2022-02-19

Only the BBC could invent this?

Climate change: Covid shutdown linked to record rainfall in China

As I recall, super-cooled water vapour remains as a vapour - until it meets a catalyst such as aerosol particles, when it breaths a huge sigh of relief and condenses around them, forming snow particles or water droplets depending on conditions.

It's a bit like a sugar concentrate in water - when the concentration reaches saturation, any disturbance will cause a sudden crystallisation of the sugar, separating it out. 

The same thing happens in a cloud - as warm air rises the pressure drops, the volume expands and the temperature drops, reducing the capacity of the air to dissolve the water vapour. If it was warm enough initially, it reaches such a height that it becomes saturated, but precipitation requires a catalyst of some sort. In the absence of a catalyst, super-cooling, where the air becomes super-saturated, occurs.

The early experiments in making rain were successful because they seeded the clouds with various small particulates, enabling raindrops to condense out. If that happens suddenly (as in cloud seeding) the resulting downpour will likely cause localised flooding.

So if the small particulates and aerosol particles are reduced due to lockdowns etc, we should have less rain rather than more (all other things being equal).

On that basis, then it's sorry BBC, "null points".

Of course other factors may be at play, such that a reduction in particles over western countries such as Myanmar might cause water that would have fallen over Myanmar / India / Bangla Desh / Nepal to be carried further east over the Himalayas to be precipitated over China - none of these countries would seem to be rich enough that the non-affluent majority would cease to burn any available fuel for cooking and heating (and a number of these mostly escaped the depredations of Covid for whatever reason), so this possibility seems unlikely.

The James Neil Cooper channel often shows wind and weather conditions over China, and he has been assiduously reporting on the flooding this past year - as he does every year, it being a seasonal phenomenon.

So is the BBC right or wrong? It's your judgement hat counts.