Shuāngchóng xìngyùn means "double lucky" in Mandarin. On my trip to China from the last part of March to the first half of April 2010; I was lucky twice.
A week or so before I arrived in Beijing, there was a terrible sand storm which would have halted photography (and just about anything else) totally. Here is a China News Photo of the sandstorm.
The day I arrived in Beijing, it was unusually clear and crisp allowing great imagery of the Great Wall (pun intended). I didn't end up with the smog obscurred Wall images I have seen so many times.
Later, I spent a couple of days in Guilin and Yangshou during the first week of April. There had been a drought at the headwaters of the LI River and I complained that the river was low. Here is a shot of my tour bus in Guilin.
And here is a China News shot of a tour bus in the same general area of that city on 17 April 2010 after immense rainfall caused the Li River to overflow its banks. WOW - I was double lucky on that trip! Lucky on the Wall and lucky that I didn't get my wish that the river had more water.