Winter is very clean nowadays in Beijing which was like a dream for the native Beijing people a decade ago as the industries and the sandstorm from the north-western desert degrade the air quality. Also the eyesight becomes very short during this dry season with no clear view of the sun and blue sky becomes white.
But in recent years the air quality becomes so clean and air quality is excellent with crystal views. The clean view becoes so beautiful with deep blue sky and the surrounding sight is more colorful and bright with the shining sun in the clear blue sky.
When I was exploring the mountain region of the Huairou district, I found this amazing incident with two airplanes and there was one running rocket engine that was creating the white line with burning fuel. It was a sudden views and I have clicked some imgaes back to back with this amazing blue beauty with my phone.