CN114414045A - Calibration method of solar radiometer - Google Patents

Abstract

The invention discloses a calibration method of a solar radiometer, and relates to the technical field of calibration methods. The invention comprises the following steps: BVOCs data are obtained and are subjected to cyclic calculation to generate comparison data; acquiring radiation data, and screening the radiation data by taking the comparison data as a standard; acquiring the screened radiation data, and calculating various numerical values in the radiation data; comparing the calculated values; and determining a calibration result. The calibration work can be carried out in the on-site daily measurement of the station, and the calibration instrument and the matched equipment thereof, the radiation meter for the station work, manpower and material resources and the transportation cost of the radiation meter can be saved though depending on the sunny condition; the radiation standard used for calibration is the radiation value of the atmospheric cap, and the value is relatively stable and can be timely obtained by the methods of literature, international satellite and airplane measurement and the like; the calibration work can be carried out without depending on the standard radiation table identified by the industry and going to the specified department of the country.

Description

Calibration method of solar pyranometer

technical field

The invention belongs to the technical field of calibration methods, in particular to a calibration method of a solar pyranometer.

Background technique

At present, the calibration of domestic pyranometers needs to send the pyranometers used by the stations to the state-designated departments, and measure the pyranometers with the nationally recognized standard tables that meet the international and domestic solar radiation standards under clear and cloudless conditions. The measurement results are compared. According to the comparison results, determine the new calibration value of the pyranometer to be calibrated, and complete the calibration work. The calibrated pyranometers are transported back to the station again to carry out subsequent measurement work; however, the pyranometer calibration work in the prior art is heavily affected by the weather, and the labor cost is high, and the calibration work relies too much on the standard pyranometer recognized by the industry.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for calibrating a pyranometer, which solves the technical problems of the prior art that the pyranometer calibration work is heavily influenced by weather, has a large labor cost, and relies too much on industry-approved standard pyranometers.

For reaching the above-mentioned purpose, the present invention is achieved through the following technical solutions:

A method for calibrating a solar pyranometer, comprising the following steps:

Step 1: Obtain BVOCs data, and perform cyclic calculation on it to generate comparative data;

Step 2: Obtain radiation data, and screen the radiation data based on the comparison data;

Step 3: Obtain the filtered radiation data, and calculate the values in the radiation data;

Step 4: Compare the calculated values;

Step 5: Determine the calibration result.

Optionally, each value in the calculated radiation data includes the absorption value and the scattering value involved in the transmission of solar radiation, the value of the solar radiation flux density absorbed by the entire atmosphere, the value of isoprene, and the value of monoterpene;

The calculation formula of solar radiation transmission absorption value is (e ^-kwm ): e ^-kwm =1-ΔSI ₀ cosZ;

The solar constant is I ₀ =1367W·m ^-2 , where Z is the zenith angle of the sun;

The value of the solar radiation flux density absorbed by the whole atmosphere is △S=0.172(mW×0.1×30) ^0.303 (cal·cm ^-2 ·min ^-1 , 1cal·cm ^-2 ·min ^-1 =696.7W·m ^-2 ), where k is the water vapor absorption coefficient (m ^-1 ), m is the air mass, W is the water vapor content of the entire atmosphere (W=0.21E), and E is the ground water vapor pressure (hPa);

The calculation formula of solar radiation transmission scattering value is (e ^-S/Q ): e ^-S/Q , where S and Q are scattered radiation and total radiation (W·m ^-2 ), respectively;

The calculation formula of isoprene value and monoterpene value is (e ^-k1Etm ): e ^-k1Etm , where k ₁ is the attenuation coefficient (tentatively set to 1), and E is the emission of isoprene or monoterpene Flux (mg·m ^-2 ·h ^-1 ); t is the sampling time (30min);

According to the principle of energy balance, the relationship between total radiation and absorption term, scattering term, isoprene or monoterpene term is established, and the relationship is Q=(A ₁ e ^-kwm +A ₂ e ^-S/Q + A ₃ e ^-k1Et m+A ₀ )cosZ.

Optionally, when comparing the calculated values, if the calculated value deviates greatly from the budget value, perform the above steps again, and if the calculated value deviates from the budget value by less than 15%, generate a calibration result.

