自1992年以来，自动气象观测系统逐渐取代了手动观测系统。新的自动化系统采用了新的观测采样频率、报告值的时间平均、观测和仪器的实时质量评估，这些都包括了与手动观测相比的优点和缺点。人工观察者和自动化系统使用的仪器和方法之间的这些差异给观测带来了偏差，这些数据的用户必须意识到这些偏差。其中包括美国国家气象局的自动地面观测系统（ASOS）观测到的干球温度和风速的负偏差。此外，ASOS无法探测12600英尺以上的云层，这是使用天气观测进行建筑能耗计算时最具影响力的差异之一。 已经开发了一个利用ASOS观测值估算每小时全球水平、垂直和漫反射水平太阳辐射的模型。以前开发的太阳辐射模型需要人类气象观察员的输入数据，并且不考虑使用ASOS等观测系统的数据时引入的偏差。由于云高计的空间限制，ASOS报告的晴朗天气小时数几乎是原来的两倍。同样，手动观察者报告，在大多数天空条件下，云层覆盖的频率更高。此外，更高的云检测垂直分辨率使ASOS能够区分由小高度分隔的云层。由于使用ASOS代替手动观察仪，因此有必要计算用于太阳辐射估算的新模型透过率。除了新的透射率，还使用更新的方法来解释多个云层相互作用发生时的情况。

Automated weather observing systems have provided gradual replacement of manual observers since 1992. New automated systems implemented the use of new observation sampling frequencies, temporal averaging for reported values, real-time quality assessment of observations and instrumentation that include both advantages and disadvantages over manual observers. These differences between instrumentation and methods used by manual observers and automated systems introduced biases into observations that users of these data must be aware of. These include negative biases for dry-bulb temperature and wind speed observed by the U.S. National Weather Service’s Automated Surface Observation Systems (ASOS). Additionally, the inability of ASOS to detect cloud cover above 12,600 feet is one of the most influential differences when using weather observations for building energy calculations.A model that uses observations from ASOS to estimate hourly global horizontal, direct normal and diffuse horizontal solar radiation has been developed. Previously developed solar radiation models require input data from human meteorological observers and do not account for biases introduced when using data from observing systems such as ASOS. Nearly twice as many hours with clear conditions are reported by ASOS because of the spatial limitations of ceilometers. Likewise, manual observers report a higher frequency of cloud cover for most sky conditions. Also, greater vertical resolution of cloud detection gives ASOS the ability to distinguish cloud layers that are separated by small heights. Changes such as these resulting from the use of ASOS instead of manual observers made it necessary to calculate new model transmissivities used for solar radiation estimation. In addition to new transmissivities, updated methods are used to account for conditions when multiple cloud layer interactions occur.