阅读说明：本技术 晴天筛选方法 (Sunny screening method ) 是由 赵晓莉 成翔 靳小兵 杨进 卜俊伟 王华荣 曹杨 李一丁 王维佳 耿蔚 苑跃 于 2020-12-28 设计创作，主要内容包括：本发明涉及气象领域,公开了一种晴天筛选方法,用以准确地确定和统一晴天条件。本发明综合目标区域内观测到的降水量、风速、能见度、云量以及闪电情况,来判断目标区域的天气状况是否为晴天；其中,所述风速、能见度、云量均为目标区域内的观测点在判别时刻所观测到的瞬时数据,所述降水量为目标区域内的观测点在观测时段所观测到的累积数据,所述闪电情况为目标区域内观测点在观测范围、观测时段所观测到的闪电出现次数。本发明适用于气象相关领域各行业进行晴天筛选。(The invention relates to the field of weather, and discloses a sunny screening method which is used for accurately determining and unifying sunny conditions. The method integrates the rainfall, wind speed, visibility, cloud cover and lightning conditions observed in the target area to judge whether the weather condition of the target area is sunny or not; the wind speed, the visibility and the cloud cover are all instantaneous data observed by observation points in a target area at a distinguishing moment, the precipitation is accumulated data observed by the observation points in the target area in an observation period, and the lightning condition is the number of lightning occurrences observed by the observation points in the target area in an observation range and the observation period. The invention is suitable for all industries in the meteorological related field to carry out sunny day screening.)

1. A fine day screening method is characterized in that precipitation, wind speed, visibility, cloud cover and lightning conditions observed in a target area are integrated to judge whether the weather condition of the target area is a fine day or not; the wind speed, the visibility and the cloud cover are all instantaneous data observed by observation points in a target area at a distinguishing moment, the precipitation is accumulated data observed by the observation points in the target area in an observation period, and the lightning condition is the number of lightning occurrences observed by the observation points in the target area in an observation range and the observation period.

2. The clear-sky screening method of claim 1, wherein when precipitation, wind speed, visibility, cloud cover and lightning conditions all satisfy the following conditions, it is determined that the weather condition of the target area is clear-sky;

the observation point does not observe precipitation in the observation period before the judgment moment;

the observation point has no low cloud in the visibility range at the moment of judgment;

the wind speed of the observation point at the judgment moment and the height of 10 m from the ground is less than 8 m/s;

the observation point is in the area range with the radius of 30 kilometers, and the frequency of lightning occurrence in the observation period before the moment is judged to be not more than the threshold value;

the visibility of the observation point at the judging moment is more than 8 kilometers.

3. A sunny screening method according to claim 2, characterised in that if the observed wind speed is not at ground level 10 meters, the conversion is made by the following formula:

wherein u is₁₀Wind speed u of 10 m height_hFor the wind speed at h altitude, p is the terrain-dependent coefficient.

4. The sunny day screening method of claim 2, wherein when it is determined whether an hour is a sunny day, and when precipitation and lightning conditions respectively satisfy conditions a1 and a2, it is determined that the weather condition of the target area is an hourly sunny day;

a1, no precipitation is observed at the observation point 60 minutes before the judgment time;

a2, judging that the number of lightning occurrence in 60 minutes before the moment is not more than 0;

when judging whether a certain day is a sunny day, and when the precipitation and the lightning conditions respectively meet the conditions B1 and B2, judging that the weather condition of the target area is the sunny day;

b1, no precipitation is observed on the observation point on the day before the judgment time;

b2, judging the occurrence frequency of lightning in the day before the moment is not more than 5 times.

Technical Field

The invention relates to the field of weather, in particular to a sunny screening method.

