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Australia. We developed the Seasonally Coherent Calibration (SCC) model to post-process precipitation forecasts from numerical weather prediction (NWP) models. The SCC model is capable of generating high-quality calibrated forecasts which are coherent in climatology, including seasonality, consistent with observations, despite only a short period of forecasts being available. In this study, we post-process deterministic precipitation forecasts from the Australian Bureau of Meteorology’s Australian Community Climate and Earth System Simulator G2 version (ACCESS-G2) NWP model to generate calibrated ensemble forecasts across Australia. We evaluate the effectiveness, robustness, and computational feasibility of forecast post-processing with the SCC model at a high spatial resolution across the continental scale. Inadequate representation of forecast seasonality in calibration models poses a challenge for the calibration of NWP forecasts. Through this investigation, the statistical assumptions and reparameterization algorithms of the SCC model are confirmed to be effective and robust in addressing the challenge. Calibrated precipitation forecasts could be used to support operational water balance forecasting in Australia. Post-processing of NWP precipitation forecasts with the SCC model will also benefit a broad range of forecast users in Australia by providing accurate, skillful, and reliable ensemble forecasts. Computation strategies adopted in this study will help develop effective procedures for future post-processing of NWP forecasts with sophisticated calibration models at a large spatial scale.
Qichun Yang; Quan J. Wang; Kirsti Hakala. Achieving effective calibration of precipitation forecasts over a continental scale. Journal of Hydrology: Regional Studies 2021, 35, 100818 .
AMA StyleQichun Yang, Quan J. Wang, Kirsti Hakala. Achieving effective calibration of precipitation forecasts over a continental scale. Journal of Hydrology: Regional Studies. 2021; 35 ():100818.
Chicago/Turabian StyleQichun Yang; Quan J. Wang; Kirsti Hakala. 2021. "Achieving effective calibration of precipitation forecasts over a continental scale." Journal of Hydrology: Regional Studies 35, no. : 100818.
Published reports suggest efforts designed to prevent the occurrence of harmful algal blooms and hypoxia by reducing non‐point and point source phosphorus (P) pollution are not delivering water quality improvements in many areas. Part of the uncertainty in evaluating watershed responses to management practices is the lack of standardized estimates of phosphorus inputs and outputs. To assess P trends across the conterminous United States, we compiled an inventory using publicly available datasets of agricultural P fluxes, atmospheric P deposition, human P demand and waste, and point source discharges for 2002, 2007 and 2012 at the scale of the 8‐digit Hydrologic Unit Code subbasin (∼1800 km2). Estimates of agricultural legacy P surplus accumulated from 1945‐2001 were also developed. Fertilizer and manure inputs were found to continue exceed crop removal rates by up to 50% in many agricultural regions. This excess in inputs has led to the continued accumulation of legacy P in agricultural lands. Atmospheric P deposition increased throughout the Rockies, potentially contributing to reported increases in surface water P concentrations in undisturbed watersheds. In some urban areas, P fluxes associated with human waste and non‐farm fertilizer use has declined despite population growth, likely due, in part, to various sales bans on P‐containing detergents and fertilizers. Although regions and individual subbasins have different contemporary and legacy P sources, a standardized method of accounting for large and small fluxes and ready to use inventory numbers are essential for coordinated and targeted interventions to reduce P concentrations in the nation's waters.
Robert D. Sabo; Christopher M. Clark; David A. Gibbs; Geneviève S. Metson; M. Jason Todd; Stephen D. LeDuc; Diana Greiner; Meridith M. Fry; Robyn Polinsky; Qichun Yang; Hanqin Tian; Jana E. Compton. Phosphorus Inventory for the Conterminous United States (2002–2012). Journal of Geophysical Research: Biogeosciences 2021, 126, 1 .
AMA StyleRobert D. Sabo, Christopher M. Clark, David A. Gibbs, Geneviève S. Metson, M. Jason Todd, Stephen D. LeDuc, Diana Greiner, Meridith M. Fry, Robyn Polinsky, Qichun Yang, Hanqin Tian, Jana E. Compton. Phosphorus Inventory for the Conterminous United States (2002–2012). Journal of Geophysical Research: Biogeosciences. 2021; 126 (4):1.
Chicago/Turabian StyleRobert D. Sabo; Christopher M. Clark; David A. Gibbs; Geneviève S. Metson; M. Jason Todd; Stephen D. LeDuc; Diana Greiner; Meridith M. Fry; Robyn Polinsky; Qichun Yang; Hanqin Tian; Jana E. Compton. 2021. "Phosphorus Inventory for the Conterminous United States (2002–2012)." Journal of Geophysical Research: Biogeosciences 126, no. 4: 1.
