Coupling of a Regional Climate Model with a Crop Development Model and Evaluation of the Coupled Model across China

In this study, the CERES(Crop Estimation through Resource and Environment Synthesis) crop model was coupled with CLM3.5, the land module of the regional climate model RegCM4. The new coupled model was named RegCM4_CERES; and in this model, crop type was further divided into winter wheat, spring wheat, spring maize, summer maize, early rice, late rice,single rice, and other crop types based on each distribution fraction. The development of each crop sub-type was simulated by the corresponding crop model separately, with each planting and harvesting date. A simulation test using RegCM4_CERES was conducted across China from 1999 to 2008; a control test was also performed using the original RegCM4. Data on crop LAI(leaf area index), soil moisture at 10 cm depth, precipitation, and 2 m air temperature were collected to evaluate the performance of RegCM4_CERES. The evaluation provided comparison of single-station time series, regional distributions,seasonal variations, and statistical indices for RegCM4_CERES. The results revealed that the coupled model had an excellent ability to simulate the phonological changes and spatial variations in crops. The consideration of dynamic crop development in RegCM4_CERES corrected the wet bias of the original RegCM4 over North China and the cold bias over South China.However, the degree of improvement was minimal and the statistical indices for RegCM4_CERES were roughly the same as the original RegCM4.

Flood variability in the upper Yangtze River over the last millennium——Insights from a comparison of climate-hydrological model simulated and reconstruction

Understanding hydrological responses to rising levels of greenhouse gases are essential for climate and impact research.It is,however,often limited by a lack of long record of observational data to provide a basis for understanding the longterm behavior of the climate system.Integrating reconstructed data and(global climate and hydrological)model simulations will help us to better understand the variability of climate and hydrology over timescales ranging from decades to centuries.In this study,we proposed an integrated approach to study flood variability in the upper reach of the Yangtze River over the last millennium to the end of the 21st century.To accomplish this,we first drove hydrological models using the precipitation and temperature from four Global Climate Models(GCM),BCC-CSM1.1,MIROC,MRI-CGCM3,and CCSM4,to simulate daily discharge for the upper reach of the Yangtze River during the period of the last millennium(850–1849),historical period(1850–2005),and a future period(2006–2099).Then,we evaluated whether the modeled precipitation,temperature,and extreme discharge had statistical properties similar to those shown in the documented dry-wet periods,temperature anomalies,and paleoflood records.Finally,we explored the extreme discharge variability using model simulations.The results indicate that:(1)The MIROC-ESM model,differing from the other three GCM models,revealed positive temperature changes from the warm period(Medieval Climate Anomaly;MCA)to the cold period(Little Ice Age;LIA),while the temperature variability of the other models was similar to the records.(2)The BCC-CSM1.1 model performed better than the others regarding correlations between modeled precipitation and documented dry-wet periods.(3)Over most of the subbasins in the upper Yangtze River,the magnitude of extreme discharge in the BCC-CSM1.1 model results showed that there was a decrease from the MCA to the LIA period and an increase in the historical period relative to the cold period,while a future increase was projected by the four GCMs under the influence of climate change.

LUCC and its impact on run-off yield in the Bai River catchment—upstream of the Miyun Reservoir basin

Aims The Miyun Reservoir is the most important drinking water source for Beijing—the capital of China with a population of more than 16 million.Since the 1980s,the inflow to the reservoir has been decreasing,which seriously threatens the security of water use in Beijing.Our goal was to analyze the impact of land use and cover change(LUCC)on run-off yield in the upstream of the Miyun Reservoir.Methods In this study,the Soil andWater Assessment Tool(SWAT)was used to simulate the impacts of LUCC on the run-off yield in the Bai River catchment—upstream of the Miyun Reservoir basin in northern China.The investigation was conducted using two 6-year historical streamflow records:from 1986 to 1991 and from 2000 to 2005.A split sample procedure was used for model calibration and validation.The data from 1986 to 1988 and from 2000 to 2002 were used for calibration,while those from 1989 to 1991 and from 2003 to 2005 for validation.The SWAT calibration was based on monthly measured discharge at Zhangjiafen station at the catchment outlet from Bai River catchment.Additionally,the influence of LUCC on the surface run-off was distinguished from that of climate change on the surface runoff through SWAT scenarios modeling,the twoway analysis of variance(ANOVA),and the rainfall–run-off double-mass analysis in the Bai River catchment.Important Findings We found that the SWAT model could be used successfully to accurately simulate run-off yield and different LUCC patterns affecting water quantity in this catchment.During calibraion for the two periods the simulated monthly run-off satisfactorily matched the observed values,with the Nash–Sutcliffe coefficient>0.9 and 0.7 and a coefficient of determination of 0.9 and 0.65 at the outlet station(Zhangjiafen station),while during validation for the two periods the obtained values were 0.85,0.65 and 0.9,0.65,respectively.During the period of 1986–91,both the SWAT scenarios modeling and the analysis of the two-way ANOVA method showed that LUCC and climate change had some impact on run-off,and the impact of climate change was more significant than that of LUCC.Compared with the period during 1986–91,the run-off yield in the period during 2000–05 significantly decreased.The obtained results from the rainfall–run-off double-mass analysis indicate that since 1998 LUCC has had an increasing influence on the run-off,while the response of the run-off to rainfall has been decreasing.Since 1998,the LUCC has been a major driving force for run-off change in Bai River catchment.

An enhanced environmental multimedia modeling system based on fuzzy-set approach： II. Model validation and application

Part I of this study develops an enhanced environmental multimedia modeling system （EMMS） based on fuzzy-set approach. Once the model development is complete, the composite module and the entire modeling system need to be tested and validated to ensure that the model can simulate natural phenomena with reasonable and reliable accuracy. The developed EMMS is first tested in a complete case study. And then verification results are conducted to compare with extensively researched litera- ture data. In the third step, the data from an experimental landfill site is used for a pilot-scale validation. The comparisons between EMMS outputs and the literature data indicate that the EMMS can perform accurate modeling simulation. The modules of EMMS could support the entire environmental multimedia modeling system. Further field-scale validation is finished. The results are satisfactory. Most of the modeling yields closely match the monitoring data collected from sites. In addition, with the aid of fuzzy-set approach, EMMS can be a reliable and powerful tool to address the complex environmental multimedia pollution problems and provide an extensive support for decision makers in managing the contaminated environmental systems.

An enhanced environmental multimedia modeling system based on fuzzy-set approach： I. Theoretical framework and model development

Multimedia environmental modeling is extremely complex due to the intricacy of the systems with the consideration of many related factors. Traditional environmental multimedia models （EMMs） are usually based on one-dimensional and first-order assumptions, which may cause numerical errors in the simulation results. In this study, a new user-friendly fuzzy-set enhanced environmental multimedia modeling system （FEEMMS） is developed, and includes four key modules： an air dispersion module, a polluting source module, an unsaturated zone module, and a groundwater module. Many improvements over previous EMMs have been achieved through dynamically quantifying the intermedia mass flux; incorporating fuzzy-set approach into environmental multimedia modeling system （EMMS）; and designing a user-friendly graphic user interface （GUI）. The developed FEEMMS can be a useful tool in estimating the timevarying and spatial-varying chemical concentrations in air, soil, and groundwater; characterizing the potential risk to human health presented by contaminants released from a contaminated site; and quantifying the uncertainties associated with modeling systems and subsequently providing robustness and flexibility for the remediationrelated decision making.