Prem Woli

Evaluation of Various Methods for Estimating Global Solar Radiation in the Southeastern United States

AbstractGlobal solar radiation Rg is an important input for crop models to simulate crop responses. Because the scarcity of long and continuous records of Rg is a serious limitation in many countries, Rg is estimated using models. For crop-model application, empirical Rg models that use commonly measured meteorological variables, such as temperature and precipitation, are generally preferred. Although a large number of models of this kind exist, few have been evaluated for conditions in the United States. This study evaluated the performances of 16 empirical, temperature- and/or precipitation-based Rg models for the southeastern United States. By taking into account spatial distribution and data availability, 30 locations in the region were selected and their daily weather data spanning eight years obtained. One-half of the data was used for calibrating the models, and the other half was used for evaluation. For each model, location-specific parameter values were estimated through regressions. Models were...

Forecasting Drought Using the Agricultural Reference Index for Drought (ARID): A Case Study

AbstractDrought forecasting can aid in developing mitigation strategies and minimizing economic losses. Drought may be forecast using a drought index, which is an indicator of drought. The agricultural reference index for drought (ARID) was used as a tool to investigate the possibility of using climate indices (CIs) as predictors to improve the current level of forecasting, which is El Nino–Southern Oscillation (ENSO) based. The performances of models that are based on linear regression (LR), artificial neural networks (ANN), adaptive neuron-fuzzy inference systems (ANFIS), and autoregressive moving averages (ARMA) models were compared with that of the ENSO approach. Monthly values of ARID spanning 56 yr were computed for five locations in the southeastern United States, and monthly values of the CIs having significant connections with weather in this region were obtained. For the ENSO approach, the ARID values were separated into three ENSO phases and averaged by phase. For the ARMA models, monthly time ...

Soil and Variety Effects on Energy Use and Carbon Emissions Associated with Switchgrass-Based Ethanol Production in Mississippi

High biomass production potential, wide adaptability, low input requirement, and low environmental risk make switchgrass an economically and ecologically viable energy crop. The inherent variability in switchgrass productivity due to variations in soil and variety could affect the sustainability and eco-friendliness of switchgrass-based ethanol production. This study examined the soil and variety effects on these variables. Three locations in Mississippi were selected based on latitude and potential acreage. Using ALMANAC, switchgrass biomass yields were simulated for several scenarios of soils and varieties. The simulated yields were fed to IBSAL to compute energy use and CO2 emissions in various operations in the biomass supply chain. From the energy and emissions values, the sustainability and eco-friendliness of ethanol production were determined using net energy value (NEV) and carbon credit balance (CCB) as indicators, respectively. Soil and variety effects on NEV and CCB were analyzed using the Kruskal-Wallis test. Results showed significant differences in NEV and CCB across soils and varieties. Both NEV and CCB increased in the direction of heavier to lighter soils and on the order of north-upland, south-upland, north-lowland, and south-lowland varieties. Only north-upland and south-lowland varieties were significantly different because they were different in both cytotype and ecotype. Gaps between lowland and upland varieties were smaller in a dry year than in a wet year. The NEV and CCB increased in the direction of dry to wet year. From south to north, they decreased for lowland cytotypes but increased for upland cytotypes. Thus, the differences among varieties decreased northwards.