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 OJAppS  Vol.11 No.3 , March 2021
Performance of Incoming Solar Radiation Components in Partial Annular Solar Eclipse on June 21st, 2020 in Helwan, Egypt
Abstract: Observing and studying the solar radiation during solar eclipses is important in knowing the changes that occur to the environmental elements during this event. The main objective of this paper is the performance of the incoming variation of solar radiation components, global, direct and diffuse and their fractions during the partial annular solar eclipse on June 21st, 2020 in Helwan, Egypt (Lat. 29.866°N and Long. 31.20°E) has been made. A pyrheliometer for measuring the direct solar radiation, in three different bands; direct yellow (Y), direct red (R), direct infrared (IR), and also the total direct band (I); A pyranometers for measuring the different components of global solar radiation (G), global ultraviolet (GUV), global infrared (GIR) and a meteorological station to measure the different meteorological parameters. The duration of the solar eclipse was 01 h:59 m, and the maximum magnitude of the eclipse in this region was 0.449. The depression is clear at the solar radiation of all components due to the annular solar eclipse, while the depressions of the diffuse and global infrared solar radiation are lower. In all direct radiation compounds (I, Y, R and IR) are greatly affected by the eclipse. The diffuse fraction Kd is higher in the early time, before the partial eclipse, but during the partial annular eclipse time Kd values are suffers variation and through the day, where the values of Kd lies between Kt and KUV. The values of direct infrared solar radiation are dominant before and after the partial annular solar eclipse. The intensity of color bands (W∙m−2∙nm−1) are DIB3 > DIB2 > DIB4, and DIB1 is opposite direction with DIB3 and DIB2, the highest intensity is direct red and the lowest intensity is the direct infrared. The highest values of extinction coefficient in (GIR) solar radiation and the lowest values occur in (GUV) solar radiation, while the values of (G) solar radiation occur between them. In general trend, the values of extinction coefficient during the partial eclipse are increasing, while the minimum values of extinction coefficient occur at noon time due to the air mass is less value in the noon.

1. Introduction

A solar eclipse is a natural event that takes place on Earth when the Moon moves in its orbit between Earth and the Sun (this is also known as an occultation). Solar eclipses provide an unusual opportunity to study a rapid and well-characterized change in the solar radiation entering the atmosphere. While radiation measurements related to eclipse changes have been made at the Earth’s surface [1] [2] [3]. A total solar eclipse occurs when the Moon completely blocks the solar disk. In a total solar eclipse, the narrowest part of the path (where the Sun is completely blocked and the Moon casts its darkest shadow (called the umbra)) is called the “zone of totality”. Total solar eclipses have not always been visible from Earth. When the Moon is farther away in its orbit than usual, it appears too small to completely cover the Sun’s disk. During such an event, a bright ring of sunlight shines around the Moon. This type of eclipse is called an “annular” or “partial” eclipse. It comes from the Latin word “annulus” which means “ring” [4] [5]. Partial and total solar eclipses have been the exclusive concern of Astronomy and Astrophysics. The greatest eclipse is defined as the instant when the axis of the Moon’s shadow passes closest to the Earth’s center. For the total eclipses, the instant of greatest eclipse is virtually identical to the instants of greatest magnitude and greatest duration. However, for annular eclipses, the instant of greatest duration may occur either at the time of greatest eclipse or near the sunrise and sunset points of the eclipse path [6]. On Saturday June 21st, 2020 in Helwan, Egypt, a partial annular solar eclipse of the Sun was visible from within a narrow cored or which traversed half the Earth. The partial solar eclipse was started at 06:23:09, the maximum eclipse will occur at 07:19:29 when the Sun reaches an altitude of 29.866˚ and azimuth of 078˚; this event will come to an end at 08:22:20 and will have a magnitude of 0.457 (the magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse), and an obscurity of 0.343 (the fraction of the Sun obscured).

