Light rain high-precision measurement method based on microwave link

Abstract

The invention discloses a light rain high-precision measurement method based on a microwave link, and the method comprises the steps: building a microwave link composed of a microwave transmitting end and a microwave receiving end, and collecting the level value of the microwave link in real time; selecting a microwave link level value cardinal number in the nearest period at the current moment in a clear sky state as a base line J; the average value of the microwave link level values in a period of time T1 before the current moment is collected to serve as a current microwave link subline NJ; preliminarily judging whether rain exists or not based on the base line J and the current microwave chain roadbed line NJ; when it is preliminarily judged that rain exists, whether rain exists finally or not is judged according to the variation K of the microwave link level value within the time T2 by collecting the microwave link level value within the time T2 before the current moment; when it is judged that the rainfall finally exists, whether the rainfall is light rain or not is judged by adopting an ITU-R rainfall intensity inversion model according to the collected microwave link level value, and when the rainfall is light rain, the high-precision final light rain rainfall is obtained through inversion by adopting the ITU-R rainfall intensity inversion model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rainfall detection, and particularly relates to a method for small-rain high-precision measurement based on a microwave link. BACKGROUND

[0002] The microwave link rainfall monitoring technology relies on the microwave transmission end level signal to the receiving end, and the receiving end feeds back the received level signal strength to the algorithm service, and calculates and inverts the rainfall on the link according to the level signal strength. Due to the current process level and various interference factors in the actual environment, the microwave link level signal is not stable in the transmission process, and will fluctuate to different degrees, which makes it difficult to determine whether it is normal fluctuation or rain-induced attenuation in small rain, so it is difficult to calculate and invert the accurate rain intensity and rainfall; the microwave level signal value fluctuation in small rain is similar to the normal fluctuation in sunny day, and the rain attenuation model cannot calculate the rainfall. SUMMARY

[0003] The present application provides a method for small-rain high-precision measurement based on a microwave link, which realizes the distinction between sunny and rainy days and adopts the rain intensity inversion model of ITU-R to invert the corresponding rainfall, and improves the inversion precision of small-rain rainfall.

[0004] Technical scheme: In order to achieve the above object, the method for small-rain high-precision measurement based on a microwave link comprises the following steps:

[0005] S1, a microwave link composed of a microwave transmission end and a microwave receiving end is established, and the microwave link level value is collected in real time;

[0006] S2, the microwave link level value in the latest period at the current time in the sunny state is selected, and the radix of the microwave link level value in this period is taken as the baseline J;

[0007] S3, the microwave link level value in a period T1 before the current time is collected, and the mean value of the microwave link level value in the period T1 is taken as the current microwave link baseline NJ;

[0008] S4, the baseline J and the current microwave link baseline NJ are compared, and whether it rains is preliminarily judged based on the size of the baseline J and the current microwave link baseline NJ, and when it is preliminarily judged that it rains, the next step is entered;

[0009] S5, the microwave link level value in a period T2 before the current time is collected, and whether it finally rains is judged according to the change amount K of the microwave link level value in the period T2, and when it is finally judged that it rains, the next step is performed;

[0010] S6, determining whether the rainfall is light rain by using the rain intensity inversion model of ITU-R according to the collected microwave link level value, and using the rain intensity inversion model of ITU-R to obtain the final light rain amount when the rainfall is light rain.

[0011] Further, in the step S4, it is preliminarily determined whether it rains or not based on the size of the baseline J and the current microwave link baseline NJ; when the baseline J is less than or equal to the current microwave link baseline NJ, it is preliminarily determined that it is not raining at the current time; when the baseline J is greater than the current microwave link baseline NJ, it is preliminarily determined that it is raining at the current time.

[0012] Further, in the step S5, the microwave link level values in a time T2 before the current time are collected, and the maximum variation K of the microwave link level values in the time T2 is calculated; when the variation K is less than a weather threshold H1, it is determined that the microwave attenuation is caused by the micro-particles in the air, and it is determined that it is not raining finally; when the variation K is less than a weather threshold H2, it is determined that the microwave attenuation is caused by the heavy fog weather, and it is determined that it is not raining finally; when the variation K is greater than a weather threshold H3, it is determined that it is raining finally; the calculation process of the variation K is as follows:

[0013]

[0014] In the formula, Dmax is the maximum microwave link level value in the time T2, and Dmin is the minimum microwave link level value in the time T2.