Optionally, before comparing the calculated values, first establish a calculation model to calculate the radiation values of total radiation, ultraviolet, visible light, PAR, near-infrared, and direct radiation, and compare these calculated values with the solar radiation values corresponding to the ground and the top of the atmosphere. Compare and evaluate the calculation effect and calibration quality of the calculation model.

Embodiments of the present invention have the following beneficial effects:

The calibration work of the invention can be carried out in the daily measurement of the station, and does not rely too much on sunny conditions, which can save the cost of calibration instruments and their supporting equipment, pyranometers for station work, manpower and material resources and pyranometer transportation; The standard is the radiation value at the top of the atmosphere, which is relatively stable and can be obtained in a timely manner through literature and international satellite and aircraft measurements.

Of course, it is not necessary for any product embodying the present invention to achieve all of the above-described advantages simultaneously.

Description of drawings

The accompanying drawings forming a part of the present application are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

FIG. 1 is a flow chart of calibration according to an embodiment of the present invention.

FIG. 2 is a flowchart of a calibration method according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

In order to keep the following description of the embodiments of the present invention clear and concise, the present invention omits detailed descriptions of well-known functions and well-known components.

Referring to Figures 1-2, this embodiment provides a method for calibrating a solar pyranometer, including the following steps:

Step 1: Obtain BVOCs data, and perform cyclic calculation on it to generate comparative data. Among them, the data within 2 times the standard deviation of the BVOCs emission flux is selected, and after each cycle calculation, according to the newly generated data, determine The new standard deviation for the next data screening and elimination;

Step 2: Acquire radiation data, and screen the radiation data based on the comparison data, among which the primary selection of the radiation data is performed;

Step 3: Obtain the filtered radiation data, and calculate various values in the radiation data, where the values in the calculated radiation data include the absorption and scattering values involved in the transmission of solar radiation, and the solar radiation flux absorbed by the entire atmosphere. Density values, isoprene values and monoterpene values;

Step 4: Compare the calculated values, in which, use the established calculation model to calculate the solar radiation values of each band (total radiation, ultraviolet, visible light and PAR, near-infrared, direct radiation, etc.), and compare these calculated values with the ground and The solar radiation values corresponding to the top of the atmosphere are compared to evaluate the calculation effect and calibration quality of the calculation model. The parameters involved include the calculated value and the measured value and the deviation between the calculated value and the measured value; before comparing the calculated values, First, a calculation model is established to calculate the radiation values of total radiation, ultraviolet, visible light, PAR, near-infrared, and direct radiation, and these calculated values are compared with the solar radiation values corresponding to the ground and the top of the atmosphere to evaluate the calculation effect and calibration of the calculation model. Quality; for the filtered solar radiation, atmospheric column substance content (S/Q), temperature and humidity, ground water vapor pressure, BVOCs emission flux, etc., calculate the absorption and scattering involved in solar radiation transmission, and other items, based on solar radiation The principle of energy balance of each band, find and determine the calculation model of each band, determine the coefficients, constants and calibration coefficients of the calculation model;

Step 5: Determine the calibration result, in which the calibration result needs to go through multiple cycles and calculations until a reasonable and minimum calculation deviation (absolute deviation, relative deviation, root mean square, standard deviation, etc.), a relatively stable coefficient and (3) are obtained. The factor is A ₁ +A ₂ +A ₃ +|A ₀ |, and the factor of ₂ is A ₁ + _{A 2} +|A ₀ |) _; The energy of the top of the atmosphere related to scattering substances, isoprene/monoterpenes, etc. A ₀ expresses the solar radiation reflected by the top of the atmosphere.

The final conditions that the determined coefficients need to meet: the coefficients A ₁ , A ₂ , A ₃ and A ₀ in the 3-factor calibration method are positive, positive, negative and negative values respectively; the coefficients A ₁ , A ₂ in the 2-factor calibration method , A ₀ are positive, positive and negative values, respectively.

The calibration work of the invention can be carried out in the daily measurement of the station, and does not rely too much on sunny conditions, which can save the cost of calibration instruments and their supporting equipment, pyranometers for station work, manpower and material resources and pyranometer transportation; The standard is the radiation value at the top of the atmosphere, which is relatively stable and can be obtained in a timely manner through literature and international satellite and aircraft measurements.