Many several studies claiming of the variation of solar radiation and transparency has been carried out in recent years, dealing with solar eclipse totality and partiality in different countries. The around about this subject was carried out in the world, especially in this region. In Romania, a study of atmospheric responses due to August 11th, 1999 total solar eclipse indicated that both of the global and UVB radiation dropped dramatically to a minimum around totality. There was a chance to study attenuation of such a radiation due to clouds [7] [8] [9]. The concluding indicated that there is an increase in the hole with different zonal summer times in the interval 350 - 450 nm but without risks on the human eye, that interval lied at the end of the ultraviolet solar radiation, minimum lied from 500 - 700 nm. This interval represented the normal maximum peak of the solar spectrum and go from 700 nm up to 900 nm, which related to the infrared interval and down in the deep infrared from 900 nm to the end. The ultraviolet band was suffering low depression with respect to other bands, but was not given any risks on the human life as common [10] [11] [12] [13] [14]. A study was made of the depression of the different solar radiation components during the solar eclipse, August 11th, 1999, over Egypt (as a partial solar eclipse, 70% covering of the solar disk in Helwan, Egypt). The maximum depression values of the different components of solar radiation were 54% in red solar radiation (for global and direct), while the minimum depression was in infrared solar radiation (34% for global and 41% for direct). The clearness index and the diffuse fraction were 0.634 and 0.232, respectively. The atmospheric red radiation was 7.4% and the atmospheric infrared radiation was 10.7%. The percentage of ultraviolet was 3%. A study of the spectral composition of global solar radiation by interference metallic filters was carried out during the same previous eclipse on August 11th, 1999 in Helwan, Egypt [15].

A Solar eclipse is one of the most spectacular astronomical phenomena which occur when the Moon covers the Sun, casting its shadow on the Earth a dating spires meteorologist to conduct special investigations. Eclipses are connected with the rapid and short time, impulse-like decrease of the solar energy flux reaching the area of its visibility, which can be exactly predicted before the occurrence of the phenomenon. It also provides a unique opportunity for meteorology is to study the response of the atmosphere or biosphere to the sudden turn off/turn on of the incidental solar radiation during and after the solar eclipse [16] [17] [18]. There are a number of studies and observations made during the solar eclipses, which include observations of meteorological parameters, such as wind speed and direction, air temperature, atmospheric pressure, humidity, ozone measurements and heat and momentum fluxes within the boundary layer [6] [19] [20]. The impact of a solar eclipse on atmospheric and surface temperature has been widely reported changes in wind speed during the eclipse with a minimum value during totality but without much change in wind direction. Observed sharp increases in the UV flux after the last two hours of contact of the eclipse on 24 October, 1995, these authors attributed the observed increases in ground-based UV flux to the reduction of stratospheric ozone [21].

Solar eclipse episodes are often favorable opportunities for closely observing the effects of interactions between solar irradiance and the terrestrial atmosphere, studies on this topic can be very useful for testing and improving the radiated transform models used to simulate the spectrum of ultraviolet (UV) solar irradiance reaching the surface [22] [23] [24]. In addition, the solar radiation partly reflected upward from the surface or by cloud scan be scattered by air molecules and aerosols, sometimes enhancing considerably the incoming diffuse radiance flux measured at the observation site. Since Rayleigh scattering closely depends on wavelength, the diffuse radiance is comparable to, or may become even more intense than the direct component of UV wavelengths, with significantly lower values at the longer wavelengths in the visible and near-infrared spectral ranges. Depending strongly on the atmospheric turbidity conditions and surface reflectivity characteristics, UV diffuse radiance can vary greatly as a function of the environmental parameters. These dependence features have been the subject of numerous studies. The absorbing components of the atmosphere are O2, O3, H2O, CO2, N2, O, N, NO, N2O, CO, CH4 and their isotopic modifications, though the contributions of the latter are small spectra due to electronic transitions of molecular and atomic of O, N, O3, lie chiefly in the UV region, while those due to the vibration and rotation of polyatomic molecules such as H2O, CO2 and O3, lie in the IR region. The Angstrom turbidity (β) typically ranges from 0.02, for low aerosol load, to 0.5, for high aerosol load [11] [25] [26] [27]. The main objective of the study is the performance and determines the percentage of color portion, variations of the different solar radiation components in Partial Annular Solar Eclipse on June 21st, 2020 in Helwan, Egypt.

2. Sit Observation and Measurements

Helwan site is selected on a hilltop of height 130 m above sea level (29˚52'N & 30˚20'E) at a distance of about 30 km South of Cairo in a desert surrounding in the East and the Nile valley (cultivated land) in the West. The western desert exists in the far west, where Saqqara and Dahshur Pyramids can be seen under good conditions of visibility. The observation conditions at this site are suffering now from the existence of strong pollution sources in the West (Helwan Town, Portland Cement Company and a power Station), Southwest. Equipment was installed on the roof of the National Research Institute of Astronomy and Geophysics (NRIAG) building in Helwan, the background is taken as desert and pollution.