[0015] Further, in the step S6, firstly, the rainfall amount R is calculated by using the rain intensity inversion model of ITU-R; the microwave link level values in a time T3 before the current time are collected, and the average value AJ of the microwave link level values in the time T3 is calculated; the microwave attenuation value γ is calculated based on the average value AJ of the microwave link level values in the time T3 and the current microwave link baseline NJ R , and the calculation process is as follows:

[0016]

[0017] In the formula, L is the length of the microwave link.

[0018] Based on the calculated microwave attenuation value γ R , the rainfall amount R is calculated by using the rain attenuation formula of ITU-R; the rain attenuation formula of ITU-R is as follows:

[0019]

[0020] In the formula, k and a are both ITU-R recommended parameters, and R is the rainfall amount.

[0021] Further, according to the rainfall amount R, it is determined whether it is raining again and whether it is light rain; including the following steps:

[0022] S1-1, compare the rainfall amount R with zero, and determine whether it is raining again; when R is less than or equal to 0, it is determined that it is not raining at the current time; when R is greater than 0, it is determined that it is raining at the current time;

[0023] S1-2, when R is greater than 0, compare R / 60 with the rainfall threshold RT to determine whether the rainfall is light rain; when R / 60 is less than the rainfall threshold RT, it is determined that the rainfall is light rain, and R / 60 is the light rain amount; when R / 60 is greater than or equal to the rainfall threshold RT, it is determined that the rainfall is moderate rain or heavy rain.

[0024] Further, when it is determined that the current rainfall is light rain, light rain recalculation is performed to recalculate the light rain amount; the light rain recalculation includes the following steps:

[0025] S2-1, calculate the area of the microwave link level value data in the rectangular coordinate system within a period of time T4 before the current time, denoted as the level value area S within time T4;

[0026] S2-2, subtract the area of the current microwave link baseline NJ within time T1 from the level value area S within time T4 to obtain the rain-induced attenuation area SS;

[0027] S2-3, obtain the fitting formula RR=aSS+bSS+c of the rain-induced attenuation area SS and the recalculated light rain amount RR through the LSTM long short-term memory network, and calculate the recalculated light rain amount RR by using the fitting formula. 2

[0028] Further, according to the recalculated light rain amount RR and the light rain amount R / 60, the final light rain amount is determined; including the following steps:

[0029] S3-1, determine whether the recalculated light rain amount RR calculated by using the fitting formula is valid; when the recalculated light rain amount RR is greater than 0 and less than the rainfall threshold RT, the recalculated light rain amount RR is valid; otherwise, the recalculated light rain amount RR is invalid;

[0030] S3-2, when the recalculated light rain amount RR calculated by using the fitting formula is invalid, the light rain amount R / 60 is the final light rain amount at the current time;

[0031] S3-3, when the recalculated light rain amount RR calculated by using the fitting formula is valid, compare the recalculated light rain amount RR with the light rain amount R / 60;

[0032] ​When the recalculated light rain amount RR is greater than the light rain amount R / 60, the recalculated light rain amount RR is the final light rain amount at the current time; when the light rain amount R / 60 is greater than the recalculated light rain amount RR, the light rain amount R / 60 is the final light rain amount at the current time; when the recalculated light rain amount RR is equal to the light rain amount R / 60, both the recalculated light rain amount RR and the light rain amount R / 60 are the final light rain amount at the current time.

[0033] Further, in the step S2-1, the area of the microwave link level value data in the Cartesian coordinate system within the time T4 is calculated, Simpson algorithm is used for calculation, all microwave link level values within the time T4, i.e. the level value intervals in the interval [a, b] are divided into n small level value intervals, n is an even number; the formula for calculating the level value area S within the time T4 is as follows:

[0034]

[0035] In the formula, X1, X2, X3,..., X n-1 are the average level values in each level value interval of the n small level value intervals.