Background

In 1779, this jiming franklin proposed a Global Circuit preliminary model, and in recent 100 years, through the development of william thomson (gazel) and c.t.r. wilson, etc., a modern Global Circuit model (GEC) was formed. GEC mainly means that between earth (potential 0kV) of high conductivity and ionosphere (height 60km, potential about +250kV), there is an atmosphere of low conductivity, just like a huge spherical capacitor. Thus, between the ionosphere and earth, there is a Potential Gradient (PG) of 250 kV. In GEC, there is a weak downward conduction current in the area of the atmosphere on sunny days (FW), and there is an upward conduction current in the area of disturbing atmosphere (such as precipitation, lightning, strong wind, strong turbulence, cloud cover, low visibility, etc.). In the global range, downward conduction current in a sunny day area and upward conduction current in a disturbance area occur simultaneously, and the ionosphere +250kV potential balance is maintained together.

Recent studies have shown that GEC is a technical means of monitoring global warming and an alternative technical method of monitoring aerosol concentration in air. In addition, with the advance of the atmospheric potential gradient observation technology, in combination with the gas radon observation, it has been found that abnormal changes in the atmospheric potential gradient may be related to the premonition of major earthquake, and verified in a plurality of atmospheric potential gradient and gas radon observation data before the major earthquake in venture and the geoseis in kyushai. The clear sky area, which is an important component of global circuits, is also a necessary condition for determining and identifying disturbed atmospheric areas. The intradyne curve shows that a positive potential gradient of a daily mean value of +110V exists on the sea level in a sunny area, and the intradyne curve has a typical daily variation characteristic, and the variation interval is 88-124V. On the land, local interference caused by local terrain, local meteorological factors, vegetation and building structures has the characteristic of daily change, but the form and the change amplitude of the daily change are greatly different from the sea level. Therefore, the atmospheric potential gradient in the sunny day is a background condition of a global circuit, and how to accurately determine and unify the sunny day condition is particularly important.

However, there is no unified clear sky definition and standard in the world, and different conclusions can be drawn by adopting different clear sky definitions and standards in the same weather. The following methods are more popular:

1. clear day screening conditions recommended by the british weather department:

1) without any form of aquatic life (i.e. without precipitation, snow, hail);

2) no low-level clouds;

3) the maximum cloud can reach 3. If the atmospheric electric effect is obvious, the atmospheric electric effect does not exceed 1 to form an integral cloud;

4) the wind speed at 10 m height on the ground is less than 8m/s (or the wind speed at 2 m height on the ground is less than 7 m/s);

5) there is no negative potential.

2. On the basis of the English sunny screening condition, the English thunderbolt university provides a sunny screening method for a representative scholarer:

1) no discharge in precipitation, snow and hail;

2) no cloud layer or cloud accumulation with the cloud base height of less than 1500 m;

3) fractional diffusion (S)_d/S_g)<0.4；

4) The wind speed near the 2 m high position on the ground surface is more than 1 m/s and less than 7 m/s;

5) relative Humidity (RH) < 95%;

6) with a ceilometer and scene observation (used only in atmospheric electricity research at the university of latin, with essentially no actual cloud observation), the low/total cloud is less than 3/8.

7) The visibility is greater than 2 km.

3. The atmospheric electric observation in China is carried out later, and the conditions in sunny days mainly adopt the conditions recommended by the British weather department.

1) Direct sunlight exists within 90% of the time of 08: 00-18: 00 (local time);

2) low cloud/cloud less than 3/8;

3) the average wind speed is less than or equal to 8 m/s;

4) no precipitation;

5) the atmospheric potential gradient makes the electric field value between 0 and 2.5kV/m (no negative value).

6) Has good visibility.

However, the applicant found that the following errors and differences exist regardless of domestic or foreign sunny screening conditions:

1. cloud amount observation: according to the ground meteorological observation standard-cloud (national standard of the people's republic of China, GB/T35222-. In actual observation, only clouds and cloud cover were recorded based on manual visual observation. Wherein the cloud cover is recorded as; the cloud cover is "the sky is divided into 10, and the total cloud cover/low cloud cover sky number is recorded", so the total cloud cover/low cloud cover range is: 0-10/0-10, no description of cloud base height. Through historical data query, the fact that the total cloud amount is 8 is hardly found, so that the fine day screening condition of low cloud/total cloud amount observation at home and abroad 3/8 does not meet the national standard of cloud amount observation at China. The foreign low cloud base height is defined as being less than 1500 m, the cloud base height is automatically and continuously recorded by a cloud height instrument, and the cloud base height cannot be recorded in formal meteorological observation or not in China except individual scientific experimental projects. Therefore, all descriptions of cloud base height in domestic literature refer to foreign data at present, and the method is not suitable for the cloud amount screening conditions in domestic fine days.

