CN103902828A - Method for determining urban 24-hours long-duration rainstorm intensity - Google Patents

Abstract

The invention relates to a method for determining urban 24-hours long-duration rainstorm intensity. The method includes starting from data records of a rainstorm intensity formula, recording raw data as papery pluviograph records, performing digital processing on pluviograph data by means of computer vectorization technology, standardizing the raw data to further obtain appropriate rainfall data, adopting a sampling method giving consideration to municipal drainage, water conservancy drainage and waterlogging prevention, performing frequency analysis by applying a theoretic frequency distribution curve conforming to local rainfall probability distribution, adopting various computing methods to derive parameters of the rainstorm intensity formula according to a result obtained by frequency distribution, and preferably selecting the parameters with minimum error. The newly derived rainstorm intensity formula is outstanding in showing relation between design rainfall of three subsystems of municipal drainage, water conservancy drainage and waterlogging prevention, great convenience is brought to urban rainwater drainage planning and design, and even the problem that normal meanings of municipal design and water conservancy design are unmatched is solved fundamentally.

Description

The little duration in city 24 lasts definite method of storm intensity

Technical field

The present invention relates to definite method that the little duration in a kind of city 24 lasts storm intensity, belong to municipal works technical field.

Background technology

Urban rainwater removal system is the important infrastructure of modern city, and the planning on city, the location in city and civic daily life etc. have extremely important impact.In recent years, along with climate change is increasing to precipitation affects, economic development more and more quickly, the water quality type lack of water that requirement to urban infrastructure improves constantly, water environment pollution causes and the life of urban resident quality equal pressure that constantly declines, planning, design and the management of people to urban rainwater removal system proposed to be more strict with, have and be clearly familiar with and study and the prerequisite of municipal drainage is situation to Urban Rain and rule, have the Rain Intensity Formula Based that is suitable for this area rainfall rule.Rain Intensity Formula Based be reoccurrence period (P), storm intensity (i), the mathematic(al) representation of relation between rainfall duration (t) three, it is the basis of Drainage Design, it is the basic foundation of determining design flow of storm drain, urban rainwater drainage system design, be by Statistics Method to original data conformity rainfall rule out, it directly has influence on the investment of drainage system and the safety in city.Municipal drainage at present, water conservancy water drainage is each own a set of Rain Intensity Formula Based all, but in fact both take from same rainfall data, the just method difference of statistics, meanwhile, the design of city waterlogging prevention and cure project is also closely bound up with municipal drainage facility and water conservancy water drainage facility, the design of three cover subsystems, under same frequency, adopt same design rainfall can not only overcome the problem in storm frequency intercommunity, also getting rid of planning design work for urban rainwater provides scientific basis and reference.

Summary of the invention

For the problems referred to above, in order to solve city's unmatched problem of hydraulic engineering design normal meaning of having stable political situation.The present invention relates to definite method that the little duration in a kind of city 24 lasts storm intensity, be used for setting up a design storm statistical analysis technique that can comprise three individual system demands.

The present invention, take regional rainfall source book as basis, is intended to inquire into one and comprises municipal drainage, water conservancy water drainage, and the little duration in city 24 of waterlogging control lasts Rain Intensity Formula Based.First the pluviograph of papery is recorded to traditional rainfall data and carry out digitized processing, thereby obtain annual precipitation information, the precipitation data that it has comprised per minute every day, the time interval is 1min, comprise rain time (year, month, day, time, point) and the information such as the rainfall amount (0.1mm is the unit of record) of per minute, employing takes into account municipal drainage, water conservancy water drainage, the method of sampling of waterlogging control, choose 5min, 10min, 15min, 20min, 30min, 45min, 60min, 90min, 120min, 150min, 180min, 240min, 360min, 720min, 1440min, totally 15 rainfall duration, select the method for sampling of year maximum value process consistent with the sampling mode of hydrology specialty, corresponding reoccurrence period scope is elected 2～100 years as, the sample data of electing is tentatively chosen, select suitable frequency analysis method to carry out frequency analysis, the method of the suitable line of employing is matched one and is coordinated good theoretic frequency curve with sample point, determine the estimated value of suitable statistical parameter as population parameter, obtain corresponding frequencies according to corresponding parameter by theoretic frequency formula and divide the reoccurrence period planting (P), storm intensity (i), rainfall duration (t) three mathematical relation table, the P-i-t table that utilizes frequency analysis to obtain, adopt six kinds of classical way (Beijing methods, Beijing short cut technique, Nanjing method, curved surface least square method, Tongji University's method and direct approach to fitting) inquire into Rain Intensity Formula Based parameter, use average absolute mean square deviation

