The light is different. And the way the air feels. Not just because of the pollution, which is everpresent in Beijing, even when it is not polluted. Those rare days are experienced in heightened joy exactly because there is (almost) no pollution.
But also on those clear days one feels the air is very different from what I am used to in northern Europe. Must be the humidity. Beijing air cracks my skin half of the time. In winter, when pollution is at it's worst, and in early spring, when the sandstorms come, it doesn't just crack it, it blasts the skin, parches it, wraps it in dust and soot.
More so, even, in Song Zhuang, where I had my studio for two years, where the buildings were heated with old coal stacks, their low, small chimneys barely higher then the rooftops, the smoke they bellowed ominously darkbrown. That heating, which I paid for inclusive in the yearly rent, was not really heating. It kept the studio from freezing in winter, which meant it was about 6 degrees celcius in there during winter months. Acrylic becomes less fluid then. And painting for more then three hours becomes a really cold endeavour, even in old ski clothes.
For that reason, I did not go to my studio in the winter months, and every time I returned in march, the dust was piled up half a centimetre inside. I did not have an air purifyer there. I have made many a brushstroke with a slight headache. That is how it goes.