Abstract:High-quality hydrometeorological observation data are the base for the monitoring, forecasting, prediction of hydrometeorological hazards, and also the basic support for long-term climate trend analysis. Focusing on the fundamental elements such as precipitation of water cycle, this paper summarizes the great progress in developing hydrometeorological observation datasets, two and three dimensional fusion analysis products, and multi-dimensional reanalysis products as well as their application in hydrological and climate monitoring and forecasting. The analysis shows that meteorological and hydrological data are two most important embodiments of water cycle in the earth system. Their effective integration and collaborative quality control can effectively promote their application in various components of the earth system model. Produced through intensive data processing such as data fusion analysis and assimilation analysis of multi-source earth observation data, the gridded analysis products with multi spatiotemporal scale, high precision, high timeliness and continuous space-time are used to be the initial points of intelligent grid forecasting and climate prediction, having become an integral part of seamless fine gridded forecasting operation. The global long-series atmospheric and land surface reanalysis products produced by assimilation of historical observational data play important roles in the assessment and monitoring of long-term evolution of climate change, and their application values are far beyond the observation data itself.