Surface runoff and infiltration partition is a primary process of hydrologic cycle. Here, we compare four different surface runoff and infiltration partition methods within a Richards-equation-based SWAT model (RSWAT) to understand their effects on watershed modeling. Four surface runoff and infiltration partition methods include a Daily Curve Number method (DCN-RSWAT), a Hourly Curve Number method (HCN-RSWAT), a Green-Ampt method (GA-RSWAT), and an Effective Infiltration Capacity method (EIC-RSWAT). These four versions of RSWAT and a Daily Curve Number based original SWAT (DCN-SWAT) were applied to simulate daily stream flow and baseflow (from 2001 to 2015) at the Tuckahoe Creek Watershed (TCW) and Greensboro Watershed (GW) in Maryland, US. The global sensitivity analysis algorithms within SWAT-CUP was used to identify sensitive parameters, and the Sequential Uncertainty Fitting algorithm version 2 (SUFI-2) was used to analyze uncertainty for different models in both calibration and validation periods. Comparison of the results from different models highlight the sensitivity of watershed modeling to the differences between surface runoff and infiltration partition methods. In general, DCN-RSWAT outperformed other versions of RSWAT and the standard SWAT model with reduced daily flow rate perdition uncertainty and improved simulation of daily baseflow in both test watersheds. We anticipate the numerical experiments examined here will provide new insights into better practices in choosing surface runoff and infiltration partition methods for SWAT and other watershed models, thereby supporting sustainable water resources assessment and management.
Junyu Qi; Sangchul Lee; Xuesong Zhang; Qichun Yang; Gregory W. McCarty; Glenn E. Moglen. Effects of surface runoff and infiltration partition methods on hydrological modeling: A comparison of four schemes in two watersheds in the Northeastern US. Journal of Hydrology 2019, 581, 124415 .
AMA StyleJunyu Qi, Sangchul Lee, Xuesong Zhang, Qichun Yang, Gregory W. McCarty, Glenn E. Moglen. Effects of surface runoff and infiltration partition methods on hydrological modeling: A comparison of four schemes in two watersheds in the Northeastern US. Journal of Hydrology. 2019; 581 ():124415.
Chicago/Turabian StyleJunyu Qi; Sangchul Lee; Xuesong Zhang; Qichun Yang; Gregory W. McCarty; Glenn E. Moglen. 2019. "Effects of surface runoff and infiltration partition methods on hydrological modeling: A comparison of four schemes in two watersheds in the Northeastern US." Journal of Hydrology 581, no. : 124415.
Statistical calibration of forecasts from numerical weather prediction (NWP) models aims to produce forecasts that are unbiased, reliable in ensemble spread, and as skillful as possible. We suggest that the calibrated forecasts should also be coherent in climatology, including seasonality, consistent with observations. This is especially important when forecasts approach climatology as forecast skill becomes low, such as at long lead times. However, it is challenging to achieve these aims when data available to establish sophisticated calibration models are limited. Many NWP models have only a short period of archived data, typically one year or less, when they become officially operational. In this paper, we introduce a seasonally coherent calibration (SCC) model for working effectively with limited archived NWP data. Detailed rationale and mathematical formulations are presented. In the development of the model, three issues are resolved. These are 1) constructing a calibration model that is sophisticated enough to allow for seasonal variation in the statistical characteristics of raw forecasts and observations, 2) bringing climatology that is representative of long-term statistics into the calibration model, and 3) reducing the number of model parameters through sensible reparameterization to make the model workable with short NWP dataset. A case study is conducted to examine model assumptions and evaluate model performance. We find that the model assumptions are sound, and the developed SCC model produces well-calibrated forecasts.
Quan Wang; Tony Zhao; Qichun Yang; David Robertson. A Seasonally Coherent Calibration (SCC) Model for Postprocessing Numerical Weather Predictions. Monthly Weather Review 2019, 147, 3633 -3647.
AMA StyleQuan Wang, Tony Zhao, Qichun Yang, David Robertson. A Seasonally Coherent Calibration (SCC) Model for Postprocessing Numerical Weather Predictions. Monthly Weather Review. 2019; 147 (10):3633-3647.
Chicago/Turabian StyleQuan Wang; Tony Zhao; Qichun Yang; David Robertson. 2019. "A Seasonally Coherent Calibration (SCC) Model for Postprocessing Numerical Weather Predictions." Monthly Weather Review 147, no. 10: 3633-3647.