The average concentration of total suspended particulates (TSP) is ranged 500 - 600 μg/m3. Tura EL-Cement and Helwan Portland cement factories were found to represent 50% of the pollution sources in Helwan region. XRD (X-ray diffraction) patterns of PM2.5 samples are (CaSO4∙H2O, Al2Si2O5(OH)4, SiO2, CaCO3 and CaMg(CO3)2, Fe2O3, NaCl) respectively. The elements follows the trend as Si > Ca > Ba > Al > K > Zn > Na > Mg > Fe > CL > S > Ni > Ti, P > Sr > Cu. The XRF (X-Ray Fluorescence) and XRD analyses for lead differ somewhat more, being 44 and 2.2%, respectively [28]. The instruments used in the present research (see Table 1), and a meteorological station (Davis vantage pro 26,152 weather stations) to measure the different meteorological parameters.

The data collection by the computerized data logger for the different global component and the meteorological parameters, while for the different direct components are taken by the manual.

The extraterrestrial solar radiation (Go, Io, Yo, Ro and IRo) and the terrestrial solar radiations (G, GUV, GIR, I, Y, R and IR) calculated by W/m2 are defined bands as:

Table 1. The instruments of solar radiation measurements used in the work.

Go, G and I = 280 - 2800 nm, UVo and GUV = 285 - 385 nm, Yoand Y = 530 - 2800 nm, Ro and R = 630 - 2800 nm, IRo and IR = 695 - 2800 nm.

The color intensity bands, Bi (W/m2) calculated as: IB1 = IY = 280 - 530 nm, ΔB1 = 250 nm, IB2 = YR = 530 - 630 nm, ΔB2 = 100 nm,IB3 = RIR = 630 - 695 nm, ΔB3 = 65 nm,IB4 = IR = 695 - 2800 nm, ΔB4 = 2105 nm.

The color intensity bands, DIBi (W∙m−2∙nm−1) calculated as: DIB1 = IB1/ΔB1 (W∙m−2∙nm−1),DIB2 =IB2/ΔB2 (W∙m−2∙nm−1), DIB3 = IB3/ΔB3 (W∙m−2∙nm−1). DIB4 = IB4/ΔB4 (W∙m−2∙nm−1).

The color portion bands, DCBi (% or ratio∙nm−1) calculated as: DCB1 = DIB1/I, DCB2 = DIB2/I, DCB3 = DIB3/I and DCB4 = DIB4/I (% or ratio∙nm−1).

Global event of the partial annular solar eclipse at 21 June 2020 at Helwan and the eclipse duration is 01 h:59 m (see Table 2).

Mie’s theory and Rayleigh’s classified the size particle of a scattering as the function in the wavelength λ as: πd/λ, where d is the particle diameter. Let n be the index of refraction and λ the wavelength in micrometers. It is considered that, 1) when πd/λ < 0.6/π, scattering is governed by Rayleigh’s theory, and in a cloudless atmosphere applies to air molecules, most of which have a size ≈ 1 Ä; 2) when πd/λ > 5, scattering is chiefly a diffuse reflection process seldom occurring in the earth’s atmosphere; and 3) when 0.6/n < πd/λ < 5, scattering is governed by Mie’s theory, and applies to scattering by particles of size greater than 10 Ä, such as aerosols [11].

3. Methodology

During the overshadowing, the solar radiation is diminished from that normal for a similar area and season, by the extent of the sun powered circle's territory covered (the obscuration). Ascertaining the solar radiation during the overshadowing can be accomplished by consolidating the standard count of the everyday variety in top-of-air sun powered radiation with a regulating capacity to speak to the shroud. The highest point of-air sun powered radiation is basically a cosmic count: the genuine radiation in the lower environment will be decreased from the highest point of-air and incentive through ingestion by ozone and water fume, which is variable. Expecting unimportant distinction between the real and mean Sun-Earth separates the time variety in sun powered irradiance on an even surface at the highest point of the climate ST(t) is given roughly by [27].