The proposal that direct sunlight exists within 90% of the time of 08: 00-18: 00 (local time) in China is to determine whether clouds exist by utilizing the observation of visible light of the sun. However, such observations are clearly ineffective when observed at night (after-sunset to sunrise hours).

2. And (3) observing wind speed: due to the fact that the ground is dusted due to too high wind speed, the concentration of heavy/large ions in the air is increased, and therefore the atmospheric potential gradient measurement is affected due to too high wind speed, and the previous day screening condition is affected. Foreign countries usually adopt 10 m or 2 m high wind speed observation results to judge the influence of wind speed on atmospheric potential gradient, and the wind speed of 1-7m/s is taken as a wind speed screening condition on a sunny day. According to the ground meteorological observation specification-wind direction and wind speed (national standard of the people's republic of China, GB/T35227) 2017), the wind direction and wind speed observation in China adopt automatic observation, and the sensor is arranged 10 meters away from the ground. While foreign sensor heights are sometimes 2 meters. In addition to mainstream observation of weather, hydrology, aviation and the like in China, field scientific investigation, earthquake-atmospheric electric observation, emergency observation, rock layer-atmosphere layer-ionized layer observation of Chinese academy of sciences do not indicate specific observation height, and the observation height is changed between 1.5 and 10 meters due to different observation equipment. Because the wind speed increases exponentially along with the increase of the height of the sensor, part of nonstandard wind speed observation data cannot be used for screening wind speed conditions in China on sunny days.

3. Atmospheric potential gradient observation: although foreign atmospheric potential gradient observation began about 100 years ago, it has only started to be prevalent in countries in the last 20 years. In addition to the beginning of a few potential gradient experimental observation experiments in 70 years by China academy of sciences, China meteorology Bureau and China earthquake Bureau, only China meteorology Bureau gradually started systematic and large-scale atmospheric potential gradient observation after 2008. Because the atmospheric potential gradient observation has short development time, no national/industrial/local standard exists at home. However, "no negative potential" is provided by foreign atmospheric electrical observation, "no discharge occurs in precipitation, snowfall and hail," and "atmospheric potential gradient" is provided domestically, and indexes such as electric field value of 0-2.5 kV/m are taken as the atmospheric potential gradient clear-day screening conditions, so that the interference of lightning and charged clouds on the atmospheric potential gradient is eliminated. However, these indicators are qualitative and hypothetical, lacking in quantification and authenticity. Previous studies have shown that the effect of lightning and possibly charged clouds of lightning on the atmospheric potential gradient can be quantitatively estimated by measuring the occurrence of lightning. Because the influence of lightning on the atmospheric potential gradient has no national standard or international standard, the quantitative influence of the lightning on the atmospheric potential gradient is estimated by adopting the latest research result of the patent application team. In the patent "lightning short-term temporary local warning method based on atmospheric electric field" (ZL201810558517.0), we have obtained atmospheric potential gradient conditions of charged clouds that produce or are about to produce lightning. This condition is exactly the reverse of the interference of lightning and charged clouds on the atmospheric potential gradient. Therefore, the lightning condition can be used as the quantitative condition for screening the atmospheric potential gradient in the sunny days of China. In addition, atmospheric potential gradient can be reduced and even negative potential gradient can be generated before earthquakes due to the rising of radon concentration. Therefore, misjudgment may be caused by only adopting the condition that negative potential does not appear as the screening sunny condition.

