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Egamberdiev Khamrakul Tursunkulovich, Petrov Yuriy Vasilovich, Prof. Dr., National University of Uzbekistan named after Mirzo Ulugbek, lecturer, of the Faculty of physics, Tashkent city, Uzbekistan E-mail: ext1961@mail.ru
THE TECHNIQUE FOR CALCULATION OF THE NORMALIZED FACTOR OF THE DIRECT SOLAR RADIATION WEAKENING
Abstract: The technique is developed for the calculation of the new parameter: normalized factor of the attenuation of the direct solar radiation, as well as of its components - attenuation in the ideal atmosphere, attenuation with water vapor and atmospheric aerosols.
Keywords: Normalized factor for the solar radiation attenuation, attenuation of solar radiation with water vapor and atmospheric aerosols.
Introduction.Only part of the solar radiation which enters the upper atmosphere border reaches the Earth surface. After penetration through the atmosphere layer it is attenuated substantially due to the following main physical processes: molecular (Riehl) and aerosol (Mi) dissipation, as well as with the water vapor absorption and by the aerosol of the natural and anthropogenic origin.The part of the solar radiation which reaches the underlying surface, presents the direct and solar radiation [2].
The ability of atmosphere to transmit the directed solar radiation is called as the Earth atmosphere transparency. Spectral and integral atmosphere transparencies are distinguished.Spectral transparency is the ability of atmosphere to transfer the directed radiation in the relatively narrow parts of spectrum. Integral transparency - is the ability of atmosphere to transfer the directed radiation in the wide wave range.The transparency of atmosphere is one of indicators of physical processes taking part in the atmosphere. Different characteristics which are used in the studies on the formation and change of weather ad climate of our planet are used for the quantitative expression of the atmosphere transparency. They are also used for the solution of tasks of the surface monitoring of atmospheric transparency by the measured values of the direct solar radiation [2].
Objective of the work: to elaborate the method for calculation of the new normalized factor of the solar
radiation attenuation by the atmosphere as the integral transparency index.
This index characterizes the optical characteristics of the air mass located over the observation point, and depends on the moisture content of air and on the concentration of atmosphere aerosol in it, i.e.
P = Pud + Pae + Paa , (1)
where: Pud- the portion of the weakened solar radiation
in the ideal atmosphere, P - attenuation of solar radiai 'as
tion with the water vapor, Paa - attenuation of solar radiation with the atmosphere aerosol.
Discussion of results. Let us consider the sequence of calculation of all summands in the formula (1).
P - normalized factor of attenuation of solar radiaa
tion with the Earth atmosphere is calculated with the formula:
J 0 — Jm =2
P =-
J0
(2)
where: Jo - solar constant which is 1,367 kWt/m2, Jm=2 -direct solar radiation reduced to the optical mass the value of which is two by the method of Sivkov S. I. [4].
Survey of works on the investigation of the solar radiation attenuation in the ideal atmosphere at the Earth surface level is given in [1, 3]. The data of Sivkov S. I. [4] calculation are the most reliable and comprehensive ones. Calculations of the change of the direct solar radiation with height in the ideal atmosphere with the unit optical mass are made by Kastrov V. G. [1]. The vertical
profile of the direct solar radiation in the ideal atmosphere with m = 1 is given in (Fig. 1).
The obtained data are reduced to the optical mass value which equals 2 by the technique of Sivkov S. I.
Jm=1, BT/M2 1290
1280 1270 1260 1250 1240 1230 1220
h, m
0
1000
2000
3000
4000
5000
Figure 1. Vertical profile of the direct solar radiation in the ideal atmosphere with m =1 Attenuation of the direct solar radiation in the ideal where: J'm=2 - direct solar radiation in the ideal atmo-
atmosphere P is calculated with the formula:
r HA
J - J '
J 0 J m=2
P =
ud
J0
Pa
sphere reduced to the optical mass value which equals 2. (3) Figure 2 presents the vertical distribution of the at-
tenuation of the direct solar radiation in the ideal atmosphere up to 5 km elevation from the sea level.
0,200 0,190 0,180 0,170 0,160 0,150 0,140 0,130 0,120 0,110 0,100
h, m
1000
2000 3000 4000 5000
Figure 2. Vertical profile of the normalized factor of the attenuation of the direct solar radiation in the ideal atmosphere
In (Table 1.) Pud values are given for the actinometrical stations of Uzbekistan.