Among them, the BVOCs, radiation and other data used in the development and establishment of the calculation and calculation model are all measured data under all (or various) weather conditions; It is transported to the national designated department for calibration work, and there is no need to use another set of replacement instruments to replace the pyranometer that needs to be calibrated, and it also avoids the interruption of measurement work caused by instrument replacement; the radiation value at the top of the atmosphere, such as the solar constant 1367±7W m ^-2 is recommended by the World Meteorological Organization (WMO) in 1981 and has been widely used by related industries. At present, with the rapid development of measurement technology in the world, the solar constant and the corresponding values of other various frequency bands can be measured on satellites and airplanes. These data can be obtained in a timely and public manner from papers published in international journals; that is, the radiation standard used in the calibration work is the radiation value at the top of the atmosphere, the solar constant (1367W·m ^-2 ) and the solar radiation values of the corresponding bands are available in China Research papers and books published in foreign journals can be searched.

The calculation formula of the solar radiation transmission absorption value in this embodiment is (e ^-kwm ): e ^-k1Etm =1-ΔSI ₀ cosZ;

The solar constant is I ₀ =1367W·m ^-2 , where Z is the zenith angle of the sun;

The value of the solar radiation flux density absorbed by the whole atmosphere is △S=0.172(mW×0.1×30) ^0.303 (cal·cm ^-2 ·min ^-1 , 1cal·cm ^-2 ·min ^-1 =696.7W·m ^-2 ), where k is the water vapor absorption coefficient (m ^-1 ), m is the air mass, W is the water vapor content of the entire atmosphere (W=0.21E), and E is the ground water vapor pressure (hPa);

The calculation formula of solar radiation transmission scattering value is (e ^-S/Q ): e ^-S/Q , where S and Q are scattered radiation and total radiation (W·m ^-2 ), respectively;

The calculation formula of isoprene value and monoterpene value is (e ^-k1Etm ): e ^-k1Etm , where k ₁ is the attenuation coefficient (tentatively set to 1), and E is the emission of isoprene or monoterpene Flux (mg·m ^-2 ·h ^-1 ); t is the sampling time (30min);

According to the principle of energy balance, the relationship between total radiation and absorption term, scattering term, isoprene or monoterpene term is established, and the relationship is Q=(A ₁ e ^-kwm +A ₂ e ^-S/Q + A ₃ e ^-k1Etm +A ₀ )cosZ.

Specifically, in the above calculation formula: Z is the solar zenith angle, k is the water vapor absorption coefficient (m ^-1 ), m is the air mass, W is the water vapor content of the entire atmosphere (W=0.21E), and E is the ground water vapor pressure (hPa), S and Q are scattered radiation and total radiation (W·m ^-2 ), respectively, k ₁ is the attenuation coefficient (tentatively set to 1), and E is the emission flux of isoprene or monoterpene ( mg·m ^-2 ·h ^-1 ), and t is the sampling time (30 min).

When comparing the calculated values in this embodiment, if the calculated value deviates greatly from the budget value, the above steps are re-executed, and if the calculated value deviates from the budget value by less than 15%, a calibration result is generated.

The specific purpose of the present invention is to propose a new method for calibrating various pyranometers used by radiation and meteorological stations at home and abroad for the first time at home and abroad. These pyranometers include ultraviolet, visible light, PAR (photosynthetically active radiation), near infrared, direct radiation, and pyranometers.

The technical problem solved: Solve the dependence on pyranometers with different international and domestic radiation level standards, and save the manpower, material resources and transportation costs used in the previous general calibration method. The calibration work can be carried out at the station (that is, without affecting the daily observation work), improving the efficiency of station observation and calibration work (for example, saving a set of measuring pyranometers, eliminating the steps and operation procedures such as the transmission of solar radiation standards from international to domestic, etc.) . The calibration quality of the new calibration method can be verified and verified by the measurement of the top of the atmosphere, which can be obtained and updated in time from literature and internationally recognized measurement data from satellites and aircraft.

