In an effort to clear all this up, we called 12345, the Beijing City General Hotline for Non-Emergency Issues, listed by the city government as the place to call for updates on pollution alerts. The person on the other end of the phone said they he had no idea what time alerts were issued, and would look it up and call us back. That response was not received at press time.
The hotline called me back this morning. I give them credit for doing so. The guy on the other end of the phone told me to call 12121 for the bureau of weather forecast (气象局) for the answer to my question. I thanked him and hung up the phone.
Then I dialed 12121, but it turned out that the number didn't go to any government office. Instead it is a 100% automated weather forecast hotline and you pay 0.3 RMB/minute to listen. The whole thing is 100% automated---there isn't even an option for "speaking with an assistant/operator".
So finally what they found for me was a goddamn automated weather forecast hotline and they told me that's the number of the the bureaur of weather forecast and that's where I can get my asnwer---that really irritates me.