Evaluation of NCEP-Products (NCEP-NCAR, NCEP-DOE, NCEP-FNL, NCEP-GFS) of Solar Radiation for Karachi, Pakistan
Abstract
Th evaluation of the NCEP solar radiation products is performed, the solar radiation data measured by ESMAP for Karachi, Pakistan is compared with four NCEP products (NCEP-NCAR, NCEP-DOE, NCEP FNL, NCEP-GFS). The validation of satellite estimates of solar radiation against surface measured data is performed on the basis of statistical analysis and daily mean time series. The statistical analysis indicates that the mean bias error (MBE), root mean square error (RMSE) and correlation coefficient (R) for four datasets range from -4.48 to 63.24 W/m2, 55.70 to 108.77 W/m2 and 0.966 to 0.976 respectively. The monthly analysis of solar radiation is performed on the basis of daily mean time series to assess the impact of season on their accuracy. Cloud fraction is the main reason for less accuracy of solar radiation products for July and August because of Monsoon in Pakistan. Three-months evaluation of NCEP-FNL is also performed on the basis of monthly mean time series and scatter plots to assess the model performance of dataset. in different seasons. The estimates from NCEP-NCAR are least accurate among all datasets whereas performance of NCEP-FNL is most accurate for initial assessment of solar for Karachi. The results of NCEP-GFS are closer to NCEP-FNL hence NCEP-GFS can be used to forecast solar energy for Karachi.