The new calibration method for various types of pyranometers (ultraviolet, visible light, near-infrared, direct radiation, and total radiation) in this embodiment takes the measured values of solar radiation at the top of the atmosphere (including ultraviolet, visible light, near-infrared, and total radiation) as the standard. It is carried out at the local station, using the solar radiation, meteorological parameters, and volatile organic compound (BVOCs) emission flux data measured by the station, according to the inherent laws and variation characteristics of each parameter of solar radiation, meteorological parameters, and BVOCs emissions, as well as their mutual relationship. According to the principles of coordination, unification, harmony, etc., constantly search and determine the optimal energy action state that expresses the physical, chemical and biological processes and their interactions, and then determine the solar radiation, solar elevation angle (h), atmospheric column material content (S/Q), The value and value range of meteorological parameters (temperature and humidity, ground water vapor pressure), BVOCs emission flux, etc., and finally determine the various coefficients and calibration coefficients in the calculation method;

In the process of screening and eliminating the above types of data, it is necessary to perform multiple cycles one by one and in sequence.

Specifically include:

1) Select the data within 2 times the standard deviation for the BVOCs emission flux; after each cycle calculation, determine the new standard deviation based on the newly generated data for the next data screening and elimination;

2) Preliminary selection of radiation data. The specific method should refer to the internal relationship between total radiation, direct radiation and scattered radiation (such as ratio, sum-difference relationship, etc.). For example, the measured value of total radiation should not exceed the solar constant. The total radiation should be equal to the direct radiation + scattered radiation, and the scattered radiation/total radiation should be less than 1, etc.;

3) Calculate the absorption and scattering involved in the transmission of solar radiation, and other items based on the filtered data of solar radiation, atmospheric column substance content (S/Q), temperature and humidity, ground water vapor pressure, and BVOCs emission flux, based on solar radiation The principle of energy balance of each band, find and determine the calculation model of each band, determine the coefficients, constants and calibration coefficients of the calculation model;

When considering the 2-factor case, there are no isoprene and monoterpene terms.

When calibrating other pyranometers, replace the total radiation (270-3200nm) with the amount of radiation that needs to be calibrated, namely ultraviolet (270-400nm), visible light/PAR (400-700nm), near-infrared (700-3200nm), direct Radiation (270-3200nm);

Calculate the solar radiation values of each band (total radiation, ultraviolet, visible light, PAR, near-infrared, etc.) using the established calculation model, and compare these calculated values with the solar radiation values corresponding to the ground and the top of the atmosphere to evaluate the calculation of the calculation model. Effect and calibration quality, the parameters involved include, calculated and measured values, and the deviation of calculated and measured values, etc. (such as mean, median, absolute deviation and its interval, relative deviation and its interval, root mean square , standard deviation, etc.).

4) If the calculated deviation and calibration coefficient do not achieve the expected effect, repeat the process of 1-3 until the calculated relative deviation is less than 15%, and the calibration coefficient tends to be stable. With the change of data after each cycle, various data are further filtered and eliminated. For the screening and exclusion criteria of a new round of data, new criteria will be adopted based on new data (including mean, median, interval, standard deviation, etc.). After that, continue to compare the calculated values of solar radiation in each band with the solar radiation values corresponding to the ground and the top of the atmosphere, and re-evaluate the calculation effect and calibration quality of the model;

5) After many cycles and calculations, until a reasonable and minimum calculation deviation (absolute deviation, relative deviation, root mean square, standard deviation, etc.), a relatively stable coefficient and (3 factors are A ₁ +A ₂ +A) are obtained ₃ +|A ₀ |, the factor of 2 is A ₁ +A ₂ +|A ₀ |). The coefficients A ₁ , A ₂ , and A ₃ express the energy of the top of the atmosphere related to absorbing substances, scattering substances, isoprene/monoterpenes, etc. in the atmosphere, respectively, and A0 expresses the solar radiation reflected by the top of the atmosphere.

The final conditions that the determined coefficients need to meet: the coefficients A ₁ , A ₂ , A ₃ and A ₀ in the 3-factor calibration method are positive, positive, negative and negative values respectively; the coefficients A ₁ , A ₂ in the 2-factor calibration method , A ₀ are positive, positive and negative values, respectively.

