Since entering the flood season, many regions in China have encountered heavy rain and floods. How can we gain the upper hand in personnel transfer and flood prevention decisions before heavy rain and floods arrive? The Ministry of Water Resources is continuously promoting the construction of the “three lines of defense,” among which the hydrological rainfall radar, as part of the “first line of defense,” plays an important role in early prediction. Today, Wang Lin, Chief Forecaster of the Hydrology Department of the Ministry of Water Resources, provided us with detailed answers to related questions.
Question 1: What are the differences between hydrological rainfall radar and meteorological weather radar? What are the characteristics of hydrological rainfall radar?Hydrological rainfall radar and meteorological weather radar have significant differences in terms of observation targets, deployment locations, appearance sizes, and the ease of installation and operation.Observation Targets
Hydrological Rainfall Radar: Observes liquid water in the near-surface layer of the atmosphere from the ground up to a height of 2 kilometers.
Meteorological Weather Radar: Observes all meteorological elements in the atmosphere from the ground up to the tropopause, which ranges from 20 to 30 kilometers in height.
The hydrological rainfall radar addresses the observation of rainfall amounts. It can observe liquid water in the near-surface layer of the atmosphere from the ground up to below 2 kilometers, generating real-time high-precision rainfall data with a grid of 30 meters by 30 meters and a temporal resolution of up to 40 seconds. It also has the capability to extrapolate forecasts for 1 to 3 hours. In contrast, meteorological weather radar samples the atmosphere over a large area from the ground to the tropopause at 20 to 30 kilometers, addressing the issue of vertical atmospheric detection.
Deployment LocationsHydrological Rainfall Radar: Mainly deployed in areas prone to heavy rain and floods, as well as areas prone to mountain flood disasters.Meteorological Weather Radar: Mainly deployed around urban areas.The main purpose of hydrological rainfall radar is to observe rainfall in areas prone to heavy rain and floods, typically deployed in flood-prone areas and mountainous or hilly regions prone to flash floods. Due to the special deployment environment, there are higher requirements for the radar’s ability to resist interference from ground objects and suppress ground noise. Meteorological weather radar is more focused on serving public weather forecasting needs, thus mainly deployed around cities.Appearance Size and Operational Costs
Hydrological Rainfall Radar: Compact and easy to maintain.
Meteorological Weather Radar: Larger in size, with higher operational costs.
Hydrological rainfall radar primarily observes liquid water in the near-surface layer, and its small size, light weight, low power consumption, and low power make it easy to install and maintain. In contrast, meteorological weather radar is larger, heavier, has higher installation requirements, and incurs higher operational costs.
Based on these characteristics, hydrological rainfall radar serves as an important infrastructure for observing rainfall amounts, offering significant advantages over traditional meteorological weather radar in terms of time efficiency for rainfall monitoring, spatial resolution, accuracy of networked monitoring, and stability, thereby providing more comprehensive and reliable data support for flood forecasting.
Question 2: From “Ground Rain” to “Cloud Rain”, how does hydrological rainfall radar play a role?Since the Ministry of Water Resources has promoted the construction of rainfall radar, China’s rainfall monitoring is gradually transitioning from “ground rain” to “cloud rain.” The “first line of defense” will continue to be strengthened, and monitoring and forecasting will achieve “a step ahead.”Traditional flood forecasting systems primarily rely on observations of “ground rain” for flood forecasting, with a relatively limited forecasting period. This is because, in areas prone to small and medium rivers and flash floods, the time from rainfall to flood formation can be as short as half an hour to an hour. However, the time taken to monitor rainfall data from rain gauges, input it into models, and then provide defense decisions is relatively long, leaving very little time to respond to floods.By using phased array rainfall radar to monitor “cloud rain,” the monitoring time can be brought forward. Additionally, with three rainfall radars networked, the coverage can reach 10,000 square kilometers. Within this area, ultra-high spatial and temporal resolution rainfall data can be observed, providing detailed data support for flood forecasting and effectively improving the accuracy of flood predictions. Based on the three radars, the rainfall radar has the capability to extrapolate high-resolution networked precipitation forecasts for 1 to 3 hours, enhancing its ability to perceive and warn against short-duration heavy rainfall, thus extending the flood forecasting period.
Question 3: What application cases have hydrological rainfall radar had this flood season?Hunan: 10 effective flood disaster risk SMS warnings issued this year.In 2022, Hunan was one of the first pilot areas in the country for X-band phased array rainfall radar in the water resources sector, deploying three phased array rainfall radars in the Laodao River and Liuyang River basins, achieving coupling between hydrological rainfall radar monitoring and forecasting data with the flood forecasting system.Since the onset of the flood season this year, Hunan has effectively issued 10 SMS warnings for flood disaster risks based on the rainfall monitoring and forecasting from hydrological rainfall radar, successfully warning about changes in water levels of small and medium rivers such as the Jinjing River and the Guitang River, allowing water resources departments to make timely decisions.Beijing: The monitoring effects of three hydrological rainfall radars are beginning to show.On July 12 and 15, Beijing experienced two consecutive heavy rainfall events, and the monitoring effects of the three hydrological rainfall radars deployed in the Yongding River Guanting Mountain Gorge section began to show. On July 12, the rainfall forecasts extrapolated by the hydrological rainfall radar for 1 hour and 2 hours had a high hit rate compared to actual rainfall amounts; on July 15, the real-time monitoring by the radar corresponded well with the heavy rainfall intensity and location observed by rain gauges.Currently, the networked monitoring of the three hydrological rainfall radars effectively addresses the spatial accuracy issues of area rainfall monitoring, achieving ultra-fine grid monitoring of “cloud rain” in the Beijing section of the Yongding River basin and the main urban area of Beijing, while also being able to extrapolate a high-resolution networked precipitation forecast for 3 hours, enhancing the ability to perceive and warn against short-duration heavy rainfall. The establishment of the networked monitoring of the three hydrological rainfall radars has compensated for the insufficient monitoring and forecasting capabilities for short-duration heavy rainfall in the Guanting Mountain Gorge area, providing effective support for this year’s flood prevention efforts in Beijing.In the next step, the Ministry of Water Resources will focus on promoting the application and construction of hydrological rainfall radar in small and medium rivers and areas prone to heavy rain and floods, fully leveraging the “cloud rain” monitoring capability of hydrological rainfall radar to further extend the flood forecasting period and improve accuracy, achieving effective integration of both.
Source: China Water Affairs
Editor: Xu Puqiong
First Review: Du Zhongying
Second Review: Zhang Jixiao
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