Table 1.- P values for the actinometrical stations of Uzbekistan
0
Station Elevation, m Pug
1 2 3
Tashkent 477 0.17
Fergana 578 0.16
Samarkand 726 0.16
1 2 3
Karakalpakiya 124 0.18
Takhiatash 76 0.19
Tamdy 236 0.17
Termez 308 0.17
Kyzylcha 2070 0.14
Attenuation of direct solar radiation by water vapor is calculated with the Meller's formula [2]:
AJ = 0.172(mWja303, (4)
where: AJ - intensity of radiation absorbed with the water vapor in cal/sm2 min, m = 2 - optical atmosphere mass, W^ - the layer of deposited water in sm.
The layer of deposited water is calculated with empirical formula (5):
W^= 0.163e + 0.367, (5)
where: e - water vapor pressure. This formula was derived by Yu. V. Petrov and Kh. T. Egamberdiev for the conditions of Uzbekistan.
Attenuation of the direct solar radiation with the water vapor is calculated with formula:
(6)
p -J
as j ' ' 0
where: AI - intensity of radiation absorbed with the water vapor in kWt/m2,
Jo - solar constant which is 1.367 kWt/m2. Attenuation of the direct solar radiation with atmospheric aerosol is calculated as the remainder term in the equation (1).
Table 2.- Attenuation of the direct solar radiation with the water vapor (PaB) and atmospheric aerosol(P) on the selected stations of Central Asia
Station months
March May July September November
P as P aa P as P aa P as P aa P as P aa P as P aa
Aral Sea [3] 0.12 0.07 0.13 0.12 0.15 0.13 0.13 0.08 0.11 0.04
Tashkent[3] 0.12 0.09 0.14 0.13 0.14 0.15 0.13 0.15 0.12 0.09
Ashgabad [3] 0.12 0.11 0.14 0.16 0.15 0.20 0.13 0.19 0.12 0.10
Tashkent [a*] 0.12 0.16 0.13 0.20 0.14 0.21 0.13 0.20 0.12 0.16
* the author's data
Table 2 presents the values of attenuation of the direct solar radiation with water vapor and atmospheric aerosol for the actinometrical stations of Central Asia which are characterized with similar physical-and-geographic conditions. The data are taken from the monograph [3], where the data of actinometrical observations for the first half of XXth century are generalized. Separate row presents the author's calculations made by the data of observations for the last decades. Analysis of data presented in the table gives the ground to make the following conclusions. First, there is no difference between the values of attenuation of the direct solar radiation with water vapor, both between the stations and the values measured at the same station (Tashkent) for the different periods of time. In addition, the data of the direct measurements of the water layer deposited in atmosphere which were
obtained in Astronomy Institute of the Academy of Sciences of the Republic of Uzbekistan were used. From these data it follows that this layer in May of 2015 was 14-17 mm which corresponded to the attenuation factor of 0.12-0.13. This result does not differ too much from our calculation data. It proves that we used the formula applied for calculation of attenuation of the direct solar radiation with water vapor correctly. Second, attenuation of the direct solar radiation with aerosol in Tashkent during the last years increased 1.4-1.8 times comparing with the first half of XXth century. Third, the input of atmospheric aerosol to the general attenuation of the direct solar radiation increased during these years.
Conclusions. Thus, the technique for calculation of new index of the atmosphere transparency is proposed: the normalized factor of the solar radiation
attenuation in the Earth atmosphere. The graph for posed for attenuation of the direct solar radiation with
estimation of the attenuation of the direct solar radia- the account of physical-and-geographic conditions of
tion in the ideal atmosphere depending on the height Uzbekistan. Attenuation of the direct solar radiation
of the point of actinometrical measurements is con- with atmosphere aerosol is calculated as the reminder
structed. The empiric factor in Meller's formula is pro- term in equation (1).
References:
1. Kastrov V. G. Selected works on the physics of atmosphere. Gidrometeoizdat. - L.,- 1979.- 328 p.
2. Prokhorov A. (chief editor). Physical encyclopedic dictionary.- Moscow. Pub. "Soviet Encyclopedy", - 1984.945 p.
3. Radiation characteristics of atmosphere and Earth surface. Edited by Kondratjev K. Ya. Gidrometeoizdat. - L.,-1969.- 564 p.
4. Sivkov S. I. Methods of calculation of the solar radiation characteristics. Gidrometeoizdat, - L.,- 1968.
