Cloud occurrence and layering at Arctic atmospheric observatories

Cloud occurrence fraction determines the first order impact of clouds on the climate system. This collection of data sets documents cloud occurrence and, to the degree possible, cloud vertical distribution at multiple locations across the Arctic. Observations are based on the available surface-based, remote-sensor measurements. From this perspective, the definition used here for cloud presence is based on the ability for remote-sensors to detect hydrometeors in the atmosphere. While an attempt has been made to maintain a consistent definition of cloud occurrence across the many observatories, each has a unique set of cloud observations instruments.