Responses of streamflow and nutrient export to changing climate conditions should be investigated for effective water quality management and pollution control. Using downscaled climate projections and the Soil and Water Assessment Tool (SWAT), we projected future streamflow, sediment export, and riverine nutrient export in the St. Croix River Basin (SCRB) during 2020–2099. Results show substantial increases in riverine water, sediment, and nutrient load under future climate conditions, particularly under the high greenhouse gas emission scenario. Intensified water cycling and enhanced nutrient export will pose challenges to water quality management and affect multiple Best Management Practices (BMPs) efforts, which are aimed at reducing nutrient loads in SCRB. In addition to the physical impacts of climate change on terrestrial hydrology, our analyses demonstrate significant reductions in ET under elevated atmospheric CO2 concentrations. Changes in plant physiology induced by climate change may markedly affect water cycling and associated sediment and nutrient export. Results of this study highlight the importance of examining climate change impacts on water and nutrient delivery for effective watershed management.
Qichun Yang; Xuesong Zhang; James E. Almendinger; Maoyi Huang; Xingyuan Chen; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Xia Li. Climate change will pose challenges to water quality management in the st. Croix River basin. Environmental Pollution 2019, 251, 302 -311.
AMA StyleQichun Yang, Xuesong Zhang, James E. Almendinger, Maoyi Huang, Xingyuan Chen, Guoyong Leng, Yuyu Zhou, Kaiguang Zhao, Ghassem R. Asrar, Xia Li. Climate change will pose challenges to water quality management in the st. Croix River basin. Environmental Pollution. 2019; 251 ():302-311.
Chicago/Turabian StyleQichun Yang; Xuesong Zhang; James E. Almendinger; Maoyi Huang; Xingyuan Chen; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Xia Li. 2019. "Climate change will pose challenges to water quality management in the st. Croix River basin." Environmental Pollution 251, no. : 302-311.
In recent decades, village abandonment as a result of migration from rural areas constitutes a serious socioeconomic problem in China and many other developing countries. The aim of this study is to identify the drivers of village abandonment in the mountainous areas of Southeast China. Pucheng County was selected as the study case. A conceptual framework for the primary drivers of village abandonment was established to link rural depopulation, farmland abandonment, and house abandonment, which are three integral parts of village abandonment. Results show that the intense rural‐urban migration propelled by new urban economic opportunities is the most significant driver of sparse rural population distribution, though this does not usually result in the straightforward abandonment of villages. Instead, the scarcity of public services in mountainous villages is a decisive factor in local resettlement and resultant village abandonment. Limited school access and a demand for high‐quality education is the foremost and most immediate motivation for rural–town migration and resettlement in townships, which directly leads to the substantial abandonment of mountainous settlements. Additionally, isolation, higher transportation costs, and non‐viability of traditional subsistence agriculture are minor drivers which are interwoven, aggravating the abandonment of remote villages. Our study highlights the aggregated characteristics of village abandonment, heterogeneity of rural emigration and its corresponding primary drivers. These findings will have significant policy implications for decision‐makers by helping to identify areas with a high probability of village abandonment, and predict the future magnitude of intra‐county migration and subsequent In situ urbanization.
Chengchao Wang; Yaoqi Zhang; Yusheng Yang; Qichun Yang; Jing Hong. What is driving the abandonment of villages in the mountains of Southeast China? Land Degradation & Development 2019, 30, 1183 -1192.
AMA StyleChengchao Wang, Yaoqi Zhang, Yusheng Yang, Qichun Yang, Jing Hong. What is driving the abandonment of villages in the mountains of Southeast China? Land Degradation & Development. 2019; 30 (10):1183-1192.
Chicago/Turabian StyleChengchao Wang; Yaoqi Zhang; Yusheng Yang; Qichun Yang; Jing Hong. 2019. "What is driving the abandonment of villages in the mountains of Southeast China?" Land Degradation & Development 30, no. 10: 1183-1192.
Water management substantially alters natural regimes of streamflow through modifying retention time and water exchanges among different components of the terrestrial water cycle. Accurate simulation of water cycling in intensively managed watersheds, such as the Yakima River basin (YRB) in the Pacific Northwest of the US, faces challenges in reliably characterizing influences of management practices (e.g., reservoir operation and cropland irrigation) on the watershed hydrology. Using the Soil and Water Assessment Tool (SWAT) model, we evaluated streamflow simulations in the YRB based on different reservoir operation and irrigation schemes. Simulated streamflow with the reservoir operation scheme optimized by the RiverWare model better reproduced measured streamflow than the simulation using the default SWAT reservoir operation scheme. Scenarios with irrigation practices demonstrated higher water losses through evapotranspiration (ET) and matched benchmark data better than the scenario that only considered reservoir operations. Results of this study highlight the importance of reliably representing reservoir operations and irrigation management for credible modeling of watershed hydrology. The methods and findings presented here hold promise to enhance water resources assessment that can be applied to other intensively managed watersheds.
