A rare occurrence of stratospheric cirrus at 18.6 km height persisting for about 5 days during 3-7 March 2014 is inferred from the ground-based Mie lidar observations over Gadanki (13.5° N, 79.2° E) and spaceborne observations. Due to the vertical transport by large updrafts on 3 March in the troposphere, triggered by a potential vorticity intrusion, the water vapour mixing ratio shows an increase around the height of 18.6 km. Relative humidity with respect to ice is ∼ 150%, indicating that the cirrus cloud may be formed though homogeneous nucleation of sulfuric acid. The cirrus cloud persists due to the cold anomaly associated with the presence of a 4-day wave.
Sandhya, M., Sridharan, S., Devi, M. I., Niranjan, K., & Jayaraman, A. (2015). A case study of formation and maintenance of a lower stratospheric cirrus cloud over the tropics. Annales Geophysicae, 33(5), 599–608. https://doi.org/10.5194/angeo-33-599-2015