with average relative mean square deviation

judge the precision of the Rain Intensity Formula Based of inquiring into.Select the error corresponding method that meets the requirements, get the parameter value that its parameter value calculating is final Rain Intensity Formula Based.With existing formula comparison, the difference in analysis project design application, for urban rainwater eliminating planning design work provides scientific basis and reference on this basis.

Technical scheme of the present invention is as follows:

The little duration in city 24 lasts a definite method for storm intensity, and described method concrete steps are as follows:

(1) rainfall data processing

The rainfall data of the pluviograph record to papery carries out digitized processing by precipitation recording paper digitalized processing software system, the picture file of precipitation recording paper is converted into corresponding digital document, it is the final normative document generating of precipitation recording paper digital processing system, show with DAT form, it has comprised annual precipitation information, every day per minute precipitation data, the time interval is 1min, comprise rain time (year, month, day, time, point) and the information such as the rainfall amount (0.1mm is the unit of record) of per minute.

(2) data sample collection

(2.1) database design

At inquiring in process of Rain Intensity Formula Based, collection arrangement and the relevant computing of rainfall data are all carried out in database.Wherein, initial field rainfall and one minute rainfall data come from digitizing from note rainfall data.For the ease of operation afterwards, should first reasonably design corresponding database.

In ACCESS, newly-built following form a: rainfall, rainfall in 1 minute, x minute rainfall, version.Wherein, each table design is as follows:

In rainfall form, set up field and be: ID, time, initial time, end time, total rainfall amount; Data type is: numeral, numeral, text, text, numeral.The former two's numeric field size is that long, last column number word field size are double.

In 1 minute rainfall form, set up field and be: ID, time, rainfall amount, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, numeral, numeral.First digit field size is double, and rear two column number word field size are long.

Rainfall in x minute: setting up field is: ID, time, rainfall amount, maximum moment, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, text, numeral, numeral.Previous numeric field size is double, and rear two column number word field size are long.

Version: setting up field is value, numeric type is numeral.Meanwhile, in version form, the value of the longest rain battle array of input.

(2.2) sample is chosen

(2.2.1) choosing of rainfall duration

Consider municipal drainage, unified 5min, the 15min of adopting of water conservancy water drainage and waterlogging control, 30min, 45min, 60min, 90min, 120min, 150min, 180min, 240min, 360min, 720min, 1440min totally 15 last, in the sub-table of setting up rainfall in 15 minutes of (2.1) newly-built ACCESS lane database.

(2.2.2) sampling method

Along with the development in city, consider again the problem such as linking of the responsible urban rainwater pipe duct unwatering system (the less unwatering system in basin) of urban rivers and lakes water system unwatering system (unwatering system that basin is larger) that hydraulic department is responsible and urban construction department simultaneously, choosing year maximum value process is sampling method, annual each lasting chosen a maximal value, no matter then year time, by the order arrangement by size of each rainfall rain sample lasting, each lasting set up a txt file.The form of file is: the first row: last size, from the second row, descending order is arranged the size of raininess, and raininess can be obtained by rainfall and the relation of lasting.

(2.2.3) choosing of reoccurrence period

According to the sampling method of (2.2.2), reoccurrence period minimum is chosen 2 years, and maximum is chosen 100 years, and scope is 2～100 years.

