Abstract: | Water scarcity is a pressing global challenge exacerbated by population growth and climate change. While various solutions exist to address limited water supply, rainfall triggering techniques have garnered significant attention since the 1950s [1]. Cloud seeding, the most common method, involves dispersing chemicals like Silver Iodide or dry ice into clouds. Subsequently, other techniques have been explored to address the limitations of cloud seeding. Filament produced by intense ultrafast laser pulses is found to induce water condensation in air [2]. Femtosecond laser’s interaction with air molecules results in ionization and dissociation, leading to the formation of diverse compounds via photo-oxidation reactions that can serve as cloud condensation nuclei (CCN). Ammonium nitrate formed by laser-induced condensation, trace gases like SO2 and oxidize volatile organics can lead to particle growth [3]. Thus, it is imperative to investigate the ionization processes in-situ and monitor the constituents in the atmosphere. Remote Filament-induced breakdown spectroscopy (FIBS) has been utilized to probe clouds of aqueous aerosols containing a mixture of PbCl2, CuCl2, FeCl2, and NaCl, demonstrating its capability as a sensitive technique for remotely determining the composition of microdroplets in distant clouds [4]. Previous report [4] has utilized Chirp Pulse Amplification (CPA) Ti: Sapphire laser system delivering pulses at a repetition rate of 10 Hz. In contrast, high-repetition-rate, intense ultrafast lasers present several advantages for remote sensing applications, especially due to their capacity for rapid data collection, which enables near-real-time monitoring of changing atmospheric conditions and cloud dynamics. This research employs a high-repetition-rate femtosecond laser source operating at maximum rate of 10 kHz to create the filament in a controlled laboratory setting with variable pulse parameters. The filaments are characterized using optical emission spectroscopy and imaging techniques. The optical emission spectra of the filaments exhibit various features corresponding to N₂, N₂⁺, and neutral oxygen atoms (O I). Solid targets have been used to conduct filament-induced breakdown spectroscopy remotely. This research aims to detect air molecules and aerosols present in the ambient air, providing deeper insights into the condensation nuclei required for precipitation. By advancing our understanding of these processes, this study contributes to the development of more efficient and environmentally friendly rainfall triggering techniques, potentially offering a sustainable solution to water scarcity challenges.
[1] Singh et al. (2023). Safety Concerns and Consequences of Cloud Seeding Implications—A Systematic Review. In: Siddiqui, N. A., Baxtiyarovich, A. S., Nandan, A., Mondal, P. (eds) Advances in Waste Management. AIR 2021. Lecture Notes in Civil Engineering, vol 301. Springer, Singapore.
[2] Rohwetter et al. Nature Photon 4, 451–456 (2010).
[3] Sun et al. Opt. Express 24, 20494 (2016).
[4] Daigle et al. Opt. Commun. 278, 147–152 (2007). |
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