S T ( t ) = S 0 cos [ Z ( t ) ] (1)

Table 2. Phases of the annular partial solar eclipse in Helwan, Egypt 21 June 2020.

where (S0) is the total solar irradiance (TSI) and (Z) is the solar zenith angle at a time t. For a site at latitude (φ) when the solar declinations (δ), the variation in (Z) during the day are found from the hour angle H(t) as:

cos [ Z ( t ) ] = sin φ sin δ + cos φ cos δ cos H ( t ) (2)

The solar irradiance variation with time at a particular position is conventionally calculated by combining Equations (1) and (2) to give

S T ( t ) = S 0 [ sin φ sin δ + cos φ cos δ cos H ( t ) ] (3)

On a day with a total solar eclipse, an additional modulation function is needed to represent the effect of the eclipse. The solar irradiance can then be written as [27].

S T ( t ) = [ 1 E ( t ) ] S 0 [ sin φ sin δ + cos φ cos δ cos H ( t ) ] (4)

where E(t) is the eclipse function which gives as:

E ( t ) = 1 ( 2 / π ) cos 1 [ f e ( t ) ] ( 2 / π ) f e ( t ) { 1 f e ( t ) 2 } 1 / 2 (5)

where fe(t) is the eclipse magnitude, the proportion of the Sun’s radius obscured by the Moon at a time. The extraterrestrial solar radiation at any time during the partial solar eclipse can be calculated as following [25].

E i at eclipse = ( E i ) ( 1 M ) (6)

where (M) is magnitude of solar eclipse defined as the fraction of the solar diameter that is obscured and Ei is substituted by any radiation quantity, e.g. Go, GIR, GUV, B1, B2, B3 and B4. Extinction coefficient (α) calculated by the:

I b λ = I o λ exp ( α m A ) (7)

where (I) is the measured spectral irradiance at wavelength (λ) and (I) is the extraterrestrial spectral irradiance corrected for the actual sun-earth distance.

Also we can calculate the extinction coefficient values of (α) as following equation [25]:

α = ln ( I b λ / I o λ ) ( 1 / m A ) (8)

Air transparency, (Tr),

T r = e α (9)

The calculations of the extraterrestrial solar radiation for the bands of various components bands are based on [11] [25].

The diffuse infrared (DIR) was calculated from the equation:

D I R = G I R I R cos ( Z ) (10)

The Linke turbidity factor, LT is given by:

L . T . = ( 1 / δ R m A ) ln ( I o / I ) (11)

where δR is given by:

δ R = 1 / ( 9.4 + 0.9 m A ) (12)

where mA is relative optical air mass and given by:

m A = ( P / 1013.25 ) [ ( 1 / cos Z ) + 0.15 ( 93.885 Z ) 1.25 ] (13)

where, (P) is the air pressure (hpa).

The total amount of water vapor in the atmosphere in the vertical direction is highly variable and depends on the instantaneous local conditions. This amount, expressed as perceptible water W (cm), and can be readily computed through a number of standard routine atmospheric observations. The perceptible water vapor can vary from 0.0 to 5 cm [25] [29].

W = { 0.493 ( φ r ) exp [ 26.23 ( 5416 / T k ) } / T k (14)

where, (Tk) is the ambient temperature in kelvins and (φr) is the relative humidity in fraction of one (φr = RH/100).

The Angstrom turbidity coefficient is a dimensionless index that represents the amount of aerosol, and the relation between the Linke turbidity (LT) and the Angstrom turbidity (β) for Helwan is [25] [30]:

β = 0.194933 + 0.0620059 L T (15)

4. Results and Discussion

Figure 1 shows the hourly variation of extraterrestrial solar radiation components bands, global (Go), ultraviolet (UVo), yellow (Yo), red (Ro) and infrared (IRo) in W/m2 and it shows the decrease in the solar energy interior in all components.

Figure 1. The hourly variation of extraterrestrial solar radiation (W/m2).

Figure 2 shows the hourly variation measurements of incoming solar radiation components, global (G), global infrared (GIR), diffuse (D) and global ultraviolet (Guv) in W/m2during the day, including the depression of the solar radiation components at the interval of partial annular solar eclipse. From this figure, we noticed that the depression of the solar radiation of all components due to the partial annular solar eclipse, while the depressions of the diffuse and global infrared solar radiation are lower. The behavior of the turbulent diffuse radiation (D) expresses the state of change in the transparency of the atmosphere.