[0036] Beneficial effects: the method for high-precision measurement of light rain based on a microwave link, judges whether it rains or not through the baseline of the microwave link level value and the change amount of the microwave link level value, realizes the distinction between sunny and rainy days; the corresponding rainfall is inversely calculated by using the rain intensity inversion model of ITU-R, the inversion precision of the light rain amount is improved; the weather is determined to be rainy by multiple judgment of whether it rains or not, the accuracy of the determination is improved; the rainfall amount is calculated by using the rain attenuation formula of ITU-R, the light rain amount is recalculated again, the final light rain amount is determined by comparing the rainfall amounts calculated twice, and the measurement precision of the light rain amount is improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a flow chart of the method for high-precision measurement of light rain based on a microwave link. DETAILED DESCRIPTION

[0038] The application will be described further with reference to the drawings.

[0039] As Figure 1 shown, a method for high-precision measurement of light rain based on a microwave link, comprising the following steps:

[0040] S1, establish a microwave link composed of a microwave transmitting end and a microwave receiving end, and collect microwave link level values in real time; the frequency of collecting microwave link level values is 1 second / time, and the collected microwave link level value data is filtered by using a Kalman filtering formula, so as to obtain the change process of the level values in a period of time; it is assumed that the microwave link level value data in 1 hour is recorded, and the recorded microwave link level value is denoted as d1-d3600.

[0041] S2, select the microwave link level value in the latest period at the current time in a clear sky state, take the radix of the microwave link level value in the period as the baseline J, that is, take the average value of the microwave link level value in the period as the baseline J; in the case of no rain, that is, in the clear sky state, the radix of the microwave link level value in the clear sky state is monitored for a long time and is taken as the baseline J in the clear sky state; for example, a period is 5 days, then all the microwave link level values in the clear sky state in 5 days are measured continuously, and the average value is taken as the baseline J; at the same time, when a period is 5 days, as long as the clear sky state of 5 days appears when the microwave link level value is collected, the average value of all the microwave link level values in the 5 days is immediately taken as the new baseline J, and is updated regularly.

[0042] S3, collect the microwave link level values in a period T1 before the current time, and take the average value of the microwave link level values in the period T1 as the current microwave link baseline NJ; the level value data monitored in the past 55 minutes is distinguished between clear sky and rain, that is, the clear sky and the rainy day are distinguished, the current microwave link baseline NJ is judged by using a sliding time window, and the average value of all the microwave link level values in the past 55 minutes is collected as the current microwave link baseline NJ; the calculation process is as follows:

[0043]

[0044] In the formula, di is the i-th microwave link level value collected, n is the number of microwave link level values collected in the past 55 minutes at the current time, and n=3300.

[0045] S4, compare the baseline J and the current microwave link baseline NJ, and preliminarily judge whether it rains based on the size of the baseline J and the current microwave link baseline NJ, and when it is preliminarily judged that it rains, the next step is entered; in the step S4, whether it rains is preliminarily judged based on the size of the baseline J and the current microwave link baseline NJ; when the baseline J is less than or equal to the current microwave link baseline NJ, it is preliminarily judged that it is not raining at the current time; when the baseline J is greater than the current microwave link baseline NJ, it is preliminarily judged that it is raining at the current time.

[0046] S5, when it is preliminarily judged that it is raining, microwave link level values in a period of time T2 before the current time are collected, and whether it is finally raining is judged according to the variation K of the microwave link level values in the period of time T2, when it is judged that it is finally raining, the next step is performed; the period of time T2 can be 10 minutes.

[0047] In the step S5, the microwave link level values in a period of time T2 before the current time are collected, and the maximum variation K of the microwave link level values in the period of time T2 is calculated; when the variation K is less than a weather threshold H1, it is judged that the microwave attenuation is caused by the micro particles in the air, and it is judged that it is finally not raining; when the variation K is less than a weather threshold H2, it is judged that the microwave attenuation is caused by the heavy fog weather, and it is judged that it is finally not raining; when the variation K is greater than a weather threshold H3, it is judged that it is finally raining; the calculation process of the variation K is as follows:

[0048]

[0049] In the formula, Dmax is the maximum microwave link level value in the period of time T2, and Dmin is the minimum microwave link level value in the period of time T2.