4. Visibility observation: at home and abroad, the visibility is generally considered to be related to aerosol concentration, fog, haze and the like. The lower the visibility, the lower the concentration of light/small ions in the atmosphere and the higher the concentration of heavy/large ions in the atmosphere. According to the atmospheric ion equation, the lower the light/small ion concentration (the higher the heavy/large ion concentration in the atmosphere), the lower the atmospheric conductivity (the higher the air resistance). According to ohm's law, the lower the atmospheric conductivity (the higher the air resistance), the higher the atmospheric potential gradient will result. Thus, visibility can also affect the atmospheric potential gradient. In order to eliminate the influence of aerosol concentration, fog and haze on the atmospheric potential gradient and obtain the atmospheric potential gradient in a clear day, the visibility of more than 2 kilometers is generally adopted by foreign countries as visibility screening conditions (both foreign visibility manual observation and automatic instruments are available) in the clear day to eliminate the influence of meteorological factors on the atmospheric potential gradient. Visibility automatic instrument observation has been implemented in China for a long time, but specific visibility condition screening in sunny days is not proposed. According to the ground meteorological observation specification-meteorological visibility (national standard of people's republic of China, GB/T35223-. By combining the latest research results and experimental results of the patent application team, the quantitative influence of visibility on the atmospheric potential gradient can be estimated. Research and experimental results show that the visibility condition screened in sunny days in China is that the visibility is more than 8000 m, and the influence of aerosol concentration, fog and haze on atmospheric potential can be effectively eliminated. Namely, the visibility is more than 8 km, and the method can be used as a screening condition of the visibility of the atmospheric potential gradient in China in sunny days.

5. And (3) precipitation observation: at home and abroad, precipitation is also an important factor influencing the atmospheric potential gradient. The increase of the precipitation intensity can cause the sharp drop of the potential gradient, so the precipitation is an important condition for screening in sunny days. In order to eliminate the influence of precipitation on the atmospheric potential gradient as much as possible, the precipitation amount should be used as a sunny screening condition for eliminating the influence of precipitation on the atmospheric potential.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a sunny screening method is provided for accurately determining and unifying sunny conditions.

In order to solve the problems, the invention adopts the technical scheme that: the method comprises the steps of integrating rainfall, wind speed, visibility, cloud cover and lightning conditions observed in a target area to judge whether the weather condition of the target area is sunny or not; the wind speed, the visibility and the cloud cover are all instantaneous data observed by observation points in a target area at a distinguishing moment, the precipitation is accumulated data observed by the observation points in the target area in an observation period, and the lightning condition is the number of lightning occurrences observed by the observation points in the target area in an observation range and the observation period.

Further, when precipitation, wind speed, visibility, cloud cover and lightning conditions all meet the following conditions, the weather condition of the target area is judged to be sunny;

the observation point does not observe precipitation in the observation period before the judgment moment;

the observation point has no low cloud in the visibility range at the moment of judgment;

the wind speed of the observation point at the judgment moment and the height of 10 m from the ground is less than 8 m/s;

the observation point is in the area range with the radius of 30 kilometers, and the number of times that lightning does not appear in the observation time period before the moment is judged to not exceed a threshold value;

visibility of observation points is greater than 8 kilometers.

Further, if the observed wind speed is not a wind speed 10 meters above the ground, a conversion is made by the following equation:

wherein u is₁₀Wind speed u of 10 m height_hThe wind speed is h height, p is a coefficient related to terrain, the value is between 0.1 and 0.4, and if the surrounding terrain is smooth, the value is smaller.

Further, whether lightning exists in the observation period before the moment can be determined through lightning monitoring. When judging whether a certain hour is a sunny day or not, judging whether the weather condition of the target area is a small sunny day or not when the precipitation amount and the lightning condition respectively meet the conditions of A1 and A2;

a1, no precipitation is observed at the observation point 60 minutes before the judgment time;

a2, judging that the number of lightning occurrence in 60 minutes before the moment is not more than 0;

when judging whether a certain day is a sunny day, judging whether the weather condition of the target area is the sunny day when the precipitation and the lightning respectively meet the conditions B1 and B2;

b1, no precipitation is observed on the observation point on the day before the judgment time;

b2, judging the occurrence frequency of lightning in the day before the moment is not more than 5 times.