Figure 3 shows the hourly measurements of various direct solar radiation components; total (I), yellow (Y), red (R) and infrared (IR) in W/m2. This figure pointing to the depression gradient starting from the direct total two infrared bands passing through the yellow and red bands before and after the partial annular solar eclipse, the difference between the bands is narrow during the maximum eclipse. To compare between the global and direct components, in all direct solar radiation compounds (I, Y, R and IR) is greatly affected by the eclipse, while the effect is small in case the total solar radiation compounds (G, Guv, GIR and D).

Figure 2. The hourly variation of measured global and diffuse solar radiation (W/m2).

Figure 3. The hourly variation of measured direct solar radiation components (W/m2).

Figure 4 shows the hourly variation of clearness index for each of the global (Kt), ultraviolet (Kuv), and infrared (KGIR) addition to the diffuse fraction (D/G). From this figure, the diffuse fraction Kd is higher in the early time, before the partial eclipse, but during the partial annular eclipse time Kd values are suffers variation and through the day, where the values of Kd lies between Kt and KUV. Where the diatomic oxygen (O2), nitrogen (N2), atomic oxygen (O), nitrogen (N), and ozone (O3) are the five principal absorbers in the ultraviolet and visible spectrum [11]. During the partial annular solar eclipse, the behavior of Kt and KUV are similar, while the (Kd) is opposite direction, this means that the scattered radiation is greater during the eclipse. Also from this figure, the clearness indices have higher values during the partial annular eclipse, but after the partial eclipse, the values of Kt are higher and the values of (Kd) are lowest. The observers notice that by the naked eye there are a light cloud of air pollutants at the altitude of the Sun (a ≈ 50.307˚ - 63.284˚).

Figure 5 shows the hourly variation of the horizontal global infrared GIR and the direct infrared IR over the whole day. The IR is predominant outside the partial annular solar eclipse, but these changes during a partial eclipse. The difference between the values of GIR and IR solar radiation is the diffuse infrared solar radiation, where a part of the direct red and infrared radiation are converted into diffuse infrared by the artificial of air pollutants during this period. Figure 6 shows the hourly variation of the irradiance of the total diffuse solar radiation (D) and the diffuse infrared solar radiation (DIR). From this figure, we clear that the total diffuse solar radiation values were higher than the diffuse infrared solar radiation values before, after and during the partial annular solar eclipse. A number of gases absorb solar electromagnetic radiation in the infrared wavelengths; the important absorbers of these gases are H2O, CO2, O3, N2O, CO, O2, CH4, and N2. The water-vapor bands of importance are at 720, 820, 940, 1100, 1380, 1870, 2700, 3200, and 6300 nm; those of carbon dioxide are at 1450, 1600, 2000, 2700, 4300, 4800, and 5200 nm; and those of oxygen are at 690 nm and 760 nm [11].

Figure 4. The hourly variation of clearness index for global and diffuse fraction (ratio).

Figure 5. The hourly variation of infrared solar radiation (W/m2).

Figure 6. The hourly variation of diffuse and diffuse infrared solar radiation (W/m2).

Figure 7 shows the hourly variation of the color bands intensity for the direct radiation components of DIBi (W∙m−2∙nm−1) over the whole day. Generally, this figure shows, the intensity of bands are DIB3 > DIB2 > DIB4, DIB1 is opposite direction with DIB3 and DIB2, it turns out that, the highest intensity is direct red and the lowest intensity is the direct infrared.

Figure 8 shows the different percentage of the color portion, DCBi (%∙nm−1) bands through the day passing during the partial annular solar eclipse. This figure shows that the prevailing color portion bands in the clear case are DCB3 > DCB2 >DCB4, and DCB1 is opposite direction with DCB3 and DCB2, where the high percent of color portion bands generally is the red color (DCB3). From Figure 7 and Figure 8, it is similar prevailing in theDIBi (W∙m−2∙nm−1) and DCBi (%∙nm−1) for all bands, which indicated the band 530 - 630 nm is the largest percent of color portion.