(3) frequency analysis

For the rainfall data with larger randomness, must calculate it by mathematical statistics medium frequency analytical approach, just can draw suitable P-i-t relation, Rain Intensity Formula Based exactly thereby inquire into.

(3.1) frequency analysis model is tentatively chosen

In order to determine which kind of frequency analysis method sample uses, its that need to be right tentatively chosen.Take the scope of raininess as horizontal ordinate, the probability that raininess is corresponding is that ordinate does two-dimensional histogram, can judge from the trend of figure which kind of curve of frequency distribution it belongs to, if histogram mostly is parabolic type, substantially meet P-III type and distribute, if mostly be as linear pattern, substantially meet Gumbel and distribute.(as accompanying drawing 2)

(3.2) frequency analysis method

Adopt extra large gloomy probability ruled paper coordinate system, horizontal ordinate is empirical Frequency Pn(%), ordinate is storm intensity (mm/min), by a representative sample data point, curve is the theoretic frequency curve drawing according to these sample point matchings, what show in curve ending place is the correlation parameter of curve, and straight line represents the position (as accompanying drawing 3) of each reoccurrence period.Because the error that statistics produces, it is good that both not necessarily coordinate, and just must determine the estimated value of suitable statistical parameter as population parameter by the method for suitable line.In fitting line, should analyze the precision of experimental data, make curve as best one can approach or by reliable some certificate, look after as far as possible the trend of point group, make frequency curve by the center of point group, for especially big value, can not machinery pass through these points, should, in the error range allowing, improve as much as possible the precision of especially big value point distance.Meeting under point group trend suitably to consider top and middle part point certificate more, substantially be exactly the curve of reoccurrence period between 2～100 years, rule of thumb adjust each and last corresponding Cs value, until theoretic frequency curve and sampling point group under this Cs value are applicable to, record final Cs size, write down corresponding Cs/Cv value.Then, all curves that last are carried out to entirety adjustment, make Cs/Cv value as much as possible close to some values, to become cluster curve.Finally, according to corresponding parameter by theoretic frequency formula obtain corresponding frequencies divide reoccurrence period (P) of planting, storm intensity (i), rainfall duration (t) three mathematical relation table.

(4) formula is inquired into

Recommend and related documents according to existing Water And Drainage System Design handbook, the P-i-t table that utilizes frequency analysis to obtain, adopts six kinds of classical ways (Beijing method, Beijing short cut technique, Nanjing method, curved surface least square method, Tongji University's method and direct approach to fitting) to inquire into Rain Intensity Formula Based parameter.Formula form is:

$i=\frac{A_1(1+\mathrm{ClgP})}{{(t+b)}^n}$

In formula: i---storm intensity, the mm/min of unit;

T---rainfall duration, the min of unit;

P---be the reoccurrence period, unit year.

N, A ₁, b, C---regional parameters, its value is different and different with regional disparity with meteorological condition.

(5) formula error analysis

According to draining code requirement, use average absolute mean square deviation

with average relative mean square deviation

judge the precision of the Rain Intensity Formula Based of inquiring into.By the parameter A calculating ₁, C, n, in the value difference substitution formula of b, obtains respectively the storm rainfall value x of total formula, and relatively this raininess value and (3.2) are described can obtain corresponding residual sum of squares (RSS) σ by the raininess value in the P-i-t table obtaining after frequency analysis, absolute mean square deviation S ₁₁, relative mean square deviation S ₁₂.

$s_{11}=\sqrt{\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}$ $\stackrel{\&OverBar;}{s_{11}}=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_2}\underset{1}{\overset{m_2}{\mathrm{\&Sigma;}}}\left(\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2\right)$

$s_{12}=\frac{1}{{\stackrel{\&OverBar;}{x}}_{\mathrm{jp}}}\sqrt{\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}$ $\stackrel{\&OverBar;}{s_{12}}=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_2}\underset{1}{\overset{m_2}{\mathrm{\&Sigma;}}}\left(\frac{1}{{\stackrel{\&OverBar;}{x}}_{\mathrm{jp}}}\sqrt{\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA0000486426630000021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}\right)$

In formula, σ---residual sum of squares (RSS);

M ₁---the number of rainfall duration;

M ₂the number of one-reoccurrence period;

Xi _j---the raininess value (mm/min) of calculating after parameter value substitution formula;

X _jp,

---the intensity level that calculates after frequency analysis with and average (mm/min);

S ₁₁, S ₁₂---absolute mean square deviation and the relative mean square deviation of each reoccurrence period of total Rain Intensity Formula Based;

---average absolute mean square deviation and the average relative mean square deviation of total Rain Intensity Formula Based.