Jiali Qiu; Qichun Yang; Xuesong Zhang; Maoyi Huang; Jennifer C. Adam; Keyvan Malek. Implications of water management representations for watershed hydrologic modeling in the Yakima River basin. Hydrology and Earth System Sciences 2019, 23, 35 -49.
AMA StyleJiali Qiu, Qichun Yang, Xuesong Zhang, Maoyi Huang, Jennifer C. Adam, Keyvan Malek. Implications of water management representations for watershed hydrologic modeling in the Yakima River basin. Hydrology and Earth System Sciences. 2019; 23 (1):35-49.
Chicago/Turabian StyleJiali Qiu; Qichun Yang; Xuesong Zhang; Maoyi Huang; Jennifer C. Adam; Keyvan Malek. 2019. "Implications of water management representations for watershed hydrologic modeling in the Yakima River basin." Hydrology and Earth System Sciences 23, no. 1: 35-49.
Land use and land cover change has a slow but prolonged impact on various aspects of environment on local, regional and global scales. In developing countries especially population pressure and food demand have compelled conversion of wetlands to built-up and agricultural lands. One such unique example is the East Kolkata Wetlands (EKWs) located on the eastern fringes of Kolkata City in India where such land cover change is very intense and rapid. In this study, wetland conversions in EKWs from 1972 to 2011 were analyzed with four Landsat images using the Geographic Object-Based Image Analysis (GeOBIA) and a post-classification comparison. Results suggested that wetland areas decreased by 17.9 percent during the study period. The western part of the wetlands saw the maximum conversion of wetlands to built-up areas with time, whereas the east and south experienced more of wetlands to agricultural and other land conversions
Xia Li; Chandana Mitra; Luke Marzen; Qichun Yang. Spatial and Temporal Patterns of Wetland Cover Changes in East Kolkata Wetlands, India From 1972 to 2011. Environmental Information Systems 2019, 1163 -1177.
AMA StyleXia Li, Chandana Mitra, Luke Marzen, Qichun Yang. Spatial and Temporal Patterns of Wetland Cover Changes in East Kolkata Wetlands, India From 1972 to 2011. Environmental Information Systems. 2019; ():1163-1177.
Chicago/Turabian StyleXia Li; Chandana Mitra; Luke Marzen; Qichun Yang. 2019. "Spatial and Temporal Patterns of Wetland Cover Changes in East Kolkata Wetlands, India From 1972 to 2011." Environmental Information Systems , no. : 1163-1177.
Insufficiently calibrated forest parameters of the Soil and Water Assessment Tool (SWAT) may introduce uncertainties to water resource projections in forested watersheds. In this study, we improved SWAT forest parameterization and phosphorus cycling representations to better simulate forest ecosystems in the St. Croix River Basin (SCRB) and further examined how those improvements affected model projections of streamflow, sediment, and nitrogen export under future climate conditions. Simulations with improved forest parameters substantially reduced model estimates of water, sediment, and nitrogen fluxes relative to those based on default parameters. Differences between improved and default projections can be attributed to the enhanced representation of forest water consumption, nutrient uptake, and protection of soil from erosion. Better representation of forest ecosystems in SWAT contributes to constraining uncertainties in water resource projections. Results of this study highlight the importance of improving SWAT forest ecosystem representations in projecting delivery of water, sediment, and nutrients from land to rivers in response to climate change, particularly for watersheds with large areas of forests. Improved forest parameters and the phosphorus weathering algorithms developed in this study are expected to help enhance future applications of SWAT to investigate hydrological and biogeochemical consequences of climate change.
Qichun Yang; Xuesong Zhang; James E. Almendinger; Maoyi Huang; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Xia Li; Jiali Qiu. Improving the SWAT forest module for enhancing water resource projections: A case study in the St. Croix River basin. Hydrological Processes 2018, 33, 864 -875.
AMA StyleQichun Yang, Xuesong Zhang, James E. Almendinger, Maoyi Huang, Guoyong Leng, Yuyu Zhou, Kaiguang Zhao, Ghassem R. Asrar, Xia Li, Jiali Qiu. Improving the SWAT forest module for enhancing water resource projections: A case study in the St. Croix River basin. Hydrological Processes. 2018; 33 (5):864-875.
Chicago/Turabian StyleQichun Yang; Xuesong Zhang; James E. Almendinger; Maoyi Huang; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Xia Li; Jiali Qiu. 2018. "Improving the SWAT forest module for enhancing water resource projections: A case study in the St. Croix River basin." Hydrological Processes 33, no. 5: 864-875.
Qichun Yang; James E. Almendinger; Xuesong Zhang; Maoyi Huang; Xingyuan Chen; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Raghavan Srinivasan; Xia Li. Enhancing SWAT simulation of forest ecosystems for water resource assessment: A case study in the St. Croix River basin. Ecological Engineering 2018, 120, 422 -431.
