Rainstorm Intensity Formula System and Guidelines

20-04-2018Source:China Meteorological News Press

On March 25, 2015, it is reported from the urban waterlogging risk warning seminar that by the joint efforts of China Meteorological Administration (CMA) and Ministry of Housing and Urban-Rural Development, the amendment of rainstorm intensity formula in 102 cities was completed in China. Based on the amendment, urban waterlogging warning and preparedness work has been carried out smoothly.


Owing to enormous influence brought by rainstorm and other extreme weather to social management, urban operation and people's life, sound urban drainage system has become more and more important. Therefore, the State Council released a Notice to prevent from urban water-logging urging meteorological, hydrologic and other departments to enhance evaluation and revision for exiting rainstorm intensity formula. Rainstorm intensity formula and rainstorm profile all can reflect objectively urban short term severe precipitation patterns. Therefore, it's important to establish a climate demonstration technological system which made urban rainstorm intensity formula and rainstorm profile as main contents in China.

Extreme rainstorm brought urban waterlogging for Beijing on July 21, 2012.


CMA established cooperative working system with MOHURD for editing and revising urban rainstorm intensity formula.


With the analysis of recent evolution characters of short-term rainstorm among megacities and urban drainage and water-logging prevention technological achievements, CMA and Ministry of Housing and Urban-Rural Development (MOHURD) established effective working system, signed cooperative agreement for preventing urban water-logging and issued the Notice to revise rainstorm intensity formula.


Computing & analysis system of rainstorm intensity formula and rainstorm profile developed.


In recent years, CMA developed computing & analysis system of rainstorm intensity formula and rainstorm profile (2.0 Version), improved rainstorm profiles analysis module and carried out training for operators in city-level meteorological departments.


The system provides scientific and standardized function for staff to deal with basic data, calculate and analyze and make diagram of results. It can translate the massive materials of historical precipitation self-recording paper and automatic weather station of every minute into standard data format quickly and efficiently. This system provides a complicated solver of two equations with three parameters and a range of curves adjusting methods including Pearson-Ⅲ distribution, extremal distribution and exponential distribution and so on. As a result, users can choose the most optimized combination of the parameters and equations in order to meet the standard requirements of the fit accuracy of formula, which can reduce the time of each program from five to six months to two to three weeks. It not only improves the efficiency remarkably, but also makes it convenient and reliable because the users needn't to double-check the sample results, providing technical support for all-level meteorological departments that engage in the city drainage plan and project design. The application of this software plays an essential role in promoting meteorological departments' influence in this field.

P-Ⅲ Density Curve


CMA plays a leading role in editing Technical Guidelines for Establishment of Intensity-Duration-Frequency Curve and Design Rainstorm Profile. (click the end of this article to get full Chinese text)


CMA takes charge of editing Technical Guidelines for Establishment of Intensity-Duration-Frequency Curve and Design Rainstorm Profile (refer to Guidelines below). Experts from Guangdong Climate Centre, Beijing Climate Centre, construction departments including Jiangsu Provincial Department of Housing and Urban-Rural Development and China Academy of Urban Planning & Design are grouped to communicate with the departments, institutions and management organizations and consider suggestions and advices. In May 2014, the Guidelines was officially issued by CMA and MOHURD and published in September 2014.


Guidelines has established the basic requirements, technique flow, original materials and technological requirements of statistical samples, frequency calculation, distribution curve, parameter solver of rainstorm intensity formula, identification of rainstorm profile and adaptation analysis. It provides unified standard algorithms of rainstorm intensity formula and rainstorm profile identification and methods to deal with basic materials, improving the reliability, completeness and adequacy of setting parameters of rainstorm intensity formula. It is also an important achievement in the new round of city drainage and water-logging preparedness planning and project design in large scale. As a standardized document, it further improves the departments' influences, forming a professional technological support system combined with standard materials and software based on the analytical computing & analysis  system of rainstorm intensity formula and rainstorm profile.


Innovative Points


Taking big cities including Beijing, Guangzhou and Shanghai and other representative cities in different regions with different rainfall features, as subjects, the CMA studied the temporal and spatial change features of brief rainstorm in recent years and its impact on the results of city rainstorm intensity formula and analyzed the impacts of different sample-data means including numerous-samples and year-maximum on rainstorm intensity formula setting, and then the new formula's impacts on urban planning. It explains the key role of meteorological department plays in city drainage and water-logging preparedness planning and its professional advantages scientifically.


The computing & analysis  system of rainstorm intensity formula and rainstorm profile has been developed and given strong technical supports to the quick formation of business service ability of business units at provincial level.


In accordance with the latest editions of Design Standards of Outdoor Drainage and Guidelines, the system was created and improved, which can deal with massive accurate precipitation data efficiently and quickly, supplying solvers to complicated storm intensify formulas and providing multiple methods of curves adjusting methods as well as methods of analyzing rainstorm type. Also, this system has unified and standardized functions of tabulating and drawing. The nationwide training of this system and its promotion have given strong supports to operational capability of meteorological departments at provincial level.


CMA organized related engineering institutes, universities, and other sectors to complete the Guidelines. The Guidelines meet the needs of drainage waterlogging engineering application, and standardize the basic requirements and technical process of the preparation of rainstorm intensity formula and rainstorm profile, the raw data, the statistical sample, and distribution curve, etc. It coordinates with rainstorm intensity formula and rainstorm profile computing analysis system, to establish a better meteorological reasoning technology system for the planning and construction of urban drainage waterlogging.


Providing technical support for cross-sector cooperation


Based on the research of the influence of short-term rainstorm on urban drainage waterlogging and engineering application, CMA and MOHURD signed a Cooperation Framework Agreement, and established the cross-sector working mechanism.


CMA lead the development of 80 sets of rainstorm intensity formula and computing analysis system, and freely sent to provincial meteorological departments, and sent the Guidelines to provincial housing construction sectors and meteorological sectors, related institutes, and universities. Based on the system and the Guidelines, provincial meteorological departments utilized fully basic data and unique technology operation advantages, to actively join in the planning and construction of local urban drainage waterlogging.


As of October 30, 2014, provincial meteorological departments and local housing construction units signed 9 cooperation agreements, and jointly issued 23 documents. Meteorological departments completed the preparation of 91 urban rainstorm intensity formulas, and 30 urban rainstorm rainstorm profiles.


Training a climate demonstration technical team for the planning and construction of urban drainage and waterlogging.


The training of software and the Guidelines strongly supported the technical staff of meteorological sector at provincial and city level, making them to participate in the planning and construction of local urban drainage and waterlogging. The project effectively trained a professional team, laid a good foundation for services for future urban development, and met the meteorological service needs for modern urban development.


On March 25, 102 cities completed the amendment of rainstorm intensity formula in China.

In Beijing, the local meteorological department carried out urban waterlogging risk census, shared water monitoring data with Beijing Water Authority, and completed Beijing urban waterlogging numerical model.

Shanghai Meteorological Bureau developed meteorological risk forecast for heavy rainfall waterlogging disaster, and constructed pear to pear rainstorm waterlogging risk warning service.

In Wuhan, Wuhan Meteorological Office improved urban waterlogging disaster warning system platform and put into operation. It established Wuhan urban rainstorm waterlogging emergency consultation system, and worked with related sectors to jointly issue warning and forecast urban waterlogging products.

For the next step, meteorological departments and housing and urban-rural developments will strengthen cooperation mechanism, share data and technical achievements, and jointly develop related standards and norms. They will deepen urban waterlogging monitoring and warning service, and further promote urban waterlogging warning and prevention. (2015-04-20)



Editor Hao Jing, Shi Long and Deng Jingmian