bug for canopy interception for crop sprinkler irrigation

[cenlinhe]

https://github.com/NCAR/noahmp/blob/fa2d2098bac1e437a21ccc15494b152996d5bc84/src/CanopyWaterInterceptMod.F90#L86C60-L86C74

The PrecipAreaFrac needs to be updated when there is sprinkler irrigation water intercepted by crop canopy but no rain. CUrrently, PrecipAreaFrac will be zero for no rain days even there is sprinkler irrigation, which leads to zero intercepted water by crop canopy for sprinkler irrigation.

[cenlinhe]

@tslin2 @CharlesZheZhang Please take a look at this issue when you have time and include your thoughts as comments. Thanks!

[tslin2]

Yes, this is a bug.

Sprinkler irrigation is more like the large-scale precipitation than convective precipitation; however, it depends on other factors like the system and kind of sprinkler; therefore, the fraction of area getting precipitation (PrecipAreaFrac) might be taken to equal 1.0.

For conventional sprayheads, precipitation rates typically range from 1.3 inches to 2 inches per hour. For gear drive rotors, precipitation rates typically range from 0.4 inch to 1 inch per hour. For rotary nozzles, precipitation rates typically range from 0.4 inch to 0.6 inch per hour. (https://www.landscapemanagement.net/know-your-sprinkler-precipitation-rate/)