AMA StyleQichun Yang, James E. Almendinger, Xuesong Zhang, Maoyi Huang, Xingyuan Chen, Guoyong Leng, Yuyu Zhou, Kaiguang Zhao, Ghassem R. Asrar, Raghavan Srinivasan, Xia Li. Enhancing SWAT simulation of forest ecosystems for water resource assessment: A case study in the St. Croix River basin. Ecological Engineering. 2018; 120 ():422-431.
Chicago/Turabian StyleQichun Yang; James E. Almendinger; Xuesong Zhang; Maoyi Huang; Xingyuan Chen; Guoyong Leng; Yuyu Zhou; Kaiguang Zhao; Ghassem R. Asrar; Raghavan Srinivasan; Xia Li. 2018. "Enhancing SWAT simulation of forest ecosystems for water resource assessment: A case study in the St. Croix River basin." Ecological Engineering 120, no. : 422-431.
Water management substantially alters natural regimes of streamflow through modifying retention time and water exchanges among different components of the terrestrial water cycle. Accurate simulation of water cycling in intensively managed watersheds, such as the Yakima River Basin (YRB) in the Pacific Northwest of the U.S., faces challenges in reliably characterizing influences of management practices (e.g., reservoir operation and cropland irrigation) on the watershed hydrology. Using the Soil and Water Assessment Tool (SWAT) model, we evaluated streamflow simulations in the YRB based on different reservoir operation and irrigation schemes. Simulated streamflow with the reservoir operation scheme optimized by the RiverWare model better reproduced measured streamflow than the simulation using default SWAT reservoir operation scheme. Scenarios with irrigation practices demonstrated higher water losses through evapotranspiration (ET), and matched benchmark data better than the scenario that only considered reservoir operations. Results of this study highlight the importance of reliably representing reservoir operations and irrigation management for credible modeling of watershed hydrology. Both SWAT and RiverWare are community-based and have been widely tested and applied for reservoir operations and agricultural watershed modeling in regions across the globe. As such, the methods and findings presented here hold the promise to apply to other intensively managed watersheds to enhance water resources assessment.
Jiali Qiu; Qichun Yang; Xuesong Zhang; Maoyi Huang; Jennifer C. Adam; Keyvan Malek. Implications of water management representations for watershed hydrologic modeling in the Yakima River Basin. 2018, 2018, 1 -30.
AMA StyleJiali Qiu, Qichun Yang, Xuesong Zhang, Maoyi Huang, Jennifer C. Adam, Keyvan Malek. Implications of water management representations for watershed hydrologic modeling in the Yakima River Basin. . 2018; 2018 ():1-30.
Chicago/Turabian StyleJiali Qiu; Qichun Yang; Xuesong Zhang; Maoyi Huang; Jennifer C. Adam; Keyvan Malek. 2018. "Implications of water management representations for watershed hydrologic modeling in the Yakima River Basin." 2018, no. : 1-30.
Xia Li; Chandana Mitra; Li Dong; Qichun Yang. Understanding land use change impacts on microclimate using Weather Research and Forecasting (WRF) model. Physics and Chemistry of the Earth, Parts A/B/C 2018, 103, 115 -126.
AMA StyleXia Li, Chandana Mitra, Li Dong, Qichun Yang. Understanding land use change impacts on microclimate using Weather Research and Forecasting (WRF) model. Physics and Chemistry of the Earth, Parts A/B/C. 2018; 103 ():115-126.
Chicago/Turabian StyleXia Li; Chandana Mitra; Li Dong; Qichun Yang. 2018. "Understanding land use change impacts on microclimate using Weather Research and Forecasting (WRF) model." Physics and Chemistry of the Earth, Parts A/B/C 103, no. : 115-126.
Snow cover dynamics are considered to play a key role on spring phenological shifts in the high-latitude, so investigating responses of spring phenology to snow cover dynamics is becoming an increasingly important way to identify and predict global ecosystem dynamics. In this study, we quantified the temporal trends and spatial variations of spring phenology and snow cover across the Tibetan Plateau by calibrating and analyzing time series of the NOAA AVHRR-derived normalized difference vegetation index (NDVI) during 1983-2012. We also examined how snow cover dynamics affect the spatio-temporal pattern of spring alpine vegetation phenology over the plateau. Our results indicated that 52.21% of the plateau experienced a significant advancing trend in the beginning of vegetation growing season (BGS) and 34.30% exhibited a delaying trend. Accordingly, the snow cover duration days (SCD) and snow cover melt date (SCM) showed similar patterns with a decreasing trend in the west and an increasing trend in the southeast, but the start date of snow cover (SCS) showed an opposite pattern. Meanwhile, the spatial patterns of the BGS, SCD, SCS and SCM varied in accordance with the gradients of temperature, precipitation and topography across the plateau. The response relationship of spring phenology to snow cover dynamics varied within different climate, terrain and alpine plant community zones, and the spatio-temporal response patterns were primarily controlled by the long-term local heat-water conditions and topographic conditions. Moreover, temperature and precipitation played a profound impact on diverse responses of spring phenology to snow cover dynamics.
