The nutrient cycling model NuCM is one of the most detailed models for simulating processes that influence nutrient cycling in forest ecosystems. A field study was conducted at Tieshanping, a Masson pine (Pinus masson...The nutrient cycling model NuCM is one of the most detailed models for simulating processes that influence nutrient cycling in forest ecosystems. A field study was conducted at Tieshanping, a Masson pine (Pinus massoniana Lamb.) forest site, in Chongqing, China, to monitor the impacts of acidic precipitation on nutrient cycling. NuCM simulations were compared with observed data from the study site. The model produced an approximate fit with the observed data. It simulated the mean annual soil solution concentrations in the two simulation years, whereas it sometimes failed to reproduce seasonal variation. Even though some of the parameters required by model running were measured in the field, some others were still highly uncertain and the uncertainties were analyzed. Some of the uncertain parameters necessary for model running should be measured and calibrated to produce a better fit between modeled results and field data.展开更多
In order to establish a rapid method for regional slope stability analysis under rainfall,matric suction and seepage force were taken into account after obtaining explicit solution of infiltration depth.Moreover,simpl...In order to establish a rapid method for regional slope stability analysis under rainfall,matric suction and seepage force were taken into account after obtaining explicit solution of infiltration depth.Moreover,simplified analysis model under 3D condition was put forward based on identification and division of slope units,as well as modification of sliding direction of each column.The result shows that explicit solution of infiltration depth is of good precision;for the given model,safety factors without taking seepage force into account are 1.82-2.94 times higher;the stagnation point of slope angle is located approximately in the range of(45°,50°);the safety factor changes insignificantly when wetting front is deeper than 2 m;when matric suction changes in the specified range,the maximum variations of safety factor are less than 0.5,which proves that matric suction plays an insignificant role in maintaining slope stability compared to the slope angle and infiltration depth.Incorporated with geographic information system,a practical application of regional slope stability assessment verifies the applicability of the proposed method.展开更多
Vertical raindrop size distributions of two stratiform rain events were measured with a Micro Rain Radar during summer 2009 at a semiarid continental site located in Xilinhot, China （43°38′N, 116°42′E）. ...Vertical raindrop size distributions of two stratiform rain events were measured with a Micro Rain Radar during summer 2009 at a semiarid continental site located in Xilinhot, China （43°38′N, 116°42′E）. The sequential intensity filtering technique （SIFT） was used to minimize the effect of the spurious variability on disdrometric data to obtain the reflectivity-rain rate （Z-R） relationship （Z = αRb）. Compared with the least squares regression （LSR） method, SIFT led to a -5% to 4% change in the coefficient （a） and an 8%-1 5% increase in the exponent （b） of the Z-R relationship at 300 m. Rainfall estimation using the Z-R relationship with SIFT had lower standard deviation than that with LSR. The vertical variability of the mean rain rate, total raindrop numbers, and parameters （a and b） of the Z-R relationship was small below a melting layer, suggesting that using the radar reflectivity of weather radar to estimate stratiform rainfall is relatively accurate, at least in the Xilinhot area.展开更多
Helicity was applied to analyze several high-wind and rainstorm processes, which occurred from May to June, 2001 over Yunnan in early summer. The results of diagnostic analyses show that the rainstorm occurs in the ar...Helicity was applied to analyze several high-wind and rainstorm processes, which occurred from May to June, 2001 over Yunnan in early summer. The results of diagnostic analyses show that the rainstorm occurs in the area in which hp is positive at 700 hPa and energy is unstable. The change of helicity can reflect the movement and development of synoptic system and the position and intensity of the rainstorm. The value of hp is a negative center at the upper level and a positive at the lower level over the rainstorm position; moreover it can reflect the characteristics of vertical distribution and rotational motion.展开更多
Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, tradit...Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, traditional distributed hydrological models based on kinematic and diffusion wave approximations ignore certain physical mechanisms of flash floods and thus bear excessive uncertainty. Here a hydrodynamic model is presented for flash floods based on the full two-dimensional shallow water equations incorporating rainfall and infiltration. Laboratory experiments of overland flows were modelled to illustrate the capability of the model. Then the model was applied to resolve two observed flash floods of distinct magnitudes in the Lengkou catchment in Shanxi Province, China. The present model is shown to be able to reproduce the flood flows fairly well compared to the observed data. The spatial distribution of rainfall is shown to be crucial for the modelling of flash floods. Sensitivity analyses of the model parameters reveal that the stage and discharge hydrographs are more sensitive to the Manning roughness and initial water content in the catchment than to the Green-Ampt head. Most notably, as the flash flood augments due to heavier rainfall, the modelling results agree with observed data better, which clearly characterizes the paramount role of rainfall in dictating the floods. From practical perspectives, the proposed model is more appropriate for modelling large flash floods.展开更多
Based on the data of NCEP, OLR and rainfall of China, we studied the influences of the East Asian winter monsoon activities on the precipitation during the raining season over China by correlation analysis and composi...Based on the data of NCEP, OLR and rainfall of China, we studied the influences of the East Asian winter monsoon activities on the precipitation during the raining season over China by correlation analysis and composite analysis. The result shows that annual and interdecadal change of East Asian winter monsoon is distinct. It is strong from 1950s to the middle of 1980s but weak after the middle of 1980s. The effect of abnormal winter monsoon on the precipitation during raining season is significant over the middle and lower reaches of the Changjiang River basin. It is revealed that the precipitation will increase when preceding winter monsoon is weak but decrease when preceding winter monsoon is strong. In this paper, some appropriate reasons are given to explain the abnormal rainfall by analyzing the distribution of SSTA and the variation of summer circulation. It is pointed out definitely that the variation of SSTA and summer circulation is a primary cause for abnormal rainfall over the middle and lower reaches of the Changjiang River.展开更多
Based on theoretical analysis and studying other methods, P-III curve is transformed into an incomplete G function by means of mathematical expression transformation, thus the mathematical model of the fast commonly-u...Based on theoretical analysis and studying other methods, P-III curve is transformed into an incomplete G function by means of mathematical expression transformation, thus the mathematical model of the fast commonly-used algorithm is drawn out. Algorithm comparison and practices demonstrate that the mathematical model has an easy algorithm, agile resolution process, very good commonality, faster convergence rate and better calculation accuracy, and can be applied to other respects.展开更多
基金the Chinese-Norwegian Cooperation Project Integrated Monitoring Program on Acidification of Chinese Terrestrial Systems (IMPACTS)the Chinese Academy of Forestry (No.CAFYBB200700X)
文摘The nutrient cycling model NuCM is one of the most detailed models for simulating processes that influence nutrient cycling in forest ecosystems. A field study was conducted at Tieshanping, a Masson pine (Pinus massoniana Lamb.) forest site, in Chongqing, China, to monitor the impacts of acidic precipitation on nutrient cycling. NuCM simulations were compared with observed data from the study site. The model produced an approximate fit with the observed data. It simulated the mean annual soil solution concentrations in the two simulation years, whereas it sometimes failed to reproduce seasonal variation. Even though some of the parameters required by model running were measured in the field, some others were still highly uncertain and the uncertainties were analyzed. Some of the uncertain parameters necessary for model running should be measured and calibrated to produce a better fit between modeled results and field data.
基金Project(kfj110207) supported by Open Fund of Key Laboratory of Road Structure and Material of Ministry of Transport,China
文摘In order to establish a rapid method for regional slope stability analysis under rainfall,matric suction and seepage force were taken into account after obtaining explicit solution of infiltration depth.Moreover,simplified analysis model under 3D condition was put forward based on identification and division of slope units,as well as modification of sliding direction of each column.The result shows that explicit solution of infiltration depth is of good precision;for the given model,safety factors without taking seepage force into account are 1.82-2.94 times higher;the stagnation point of slope angle is located approximately in the range of(45°,50°);the safety factor changes insignificantly when wetting front is deeper than 2 m;when matric suction changes in the specified range,the maximum variations of safety factor are less than 0.5,which proves that matric suction plays an insignificant role in maintaining slope stability compared to the slope angle and infiltration depth.Incorporated with geographic information system,a practical application of regional slope stability assessment verifies the applicability of the proposed method.