Figure 9 shows the ratio of diffuse infrared solar radiation to the total diffuse solar radiation (DIR/D) with the behavior of magnitude of eclipse, where the maximum ratio occur before and after the partial solar eclipse, while decrease ratio occur during the interval time of solar eclipse. Figure 10 shows the hourly

Figure 7. The hourly variation of color intensity bands of direct solar radiation components.

Figure 8. The hourly variation of color portion bands of direct solar radiation components.

Figure 9. The hourly variation of DIR/D (ratio) with the eclipse magnitude (ratio).

Figure 10. The hourly variation of ambient air temperature (˚C) and relative humidity (%).

variation of air temperature, T (˚C) and RH (%) on the day, where the relation is inversely. Figure 11 shows the variation of color portion percent bands (%∙nm−1) during the eclipse magnitude. The largest percent values occur in the red color (DCB3), while the lowest values occur at the infrared color (DCB4) and the values of DCB1 and DCB2 are approximately equal in value. It also notes that the direction and behavior of all colors are in the same phase, unlike the behavior of colors before and after the eclipse.

Table 3 shown the statistical values of the extinction coefficient (E) for each of G, GIR, GUV, I, CB1, CB2, CB3, CB4 during the day passing the partial annular solar eclipse on 21st June 2020, in addition to the atmospheric transparency (Tr) values calculated from the mean of (E) for the same types of radiation values. From this table, the highest value for transparency is GUV rays and the lowest is CB2.

Table 4 gives the different values of Link turbidity (LT), Angstrom turbidity (β), and perceptible water (W, cm) during the day passing the through the partial annular solar eclipse. Both Linke and Angstrom turbidity values are higher in the afternoon than in the morning. This is due to the high temperature in afternoon, which expands and excites the gases and the dust in the atmosphere. The distribution of perceptible water (W, cm) gives the concept of the atmospheric character during the partial eclipse. The fluctuation of LT and β beside the W (cm) give an idea of the turbidity of the day observation. The LT and β values are higher in the afternoon than in the morning. This is because of the high temperature in the afternoon, which expands and excites the gases and the fine dust in the atmosphere. During the eclipse (from the first contact to the last contact), the ranged values of the LT, β and W (cm) are 2.02 - 3.12, 0.015 - 0.027 and 3.14 - 2.68 respectively.

Table 3. The statistical values of the extinction coefficient (E) for each of G, GIR, GUV, I, CB1, CB2, CB3, CB4 during the day passing the partial annular solar eclipse on 21st June 2020, in addition to the atmospheric transparency (Tr) values calculated from the mean of E for the same types of radiation values.

Table 4. The variation values of link turbidity (LT), Angstrom turbidity (β) and perceptible water (W, cm) during the day passing through the eclipse period.

Figure 11. The variations of color portion during the eclipse magnitude (%∙nm−1).

Table 5 represents the linear regression [Y(LT, β, W) = a + bX (hour)] between the LT, β and W (cm) with the time (hour) and the correlation coefficients (CC) according values of Table 3. The rate increase of the LT with time is dLT/dt = +0.3313 (high correlate ≈ 0.96), the rate increase of β with the time is dβ/dt= +0.01697, while the rate decrease for the W (cm) with the time is dW/dt = −0.0751. It is clear that the relationship is positive with the progression of time with an increase in the intensity of solar radiation and then the direct functions in the temperature, which leads to an increase in the spread and excitation of the atmospheric air components in a tropospheric region. While the relationship is inverse and indirect in case the perceptible water (W, cm) with the time. This is caused by the average concentration of particulate matter ( TSP ) was 500 - 600 μg/m3, and Tura EL-Cement and Helwan Portland cement factories were found to represent 50% of the pollution sources in Helwan region [28]. Then the large percentage in the elements is Si and it is beige size and fall under Mei scattering and an atmosphere containing 200 μg/m3 is very clear and an atmosphere containing 800 μg/m3 is much polluted [11].

Figure 12 shows the variations of temperature (˚C) and relative humidity (RH, %) values for three days (21 June as the eclipse day) and the two days before (20 June) and after (22 June) the eclipse day from sunrise to sunset. It would be clear, that the temperature on the day of the eclipse is higher than the day before and the day after it, and vice versa with respect to the relative humidity. Figure 13 shows the change in both temperature (˚C) and RH (%) with respect to time for the three sequence days, the day of the eclipse (21 June, including the duration of the eclipse), the day before (20 June) and the day after (22 June) for the interval time 5.5 h to 12.5 h am. He notes the regular change of both temperature and relative humidity on 20 and 22 June. While the change was irregular on June 21, especially the change in temperature immediately after the time of the eclipse, then followed by a change in the RH.

