Friday, October 18, 2013

Simple 2D simulation of the Phailin Cyclone

It was the time of Dashain festival here at Nepal in 2013, which falls during the autumn season. The rainy season was supposed to have ended by then, but it had been raining for a couple of days and it was mainly because of the Tropical Cyclone Phailin that had hit the south eastern coast of India. No, the cyclone didn't reach Nepal, but it did send clouds here.
Source: Cooperative Institute for Meteorological Satellite Studies

Here is my simplified 2D simulation of the Phailin Cyclone I did using the instantaneous vorticity data as initial condition. I mainly solve the 2D Navier-Stokes equation using a forth order finite difference scheme in MATLAB.

Monday, July 8, 2013

A scar on Annapurna that had caused the Seti Flood of 2012

I had been going through different articles and papers about the Seti Flash Flood of 2012 and, I wanted to try out something for myself.

On May 5th of 2012, a flash flood full of debris, triggered in the Seti river, had devastated different parts of Pokhara with an estimated 71 people killed. A unique thing about this flood was that, it was probably triggered by an avalanche near the Annapurna range. This triggering of the avalanche was actually captured in tape by a Russian pilot who was flying over the same area at the time of avalanche, and about 40 minutes after the avalanche, the devastating  flood hit Pokhara. One of the most comprehensive reports on the cause of the flood should be the report prepared by Dr. NP Bhandary, Dr. RK Dahal and Prof. M Okamura based on their field visit (Bhandary et al. 2012).

Initial speculations on what might had caused the flood ranged from intensive rainfall-cloudburst flood, possible GLOF (Glacial lake outburst flood) as well as LDOF (Landslide Dam Outburst Flood). But no significant evidences supporting the latter two were found in the field. Also, the flood had occurred way before the monsoon, reducing the possibility of cloudburst flood . Looking at the devastation and magnitude of the flood, initiation of such a flood would require a huge source of water (millions of cubic meters) and these speculations couldn't properly explain the source of such a huge quantity of water.