Clouds

	The variable properties of clouds determines the clouds profound effects on radiation and precipitation. They are influenced by and in turn influence the motion of the atmosphere on many scales. They are affected by the presence of aerosols, and modify atmospheric composition in several ways, including the depletion of ozone when they form in the polar stratosphere.
	Domain:	Atmosphere
	Subdomain:	Atmospheric Composition
	Scientific Area:	Hydrosphere
	ECV Steward:
	Products:	Cloud Cover, Cloud Optical Depth, Cloud Liquid Water Path, Cloud Ice Water Path, Cloud Drop Effective Radius, Cloud Top Temperature, Cloud Top Height

Global Cloud Cover

Figure: Climatological mean total cloud fraction averaged over 26-year period (1984–2009) from Climate Monitoring Satellite Application Facility (CM SAF) Cloud, Albedo (CLARA-A2). The CM SAF project is a part of the ground segment of the European organization for the exploitation of meteorological satellites (EUMETSAT).

Source: Karlsson, K.-G.; Devasthale, A. Inter-Comparison and Evaluation of the Four Longest Satellite-Derived Cloud Climate Data Records: CLARA-A2, ESA Cloud CCI V3, ISCCP-HGM, and PATMOS-x. Remote Sens. 2018, 10, 1567.

ECV Products and Requirements

These products and requirements reflect the Implementation Plan 2022 (GCOS-244).

The requirements are found in the complete 2022 ECVs Requirements document as well: ECV Clouds.

Products			Cloud cover	Cloud Optical Depth		Cloud Liquid Water Path	Cloud Ice Water Path
	(*)	Unit	Values	Values	Unit	Values	Values
Horizontal Resolution	G	km	25	25	km	25	25
	B		100	100		100	100
	T		500	500		500	500
Vertical Resolution	G		-	-
	B		-	-
	T		-	-
Temporal Resolution	G	h	1	1	h	1	1
	B		24	24		24	24
	T		720	720		720	720
Timeliness	G	h	1	1	h	1	1
	B		3	3		3	3
	T		12	12		12	12
Required Measurement Uncertainty (2-sigma)	G	%	3	20	Kg m-2	0.05	0.05
	B		6	40		0.1	0.1
	T		12	80		0.2	0.2
Stability	G	%/ decade	0.3	2	Kg m-2/ decade	0.005	0.005
	B		0.6	4		0.01	0.01
	T		1.2	8		0.02	0.02

Products			Cloud Drop Effective Radius		Cloud Top Temperature		Cloud Top Height
	(*)	Unit	Values	Unit	Values	Unit	Values
Horizontal Resolution	G	km	25	km	25	km	25
	B		100		100		100
	T		500		500		500
Vertical Resolution	G		-		-		-
	B		-		-		-
	T		-		-		-
Temporal Resolution	G	h	1	h	1	h	1
	B		24		24		24
	T		720		720		720
Timeliness	G	h	1	h	1	h	1
	B		3		3		3
	T		12		12		12
Required Measurement Uncertainty (2-sigma)	G	µm	1/2	K	2	km	0.3
	B		2/4		4		0.6
	T		4/8		8		1.2
Stability	G	µm/ decade	0.1/0.2	K/decade	0.2	km/ decade	0.03
	B		0.2/0.4		0.4		0.06
	T		0.4/0.8		0.8		0.12

(*) Goal (G): an ideal requirement above which further improvements are not necessary. Breakthrough (B): an intermediate level between threshold and goal which, if achieved, would result in a significant improvement for the targeted application. The breakthrough value may also indicate the level at which specified uses within climate monitoring become possible. It may be appropriate to have different breakthrough values for different uses. Threshold (T): the minimum requirement to be met to ensure that data are useful

Data Sources

This list provides sources for openly accessible data sets with worldwide coverage for which metadata is available. It is curated by the respective GCOS ECV Steward(s). The list does not claim to be complete. Anyone with a suitable dataset who wishes it to be added to this list should contact the GCOS Secretariat.

Reanalysis:

REANALYSES.ORG (Inventory for Reanalysis)

Satellite:

Satellite ECV Inventory by the CEOS/CGMS Working Group on Climate (WGClimate)