VIEWS: 24 PAGES: 4 CATEGORY: Emerging Technologies POSTED ON: 2/13/2010
The new method for measuring of aerosol optical thickness is suggested
ON POSSIBILITY OF MEASUREMENTS OF RELATIVE WAVELENGTH DEPENDANCE OF OPTICAL DENSITY OF ATMOSPHERIC AEROSOL USING THREE WAVES METHOD H.H. ASADOV, E.S. ABBASZADEH Azerbaijan National Aerospace Agency, Azadlig ave., AZ1033, Baku, Azerbaijan email@example.com Keywords: optical density, atmospheric aerosol, measurements, compensation of errors According to the Beer’s Law aerosol is one of major components of atmosphere leading to absorbtion of UV irradiation. Existing methods for measurement of optical density of aerosol (Langley method and others) do not guarantee the necessary accuracy, because they do not envisage compensation or full mutual compensation of such factors as ozone ansorbtion and Reyleigh scattering. The Three Waves method [1, 2] designated for high accuracy ozone measurement also can be used for measurements of optical density of aerosol. According to the proposed method, measurements are to be carried out in three points: 1 , 2 and 3 . Where 1 2 3 . As a result we shall obtain appropriate itensivities of solar radiation I 1 , I 2 and I 3 . Then we should carry out calculation using following formula: I 1 I 3 I k , (1) I 2 where k 2 ; - varying index. For simplicity we assume that optical masses of aerosol, ozone and Reyleigh scattering are equal. In this case the Beer formula may be written as I I 0 A m X , (2) 2 where I 0 - initial intensity; m -optical mass, conditionally same for all components; X -total amount of ozone; , , - optical densities of ozone, Reyleigh scattering and aerosol. Taking into consideration formulaes (1) and (2) we conclude, that 3 3 3 k I 0 1 I 03 m X 1 2 m 1 2 m 1 2 I A 2 2 2 . (3) I 0 2 Using formula (3) we should carry out following steps for measuring of aerosol optical density: 1. Measurements by compensation of influence of ozone. The condition for said compensation is following 1 3 21 . (4) 2 Condition (4) can be reached by appropriate selection of wavelength 21 . Taking into consideration formulaes (3) and (4) we have 3 3 l n I1 m 1 21 m 1 21 . (5) 2 2 2. Measurements by compensation of influence of Reyleing scattering. The condition for said compensation is following: 1 3 22 . (6) 2 Taking into consideration formulaes (3) and (6) we have 3 3 l n I2 m X 1 22 m 1 22 . (7) 2 2 Now, by substraction of formula (7) from formula (5) we can obtain following formula expressing interrelation of increments I1 ln m X m , (8) I2 where 1 3 21 2 3 1 3 22 2 . 2 1 It is obvious, that for concrete time and point of measurements m X c o n s t . In this case we can measure relative increments of optical density of atmospheric aerosol within wavelength interval 21 22 . Carrying out n series of experiments ensuring partial overlap of adjacent interval i we can construct the resulting relative functional dependence f , which is illustrated in figure 1. It should be noted also, that obtained formula of increments (8) also makes it possible to carry out fast evaluation of disperse content of aerosol, i.e. shares of fine and coarse particles within aerosol content. In conclusion we would stress out that proposed three waves method as real alternative for Dobson’s method makes it possible to carry out also other interesting measurements which proves its universal feature. 1. Patent of Azerbaijan Republic. No. a20030134 dated 23.06.03. Three waves ozonometer. Authors: Asadov H.H. and Isayev A.A. 2. Asadov H.H., Isayev A.A. Three waves method for measurement of total content of ozone. Full compensation of measurements error. Proceedings Quadrennial Ozone Symposium, 1-8 June 2004, Kos, Greece, v.1, p. 477. 4 1 2 3 4 212 222 214 2 211 221 213 223 224 Figure 1.
"New method for measuring of aerosol optical thickness"