[0050] The sliding time window can be used to preliminarily distinguish between sunny and rainy weather, but the propagation of the microwave in the air is not only caused by the rainwater in the rain, the micro particles in the air can also cause the attenuation of the microwave, and if the heavy fog weather occurs, the micro water droplets in the air can also cause the attenuation of the microwave; therefore, all the microwave link level values in the period of time T2, i.e. all the microwave link level values in the 10 minutes before the current time, are collected, and the maximum variation of the microwave link level values in the 10 minutes is calculated, and multiple weather thresholds are set to judge whether it is finally raining.

[0051] Under the heavy fog weather, the microwave link is continuously affected by the water vapor, causing NJ to be lower than J for a long time, and the water vapor in the heavy fog is more stable than the raindrops in the rain, so that the level value changes more stably; therefore, the weather threshold H2 for judging that the microwave attenuation is caused by the heavy fog weather is set to 0.1 Db / 10min.

[0052] The influence of PM2.5 on the microwave level value is more obvious than that of the heavy fog weather, because under the haze weather caused by PM2.5, the air contains a large amount of water vapor in addition to the particulate matter, so that the level value attenuation is slightly greater than that in the fog, and the dynamic change of the particulate matter and the fog in the air is more stable than that of the raindrops in the rain, so that the level value changes more stably. Therefore, the weather threshold H1 for judging that the microwave attenuation is caused by the micro particles in the air is set to 0.2 Db / 10min.

[0053] Rainfall is the main factor affecting the level value of the rainfall, and the speed of the raindrops is much greater than that of the fog and haze weather, so the fluctuation of the level value will be significantly greater than the former two. Since the level value fluctuates greatly in the case of light rain, medium rain and heavy rain, the weather threshold H3 for determining the rainy weather is set to 0.5 Db / min.

[0054] Meanwhile, a weather threshold for microwave attenuation caused by multipath interference in sunny weather can be set. The multipath interference in sunny weather is caused by the influence of solar electromagnetic radiation on the microwave link, and the microwave link level value will show a sustained attenuation or enhancement phenomenon. Since the movement of the sun is a slow and stable process, the sustained attenuation or enhancement of the level value shows a regular and stable change. Affected by the multipath interference in sunny weather, the level value shows a slow downward and upward trend. The weather threshold H4 for determining the microwave attenuation caused by the multipath interference in sunny weather is set to 0.3 Db / 10min. When the change amount K is less than the weather threshold H4, it is determined that the microwave attenuation is caused by the multipath interference in sunny weather, and it is finally determined that there is no rain.

[0055] The weather threshold H1, the weather threshold H2 and the weather threshold H4 are all less than the weather threshold H3. As long as the change amount K is less than the weather threshold H3, it is determined that the microwave attenuation is not caused by rain. Therefore, when the change amount K is greater than the weather threshold H3, it is finally determined that there is rain. When the change amount K is less than or equal to the weather threshold H3, it is finally determined that there is no rain, and the microwave attenuation is caused by other reasons, such as fog weather, micro-particles in the air or microwave attenuation caused by multipath interference in sunny weather.

[0056] S6, when it is finally determined that there is rain, the rain intensity inversion model of ITU-R is used to determine whether the rainfall is light rain, and the final light rain amount is obtained by using the rain intensity inversion model of ITU-R when the rainfall is light rain.

[0057] In the step S6, first, the rain amount R of the rainfall is calculated by the rain intensity inversion model of ITU-R; the microwave link level value in a period T3 before the current time is collected, and the average value AJ of the microwave link level value in the period T3 is calculated; and the microwave attenuation value γ is calculated based on the average value AJ of the microwave link level value in the period T3 and the current microwave link baseline NJ. R , the calculation process is as follows:

[0058]

[0059] In the formula, L is the length of the microwave link;

[0060] Based on the calculated microwave attenuation value γ R , the rain amount R of the rainfall is calculated by using the rain attenuation formula of ITU-R; and the rain attenuation formula of ITU-R is as follows:

[0061]

[0062] wherein γ R is the microwave attenuation value, dB / km; k and a are both ITU-R recommended parameters; R is the rainfall of the rain, mm / h.

[0063] When the time T3 is 5 minutes, the average of all microwave link level values in the last 5 minutes is collected as the current microwave link baseline AJ; the calculation process is as follows:

[0064]

[0065] wherein di is the i-th microwave link level value collected, m is the number of microwave link level values collected in the last 5 minutes, m = 300.