The invention has the beneficial effects that:

1. the invention can unify and quantify the screening condition in the specified range (such as domestic) in sunny days, and eliminate and correct the error caused by directly citing domestic and foreign standards or research results.

2. The invention can make quantitative and accurate definition for the wind speed data, namely, the wind speed data of other heights except the wind speed of 10 meters need to be corrected to the height of 10 meters. Meanwhile, an empirical method for correcting the change of the wind speed along with the height is provided.

3. At present, lightning monitoring networks are established in many countries, and all the occurring cloud-ground flashes and part of the cloud flashes can be acquired. By adopting the lightning positioning method, a quantitative index for quantitatively eliminating interference of lightning and charged cloud to atmospheric potential can be formed according to a lightning result detected by the lightning positioning network. The invention provides the quantitative index for eliminating the interference of the electric phenomenon in the atmosphere on the atmospheric potential gradient, makes up the deficiency of the quantitative fine-day quantitative screening index of the electric phenomenon in the atmosphere, and can also avoid the misjudgment of the negative potential gradient formed by a pregnant earthquake electric field. Meanwhile, the method can replace the qualitative indexes of no discharge in precipitation, snowfall and hail at home and 'the electric field value is 0-2.5 kV/m (no negative value) by atmospheric potential gradient' at home. The lightning index is adopted as the atmospheric electric index screened in sunny days, and the method can be popularized and applied in countries with lightning monitoring networks in the world.

4. The invention can effectively and quantitatively eliminate the influence of aerosol concentration, fog and haze on atmospheric potential through visibility, unify visibility screening conditions in sunny days in a specified range, and quantitatively improve the accuracy and objectivity of the screening conditions. The visibility index is adopted as the atmospheric electric index screened in sunny days, and the method can also be popularized and applied in countries and stations in the world with automatic visibility observation equipment.

5. The invention unifies the rainfall quantitative screening indexes in sunny days, provides that the starting time and the ending time of the daily rainfall statistic time limit period of the meteorological department are different from the starting time and the ending time of the local time limit period, and is used for correcting errors caused by deviation between the daily rainfall statistic time period and other element statistic time periods in sunny conditions. The method is applicable to all the areas in the world (when the time of the different places is adjusted to the world time or the time of the world is adjusted to the different places, the method is determined according to specific standards of each country).

Drawings

FIG. 1 is a schematic diagram of the present invention;

fig. 2 is a statistical graph of low cloud cover time by time from 1 month 1 day to 5 months 31 days in the winjiang station 2008, and the ordinate in fig. 2 represents percentage, and the unit is "yield" (1 yield is 10%);

FIG. 3 is a visibility time-series distribution diagram of the Wenjiang station 2008 from 1 month to 5 months and 31 days;

FIG. 4 is a statistical chart of wind speed from 1 month to 5 months and 31 days per hour in the Wenjiang station 2008;

FIG. 5 is a statistical chart of cumulative rainfall for each season from 1 month to 5 months and 31 days in the Wenjiang station 2008;

FIG. 6 is a statistical chart of lightning activity frequency in the Wenjiang station 2008 from 1 month to 5 months and 31 days;

FIG. 7 is a timing chart of atmospheric potential gradient from 1 month to 5 months and 31 days in Wenjiang station 2008;

FIG. 8 is a comparison graph of atmospheric potential gradient daily variation in a sunny day at a Wenjiang station.

Detailed Description

As shown in fig. 1, the present invention integrates the precipitation, wind speed, visibility, cloud cover and lightning conditions observed in the target area to determine whether the weather condition of the target area is sunny; the wind speed, the visibility and the cloud cover are all instantaneous data observed by observation points in a target area at a distinguishing moment, the precipitation is accumulated data observed by the observation points in the target area in an observation period, and the lightning condition is the number of lightning occurrences observed by the observation points in the target area in a specified range and a specified period.