Siyuan Wang; Xiaoyue Wang; Guangsheng Chen; Qichun Yang; Bin Wang; Yuanxu Ma; Ming Shen. Complex responses of spring alpine vegetation phenology to snow cover dynamics over the Tibetan Plateau, China. Science of The Total Environment 2017, 593-594, 449 -461.
AMA StyleSiyuan Wang, Xiaoyue Wang, Guangsheng Chen, Qichun Yang, Bin Wang, Yuanxu Ma, Ming Shen. Complex responses of spring alpine vegetation phenology to snow cover dynamics over the Tibetan Plateau, China. Science of The Total Environment. 2017; 593-594 ():449-461.
Chicago/Turabian StyleSiyuan Wang; Xiaoyue Wang; Guangsheng Chen; Qichun Yang; Bin Wang; Yuanxu Ma; Ming Shen. 2017. "Complex responses of spring alpine vegetation phenology to snow cover dynamics over the Tibetan Plateau, China." Science of The Total Environment 593-594, no. : 449-461.
Analyses of environmental controls on riverine carbon fluxes are critical for improved understanding of the mechanisms regulating carbon cycling along the terrestrial-aquatic continuum. Here, we compile and analyze riverine dissolved organic carbon (DOC) concentration data from 1402 United States Geological Survey (USGS) gauge stations to examine the spatial variability and environmental controls of DOC concentrations in the United States (U.S.) surface waters. DOC concentrations exhibit high spatial variability in the U.S., with an average of 6.42 ± 6.47 mg C/L (Mean ± Standard Deviation). High DOC concentrations occur in the Upper Mississippi River basin and the southeastern U.S., while low concentrations are mainly distributed in the western U.S. Soil properties such as soil organic matter, soil water content, and soil sand content mainly show positive correlations with DOC concentrations; forest and shrub land have positive correlations with DOC concentrations, but urban area and cropland demonstrate negative impacts; and total instream phosphorus and dam density correlate positively with DOC concentrations. Notably, the relative importance of these environmental controls varies substantially across major U.S. water resource regions. In addition, DOC concentrations and environmental controls also show significant variability from small streams to large rivers. In sum, our results reveal that general multi-linear regression of twenty environmental factors can partially explain (56%) the DOC concentration variability. This study also highlights the complexity of the interactions among these environmental factors in determining DOC concentrations, thus calls for processes-based, non-linear methodologies to constrain uncertainties in riverine DOC cycling.
Qichun Yang; Xuesong Zhang; Xingya Xu; Ghassem R. Asrar. An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States. Water 2017, 9, 383 .
AMA StyleQichun Yang, Xuesong Zhang, Xingya Xu, Ghassem R. Asrar. An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States. Water. 2017; 9 (6):383.
Chicago/Turabian StyleQichun Yang; Xuesong Zhang; Xingya Xu; Ghassem R. Asrar. 2017. "An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States." Water 9, no. 6: 383.
Nitrous oxide (N2O) is a potent greenhouse gas (GHG) contributing to global warming, with the agriculture sector as the major source of anthropogenic N2O emissions due to excessive fertilizer use. There is an urgent need to enhance regional‐/watershed‐scale models, such as Soil and Water Assessment Tool (SWAT), to credibly simulate N2O emissions to improve assessment of environmental impacts of cropping practices. Here, we integrated the DayCent model's N2O emission algorithms with the existing widely tested crop growth, hydrology, and nitrogen cycling algorithms in SWAT and evaluated this new tool for simulating N2O emissions in three agricultural systems (i.e., a continuous corn site, a switchgrass site, and a smooth brome grass site which was used as a reference site) located at the Great Lakes Bioenergy Research Center (GLBRC) scale‐up fields in southwestern Michigan. These three systems represent different levels of management intensity, with corn, switchgrass, and smooth brome grass (reference site) receiving high, medium, and zero fertilizer application, respectively. Results indicate that the enhanced SWAT model with default parameterization reproduced well the relative magnitudes of N2O emissions across the three sites, indicating the usefulness of the new tool (SWAT‐N2O) to estimate long‐term N2O emissions of diverse cropping systems. Notably, parameter calibration can significantly improve model simulations of seasonality of N2O fluxes, and explained up to 22.5%–49.7% of the variability in field observations. Further sensitivity analysis indicates that climate change (e.g., changes in precipitation and temperature) influences N2O emissions, highlighting the importance of optimizing crop management under a changing climate in order to achieve agricultural sustainability goals.
