Performance of various gridded precipitation and temperature products against gauged observations over Turkey

Precipitation and temperature products play a critical role for hydrological, meteorological, and agricultures studies. The present study assessed the accuracy of eight gridded precipitation products (i.e., CHIRPS, CPC, CRU, ERA5-Land, GPCC, NCEP-NCAR R1, NCEP-DOE R2, and PREC/L) and three gridded temperature datasets (i.e. CPC, CRU, and, ERA5-Land) for Maximum temperature (TMAX), mean temperature (TMEAN), and minimum temperature (TMIN) over Turkey at monthly, seasonal and annual scales. Considering monthly gauge observation data from 105 stations as reference, the above precipitation and temperature products were evaluated based on using different performance indices. The results for precipitation showed that dataset performance varied by region and emphasized that GPCC is the most suitable dataset that can be used in Turkey for all evaluation criteria. CPC can be considered as the second most suitable datasets, while NCEP-NCAR R1 and NCEP-DOE R2 showed the weakest performance among the studied datasets. In addition, the findings of the study highlight that there is a better agreement between rain gauge observations and gridded products during the rainy seasons compared to the dry season. For TMAX, TMEAN, and TMIN, the regionally temporal evaluation results of the monthly scale show that in terms of overall statistical metrics, CPC generally performs better than the others. Comprehensive evaluation results showed that the gridded data showed poor performance in summer compared to other seasons in terms of Pearson coefficient of correlation (CC) and Normalized root mean square error (nRMSE), while they showed poorer skills based on Kling-Gupta efficiency (KGE) and Percentage Bias (PBias) in winter.