[0066] According to the rainfall R, it is judged again whether it is raining, and whether it is light rain; including the following steps:

[0067] S1-1, compare the rainfall R with zero, and judge again whether it is raining; when R is less than or equal to 0, it is determined that it is not raining at the current time; when R is greater than 0, it is determined that it is raining at the current time;

[0068] S1-2, when R is greater than 0, compare R / 60 with the rainfall threshold RT to determine whether the rainfall is light rain; when R / 60 is less than the rainfall threshold RT, it is determined that the rainfall is light rain, and R / 60 is the rainfall of light rain; when R / 60 is greater than or equal to the rainfall threshold RT, it is determined that the rainfall is moderate rain or heavy rain. The rainfall threshold RT is set according to the actual situation, which can be set to 0.02 here.

[0069] In the case of light rain, the fluctuation of the level value is small, which leads to the result of the conventional rain attenuation formula being smaller than the actual monitoring data, so a new light rain recalculation method is needed to calculate the light rain rainfall data. When it is determined that the current rainfall is light rain, the light rain recalculation is performed to recalculate the rainfall of light rain; the light rain recalculation includes the following steps:

[0070] S2-1, calculate the area of the microwave link level value data in a straight line coordinate system in a period of time T4 before the current time, denoted as the level value area S in the time T4; the time T4 is 1 minute, all level value data d1-d60 in the last 1 minute are collected, the area of the level value data in the straight line coordinate system in the last 1 minute is calculated, that is, the total rain attenuation in the last 1 minute, the rain attenuation is amplified by the area of the level value data in the straight line coordinate system, and the area is calculated by Simpson method.

[0071] The Simpson method is a numerical integration method, the core of which is to divide the integral interval into an even number of small segments, and to approximate the area under the curve with a quadratic parabola instead of a rectangle or trapezoidal area under the curve, so as to more accurately calculate the approximate value of the definite integral; When calculating the area covered by the microwave level curve, it has the advantages of high precision and relatively small calculation amount. In step S2-1, the area of the microwave link level value data in the time T4 in the rectangular coordinate system is calculated, and the Simpson algorithm is used to calculate the area of the microwave link level value data in the time T4, that is, the level value interval in the interval [a, b] is divided into n small level value intervals, and n is an even number; The formula for calculating the area S of the level value in the time T4 is as follows:

[0072]

[0073] In the formula, X1, X2, X3, …, X n-1 are the average level values in each level value interval of the n small level value intervals. When the time T4 is 1 minute, the level value data d1-d60 of the previous 1 minute is collected, the level value in the interval [a, b] of the previous 1 minute is divided into n small level value intervals, and each two adjacent small segments correspond to a quadratic parabola; The area under each parabola is accurately integrated, and then the areas of all segments are added to obtain the integral approximation value of the entire interval, that is, the calculated area S. When calculating the microwave level value at the minute level, a is 0, b is 60, n can be 20, and h is 1.

[0074] S2-2, subtract the area of the current microwave link baseline NJ in the time T1 from the level value area S in the time T4 to obtain the rain-induced attenuation area SS; The calculation process is as follows: SS=S-NJ*60, wherein S is the level value area in the time T4, and SS is the rain-induced attenuation area.

[0075] S2-3, obtain the fitting formula RR=aSS 2 +bSS+c of the rain-induced attenuation area SS and the recalculated small rain amount RR through the LSTM long short-term memory network; Since each microwave link is in a different environment, the LSTM long short-term memory network is used to train the rain-induced attenuation area and the measured small rain data every minute to obtain the fitting formula of the rain-induced attenuation area SS and the recalculated small rain amount RR; The correlation between the rain-induced attenuation area and the small rain amount of the microwave link is obtained through the LSTM long short-term memory network, and the best fitting formula is generally a cubic RR=aSS 2 +bSS+c, wherein a, b and c are formula parameters fitted after training by the LSTM long short-term memory network.

[0076] LSTM long short-term memory network is a variant of RNN recurrent neural network specially processing time series data, through a large number of measured level value change process line and measured light rain rainfall one by one after corresponding, a computer automatically fitted formula matched with it, the formula is generally a polynomial, and then the polynomial is regressed to view the determination coefficient R 2 ; when the determination coefficient R 2 is closer to 1, the better the fitting degree of the polynomial to the data; when the determination coefficient R 2 after regression is not ideal, the determination coefficient R 2 can be improved by adjusting the formula parameters a, b and c.

