But because clouds take different forms at different scales ? from microscopic water droplets to weather fronts that span hundreds of kilometres ? they are devilishly hard to describe in models that work by manipulating “ virtual ” chunks of the atmosphere that are 100km ( 62 miles ) across and 100km high 但由于云层以不同形式出现于不同的范围之内（有的以精微的小水点存在，有的则以数百公里的气象锋面出现） ，因此在气候模式中很难去描述云层，并且其工作原理只能是操控虚拟的大气块100公里（ 62英里）宽与100公里高。
