日际变化 meaning in English

interdiurnal change
interdiurnal variation

Diurnal variation of uv index on a sunny day
在阳光充沛的日子里，紫外线指数的日际变化。
Figure 5 diurnal variation of uv index on 2 august 1999
图五紫外线指数在1999年8月2日的日际变化。
Diurnal variation of uv index on 14 august 2001 a sunny day with some 12 hours of sunshine
图三紫外线指数在2001年8月4日的日际变化。
Figure 4 diurnal variation of uv index on 2 august 1999 . the showers around noon on that day drove down the uv index but it rose to the level of 8 to 9 in the afternoon when the showers eased off
图四紫外线指数在1999年8月2日的日际变化。当日中午时份的骤雨令紫外线指数下降，但下午骤雨过后紫外线指数又回升到8至9之间。
The biggest diurnal albedo is 0 . 24 and the smallest 0 . 11 . moreover , the peak occurs on the day that radiation is very strong and the soil surface is dry and the valley appears on the day that rainfall is much more before this day and the soil water content of upper layer is high
就反射率的日际变化而言，最大反射率为0 . 24 ，最小为0 . 11 ，相差一倍以上，其峰值均出现在辐射比较强，地表比较干燥的日期，而谷底一般是在前期降雨较大，表层土壤湿润时出现。