Do you see the difference between “The year that just ended was bad for crops” and “This year, which has been dry, was bad for crops”? With “this year,” we already know which year the writer is talking about: you could write with perfect clarity, “This year was bad for crops.” You could also write, “The year was bad for crops,” but in the context you’d need to know what year was meant; adding “that just ended” identifies the year.