Accurate predictions of wind power generation several months in advance are crucial for the effective operation and maintenance of wind farms and for facilitating efficient power purchase planning.This study evaluates...Accurate predictions of wind power generation several months in advance are crucial for the effective operation and maintenance of wind farms and for facilitating efficient power purchase planning.This study evaluates the performance of the seasonal prediction system of the National Centre for Medium-Range Weather Forecasting in forecasting near-surface winds.An analysis of 23 years of hindcast data,from 1993 to 2015,indicates that the seasonal prediction system effectively captures the inter-annual variability of near-surface winds.Specifically,predictions initialized in May demonstrate notable accuracy,with a skill score of 0.78 in predicting the sign of wind speed anomalies aggregated across various wind farms during the high wind season(June to August).Additionally,we critically examine the peculiarity of a case study from 2020,when the Indian wind industry experienced low power generation.To enhance forecasting accuracy,we employ statistical techniques to produce bias-corrected forecasts on a seasonal scale.This approach improves the accuracy of wind speed predictions at turbine hub height.Our assessment,based on root mean square error,reveals that bias-corrected wind speed forecasts show a significant improvement,ranging from 54%to 93%.展开更多
This paper deals with the comparison of cyclone forecasts from the two versions of the operational global ensemble prediction system(EPS)at the National Centre for Medium Range Weather Forecasting(NEPS).The previous v...This paper deals with the comparison of cyclone forecasts from the two versions of the operational global ensemble prediction system(EPS)at the National Centre for Medium Range Weather Forecasting(NEPS).The previous version had a horizontal resolution of 33 km with 44 ensemble members(NEPS)whereas the updated version of this EPS has a resolution of 12 km with 11 members(NEPS-UP).The ensemble mean forecasts from both the models are compared using the direct position(DPE),along(ATE)and cross track(CTE)errors.For the verification of strike probability,Brier Score(BS),Brier Skill Score(BSS),Reliability Diagram,Relative Operating Characteristic(ROC)Curve and Root Mean Square Error(RMSE)in mean Vs Spread in members are used.For verification of intensity,RMSE in maximum wind speed from the ensemble mean forecasts are compared.Comparison of ensemble mean tracks from both models showed lower errors in NEPS-UP for all forecast lead times.The decrease in the DPE,ATE and CTE in NEPS-UP was around 38%,48%and 15%respectively.NEPS-UP showed lower BS and higher BSS values indicating a better match between observed frequencies and forecast probabilities as well as higher prediction skills.The reliability diagram showed higher accuracy for NEPS-UP as compared to NEPS.The ROC curves showed that for forecasts with higher probabilities the hit rate was high in NEPSUP.There was a greater consensus between the RMSE and Spread for NEPS-UP at all lead times.It was also seen that the RMSE in mean showed a 41%decrease from NEPS to NEPS-UP.On comparing maximum wind,it was found that for all lead times the RMSE in maximum wind speed for NEPS-UP was lower than NEPS.展开更多
Protected surface states arising fromnon-trivial bandstructure topology in semimetals can potentially enable advanced device functionalities in compute,memory,interconnect,sensing,and communication.This necessitates a...Protected surface states arising fromnon-trivial bandstructure topology in semimetals can potentially enable advanced device functionalities in compute,memory,interconnect,sensing,and communication.This necessitates a fundamental understanding of surface-state transport in nanoscale topological semimetals.Here,we investigate quantum transport in a prototypical topological semimetal NbAs to evaluate the potential of this class of materials for beyond-Cu interconnects in highly-scaled integrated circuits.Using density functional theory(DFT)coupled with non-equilibrium Green’s function(NEGF)calculations,we show that the resistance-areaRAproduct in NbAs films decreases with decreasing thickness at the nanometer scale,in contrast to a nearly constant RA product in ideal Cu films.This anomalous scaling originates from the disproportionately large number of surface conduction states which dominate the ballistic conductance by up to 70%in NbAs thin films.We also show that this favorable RA scaling persists even in the presence of surface defects,in contrast to RA sharply increasing with reducing thickness for films of conventional metals,such as Cu,in the presence of surface defects.These results underscore the potential of topological semimetals as future back-end-of-line(BEOL)interconnect metals.展开更多
文摘Accurate predictions of wind power generation several months in advance are crucial for the effective operation and maintenance of wind farms and for facilitating efficient power purchase planning.This study evaluates the performance of the seasonal prediction system of the National Centre for Medium-Range Weather Forecasting in forecasting near-surface winds.An analysis of 23 years of hindcast data,from 1993 to 2015,indicates that the seasonal prediction system effectively captures the inter-annual variability of near-surface winds.Specifically,predictions initialized in May demonstrate notable accuracy,with a skill score of 0.78 in predicting the sign of wind speed anomalies aggregated across various wind farms during the high wind season(June to August).Additionally,we critically examine the peculiarity of a case study from 2020,when the Indian wind industry experienced low power generation.To enhance forecasting accuracy,we employ statistical techniques to produce bias-corrected forecasts on a seasonal scale.This approach improves the accuracy of wind speed predictions at turbine hub height.Our assessment,based on root mean square error,reveals that bias-corrected wind speed forecasts show a significant improvement,ranging from 54%to 93%.