The result that in (5), each method obtains is calculated respectively to corresponding average absolute mean square deviation and average relative mean square deviation according to above-mentioned method, all meet in two errors under the prerequisite of code requirement, select the minimum corresponding method of error, get the parameter value that its parameter value calculating is final Rain Intensity Formula Based.

(6) with existing formula comparison and analysis

In the time inquiring into formula, the total formula of the storm intensity that the above 6 kinds of methods of use are inquired into is all the parameter result that the parameter of the Rain Intensity Formula Based by first calculating each single recurrence interval is inquired into total formula again.Conversely, can ask any storm intensity of lasting of any reoccurrence period by total formula equally, the formula of inquiring into so above-mentioned can be used as equally asks short duration Rain Intensity Formula Based.

But because two system reoccurrence period scope differences have different requirements to the precision of reoccurrence period.Can compare by following method:

According to different reoccurrence period P, last t, utilize above-mentioned two apply a formula calculate separately rainfall intensity i value list the P-i-t table of computational data, the more corresponding data in form are contrasted one by one, the data in above two forms are handled as follows:

Definition rate is: take the long calculated value that lasts formula as benchmark, and short duration, the long difference ratio lasting between formula.

Its calculating formula is:

Rate × 100%

In formula: i short duration---the rainfall intensity of calculating in short duration formula P-i-t table.

I is long to last---the long rainfall intensity of calculating in formula P-i-t table of lasting.

Can more obviously compare the difference between two formula by the comparison on numerical value.

Compared with prior art, the present invention has the following advantages:

(1) choose and 15 rainfall duration made municipal drainage, water conservancy water drainage, waterlogging is prevented and treated this three covers subsystem and can be united, under same frequency, adopt same design rainfall, not only for engineering design brings great convenience, more can fundamentally solve city's unmatched problem of hydraulic engineering design normal meaning of having stable political situation.

(2) selecting year maximum value process is that the method for sampling has solved hydraulic department and is responsible for the problems such as responsible urban rainwater pipe duct unwatering system (the less unwatering system in the basin) linking of urban rivers and lakes water system unwatering system (unwatering system that basin is larger) and urban construction department, can be used for the engineering check of linking up mutually, being connected with hydraulic condition of river flood frequency simultaneously.

(3) in the suitable line process of frequency distribution except meeting under point group trend the point certificates of considering middle part and top more, more meet current designing requirement.Because along with the development in city, the standard of design storm reoccurrence period is also in continuous improve, and the low reoccurrence period of 1 year several chance seldom adopts recently, thus consider that the meeting of high reoccurrence period is more reasonable, and will in following job family, be widely adopted.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of the present invention's " the little duration in city 24 lasts definite method of storm intensity " work.72 years rainfall datas are as sample take Beijing for Fig. 2, and the frequency analysis model that lasts 30min is tentatively chosen for routine schematic diagram.

72 years rainfall datas take Beijing that Fig. 3 adopts extra large gloomy probability ruled paper coordinate system to draw, as sample, are lasted for 60min, 120min, and 240min, 1440min adopts the schematic diagram of P-III type frequency distribution.

Embodiment

As shown in Figure 1, the present invention relates to the little duration in a kind of city 24 and last definite method of storm intensity, concrete steps are as follows:

(1) rainfall data processing

The rainfall data of the pluviograph record to papery carries out digitized processing by precipitation recording paper digitalized processing software system, the picture file of precipitation recording paper is converted into corresponding digital document, can therefrom obtain annual precipitation information, the precipitation data that it has comprised per minute every day, the time interval is 1min.Comprise rain time (year, month, day, time, point) and the information such as the rainfall amount (0.1mm is the unit of record) of per minute.