[0077] According to the re-calculated light rain rainfall RR and the light rain rainfall R / 60, the final light rain rainfall is determined; including the following steps:

[0078] S3-1, judging whether the re-calculated light rain rainfall RR calculated by the fitting formula is effective, when the re-calculated light rain rainfall RR is greater than 0 and the re-calculated light rain rainfall RR is less than the rainfall threshold RT, then the re-calculated light rain rainfall RR is effective; otherwise, the re-calculated light rain rainfall RR is invalid;

[0079] S3-2, when the re-calculated light rain rainfall RR calculated by the fitting formula is invalid, then the light rain rainfall R / 60 is the final light rain rainfall at the current time;

[0080] S3-3, when the re-calculated light rain rainfall RR calculated by the fitting formula is effective, then the size of the re-calculated light rain rainfall RR and the light rain rainfall R / 60 is compared;

[0081] When the re-calculated light rain rainfall RR is greater than the light rain rainfall R / 60, the re-calculated light rain rainfall RR is the final light rain rainfall at the current time; when the light rain rainfall R / 60 is greater than the re-calculated light rain rainfall RR, the light rain rainfall R / 60 is the final light rain rainfall at the current time; when the re-calculated light rain rainfall RR is equal to the light rain rainfall R / 60, the re-calculated light rain rainfall RR and the light rain rainfall R / 60 are the final light rain rainfall at the current time.

[0082] Embodiment

[0083] When it is raining, there are still micro-particles in the air or heavy fog weather still exists, so when it is raining, there may be heavy fog weather and micro-particles in the air at the same time; therefore, when the microwave attenuation is used to calculate the light rain rainfall, the influence of the heavy fog weather and the micro-particles in the air on the microwave attenuation may exist; the actual light rain rainfall may be smaller than the calculated light rain rainfall, so a light rain rainfall supplement method is proposed to eliminate the influence of the heavy fog weather and the micro-particles in the air on the microwave attenuation as much as possible, and obtain the actual light rain rainfall.

[0084] Because when it rains, rainwater will collide with the micro-particles in the air and adsorb on the surface of the micro-particles to form larger water droplets, which will then fall to the ground; rainwater will also merge with the micro-droplets in the heavy fog weather and fall to the ground; therefore, rain will reduce the micro-particles in the air and the micro-droplets in the heavy fog weather, and the micro-particles and the micro-droplets in the air will be reduced to very small within a period of time due to the rain, and will basically not affect the microwave attenuation, at this time, the rain amount of the light rain is detected again, which is the actual rain amount of the light rain at this time; therefore, the supplement method of the rain amount of the light rain is as follows:

[0085] Firstly, all the microwave link level values within a period of time T5 are collected, and the change amount K1 of the microwave link level value and the average value D1 of the microwave link level value of each minute within the period of time T5 are obtained; and the final rain amount of the light rain of each minute within the period of time T5 is calculated by the above method; the period of time T5 can be 10 minutes.

[0086] The change amount and the average value of the microwave link level value of each minute within the period of time T5 are compared with the change amount and the average value of the microwave link level value of the previous minute respectively, when the change amount of the microwave link level value gradually decreases within the period of time T5, and the average value D1 of the microwave link level value gradually decreases within the period of time T5, it indicates that the micro-particles in the air and the micro-droplets in the heavy fog weather begin to decrease due to the rainfall, or it is also possible that the rainfall amount of the rainwater begins to decrease. Therefore, the rate S T of the decrease of the change amount of the microwave link level value and the rate S D of the decrease of the average value of the microwave link level value within the period of time T5 are calculated. T D The rates S T and S D are compared with the change amount rate threshold and the average value rate threshold respectively; the change amount rate threshold and the average value rate threshold are mainly set according to the actual rainfall amount reduction affecting the microwave link level value.