Table 5. The linear regression between the LT, β and W with the time (hour) and the correlation coefficients (CC) according to Table 4.

Figure 12. The variation of the temperature (˚C) and RH (%) values for three days (21 June as the eclipse day and the two days before (20 June) and after (22 June) the eclipse day from sunrise to sunset.

Figure 13. The change in both temperature (˚C) and RH (%) with respect to the time for three sequence days, the day of the eclipse (21 June, including the duration of the eclipse), the day before (20 June) and the day after (22 June) for the interval time 5.5 h to 12.5 h am.

5. Conclusion

The objective of this research is performance of incoming solar radiation components in partial annular solar eclipse on June 21st, 2020, at Helwan, Egypt. The depression is clear at the solar radiation of all components due to the annular solar eclipse, while the depressions of the diffuse and global infrared solar radiation are lower. n all direct radiation compounds (I, Y, R and IR) are greatly affected by the eclipse, while the effect is small in the case of total radiation compounds (G, Guv, GIR and D). The diffuse fraction Kd is higher in the early time, before the partial eclipse, but during the partial annular eclipse time Kd values are suffers variation and through the day, where the values of Kd lies between Kt and KUV. The clearness indices have higher values during the partial annular eclipse, but after the partial eclipse the values of Kt are higher and the values of Kd are lowest. The IR solar radiation component is predominant outside the partial annular solar eclipse, but these changes during a partial eclipse. The values of direct infrared solar radiation are dominant before and after the partial annular solar eclipse, and also the global infrared solar radiation is dominant. The intensity of color bands as the W∙m−2∙nm−1 are DIB3 > DIB2 > DIB4, andDIB1 is opposite direction with DIB3 and DIB2, the highest intensity is direct red and the lowest intensity is the direct infrared. The different percentage of the color portion bands, DCBi (%∙nm−1) shows the prevailing color portion bands are DCB3 > DCB2 > DCB4, and DCB1 is opposite direction with DCB3 and DCB2, where the high percent of color portion bands generally are the red color (DCB3). The direction and behavior of all colors percent (%∙nm−1) are in the same phase, unlike the behavior of colors before and after the eclipse. The highest values of extinction coefficient in GIR solar radiation and the lowest values occur in GUV solar radiation, while the values for G solar radiation occur between them. And the all values of extinction coefficient in the total direct solar radiation and the color bands are nearest them. In general trend, the values of extinction coefficient during the partial eclipse are increasing, while the minimum values of extinction coefficient occur at noon time due to the air mass is less value in the noon. The highest value for the transparency is GUV rays and the lowest is CB2. The Linke Turbidity (LT) and Angstrom turbidity (β) values are higher in the afternoon than in the morning. This is because of the high temperature in the afternoon, which expands and excites the gases and the dust in the atmosphere. During the eclipse (from the first contact to the last contact), the ranged values of the LT, β and W (cm) are: 2.02 - 3.12, 0.015 - 0.027 and 3.14 - 2.68 respectively. The rate increase of the (LT) with time is dLT/dt = +0.3313, the rate increase of (β) with the time is dβ/dt = +0.01697, while the rate decrease for the W (cm) with the time is dW/dt = −0.0751. It is clear that the relationship is positive with the progression of time with an increase in the intensity of solar radiation and then the direct functions in the temperature, which leads to an increase in the spread and excitation of the atmospheric air components in a tropospheric region. The relationship is inverse and indirect in case the perceptible water (W, cm) with the time. The regular change of both temperature and relative humidity on 20 and 22 June, while the change was irregular on June 21, especially the change in temperature immediately after the time of the eclipse, then followed by a change in the RH.

Cite this paper: Khalil, S. , Hassan, A. , Rahoma, U. , Abulwfa, A. and Khamees, A. (2021) Performance of Incoming Solar Radiation Components in Partial Annular Solar Eclipse on June 21st, 2020 in Helwan, Egypt. Open Journal of Applied Sciences, 11, 294-311. doi: 10.4236/ojapps.2021.113022.
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