Qichun Yang; Xuesong Zhang; Michael Abraha; Stephen Del Grosso; G. P. Robertson; Jiquan Chen. Enhancing the soil and water assessment tool model for simulating N2O emissions of three agricultural systems. Ecosystem Health and Sustainability 2017, 3, e01259 .
AMA StyleQichun Yang, Xuesong Zhang, Michael Abraha, Stephen Del Grosso, G. P. Robertson, Jiquan Chen. Enhancing the soil and water assessment tool model for simulating N2O emissions of three agricultural systems. Ecosystem Health and Sustainability. 2017; 3 (2):e01259.
Chicago/Turabian StyleQichun Yang; Xuesong Zhang; Michael Abraha; Stephen Del Grosso; G. P. Robertson; Jiquan Chen. 2017. "Enhancing the soil and water assessment tool model for simulating N2O emissions of three agricultural systems." Ecosystem Health and Sustainability 3, no. 2: e01259.
Siyuan Wang; Bing Zhang; Qichun Yang; Guangsheng Chen; Bojuan Yang; Linlin Lu; Ming Shen; Yaoyao Peng. Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China. Agricultural and Forest Meteorology 2017, 232, 235 -246.
AMA StyleSiyuan Wang, Bing Zhang, Qichun Yang, Guangsheng Chen, Bojuan Yang, Linlin Lu, Ming Shen, Yaoyao Peng. Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China. Agricultural and Forest Meteorology. 2017; 232 ():235-246.
Chicago/Turabian StyleSiyuan Wang; Bing Zhang; Qichun Yang; Guangsheng Chen; Bojuan Yang; Linlin Lu; Ming Shen; Yaoyao Peng. 2017. "Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China." Agricultural and Forest Meteorology 232, no. : 235-246.
In this study, we applied Version 4.5 of the Community Land Model (CLM) at a 0.125 degree resolution to provide the first county-scale model validation for simulating crop yields over the Conterminous United States (CONUS). Large bias was found in simulating crop yields against US Department of Agriculture (USDA) survey data, with county-level root-mean-square error (RMSE) of 42% and 38% for simulated US mean corn and soybean yields, respectively. We then synthesized crop yield, irrigation and fertilization datasets from USDA and US Geological Survey (USGS) to constrain model simulations. Compared with fertilization, irrigation has limited effects on crop yields with improvements limited to irrigated regions. In most current-generation Earth System Models (ESMs), fertilizers are applied spatially uniformly with fixed amounts and timing without considering crop fertilizer demand. To address this weakness, we propose a prognostic fertilization scheme that dynamically determines the timing and rate of each fertilizer application, with the annual amounts and valid fertilization time windows constrained by surveyed data. The optimized fertilization scheme reduces RMSE to 22% and 21% of the US mean corn and soybean yields, respectively. Compared with the default CLM4.5, our fertilization scheme substantially improves crop yield simulations especially over major crop growing regions. However, to compensate for the widely documented biases in denitrification rates simulated by CLM4.5, the dynamically determined fertilization timing and rates do not match the fertilization practices of farmers exactly. Therefore, caution should be exercised when extending this method beyond the contemporary conditions. This article is protected by copyright. All rights reserved.
Guoyong Leng; Xuesong Zhang; Maoyi Huang; Qichun Yang; Rashid Rafique; Ghassem R. Asrar; L. Ruby Leung. Simulating county‐level crop yields in the C onterminous U nited S tates using the C ommunity L and M odel: T he effects of optimizing irrigation and fertilization. Journal of Advances in Modeling Earth Systems 2016, 8, 1912 -1931.
AMA StyleGuoyong Leng, Xuesong Zhang, Maoyi Huang, Qichun Yang, Rashid Rafique, Ghassem R. Asrar, L. Ruby Leung. Simulating county‐level crop yields in the C onterminous U nited S tates using the C ommunity L and M odel: T he effects of optimizing irrigation and fertilization. Journal of Advances in Modeling Earth Systems. 2016; 8 (4):1912-1931.
Chicago/Turabian StyleGuoyong Leng; Xuesong Zhang; Maoyi Huang; Qichun Yang; Rashid Rafique; Ghassem R. Asrar; L. Ruby Leung. 2016. "Simulating county‐level crop yields in the C onterminous U nited S tates using the C ommunity L and M odel: T he effects of optimizing irrigation and fertilization." Journal of Advances in Modeling Earth Systems 8, no. 4: 1912-1931.