[0087] When the rate S T is greater than or equal to the change amount rate threshold and the rate S D is greater than or equal to the average value rate threshold, it is determined that the decrease of the change amount of the microwave link level value and the decrease of the average value of the microwave link level value are caused by the actual rainfall amount reduction; otherwise, it is determined that the decrease of the change amount of the microwave link level value and the decrease of the average value of the microwave link level value are caused by the decrease of the micro-particles in the air and the micro-droplets in the heavy fog weather; that is, when the rate S T is greater than or equal to the change amount rate threshold and the rate S D is less than the average value rate threshold, when the rate S T is less than the change amount rate threshold and the rate S D is greater than or equal to the average value rate threshold, and when the rate S Tless than the change rate threshold and the rate S D If the mean value is less than the mean rate threshold, then it is determined that the decrease in the change of the microwave link level value and the decrease in the mean value of the microwave link level value are caused by the decrease of the micro-particles and micro-droplets in the air.

[0088] When it is determined that the decrease in the change of the microwave link level value and the decrease in the mean value of the microwave link level value are caused by the decrease of the micro-particles and micro-droplets in the air, the mean value of the microwave link level value of each minute in T5 is subtracted from the mean value of the microwave link level value of the previous minute to obtain a plurality of difference values of the mean values D1; the plurality of difference values of the mean values D1 are compared with a set difference threshold value respectively; the set difference threshold value needs to be set according to the actual situation, mainly according to the change of the mean value of the microwave link level value under the condition of pure rainfall.

[0089] When the difference value of the mean value D1 is greater than or equal to the set difference threshold value, at this time the micro-particles and micro-droplets in the air are still gradually reduced with the rainfall, at this time the final light rain rainfall calculated in this minute will be greater than the actual light rain rainfall; when the difference value of the mean value D1 is less than the set difference threshold value, then it is determined that at this time the influence of the micro-particles and micro-droplets on the microwave attenuation has been eliminated as much as possible in this minute, so the final light rain rainfall calculated in this minute is the actual light rain rainfall; at this time the final light rain rainfall calculated is the accurate actual light rain rainfall, which is basically not affected by the micro-particles in the air and the micro-droplets in the heavy fog weather.

[0090] The above is only the description of the preferred embodiments of the present application, and those skilled in the art can make some modifications and optimizations according to the above disclosure without departing from the above basic principles, and these modifications and optimizations should be regarded as the protection scope of the present application.

Claims

1. A method for high-precision measurement of small raindrops based on a microwave link, characterized in that: Includes the following steps: S1. Establish a microwave link consisting of a microwave transmitter and a microwave receiver, and collect the microwave link level value in real time; S2. Select the microwave link level value of the most recent cycle under clear sky conditions, and use the base value of the microwave link level value in this cycle as the baseline J; S3. Collect the microwave link level value within a time period T1 before the current time, and take the average value of the microwave link level value within time T1 as the current microwave link baseline NJ. S4. Compare baseline J with the current microwave link baseline NJ. Based on the magnitude of baseline J and the current microwave link baseline NJ, make a preliminary judgment on whether there is rain. If it is preliminarily judged that there is rain, proceed to the next step. S5. By collecting the microwave link level value within a time period T2 before the current moment, determine whether it will eventually rain based on the change K of the microwave link level value within time T2. If it is determined that it will eventually rain, proceed to the next step. S6. Based on the collected microwave link level value, use the ITU-R rainfall intensity inversion model to determine whether the rainfall is light rain. If the rainfall is light rain, use the ITU-R rainfall intensity inversion model to invert and obtain the final light rain amount.

2. The method for high-precision measurement of small raindrops based on a microwave link according to claim 1, characterized in that: In step S4, a preliminary judgment is made on whether there is rain based on the size of baseline J and the current microwave link baseline NJ; when baseline J is less than or equal to the current microwave link baseline NJ, it is preliminarily determined that there is no rain at the current time. If the baseline J is greater than the current microwave link baseline NJ, it is preliminarily determined that it is raining at the current time.

3. The method for high-precision measurement of small raindrops based on a microwave link according to claim 1, characterized in that: In step S5, the microwave link level value is collected within a time period T2 before the current time, and the maximum change K of the microwave link level value within time T2 is calculated. When the change K is less than the weather threshold H1, it is determined that the microwave attenuation is caused by micro particles in the air, and it is determined that there will be no rain. When the change K is less than the weather threshold H2, it is determined that the microwave attenuation is caused by heavy fog, and it is determined that there will be no rain. When the change K is greater than the weather threshold H3, it is determined that there will be rain. The calculation process of the change K is as follows: In the formula, Dmax is the maximum microwave link level value within time T2, and Dmin is the minimum microwave link level value within time T2.

