combination of paclitaxel and nedaplatin is active and well tolerated as a first-line therapy for patients with metastatic ESCC.
文摘In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with strong horizontal gradient, a deep-convective cloud tower band, a passageway transporting warm and moist air flow from the summer monsoon surge in the mid and low levels to the south of the mei-yu front, and a migrating synoptic scale trough to the north of the mei-yu front, which transports cold and dry air southward in the mid and upper levels. The maintenance of the mei-yu front is realized by: (1) is a positive feedback between the moist physical process enhancing frontogenesis and the development of the strong convective system in front of the mei-yu front; (2) the sustaining system to the north of the mei-yu front which is a migrating synoptic scale trough transporting cold and dry air to the mei-yu front and positive vorticity to the mesoscale system in front of the mei-yu front.
基金The National High-Tech R&D Program of China(863 Program)under contract Nos 2012AA092301 and 2012AA092303the Project of Shanghai Science and Technology Innovation under contract No.12231203900+1 种基金the Industrialization Program of National Development and Reform Commission under contract No.2159999the Shanghai Universities First-class Disciplines Project(Fisheries)"
文摘Two predominant currents, the warm Kuroshio Current and the cold Oyashio Current, meet in the North- west Pacific Ocean. The dynamics of physical oceanographic structures in this region, including frontal zones and meandering eddies, result in a highly productive habitat that serves as a favorable feeding ground for various commercially important species. Neon flying squid, Ommastrephes bartramii, is an im- portant oceanic squid, which is widely distributed in the North Pacific Ocean. Based on the catch data col- lected by Chinese squid jigging fleets and relevant environmental data, including sea surface temperature (SST) and fronts (represented by gradients of SST and thermocline) during 1998-2009, the variations of oceanic fronts and their influence on the fishing grounds of O. bartramii were evaluated, and the differ- ences in distribution of fishing grounds of O. bartramii in 2000 and 2002 were compared by describing the differences in vertical temperature between 0-300 m. It was found that the preferred horizontal tem- perature gradient of SST for O. bartramii tended to be centered at 0.01-0.02~C/nm, which attracted nearly 80% of the total fishing effort, and the preferred horizontal temperature gradients at the 50 m and 105 m layers were mainly located at 0.01-0.03~C/nm, which accounted for more than 70% of the total fishing effort during August-October. The preferred vertical temperature gradient within the 0-50 m layer for O. bartramii tended to be centered at 0.15-0.25~C/m during August and September and at 0.10-0.15~C/m in October, implying that the mixed surface layer was distributed at depths of 0-50 m. It was concluded that the vertical temperature gradient was more important than the horizontal temperature gradient in playing a role in forming the fishing ground. The results improved our understanding of the spatial dynamics of the 0. bartramii fishery.
基金the National Natural Science Foundation of China undrer contract Nos 40376009, 40231013 ,49836010 the Ministry of Science and Technology of China under contract Nos 2003DIB4J135 , 2005DIB3J114the National Science Foundation of USA under contract No. 0PP0230284.
文摘Hydrographic data, ADCP velocity and sea level anomaly derived from the satellite altimeter have been jointly analyzed in the southeast lndian Ocean. Results show the locations and orientations of the major oceanic fronts as well as the characteristics of the currents within these fronts in the area. Double subtropical fronts are observed in the section along 120°E, which conflicts with the frontal structure frequently observed before the North Subtropical Front (NSTF) and South Subtropical Front (SSTF) merge into a single STF between 110°-115°E. The Subantarctic Front (SAF), influenced by the out-of-phase double eddies, runs across 48°S three times between 120° and 127°E. The surface current within the SAF is strengthened up to 105.4 cm/s by the geostrophic effect of these eddies. Furthermore eddies may cause the strong current to split up into two branches within the SAF. The SAF and the primary polar front (PFI) can be identified individually in the ADCP data with a separation distance of about 0.3° at latitude between 140° and 145°E, although they cannot be identified separately in the low-resolution hydrographic data. The different thcrmohaline characteristics of Circumpolar Deep Water (CDW) and Modified Circumpolar Deep Water (MCDW) result in the formation of Southern Antarctic Circumpolar Current Front (SACCF) in the southeast Indian Ocean. It consistently turns northward along the east flank of the Kerguclen Plateau after it runs through the Princess Elizabeth Trough and turns southward sharply north of 60°S with a little seasonal variations. It is shown that the locations and orientations of the SAK the primary PF and SACCF in the ACC of the southeast Indian Ocean can be identified more precisely by the current distribution derived from ADCP data than by hydrographic data, because these fronts are usually accompanied by strong currents. However, the locations and orientations of the STF and the secondary PF are more difficult to be identified through current data, since these two fronts are usually not accompanied by any jet. The STF the and the secondary PF are usually confined in the first few hundred meters of the upper ocean and the latter is often determined by the northern terminus of 2 ℃ isothermal.
