Francesca Forni^1,2, Steffen Eisele^1,2, Marcus Phua^1,2, Marcel Guillong³, Jeffrey Oalmann^1,2, Hamdi Rifai⁴, Rizaldi Putra⁴ and Caroline Bouvet de Maisonneuve^1,2, (1)Nanyang Technological University, Asian School of the Environment, Singapore, Singapore, (2)Earth Observatory of Singapore, Singapore, Singapore, (3)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (4)Universitas Negeri Padang, Department of Physics, Faculty of Mathematics and Natural Sciences, Padang, Indonesia