At present, lightning monitoring networks are established in many countries, and all the occurring cloud-ground flashes and part of the cloud flashes can be acquired. By adopting the lightning positioning method, a quantitative index for quantitatively eliminating the interference of lightning and charged cloud on atmospheric potential can be formed according to the lightning result detected by the lightning positioning network. The invention provides the quantitative index for eliminating the interference of the electric phenomenon in the atmosphere on the atmospheric potential gradient, makes up the deficiency of the quantitative fine-day quantitative screening index of the electric phenomenon in the atmosphere, and can also avoid the misjudgment of the negative potential gradient formed by a pregnant earthquake electric field. Meanwhile, the method can replace the qualitative indexes of no discharge in precipitation, snowfall and hail at home and 'the electric field value is 0-2.5 kV/m (no negative value) by atmospheric potential gradient' at home. The invention adopts the lightning index as the atmospheric electric index screened in sunny days, and can be popularized and applied in countries with lightning monitoring networks in the world.

The invention is further illustrated by the following examples.

The embodiment adopts atmosphere electric field observation data of Sichuan province, and takes lightning conditions, rainfall, visibility, wind speed and low cloud cover as criteria for judging sunny conditions in a junior region through latest experiments and verification results of inventor teams. In order to unify clear-day definition and clear-day screening conditions in an Chengdu area, the clear-day screening conditions of the Chengdu area should be satisfied at the same time according to lightning, precipitation, wind speed, visibility, cloud cover and the observation result of a lightning monitoring network of a Sichuan atmospheric potential gradient observation station in 2014-2019:

1. cloud amount:

the cloud amount condition screened in fine days should meet the condition that no Low cloud cover exists in the visibility range at the moment of judgment, the existence of medium and high clouds can be ignored, and the cloud bottom height is not considered. Namely:

Low cloud cover＝0 (1)

2. wind speed:

the wind speed condition screened in fine days should meet the wind speed u of 10 m height from the ground at the moment of judgment₁₀Wind speed less than 8 m/s. Namely:

u₁₀< 8m/s (2)

If the wind speed measured by the height h (h is not equal to 10 meters) is adopted, the wind speed measured by the height h must be converted into the wind speed measured by the height h of 10 meters, and the conversion formula is as follows:

wherein u is₁₀Wind speed u of 10 m height_hAnd the wind speed is h height, and p is a coefficient related to the terrain, and the value is between 0.1 and 0.4. If the surrounding terrain is smooth, the value is small; otherwise, the value is larger. The recommended value is 0.3.

3. The condition for screening the precipitation amount in a sunny day should meet the condition that no precipitation prediction exists in an observation period. Performing different judgments according to different statistical time intervals, wherein the hourly precipitation is used in the judgment on an hourly sunny day; the daily rainfall is used in the judgment of a sunny day, wherein the statistical time interval of the daily rainfall can be selected from the conventional statistical time interval (namely 20 days in the previous day to 20 days in the current day) of a meteorological department, or from 0 to 24 times in the current day or other time intervals, and can be reasonably selected according to the local climate.

Precipitation＝0 (4)

4. Lightning condition

The screening condition of the lightning condition (used for replacing the atmospheric potential gradient condition) on a clear day should meet the condition that the frequency of lightning occurrence in the observation time period before the judgment time is not more than the threshold within 30 kilometers of the radius (r) of the observation time of the atmospheric potential gradient observation point; specifically, if the judgment is carried out on an hourly fine day, the hourly fine day should meet the condition that the frequency of occurrence of lightning is not more than 0 within 30 kilometers of the radius (r) of the observation time of the atmospheric potential gradient observation point and within 60 minutes before the judgment time (namely-60 minutes < delta T < 0 minutes delta), namely, the lightning does not occur (N is 0). Namely, the following conditions are met:

namely, the lightning can not be used as a sunny day within 1 hour;

if the judgment is carried out on a sunny day, the number of lightning occurring within 30 kilometers of the radius (r) of the observation time of the atmospheric potential gradient observation point and within the previous day of the judgment time (namely-24 hours < delta T < 0 minute) is not more than 5, namely

5. The Visibility screening condition in sunny days should satisfy that the weather Visibility is more than 8 kilometers at the moment of discrimination. Namely:

visability > 8 km (6)

The verification process of the screening scheme in sunny days is as follows:

as shown in fig. 2, the low cloud cover and visibility time sequence distribution of the wenjiang station are obtained by using the low cloud cover data of the existing meteorological department from 1 month to 5 months and 31 days in 2008.