(2) data sample collection

(2.1) database design

At inquiring in process of Rain Intensity Formula Based, collection arrangement and the relevant computing of rainfall data are all carried out in database.Wherein, initial field rainfall and one minute rainfall data come from digitizing from note rainfall data.For the ease of operation afterwards, should first reasonably design corresponding database.

In ACCESS, newly-built following form a: rainfall, rainfall in 1 minute, x minute rainfall, version.Wherein, respectively show Design view as follows:

In rainfall form, set up field and be: ID, time, initial time, end time, total rainfall amount; Data type is: numeral, numeral, text, text, numeral.The former two's numeric field size is that long, last column number word field size are double.

In 1 minute rainfall form, set up field and be: ID, time, rainfall amount, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, numeral, numeral.First digit field size is double, and rear two column number word field size are long.

Rainfall in x minute: setting up field is: ID, time, rainfall amount, maximum moment, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, text, numeral, numeral.Previous numeric field size is double, and rear two column number word field size are long.

Version: setting up field is value, numeric type is numeral.Meanwhile, in version form, the value of the longest rain battle array of input.

(2.2) sample is chosen

(2.2.1) choosing of rainfall duration

Choosing rainfall duration is 5min, 10min, 15min, 20min, 30min, 45min, 60min, 90min, 120min, 150min, 180min, 240min, 360min, 720min, 1440min, totally 15.

(2.2.2) sampling method

Adopting a year maximum value process is sampling method, and annual each lasting chosen a maximal value, then year time no matter, by each rainfall rain sample lasting by size order arrange, each lasting set up a txt file.The form of file is: the first row: last size, from the second row, descending order is arranged the size of raininess, and raininess can be obtained by rainfall and the relation of lasting.

(2.2.3) choosing of reoccurrence period

According to the sampling method of (2.2.2), reoccurrence period minimum is chosen 2 years, and maximum is chosen 100 years, and scope is 2～100 years.

(3) frequency analysis

(3.1) frequency analysis model is tentatively chosen

Take the scope of raininess as horizontal ordinate, the probability that raininess is corresponding is that ordinate does two-dimensional histogram, can judge from the trend of figure which kind of curve of frequency distribution it belongs to.

(3.2) frequency analysis method

Adopt extra large gloomy probability ruled paper coordinate system, horizontal ordinate is empirical Frequency Pn(%), ordinate is storm intensity (mm/min), by a representative sample data point, curve is the theoretic frequency curve drawing according to these sample point matchings, curve is approached as best one can or by reliable some certificate by suitable line, look after as far as possible the trend of point group, make frequency curve by the center of point group, for especially big value, can not machinery pass through these points, should, in the error range of permission, improve as much as possible the precision of especially big value point distance.Meeting under point group trend suitably to consider top and middle part point certificate more, substantially be exactly the curve of reoccurrence period between 2～100 years, rule of thumb adjust each and last corresponding Cs value, until theoretic frequency curve and sampling point group under this Cs value are applicable to, record final Cs size, write down corresponding Cs/Cv value.Then, all curves that last are carried out to entirety adjustment, make Cs/Cv value as much as possible close to some values, to become cluster curve.Finally, according to corresponding parameter by theoretic frequency formula obtain corresponding frequencies divide reoccurrence period (P) of planting, storm intensity (i), rainfall duration (t) three mathematical relation table.

(4) formula is inquired into

Adopt six kinds of classical ways (Beijing method, Beijing short cut technique, Nanjing method, curved surface least square method, Tongji University's method and direct approach to fitting) to inquire into Rain Intensity Formula Based parameter.