As a widely used watershed model for assessing impacts of anthropogenic and natural disturbances on water quantity and quality, the Soil and Water Assessment Tool (SWAT) has not been extensively tested in simulating water and carbon fluxes of forest ecosystems. Here, we examine SWAT simulations of evapotranspiration (ET), net primary productivity (NPP), net ecosystem exchange (NEE), and plant biomass at ten AmeriFlux forest sites across the U.S. We identify unrealistic radiation use efficiency (Bio_E), large leaf to biomass fraction (Bio_LEAF), and missing phosphorus supply from parent material weathering as the primary causes for the inadequate performance of the default SWAT model in simulating forest dynamics. By further revising the relevant parameters and processes, SWAT's performance is substantially improved. Based on the comparison between the improved SWAT simulations and flux tower observations, we discuss future research directions for further enhancing model parameterization and representation of water and carbon cycling for forests.
Qichun Yang; Xuesong Zhang. Improving SWAT for simulating water and carbon fluxes of forest ecosystems. Science of The Total Environment 2016, 569-570, 1478 -1488.
AMA StyleQichun Yang, Xuesong Zhang. Improving SWAT for simulating water and carbon fluxes of forest ecosystems. Science of The Total Environment. 2016; 569-570 ():1478-1488.
Chicago/Turabian StyleQichun Yang; Xuesong Zhang. 2016. "Improving SWAT for simulating water and carbon fluxes of forest ecosystems." Science of The Total Environment 569-570, no. : 1478-1488.
Siyuan Wang; Hang Yin; Qichun Yang; Hui Yin; Xiaoyue Wang; Yaoyao Peng; Ming Shen. Spatiotemporal patterns of snow cover retrieved from NOAA-AVHRR LTDR: a case study in the Tibetan Plateau, China. International Journal of Digital Earth 2016, 10, 1 -18.
AMA StyleSiyuan Wang, Hang Yin, Qichun Yang, Hui Yin, Xiaoyue Wang, Yaoyao Peng, Ming Shen. Spatiotemporal patterns of snow cover retrieved from NOAA-AVHRR LTDR: a case study in the Tibetan Plateau, China. International Journal of Digital Earth. 2016; 10 (5):1-18.
Chicago/Turabian StyleSiyuan Wang; Hang Yin; Qichun Yang; Hui Yin; Xiaoyue Wang; Yaoyao Peng; Ming Shen. 2016. "Spatiotemporal patterns of snow cover retrieved from NOAA-AVHRR LTDR: a case study in the Tibetan Plateau, China." International Journal of Digital Earth 10, no. 5: 1-18.
Satellite-derived vegetation phenology has been recognized as a key indicator for detecting changes in the terrestrial biosphere in response to global climate change. However, multi-decadal changes and spatial variation of vegetation phenology over the Northern Hemisphere and their relationship to climate change have not yet been fully investigated. In this article, we investigated the spatial variability and temporal trends of vegetation phenology over the Northern Hemisphere by calibrating and analyzing time series of the satellite-derived normalized difference vegetation index (NDVI) during 1982–2012, and then further examine how vegetation phenology responds to climate change within different ecological zones. We found that during the period from 1982 to 2012 most of the high latitude areas experienced an increase in growing period largely due to an earlier beginning of vegetation growing season (BGS), but there was no significant trend in the vegetation growing peaks. The spatial pattern of phenology within different eco-zones also experienced a large variation over the past three decades. Comparing the periods of 1982–1992, 1992–2002 with 2002–2012, the spatial pattern of change rate of phenology shift (RPS) shows a more significant trend in advancing of BGS, delaying of EGS (end of growing season) and prolonging of LGS (length of growing season) during 2002–2012, overall shows a trend of accelerating change. Temperature is a major determinant of phenological shifts, and the response of vegetation phenology to temperature varied across different eco-zones.
Siyuan Wang; Bojuan Yang; Qichun Yang; Linlin Lu; Xiaoyue Wang; Yaoyao Peng. Temporal Trends and Spatial Variability of Vegetation Phenology over the Northern Hemisphere during 1982-2012. PLOS ONE 2016, 11, e0157134 .
AMA StyleSiyuan Wang, Bojuan Yang, Qichun Yang, Linlin Lu, Xiaoyue Wang, Yaoyao Peng. Temporal Trends and Spatial Variability of Vegetation Phenology over the Northern Hemisphere during 1982-2012. PLOS ONE. 2016; 11 (6):e0157134.
Chicago/Turabian StyleSiyuan Wang; Bojuan Yang; Qichun Yang; Linlin Lu; Xiaoyue Wang; Yaoyao Peng. 2016. "Temporal Trends and Spatial Variability of Vegetation Phenology over the Northern Hemisphere during 1982-2012." PLOS ONE 11, no. 6: e0157134.