文摘This paper deals with the comparison of cyclone forecasts from the two versions of the operational global ensemble prediction system(EPS)at the National Centre for Medium Range Weather Forecasting(NEPS).The previous version had a horizontal resolution of 33 km with 44 ensemble members(NEPS)whereas the updated version of this EPS has a resolution of 12 km with 11 members(NEPS-UP).The ensemble mean forecasts from both the models are compared using the direct position(DPE),along(ATE)and cross track(CTE)errors.For the verification of strike probability,Brier Score(BS),Brier Skill Score(BSS),Reliability Diagram,Relative Operating Characteristic(ROC)Curve and Root Mean Square Error(RMSE)in mean Vs Spread in members are used.For verification of intensity,RMSE in maximum wind speed from the ensemble mean forecasts are compared.Comparison of ensemble mean tracks from both models showed lower errors in NEPS-UP for all forecast lead times.The decrease in the DPE,ATE and CTE in NEPS-UP was around 38%,48%and 15%respectively.NEPS-UP showed lower BS and higher BSS values indicating a better match between observed frequencies and forecast probabilities as well as higher prediction skills.The reliability diagram showed higher accuracy for NEPS-UP as compared to NEPS.The ROC curves showed that for forecasts with higher probabilities the hit rate was high in NEPSUP.There was a greater consensus between the RMSE and Spread for NEPS-UP at all lead times.It was also seen that the RMSE in mean showed a 41%decrease from NEPS to NEPS-UP.On comparing maximum wind,it was found that for all lead times the RMSE in maximum wind speed for NEPS-UP was lower than NEPS.
基金the National University of Singapore was supported by MOE-2017-T2-2-114,MOE-2019-T2-2-215,and FRC-A-8000194-01-00supported by 2030 Cross-Generation Young Scholars Program from the Science and Technology Council(MOST111-2628-M-006-003-MY3)Cheng Kung University,and the Center for Theoretical Sciences.
文摘Protected surface states arising fromnon-trivial bandstructure topology in semimetals can potentially enable advanced device functionalities in compute,memory,interconnect,sensing,and communication.This necessitates a fundamental understanding of surface-state transport in nanoscale topological semimetals.Here,we investigate quantum transport in a prototypical topological semimetal NbAs to evaluate the potential of this class of materials for beyond-Cu interconnects in highly-scaled integrated circuits.Using density functional theory(DFT)coupled with non-equilibrium Green’s function(NEGF)calculations,we show that the resistance-areaRAproduct in NbAs films decreases with decreasing thickness at the nanometer scale,in contrast to a nearly constant RA product in ideal Cu films.This anomalous scaling originates from the disproportionately large number of surface conduction states which dominate the ballistic conductance by up to 70%in NbAs thin films.We also show that this favorable RA scaling persists even in the presence of surface defects,in contrast to RA sharply increasing with reducing thickness for films of conventional metals,such as Cu,in the presence of surface defects.These results underscore the potential of topological semimetals as future back-end-of-line(BEOL)interconnect metals.