(5) formula error analysis

Use average absolute mean square deviation

with average relative mean square deviation

judge the precision of the Rain Intensity Formula Based of inquiring into.By the parameter A calculating ₁, C, n, in the value difference substitution formula of b, obtains respectively the storm rainfall value x of total formula, and relatively this raininess value and (3.2) are described can obtain corresponding residual sum of squares (RSS) σ by the raininess value in the P-i-t table obtaining after frequency analysis, absolute mean square deviation S ₁₁, relative mean square deviation S ₁₂.Do not calculate again corresponding average absolute mean square deviation and average relative mean square deviation, all meet in two errors under the prerequisite of code requirement, select the minimum corresponding method of error, get the parameter value that its parameter value calculating is final Rain Intensity Formula Based.

(7) with existing formula comparison and analysis

According to different reoccurrence period P, last t, the formula that utilization inquires into out and existing formula calculate rainfall intensity i value separately and list the P-i-t table of computational data, again the corresponding data in form are contrasted one by one, utilize the comparative approach of rate to contrast, and then study the difference between two formula.

Claims (1)

1. the little duration in city 24 lasts a definite method for storm intensity, it is characterized in that: described method concrete steps are as follows:

(1) rainfall data processing

The rainfall data of the pluviograph record to papery carries out digitized processing by precipitation recording paper digitalized processing software system, the picture file of precipitation recording paper is converted into corresponding digital document, and the final normative document generating of precipitation recording paper digital processing system, shows with DAT form, it has comprised annual precipitation information, every day per minute precipitation data, the time interval is 1min, comprises the year of rain time, month, day, time, point; And the rainfall amount of per minute, 0.1mm is for recording unit information;

(2) data sample collection

(2.1) database design

Wherein, initial field rainfall and one minute rainfall data come from digitizing from note rainfall data;

In ACCESS, newly-built following form a: rainfall, rainfall in 1 minute, x minute rainfall, version; Wherein, each table design is as follows:

In rainfall form, set up field and be: ID, time, initial time, end time, total rainfall amount; Data type is: numeral, numeral, text, text, numeral; The former two's numeric field size is that long, last column number word field size are double;

In 1 minute rainfall form, set up field and be: ID, time, rainfall amount, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, numeral, numeral; First digit field size is double, and rear two column number word field size are long;

Rainfall in x minute: setting up field is: ID, time, rainfall amount, maximum moment, a rainfall time, a rainfall ID; Data type is: automatic numbering, text, numeral, text, numeral, numeral; Previous numeric field size is double, and rear two column number word field size are long;

Version: setting up field is value, numeric type is numeral; Meanwhile, in version form, the value of the longest rain battle array of input;

(2.2) sample is chosen

(2.2.1) choosing of rainfall duration

Consider municipal drainage, unified 5min, the 15min of adopting of water conservancy water drainage and waterlogging control, 30min, 45min, 60min, 90min, 120min, 150min, 180min, 240min, 360min, 720min, 1440min totally 15 last, in the sub-table of setting up rainfall in 15 minutes of the newly-built ACCESS lane database of step (2.1);

(2.2.2) sampling method

Choosing year maximum value process is sampling method, and annual each lasting chosen a maximal value, then year time no matter, by each rainfall rain sample lasting by size order arrange, each lasting set up a txt file; The form of file is: the first row: last size, from the second row, descending order is arranged the size of raininess, and raininess is obtained by rainfall and the relation of lasting;

(2.2.3) choosing of reoccurrence period

According to the sampling method of (2.2.2), reoccurrence period minimum is chosen 2 years, and maximum is chosen 100 years, and scope is 2～100 years;

(3) frequency analysis

(3.1) frequency analysis model is tentatively chosen

In order to determine which kind of frequency analysis method sample uses, its that need to be right tentatively chosen; Take the scope of raininess as horizontal ordinate, the probability that raininess is corresponding is that ordinate does two-dimensional histogram, judges from the trend of figure which kind of curve of frequency distribution it belongs to, if histogram mostly is parabolic type, substantially meet P-III type and distribute, if mostly be as linear pattern, substantially meet Gumbel and distribute;