Pyranometer calibration coefficient: sum of coefficients/solar constant (or radiation value at the top of the atmosphere in other bands), corresponding to the pyranometer and other band pyranometers (ie total, ultraviolet, visible light, PAR (photosynthetically active radiation), near-infrared radiation, etc.).

The new calibration method is suitable for calibrated pyranometers: total, ultraviolet, visible light, PAR (photosynthetically active radiation), near infrared, direct radiation.

The above-described embodiments may be combined with each other.

It should be noted that the terms "first", "second", etc. in the description and claims of the present application and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that data so used may be interchanged under appropriate circumstances so that the embodiments of the application described herein can be practiced in sequences other than those illustrated or described herein.

In the description of this specification, description with reference to the terms "one embodiment," "example," "specific example," etc. means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one aspect of the present invention. in one embodiment or example. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above-disclosed preferred embodiments of the present invention are provided only to help illustrate the present invention. The preferred embodiments do not exhaust all the details, nor do they limit the invention to only the described embodiments. Obviously, many modifications and variations are possible in light of the content of this specification. These embodiments are selected and described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims (10)

1. A calibration method of a solar radiometer is characterized by comprising the following steps:

the method comprises the following steps: BVOCs data are obtained and are subjected to cyclic calculation to generate comparison data;

step two: acquiring radiation data, and screening the radiation data by taking the comparison data as a standard;

step three: acquiring the screened radiation data, and calculating various numerical values in the radiation data;

step four: comparing the calculated values;

step five: and determining a calibration result.

2. A method of calibrating a solar radiometer according to claim 1, wherein the values in the radiation data are calculated to include absorption and scattering values related to solar radiation transmission, total atmospheric absorbed solar radiation flux density values, isoprene values and monoterpene values.

3. A method for calibrating a solar radiometer according to claim 2, wherein the calculation formula for the solar radiation transmission absorption value is (e)^-kwm)：e^-kwm＝1-ΔSI₀cosZ。

4. A method of calibrating a solar radiometer as defined in claim 3, wherein the solar constant is I₀＝1367W·m^-2Wherein Z is the solar zenith angle.

5. A method of calibrating a solar radiometer according to claim 4, wherein the total atmospheric absorption solar flux density is 0.172(mW x 0.1 x 30)^0.303(cal·cm^-2·min^-1,1cal·cm^-2·min^-1＝696.7W·m^-2) Wherein k is the water vapor absorption coefficient (m)^-1) M is the mass of the atmosphere, W is the total atmospheric moisture content (W ═ 0.21E), and E is the ground water vapor pressure (hPa).

6. A method for calibrating a solar radiometer as defined in claim 5, wherein the calculation formula for the transmission scattering value of solar radiation is (e)^-S/Q)：e^-S/QWherein S, Q are respectively scattered radiation and total radiation (W.m)^-2)。

7. A method for calibrating a solar radiometer as defined in claim 6, wherein the formula for calculating the isoprene number and the monoterpene number is (e)^-k1Etm)：e^-k1EtmWherein k is₁Is the attenuation coefficient (tentatively 1) and E is the emission flux (mg. m) of isoprene or monoterpene^-2·h^-1) (ii) a t is the sampling time (30 min).

8. A method of calibrating a solar radiometer according to claim 7, wherein the relationship between total radiation and absorption terms, scattering terms, isoprene or monoterpene terms is established according to the energy balance principle, where Q ═ A (A ═ A-₁e^-kwm+A₂e^-S/Q+A₃e^-k1Etm+A₀)cosZ。

9. A calibration method for a solar radiometer according to claim 1, wherein when comparing the calculated values, if the calculated values have a large deviation from the budget values, the steps from the first step to the fourth step are executed again, and if the calculated values have a deviation of < 15% from the budget values, the calibration result is generated.

10. The method for calibrating a solar radiometer according to claim 1, wherein before comparing the calculated values, a calculation model is established, the radiation values of total radiation, ultraviolet, visible light, PAR, near infrared, and direct radiation are calculated, and the calculated values are compared with the solar radiation values corresponding to the ground and the atmospheric dome to evaluate the calculation effect and calibration quality of the calculation model.

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