Study of Laser Scintillation in Different Atmospheric Conditions

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  • 1 Indian Institute of Tropical Meteorology, Pune, India
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Abstract

Laser scintillation observations were carried out over a flat surface in different atmospheric conditions on 33 separate days during March 1990–April 1991 and were analyzed and studied. The principal results of the analysis reveal (i) marked seasonal variations in optical turbulence (through the measurement of refractive-index structure function Cn2) and scintillation intensity (measured in terms of percent modulation Pm) with maximum Cn2 or Pm during winter (December–February) and minimum during premonsoon (March–May) seasons; (ii) close correspondence among the variations in Cn2, Pm, and atmospheric temperature; (iii) lower values of Cn2 during cloudy sky as compared to clear sky conditions; and (iv) agreement between the observations and theory in respect of the pathlength dependence of Cn2 and Pm. The results are discussed with reference to the possible meteorological origin of turbulence, and the importance of the study for making measurements of optical turbulence remotely over inaccessible regions is highlighted.

Abstract

Laser scintillation observations were carried out over a flat surface in different atmospheric conditions on 33 separate days during March 1990–April 1991 and were analyzed and studied. The principal results of the analysis reveal (i) marked seasonal variations in optical turbulence (through the measurement of refractive-index structure function Cn2) and scintillation intensity (measured in terms of percent modulation Pm) with maximum Cn2 or Pm during winter (December–February) and minimum during premonsoon (March–May) seasons; (ii) close correspondence among the variations in Cn2, Pm, and atmospheric temperature; (iii) lower values of Cn2 during cloudy sky as compared to clear sky conditions; and (iv) agreement between the observations and theory in respect of the pathlength dependence of Cn2 and Pm. The results are discussed with reference to the possible meteorological origin of turbulence, and the importance of the study for making measurements of optical turbulence remotely over inaccessible regions is highlighted.

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