## 4 Outline and Methodology
### Harmonization of Land Cover Classification  
A unified classification system is a necessary step when comparing different GLC products. Since the classification schemes and categorical scales vary between MCD12Q1 and GlobeLand30, it is highly \begin{table}
\begin{tabular}{c c} \hline \hline
**Type** & **Definition** \\ \hline Cultivated land & Lands used for agriculture, horticulture and gardens, including paddy fields, irrigated and dry farmlands, vegetation and fruit gardens. \\ Forest & Lands with trees, with vegetation cover over 30\%, including deciduous and coniferous forests, and sparse woodlands with cover from 10\% to 30\%, _etc._ \\ Grassland & Lands covered with shrubs with cover over 10\%, _etc._ \\ Shrubland & Land with shrubs cover over 30\%, including deciduous and evergreen shrubs and deserts \\  & steppe with cover over 10\%, _etc._ \\ Wetland & Lands covered with wetlands plants and water bodies, including inland marsh, lake marsh, river floodplain wetland, forest/shrub wetland, peat bogs, mangrove and salt marsh, _etc._ \\ Water bodies & Water bodies in the land area, including river, lake, reservoir and fish pond, _etc._ \\ Tundra & Lands covered by lichen, moss, hardy perennial herb and shrubs in the polar regions, including shrub tundra, herbaceous tundra, wet tundra and barren tundra, _etc._ \\ Artificial surfaces & Lands modified by human activities, including the various habitation, industrial and mining area, transportation facilities, and interior urban green zones and water bodies, _etc._ \\ Barren land & Lands with vegetation cover lower than 10\%, including desert, sandy fields, Gobi, bare rocks, saline and alkaline lands, _etc._ \\ Permanent snow and ice & Lands covered by permanent snow, glacier and icecap. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Definitions of the ten land cover types of GlobeLand30. important to reclassify the land cover categories prior to the evaluation of consistency. [PERSON] _et al._ proposed a novel method of land cover classification based on knowledge rule (KR), in which they established the accurate LULC data by the MODIS Normalized Difference Vegetation Index (NDVI), Digital Elevation Model (DEM) of Shuttle Radar Topography (SRTM), US Geological Survey (USGS) classification system and two land use maps of China [41]. [PERSON] _et al._ made the integration and comparison for the IGBP, UMD, LAI/FPAR, NPP, PFT and terrestrial ecosystem features and land cover classification schemes with six types, \"farmland\", \"forest\", \"grassland\", \"water bodies and wetland\", \"settlement\" and \"wilderness\" [42]. Considering the land cover classification method based on KR in [41] and the classification system in [42], the harmonization of land cover classification is performed in our study (Table 4). A total of five land cover types are obtained including \"woodland\", \"grassland\", \"cropland\", \"wetland\" and \"artificial surfaces\". In addition, there are no DN (digital number) values for the \"tundra\" of GlobeLand30, and it can be removed. Figure 3 illustrates the harmonization method of land cover classification based on KR, which is used to harmonize the land cover classification types between the five MCD12Q1 data layers and GlobeLand30. Firstly, the two datasets are prepared to produce the clustering center of each land cover  
Figure 2: Conceptual diagram and the general workflow. type. The 16-day composite MODIS NDVI dataset at a 500-m resolution of 2010 and the SRTM DEM at a 90-m resolution provide respectively the feature space for the classification and the auxiliary information for improving classification accuracy. Since the MCD12Q1 product has input features comprised of the nadir BRDF-adjusted reflectance (NBAR) data, the Land Surface Temperature (LST) data and the enhanced vegetation index (EVI) data [18]. It has the seasonal land cover region (SLCR) characteristics, _i.e.,_ the phonological features and the first productivity in the same SLCR are the same and they are distinctly different from those in other SLCR.