Synthesizing a Regional Territorial Evapotranspiration Dataset for Northern China

We developed a synthesis ET dataset for Northern China at a 1000 m spatial resolution with a monthly temporal resolution covering a period ranging from 1982 to 2017 using an in-depth assessment of several ET products. Specifically, assessments were performed using in situ measured ET from eddy covariance (EC) observation towers at the site-pixel scale over interannual months under the conditions of different land cover types, climatic zones and elevation levels to select the most optimally performing ET products to be used in the synthesized ET dataset. Eight indicators under 21 conditions were involved in the assessment sheet, while the statistics of the different ET product occurrences and corresponding ratios were analyzed to select the best-performing ET products to build the synthesis ET dataset using the weighted mean method. The weights were determined by the Taylor skill score (TSS) calculated with ET products and EC ET observation data. Based on the assessment results, the Penman-Monteith Leuning (PML_v2), ETWatch, and operational Simplified Surface Energy Balance (SSEBop) datasets were selected for implementation in the synthesis ET dataset from 2003 to 2017, while Global Land Evaporation Amsterdam Model (GLEAM) v3.3a, complementary relationship (CR) ET, and Numerical Terradynamic Simulation Group (NTSG) datasets were chosen for the synthesis ET dataset from 1982 to 2002. The weighted mean synthesized results from 2003 to 2017 performed well when compared to the in situ measured EC ET values produced under all of the above conditions, while the synthesized results from 1982 to 2002 performed well through the water balance method in Heihe River Basin. These results can provide more stable ET estimations for Northern China, which can contribute to relevant agricultural, ecological and hydrological studies. The spatial reference of the dataset is the Albers Conic Equal Area projection with the central meridian of 110° based on the Krasovsky datum. The unit of the data is mm/month, while the nodata values were assigned to 0. The monthly files were provided with GeoTiff format and named like "NorthernChina_syn_1982m01_eta.tif". More information on the dataset and methodology could be found in "Synthesizing a Regional Territorial Evapotranspiration Dataset for Northern China” by Wang et al. (2021).