4. The method for high-precision measurement of small raindrops based on a microwave link according to claim 1, characterized in that: In step S6, the rainfall R is first calculated using the ITU-R rainfall intensity inversion model; the microwave link level values ​​within a time period T3 prior to the current time are collected, and the average value AJ of the microwave link level values ​​within time T3 is calculated; the microwave attenuation value γ is calculated based on the average value AJ of the microwave link level values ​​within time T3 and the current microwave link baseline NJ. R The calculation process is as follows: In the formula, L is the length of the microwave link; Based on the calculated microwave attenuation value γ R The rainfall amount R is calculated using the ITU-R rainfall attenuation formula; the ITU-R rainfall attenuation formula is as follows: In the formula, k and α are ITU-R recommended parameters, and R is the amount of rainfall.

5. The method for high-precision measurement of small raindrops based on a microwave link according to claim 4, characterized in that: Based on the rainfall amount R, determine again whether there will be rain, and whether it is light rain; including the following steps: S1-1. Compare the rainfall amount R with zero to determine whether there is rain. If R is less than or equal to 0, it is determined that there is no rain at the current moment. If R is greater than 0, it is determined that there is rain at the current moment. S1-2. When R is greater than 0, compare R / 60 with the rainfall threshold RT to determine whether the rainfall is light rain; when R / 60 is less than the rainfall threshold RT, the rainfall is determined to be light rain, and R / 60 is the amount of light rain; when R / 60 is greater than or equal to the rainfall threshold RT, the rainfall is determined to be moderate rain or heavy rain.

6. The method for high-precision measurement of small raindrops based on a microwave link according to claim 4, characterized in that: When the current rainfall is determined to be light rain, a light rain recalculation is performed to recalculate the amount of light rain; the light rain recalculation includes the following steps: S2-1. Calculate the area of ​​microwave link level data within a time period T4 before the current time in the rectangular coordinate system, denoted as the area of ​​level values ​​S within time T4. S2-2. Subtract the area of ​​the current microwave link baseline NJ in time T1 from the area of ​​the level value S in time T4 to obtain the rain-induced attenuation area SS. S2-3. Obtain the fitting formula RR=aSS for the rain-induced attenuation area SS and the recalculated rainfall RR for light rain using an LSTM long short-term memory network. 2 +bSS+c, the recalculated light rain amount RR is obtained by using the fitting formula.

7. The method for high-precision measurement of small raindrops based on a microwave link according to claim 6, characterized in that: The final light rain amount is determined based on the recalculated light rain amount RR and light rain amount R / 60; including the following steps: S3-1. Determine whether the recalculated light rain amount RR obtained by using the fitting formula is valid. If the recalculated light rain amount RR is greater than 0 and less than the rainfall threshold RT, then the recalculated light rain amount RR is valid; otherwise, the recalculated light rain amount RR is invalid. S3-2. When the recalculated light rain amount RR obtained by using the fitting formula is invalid, then the light rain amount R / 60 is the final light rain amount at the current moment. S3-3. When the recalculated light rain amount RR is obtained by using the fitting formula, compare the recalculated light rain amount RR with the light rain amount R / 60. When the recalculated light rain amount RR is greater than the light rain amount R / 60, then the recalculated light rain amount RR is the final light rain amount at the current moment; when the light rain amount R / 60 is greater than the recalculated light rain amount RR, then the light rain amount R / 60 is the final light rain amount at the current moment; when the recalculated light rain amount RR is equal to the light rain amount R / 60, then both the recalculated light rain amount RR and the light rain amount R / 60 are the final light rain amount at the current moment.

8. The method for high-precision measurement of small raindrops based on a microwave link according to claim 6, characterized in that: In step S2-1, the area of ​​microwave link level values ​​within time T4 in a rectangular coordinate system is calculated using the Simpson algorithm. All microwave link level values ​​within time T4, i.e., the level values ​​within the interval [a, b], are divided into n small level value intervals, where n is an even number. The formula for calculating the area S of the level values ​​within time T4 is as follows: In the formula, X1, X2, X3, ..., X n-1 These are the average level values ​​within each of the n small level value intervals.

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