The GAME/HUBEX cooperated by China and Japan was conducted 20 yr ago. The aforementioned reviews and comments on its main achievements show clearly that this large-scale scientific experiment that lasted about 7 yr in total is successful, and many new scientific understandings and breakthroughs have been accomplished. These achievements have played an important role in the subsequent development and promotion of related scientific research and operational forecasting.
However, it should also be recognized that as the impact of global climate change continues to increase, the results and findings of the past may have also changed, especially due to the impact of climate warming caused by human activities. The hydrological processes and events corresponding to the multi-scale variability of climate background and extreme events will also change (Ding et al., 2020). Studies have shown that Meiyu in East Asia, including Meiyu in China, is characterized by multi-scale variability. They are related to quasi-biweekly and 30–60-day oscillations, ENSO events, quasi-biennial oscillations (QBO), the Pacific decadal oscillation (PDO), and the Atlantic Decadal Oscillation (ADO). In addition, many studies have also pointed out that under the influences of global warming, urbanization, and increased aerosols, the Meiyu precipitation characteristics have also changed, including precipitation continuity, precipitation increase or decrease, more uneven spatial distribution, the increase (decrease) in heavy (light) precipitation days, etc. (Li et al., 2011, 2016).
Of particular concern is that global warming is changing the global and regional water cycles. It is still unclear whether the Meiyu or related energy and water cycles may also increase in the Huaihe River basin, which is located in a fragile climate zone, and whether the risks of meteorological and hydrological disasters may also change. This involves the issues of disaster prevention and mitigation as well as economic and social sustainable development in the Huaihe River basin under the new situation. Therefore, we need to conduct more in-depth and comprehensive research and exploration from a global perspective, understand the new regularities of climate, environment and hydrological changes, avoid risks, and seek new development opportunities. This is an important issue that will benefit the people living in the vast areas of the Huaihe River basin.
Relying on the multi-scale observation network centered on the Shou County National Observatory and a variety of advanced detection equipment (Table 1), the second phase of the Huaihe River Energy and Water Cycle Experiment (HUBEX-2) will be carried out. Further in-depth and more comprehensive research and exploration of changes in the water cycle and corresponding changes in meteorological and hydrological disasters and risks will be conducted to understand new regularities of climate, environmental, and hydrological changes; to avoid risks; and to ensure healthy development of agriculture, ecology, society, and economy in the Huaihe River basin.
Dataset Content (including meta data, equipment information, data usage note, etc.) Start time Manual weather reports Barometric pressure, air temperature, air humidity, surface and soil temperature, frozen soil depth, precipitation, evaporation, current weather/weather events January 1955 National baseline meteorological station observations Barometric pressure, air temperature (mean, maximum, minimum), grass land surface temperature, water vapor pressure, precipitation, evaporation, wind direction and speed, relative humidity, dew-point temperature, cloud fraction, visibility, frozen soil depth, soil temperature (at surface, 5-, 10-, 15-, 20-, 40-, 80-, 160-, 320-cm depths), soil moisture (at 10-, 20-, 40-, 80-, 160-cm depths), insolation duration, snow cover (snow depth, snow pressure), ice load on power lines January 2005 Field agricultural science observations Seed performance evaluation for summer maize and winter wheat during budding and harvest periods January 1982 Field soil moisture observations Soil moisture content in 0–5-cm layer and each 10-cm layer between 10 and 100 cm January 1982 Boundary-layer tower observations at varied heights Air temperature, humidity, and wind speed and direction at 30-, 20-, 10-, 2-, and 1-m heights; soil temperature at 5 layers, soil moisture at 9 layers, net radiation, downward and upward shortwave radiation, downward and upward longwave radiation, photosynthetically active radiation, soil heat flux July 2007 Flux data Three-dimensional wind speed, CO2 density, water vapor density; the sensible heat flux, latent heat flux, momentum flux, H2O flux, CO2 flux, and CH4 flux between the farmland ecosystem and the atmosphere July 2007 Phenological data Ligneous plant phenological period, hydrophenological period, and animal phenological period January 1985 Baseline radiation observations Total radiation, direct radiation, scattered radiation, reflected radiation, atmospheric longwave radiation, earth longwave radiation, net radiation, ultroviolet radiation, photosynthetically active radiation January 2014 Underground water level data Underground water level January 1982 Atmospheric composition data Aerosol (mass concentration, optical characteristic, vertical profile); volume concentrations of black carbon, CO, SO2, O3, NOx, and some other reactant gases January 2014 Satellite remote sensing data Data from NOAA series satellites, FY-1 and FY-3 polar orbiting meteorological satellites, MODIS, GMS-5, FY-2 and FY-4 stationary meteorological satellites; and high-resolution satellite data from 2000 onwards January 1996 Ground-based remote sensing data Aerosol lidar, boundary-layer wind profile radar, microwave radiometer, C-band continuous wave radar, Micro Rain Radar (MRR), operational SA radar network in the surrounding area, dual-polarization radar, and so on January 2015
Table 1. Data collections from the comprehensive meteorological observation network in the Huaihe River basin of China
Aiming at the bottleneck problems in the research and meeting the actual needs of drought and flood disaster prevention and mitigation and sustainable development, we will further address the following issues. (1) Solve the problem in multi-platform and multi-method collaborative observation; rely on the National Climate Observatory at Shou County (Shouxian, Anhui Province) to achieve integrated airborne, ground-based, and satellite observations; develop multi-variable blending and retrieval technology; and realize simultaneous and stereoscopic observations of hydrological processes, land surface processes, atmospheric dynamic and thermal dynamic processes, cloud microphysical processes, atmospheric chemical processes, etc. (2) Based on analysis of historical observation data and comprehensive experiment data, further reveal the characteristics of the energy and water cycles in the Huaihe River basin; understand the land surface processes, dynamics/thermal and microphysical processes of various weather systems, and the evolution and interaction of multi-scale systems; and study the interaction between the energy and water cycles in the Huaihe River basin and weather systems such as the Meiyu front, the subtropical high, and Jianghuai cyclones. (3) Use satellite and global meteorological observation data to study the impacts of global climate change, anthropogenic forcing (greenhouse gas emissions, radiative forcing caused by land use change) and human activities (urbanization, atmospheric pollution, ecological restoration, etc.) on the Huaihe River basin energy and water cycles as well as drought and flood disasters and their mechanisms. (4) Take advantage of variable-resolution prediction models to improve the parameterization schemes of cloud microphysics and land–atmosphere interaction; develop a prediction platform suitable for the Huaihe River basin with full consideration of anthropogenic forcing and human activities; and couple the platform with hydrological models to improve the ability of simulation and forecast of drought and flood disasters. (5) Assess the energy and water cycle anomalies and the impacts of drought and flood disasters induced by these anomalies on agricultural production; combine numerical forecasting, disaster process simulation, and crop models to assess future agricultural production risks; and develop corresponding disaster mitigation technologies to effectively guarantee the increase of grain production in the Huaihe River basin.