Campaign : Cloudiness Inter-Comparison IOP

2003.02.21 - 2003.04.21

Lead Scientist : Chuck Long

Data Availability

By agreement, preliminary quality assessed guest instrument data were delivered to the ARM IOP Archive for access by the IOP participants.

For data sets, see below.


The Cloudiness Inter-Comparison IOP, conducted operations February 21 through April 21, 2003. During this period, the skies over the SGP Central Facility exhibited a wide variety of cloud types and amounts: exactly what the IOP participants were hoping for. For example, the daylight periods were nearly clear (sky cover <10%) about 25% of the time, mostly cloudy (sky cover >90%) about 44% of the time, and varying degrees of partly cloudy the remaining 31% of the time. The cloud conditions ranged from episodes of overcast and rain, to cumulus cloud fields, through high cirrus and multiple layer cases.

Both the ARM standard and IOP guest instruments critical to the IOP remained operational for the most part during the two month period. Each guest instrument managed a fairly high amount of operational time for the IOP. This was largely accomplished with the diligent daily care and feeding provided by SGP Operations, which also on occasion included support of a more technical nature. In addition, the ARM spares which were "borrowed" for the IOP were fortunately not needed elsewhere during the two months of the IOP.


The most basic cloud "measurement" is whether there are clouds present, and if so to what amount. Various means have been used to infer a "cloud amount" on various time scales. At the same time, questions of what spatial scales these various means represent at what time scales remain ill defined. In addition, retrieval of night time cloud amounts is limited by our currently fielded instrumentation.

The Cloudiness Intercomparison IOP was designed to address some of these fundamental questions, and to field test and compare some new ideas for measuring cloudiness, particularly at night.

Campaign Data Sets

IOP ParticipantData Source DescriptionFinal Data
LongHemispheric Sky Imager Order Data
LongScanning IRT Order Data
MorrisMicrowave Water Radiometer Order Data
TakaraAERI Cloud Fraction Order Data
TakaraScanning IRT Order Data
GenkovaCloud Infrared Radiometer (a.k.a. Nephelo) Order Data