Abstract. Land cover (LC) determines the energy exchange, water and
carbon cycle between Earth's spheres. Accurate LC information is a
fundamental parameter for the environment and climate studies. Considering
that the LC in China has been altered dramatically with the economic
development in the past few decades, sequential and fine-scale LC monitoring
is in urgent need. However, currently, fine-resolution annual LC dataset
produced by the observational images is generally unavailable for China due
to the lack of sufficient training samples and computational capabilities.
To deal with this issue, we produced the first Landsat-derived annual China
land cover dataset (CLCD) on the Google Earth Engine (GEE) platform, which
contains 30 m annual LC and its dynamics in China from 1990 to 2019. We
first collected the training samples by combining stable samples extracted
from China's land-use/cover datasets (CLUDs) and visually interpreted
samples from satellite time-series data, Google Earth and Google Maps. Using
335 709 Landsat images on the GEE, several temporal metrics were constructed
and fed to the random forest classifier to obtain classification results. We
then proposed a post-processing method incorporating spatial–temporal
filtering and logical reasoning to further improve the spatial–temporal
consistency of CLCD. Finally, the overall accuracy of CLCD reached 79.31 %
based on 5463 visually interpreted samples. A further assessment based on
5131 third-party test samples showed that the overall accuracy of CLCD
outperforms that of MCD12Q1, ESACCI_LC, FROM_GLC and GlobeLand30. Besides, we intercompared the CLCD with several
Landsat-derived thematic products, which exhibited good consistencies with
the Global Forest Change, the Global Surface Water, and three impervious
surface products. Based on the CLCD, the trends and patterns of China's LC
changes during 1985 and 2019 were revealed, such as expansion of impervious
surface (+148.71 %) and water (+18.39 %), decrease in cropland
(−4.85 %) and grassland (−3.29 %), and increase in forest (+4.34 %). In
general, CLCD reflected the rapid urbanization and a series of ecological
projects (e.g. Gain for Green) in China and revealed the anthropogenic
implications on LC under the condition of climate change, signifying its
potential application in the global change research. The CLCD dataset
introduced in this article is freely available at
https://doi.org/10.5281/zenodo.4417810 (Yang and Huang, 2021).