文摘Monitoring of the South China Sea is always one of the focuses in the field of ocean engineering for its particular geographic position. The modal wave number tomography is proposed for monitoring the front and numerical simulation is performed for the front of the South China Sea. With the empirical orthonormal function (EOF) applied to reduce the parameter search space, the perturbation inversion method is used for inversing sound speed profiles. The 2-D ocean environment used for numerical simulation is selected from the ocean area, located in 20°N, 118°E~20°N, 125°E, near the Luzon Strait in the South China Sea. The ocean environment sound speed distribution in the ocean area under study is obtained from the assimilation of multi-source remote sensing data. The numerical simulation shows that the modal wave number tomography can inverse the average sound speed profile, therefore,it can be used to monitor ocean internal structures such as ocean fronts and eddies which affect sound speed distribution.
基金This project was supported by the National Key Basic Research and Development Project 2004CB418301the National Natural Science Foundation of China under Grant No.40405008.
文摘The conventional and intensive observational data of the China Heavy Rain Experiment and Study (CHeRES) are used to specially analyze the heavy rainfall process in the mei-yu front that occurred during 20-21 June 2002, focusing on the meso-β system. A mesoscale convective system (MCS) formed in the warm-moist southwesterly to the south of the shear line over the Dabie Mountains and over the gorge between the Dabie and Jiuhua Mountains. The mei-yu front and shear line provide a favorable synoptic condition for the development of convection. The GPS observation indicates that the precipitable water increased obviously about 2-3 h earlier than the occurrence of rainfall and decreased after that. The abundant moisture transportation by southwesterly wind was favorable to the maintenance of convective instability and the accumulation of convective available potential energy (CAPE). Radar detection reveals that meso-β and -γ systems were very active in the MaCS. Several convection lines developed during the evolution of the MaCS, and these are associated with surface convergence lines. The boundary outflow of the convection line may have triggered another convection line. The convection line moved with the mesoscale surface convergence line, but the convective cells embedded in the convergence line propagated along the line. On the basis of the analyses of the intensive observation data, a multi-scale conceptual model of heavy rainfall in the mei-yu front for this particular case is proposed.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA01020304)the National Basic Research Program of China (Grant No.2010CB951901)the National Natural Science Foundation of China (Grant No.41276027)
文摘In summer, the Yellow Sea Cold Water Mass (YSCWM) is a stable water mass of low temperature lying at the bottom of the central Yellow Sea (YS). It is fringed by some typical tidal fronts, which separate deep, stratified water on the offshore side from the well-mixed, shallow water on the inshore side. Three striking fronts--Subei Bank Front (SBF), Shandong Peninsula Front (SPF), and Mokpo Front (MKF; a front off the southwestern tip of the Korean Peninsula)--have been iden- tified by various studies from both satellite observations and model results. Tide plays an important role in the formation and maintenance of these fronts. However, it is still a matter of debate as to the roles these two kinds of mechanisms of upwelling and tidal mixing play, and how importance they are in the maintenance processes of the above three fronts. Basing a nested high-resolution model HYCOM (the Hybrid Coordinate Ocean Model), this study focuses on the different mechanisms of tidal effects on the thermal fronts in the YS in summertime. Through comparative experiments with and without tidal forcing, the results indicate that the MKF is mainly driven by tide-induced upwelling. For the SPF, tidal mixing is the dominant factor, when lower cold water is stirred upwards along the sloping topography of the western YS. Meanwhile, the combined effect of upwelling and tidal mixing is the main cause of the formation of the SBF. Diagnostic analysis of thermal balance shows that horizontal nonlinear advection induced by strong tidal currents also contributes to the thermal balance of frontal areas.