annual mean的用法和样例：
例句
- The latter factor drops out when average annual temperatures are considered.
若考虑年平均温度，则可将后一个因素除掉。 - Although the prevalence increased with age, the annual change in mean refractive status was slower in the schoolchildren of mountain aborigines.
尽管年龄愈高，近视盛行率愈高，但原住民学童之年平均屈光变化似乎较缓慢。
