视频不对吧 https://www.weather.gov/ffc/pop What does this "40 percent" mean? ...will it rain 40 percent of of the time? ...will it rain over 40 percent of the area? The "Probability of Precipitation" (PoP) simply describes the probability that the forecast grid/point in question will receive at least 0.01" of rain. So, in this example, there is a 40 percent probability for at least 0.01" of rain at the specific forecast point of interest!
edit：以上PoP针对某一点 对一个大范围进行预测的时候，PoP是一个概率的平均值 https://www.wesh.com/article/what-does-a-chance-of-rain-really-mean/4440726 Mathematically, PoP is defined as follows: PoP = C x A where "C" = the confidence that precipitation will occur somewhere in the forecast area, and where "A" = the percent of the area that will receive measurable precipitation, if it occurs at all. So... in the case of the forecast above, if the forecaster knows precipitation is sure to occur (confidence is 100%), he/she is expressing how much of the area will receive measurable rain. (PoP = "C" x "A" or "1" times ".4" which equals .4 or 40%) But, most of the time, the forecaster is expressing a combination of degree of confidence and areal coverage. If the forecaster is only 50% sure that precipitation will occur, and expects that, if it does occur, it will produce measurable rain over about 80 percent of the area, the PoP (chance of rain) is 40%. ( PoP = .5 x .8 which equals .4 or 40%. )
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edit：以上PoP针对某一点 对一个大范围进行预测的时候，PoP是一个概率的平均值 https://www.wesh.com/article/what-does-a-chance-of-rain-really-mean/4440726 Mathematically, PoP is defined as follows: PoP = C x A where "C" = the confidence that precipitation will occur somewhere in the forecast area, and where "A" = the percent of the area that will receive measurable precipitation, if it occurs at all. So... in the case of the forecast above, if the forecaster knows precipitation is sure to occur (confidence is 100%), he/she is expressing how much of the area will receive measurable rain. (PoP = "C" x "A" or "1" times ".4" which equals .4 or 40%) But, most of the time, the forecaster is expressing a combination of degree of confidence and areal coverage. If the forecaster is only 50% sure that precipitation will occur, and expects that, if it does occur, it will produce measurable rain over about 80 percent of the area, the PoP (chance of rain) is 40%. ( PoP = .5 x .8 which equals .4 or 40%. )
所以视频里说的“100%确认在30%面积有雨”只是30%PoP的一种解读 也有可能是“50%确认在60%面积有雨”，等等 所以视频说的不对