基金partially supported by the German Research Foundation[Research Unit 536,MAGIM]National Natural Science Foundation of China[grant number 41175105],[grant number41175122],[grant number 41505091],[grant number 41575124]
文摘Vertical raindrop size distributions of two stratiform rain events were measured with a Micro Rain Radar during summer 2009 at a semiarid continental site located in Xilinhot, China （43°38′N, 116°42′E）. The sequential intensity filtering technique （SIFT） was used to minimize the effect of the spurious variability on disdrometric data to obtain the reflectivity-rain rate （Z-R） relationship （Z = αRb）. Compared with the least squares regression （LSR） method, SIFT led to a -5% to 4% change in the coefficient （a） and an 8%-1 5% increase in the exponent （b） of the Z-R relationship at 300 m. Rainfall estimation using the Z-R relationship with SIFT had lower standard deviation than that with LSR. The vertical variability of the mean rain rate, total raindrop numbers, and parameters （a and b） of the Z-R relationship was small below a melting layer, suggesting that using the radar reflectivity of weather radar to estimate stratiform rainfall is relatively accurate, at least in the Xilinhot area.
基金Applied Foundation Project of Yunnan (2000D0091M) Key Scientific Research Program for the 10th-five-year economic development plan (2001NG43)
文摘Helicity was applied to analyze several high-wind and rainstorm processes, which occurred from May to June, 2001 over Yunnan in early summer. The results of diagnostic analyses show that the rainstorm occurs in the area in which hp is positive at 700 hPa and energy is unstable. The change of helicity can reflect the movement and development of synoptic system and the position and intensity of the rainstorm. The value of hp is a negative center at the upper level and a positive at the lower level over the rainstorm position; moreover it can reflect the characteristics of vertical distribution and rotational motion.
基金funded by Natural Science Foundation of China (Grants Nos. 51279144 and 11432015)Chinese Academy of Sciences (Grant No. KZZD-EW-05-01-03)
文摘Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, traditional distributed hydrological models based on kinematic and diffusion wave approximations ignore certain physical mechanisms of flash floods and thus bear excessive uncertainty. Here a hydrodynamic model is presented for flash floods based on the full two-dimensional shallow water equations incorporating rainfall and infiltration. Laboratory experiments of overland flows were modelled to illustrate the capability of the model. Then the model was applied to resolve two observed flash floods of distinct magnitudes in the Lengkou catchment in Shanxi Province, China. The present model is shown to be able to reproduce the flood flows fairly well compared to the observed data. The spatial distribution of rainfall is shown to be crucial for the modelling of flash floods. Sensitivity analyses of the model parameters reveal that the stage and discharge hydrographs are more sensitive to the Manning roughness and initial water content in the catchment than to the Green-Ampt head. Most notably, as the flash flood augments due to heavier rainfall, the modelling results agree with observed data better, which clearly characterizes the paramount role of rainfall in dictating the floods. From practical perspectives, the proposed model is more appropriate for modelling large flash floods.
基金East Asia winter monsoon and Yunnan summertime drought and floods and their interdecadal anomalies a project of the Yunnan Province Science Foundation a Yunnan Province Foundation project (97D022G)
文摘Based on the data of NCEP, OLR and rainfall of China, we studied the influences of the East Asian winter monsoon activities on the precipitation during the raining season over China by correlation analysis and composite analysis. The result shows that annual and interdecadal change of East Asian winter monsoon is distinct. It is strong from 1950s to the middle of 1980s but weak after the middle of 1980s. The effect of abnormal winter monsoon on the precipitation during raining season is significant over the middle and lower reaches of the Changjiang River basin. It is revealed that the precipitation will increase when preceding winter monsoon is weak but decrease when preceding winter monsoon is strong. In this paper, some appropriate reasons are given to explain the abnormal rainfall by analyzing the distribution of SSTA and the variation of summer circulation. It is pointed out definitely that the variation of SSTA and summer circulation is a primary cause for abnormal rainfall over the middle and lower reaches of the Changjiang River.
文摘Based on theoretical analysis and studying other methods, P-III curve is transformed into an incomplete G function by means of mathematical expression transformation, thus the mathematical model of the fast commonly-used algorithm is drawn out. Algorithm comparison and practices demonstrate that the mathematical model has an easy algorithm, agile resolution process, very good commonality, faster convergence rate and better calculation accuracy, and can be applied to other respects.