As shown in fig. 3, the visibility time sequence distribution of the wenjiang station is obtained by using the visibility history data of the existing meteorological department when the wenjiang station is 2008 by 1 month and 1 day to 5 months and 31 days.

Referring to fig. 4, historical data of 10 meters high average wind speed by each time from 1 month to 5 months and 31 days in 2008 of the wenjiang station in the existing meteorological department are adopted to obtain the time sequence distribution of 10 meters high wind speed in the wenjiang station.

As shown in fig. 5, the precipitation historical data is accumulated by the current meteorological department every 1 month, 1 day to 5 months, 31 days and a year in the wenjiang station 2008, and the hourly precipitation time sequence distribution of the wenjiang station is obtained.

As shown in FIG. 6, the existing Sichuan province meteorological office lightning monitoring network is adopted to obtain the hourly lightning activity frequency time sequence distribution within the radius of 30km of the Wenjiang station from 1 month to 5 months and 31 days in 2008.

And (3) screening the sunny days according to the sunny day screening conditions set by the formulas (1), (2), (4), (5-1) and (6) and the low cloud cover, wind speed, precipitation, visibility and lightning frequency data shown in the figures 1, 2, 3, 4 and 5.

The screened sunny conditions can be used for computing and counting the atmospheric potential gradient in the sunny days. Referring to fig. 7, the historical data of atmospheric potential gradient of the wenjiang station is used to obtain the time sequence distribution of the time interval of the wenjiang station in sunny days and the small-average value of the atmospheric potential gradient. Data breakpoints in the atmospheric potential gradient curve before screening represent data missing, and the atmospheric potential gradient curve breakpoints in fine days after screening represent disturbance weather periods after screening.

Potential of atmosphereThe gradient (PG) hourly mean may be obtained from the PG values per second:the daily average of the atmospheric Potential Gradient (PG) can be obtained from the PG average per hour:if data loss occurs, the hourly or daily average value of PG will be subtracted with the number and number of detections of the loss. If the number of measurements per hour or day is missing<2/3 for the total number of samples observed hourly or daily, then the hourly average or daily average data would be deemed invalid and would be removed. In this study, we obtained a significant number of samples for the daily average of each observation station PG of 182 days.

And obtaining the daily change of the atmospheric potential gradient of the Yangjiang station by adopting the screened atmospheric potential gradient in sunny days, and comparing the daily change with the atmospheric potential gradient change of the standard sea level in the card. As can be seen from fig. 8, there is a daily change in atmospheric potential gradient in a sunny day at a wenjiang station compared to the standard canary plot. However, the atmospheric potential gradient of the Yangjiang station in a sunny day is in a double-peak double-valley state, and the daily change of the inner base curve of the card is in a single-peak double-valley state. The peak value of the atmospheric potential gradient in a sunny day of the Wenjiang station appears at 07 th in the morning and 17 th in the evening (Beijing is the time below); while the peak of the baseline curve in the card appeared around the point of 03 in the middle of the night. Atmospheric potential gradient valleys of a Yangtze river station in a fine day appear at 03 and 22 in the morning, and just correspond to the peak time of the inner base curve of the card; while the trough of the baseline curve in the card occurred around 11 am (local time). In addition, the atmospheric potential gradient change interval of the Yangjiang station on a fine day is larger than the change interval of the inner base of the card. The results show that the atmospheric potential gradients in sunny days in different places have different background values and different day changes. In different places, the day-change background value of the atmospheric potential gradient in the local sunny day can be obtained only by adopting the sunny screening conditions set by the formulas (1), (2), (4), (5-1) and (6). The time intervals of the sunny day screened according to the formulas (1), (2), (4), (5-1) and (6) can be regarded as objective sunny days according with actual conditions.