(3.2) frequency analysis method

Adopt extra large gloomy probability ruled paper coordinate system, horizontal ordinate is empirical Frequency Pn%, ordinate is storm intensity mm/min, by a representative sample data point, curve is the theoretic frequency curve drawing according to these sample point matchings, what show in curve ending place is the correlation parameter of curve, and straight line represents the position of each reoccurrence period; Adjust each and last corresponding Cs value, until theoretic frequency curve and sampling point group under this Cs value are applicable to, record final Cs size, write down corresponding Cs/Cv value; Then, all curves that last are carried out to entirety adjustment, make Cs/Cv value as much as possible close to some values, to become cluster curve; Finally, obtain corresponding frequencies according to corresponding parameter by theoretic frequency formula and divide reoccurrence period P, the storm intensity i, the rainfall duration t three mathematical relation table that plant;

(4) formula is inquired into

Recommend and related documents according to existing Water And Drainage System Design handbook, the P-i-t table that utilizes frequency analysis to obtain, adopts six kinds of classical ways, i.e. Beijing method, Beijing short cut technique, Nanjing method, curved surface least square method, Tongji University's method and direct approach to fitting; Inquire into Rain Intensity Formula Based parameter; Formula form is:

$i=\frac{A_1(1+\mathrm{ClgP})}{{(t+b)}^n}$

In formula: i---storm intensity, the mm/min of unit;

T---rainfall duration, the min of unit;

P---be the reoccurrence period, unit year;

N, A ₁, b, C---regional parameters, its value is different and different with regional disparity with meteorological condition;

(5) formula error analysis

According to draining code requirement, use average absolute mean square deviation

with average relative mean square deviation

judge the precision of the Rain Intensity Formula Based of inquiring into; By the parameter A calculating ₁, C, n, in the value difference substitution formula of b, obtains respectively the storm rainfall value x of total formula, and relatively this raininess value and (3.2) are described obtains right residual sum of squares (RSS) σ by the raininess value in the P-i-t table obtaining after frequency analysis, absolute mean square deviation S ₁₁, relative mean square deviation S ₁₂;

$\mathrm{\&sigma;}=\underset{i=1}{\overset{m_2}{\mathrm{\&Sigma;}}}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2$

$s_{11}=\sqrt{\frac{1}{m_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}$ $\stackrel{\&OverBar;}{s_{11}}=\frac{1}{m_2}\underset{1}{\overset{m_2}{\mathrm{\&Sigma;}}}\left(\frac{1}{m_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2\right)$

$s_{12}=\frac{1}{{\stackrel{\&OverBar;}{x}}_{\mathrm{jp}}}\sqrt{\frac{1}{m_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}$ $\stackrel{\&OverBar;}{s_{12}}=\frac{1}{m_2}\underset{1}{\overset{m_2}{\mathrm{\&Sigma;}}}\left(\frac{1}{{\stackrel{\&OverBar;}{x}}_{\mathrm{jp}}}\sqrt{\frac{1}{m_1}\underset{j=1}{\overset{m_1}{\mathrm{\&Sigma;}}}{(x_{\mathrm{ij}}-x_{\mathrm{jp}})}^2}\right)$

In formula, σ---residual sum of squares (RSS);

M ₁---the number of rainfall duration;

M ₂the number of one-reoccurrence period;

Xi _j---the raininess value (mm/min) of calculating after parameter value substitution formula;

X _jp,

---the intensity level that calculates after frequency analysis with and average (mm/min);

S ₁₁, S ₁₂---absolute mean square deviation and the relative mean square deviation of each reoccurrence period of total Rain Intensity Formula Based;

---average absolute mean square deviation and the average relative mean square deviation of total Rain Intensity Formula Based;

The result that in (5), each method obtains is calculated respectively to corresponding average absolute mean square deviation and average relative mean square deviation according to above-mentioned method, all meet in two errors under the prerequisite of code requirement, select the minimum corresponding method of error, get the parameter value that its parameter value calculating is final Rain Intensity Formula Based.

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