Assessment of agroclimatology NASA POWER reanalysis datasets for temperature types and relative humidity at 2 m against ground observations over Egypt

The climatic reanalysis datasets are one of the most important data types that could help to overcome scarce of observations. Therefore, the main objective of this study is to evaluate NASA POWER reanalysis data for surface monthly average temperatures at 2 m (maximum (T-max), minimum (T-max), mean (T-mean) and dew point (T-d), all in degrees C) and relative humidity (RH) in percentage compared to the observed data at 20 Egyptian weather stations. The results showed that there are a significant correlation and goodness of fit between NASA POWER reanalysis and observed data for all parameters except RH. For temperature variables, the coefficient of determination (R-2) and Willmott Index of agreement (WI) attain around 0.75 and 0.90 respectively, while the root mean square error (RMSE) reaches to less than 5 degrees C; and the mean bias error (MBE) ranges from -3 to +3 degrees C for 85% of stations. In addition, NASA POWER accuracy of temperature parameters increases gradually northward with the highest ratio at the northern coast of Egypt. Where, it is slightly overestimated (under 3 degrees C) T-max, T-min, and T-mean at 80, 75 and 65% of the stations respectively. While it is slightly underestimated T-d with 3 degrees C at 90% of the stations. Contrarily, NASA POWER data accuracy of RH increases southward, particularly in Aswan. Additionally, NASA POWER reanalysis has a considerable underestimation for RH data at most stations, where the dominant MBE percentage ranges from -12 to -5% for about 75% of the stations. As well as, the maximum RMSE and MBE for all elements were recorded in the Malwi station at Middle Egypt. Consequently, R-2, WI, RMSE, and MBE for temperature parameters are almost within an acceptable range for most selected Egyptian stations which are located in the area that dominated by the influence of the Mediterranean Sea (northern of 30 degrees N) and western of 30 degrees E with a distance between 2.5 and 14.5 km from the Sea. While, the good RH estimation is recorded at stations that are located south of the area that dominated by the influence of the Mediterranean Sea (south of 26 degrees N). Finally, NASA POWER reanalysis datasets can be used in case of missing or scarce of observations in Egypt. Nevertheless, it still needs improvements by taking into consideration the influence of the Mediterranean Sea and the locality of (especially middle) Egypt on temperature and in particular on relative humidity estimations. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.