Clouds

A factsheet cover for Essential Climate Variable (ECV) on clouds, featuring a sky full of clouds and logos of related climate organizations.
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.

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 coverCloud Optical Depth  Cloud Liquid Water PathCloud Ice Water Path
 (*)UnitValuesValues UnitValuesValues
Horizontal ResolutionGkm2525 km2525
B100100 100100
T500500 500500
Vertical ResolutionG --    
B--   
T--   
Temporal ResolutionGh11 h11
B2424 2424
T720720 720720
TimelinessGh11 h11
B33 33
T1212 1212
Required Measurement Uncertainty (2-sigma)G%320 Kg m-20.050.05
B640 0.10.1
T1280 0.20.2
StabilityG%/ decade0.32 Kg m-2/ decade0.0050.005
B0.64 0.010.01
T1.28 0.020.02
Products Cloud Drop Effective Radius  Cloud Top Temperature  Cloud Top Height
 (*)UnitValues UnitValues UnitValues
Horizontal ResolutionGkm25 km25 km25
B100 100 100
T500 500 500
Vertical ResolutionG -  -  -
B- - -
T- - -
Temporal ResolutionGh1 h1 h1
B24 24 24
T720 720 720
TimelinessGh1 h1 h1
B3 3 3
T12 12 12
Required Measurement Uncertainty (2-sigma)Gµm1/2 K2 km0.3
B2/4 4 0.6
T4/8 8 1.2
StabilityGµm/ decade0.1/0.2 K/decade0.2 km/ decade0.03
B0.2/0.4 0.4 0.06
T0.4/0.8 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 abombelliatwmo [dot] int (GCOS Secretariat).

Reanalysis:


Satellite:

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