**[Atmospheric and Ocean Variables (Parameters)]{.underline}**

> State and feedback variables required for the major components of
> climate observations and analysis. In parenthesis, (I/S) denotes
> measurements made by In-situ and Remote (Space-based) instruments from
> operational or systematic (research) observing systems/networks.

+-----------------------------------------------------------------------+
| +-------------------------+---------------------------------------+   |
| | **STATE VARIABLE        | **FEEDBACK VARIABLES**                |   |
| | (PARAMETERS)**          |                                       |   |
| +-------------------------+---------------------------------------+   |
| | **(1) ATMOSPHERE**      |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • wind (I/S )           |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • upper air temperature | • land surface soil                   |   |
| | (I/S)                   | moisture/temperature (I/S)            |   |
| +-------------------------+---------------------------------------+   |
| | • surface air           | • land surface structure and          |   |
| | temperature (I/S)       | topography (I/S)                      |   |
| +-------------------------+---------------------------------------+   |
| | • sea level pressure    | • land surface vegetation (I/S)       |   |
| | (I)                     |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • upper air water vapor |                                       |   |
| | (I/S)                   |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • surface air           | • evaporation and evapotranspiration  |   |
| | humidity/wv (I/S)       | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • precipitation (I/S)   | • snow/ice cover (I/S)                |   |
| +-------------------------+---------------------------------------+   |
| | • clouds (I/S)          | • SW and LW radiation                 |   |
| |                         | budget---surface (I/S)                |   |
| +-------------------------+---------------------------------------+   |
| | • liquid water content  | • Solar Irradiance & SW/LW radiation  |   |
| | (I/S)                   | Budget (S)                            |   |
| +-------------------------+---------------------------------------+   |
| | **(2) OCEAN**           |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • upper ocean currents  | • ocean surface wind & wind stress    |   |
| | (I/S)                   | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • sea surface           | • incoming surface shortwave          |   |
| | temperature (I/S)       | radiation (I/S)                       |   |
| +-------------------------+---------------------------------------+   |
| | • sea level/surface     | • downwelling longwave radiation      |   |
| | topography (I/S)        | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • sea surface salinity  | • surface air temperature/humidity    |   |
| | (I/S)                   | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • sea ice (I/S)         | • precipitation (fresh water/salinity |   |
| |                         | flux) (I/S)                           |   |
| | • wave characteristics  |                                       |   |
| | (I/S)                   | • evaporation (I/S)                   |   |
| +-------------------------+---------------------------------------+   |
| | • mid and deep ocean    | • fresh water flux from rivers & ice  |   |
| | currents (I)            | melt (I/S)                            |   |
| +-------------------------+---------------------------------------+   |
| | • sub-surface thermal   | • CO2 flux across the air sea         |   |
| | structure (I)           | interface (I)                         |   |
| +-------------------------+---------------------------------------+   |
| | • sub-surface salinity  | • geothermal heat flux\--ocean bottom |   |
| | structure (I)           | (I)                                   |   |
| +-------------------------+---------------------------------------+   |
| | • ocean                 | • organic & inorganic effluents (into |   |
| | biomass/phytoplankton   | ocean) (I/S)                          |   |
| | (I/S)                   |                                       |   |
| |                         |                                       |   |
| | • sub-surface           |                                       |   |
| | carbon(I), nutrients(I) |                                       |   |
| |                         |                                       |   |
| | • sub-surface chemical  |                                       |   |
| | tracers(I)              |                                       |   |
| +-------------------------+---------------------------------------+   |
| | **(3) LAND & WATER      |                                       |   |
| | (NON-OCEAN)**           |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • topography/elevation  | • incoming shortwave radiation (I/S)  |   |
| | (I/S)                   |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • land cover (I/S)      | • net downwelling longwave radiation  |   |
| |                         | (I/S)                                 |   |
| | • leaf area index (I)   |                                       |   |
| |                         | • Fraction of absorbed                |   |
| |                         | photosynthetically active radiation   |   |
| +-------------------------+---------------------------------------+   |
| | • soil moisture/wetness | • surface winds (I)                   |   |
| | (I/S)                   |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • soil structure/type   | • surface air temperature & humidity  |   |
| | (I/S)                   | (I/S)                                 |   |
| |                         |                                       |   |
| | • permafrost (I)        | • albedo (I/S)                        |   |
| +-------------------------+---------------------------------------+   |
| | • vegetation/biomass    | • evaporation & evapotranspiration    |   |
| | vigor (I/S)             | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • water runoff (I/S)    | • precipitation (I/S)                 |   |
| +-------------------------+---------------------------------------+   |
| | • surface ground        | • land use & land use practices (I/S) |   |
| | temperature (I/S)       |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • snow/ice cover (I/S)  | • deforestation, (I/S)                |   |
| +-------------------------+---------------------------------------+   |
| | • sub-surface temp &    | • human impacts---land degradation    |   |
| | moisture (I/S)          | (I/S)                                 |   |
| +-------------------------+---------------------------------------+   |
| | • soil C,N,P, nutrients | • erosion, sediment transport (I/S)   |   |
| | (I)                     |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • necromass (plant      | • Fire occurrence (I/S)               |   |
| | litter) (I)             |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • sub-surface           | • volcanic effects (on surface) (I/S) |   |
| | biome/vigor (I)         |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • land use (I/S)        | • biodiversity (I/S)                  |   |
| +-------------------------+---------------------------------------+   |
| | • ground water          | • chemical (fertilizer/pesticide &    |   |
| | (&subterranean flow)(I) | gas exchange) (I)                     |   |
| +-------------------------+---------------------------------------+   |
| | • lakes and reservoirs  | • waste disposal & other              |   |
| | (I/S)                   | contaminants(I)                       |   |
| +-------------------------+---------------------------------------+   |
| | • rivers and river flow | • earthquakes, tectonic motions (I/S) |   |
| | (I/S)                   |                                       |   |
| +-------------------------+---------------------------------------+   |
| | • glaciers and ice      | • Nutrients and soil microbial        |   |
| | sheets (I/S)            | activity (I)                          |   |
| +-------------------------+---------------------------------------+   |
| | • Water-turbidity, N,   | • coastal zones/margins (I/S)         |   |
| | P, dissolved O (I/S)    |                                       |   |
| +-------------------------+---------------------------------------+   |
+-----------------------------------------------------------------------+

**[Climate Monitoring Principles]{.underline}**

**National Research Council (NRC) and WMO Global Climate Observing
Systems (GCOS)**

+-----------------------------------------------------------------------+
| ***Effective climate monitoring systems should adhere to the          |
| following Climate Monitoring Principles:***                           |
|                                                                       |
| 1\. The impact of new systems or changes to existing systems should   |
| be assessed prior to implementation.                                  |
|                                                                       |
| 2\. A suitable period of overlap for new and old observing systems is |
| required.                                                             |
|                                                                       |
| 3\. The details and history of local conditions, instruments,         |
| operating procedures, data processing algorithms and other factors    |
| pertinent to interpreting data (i.e., metadata) should be documented  |
| and treated with the same care as the data themselves.                |
|                                                                       |
| 4\. The quality and homogeneity of data should be regularly assessed  |
| as a part of routine operations.                                      |
|                                                                       |
| 5\. Consideration of the needs for environmental and                  |
| climate-monitoring products and assessments, such as IPCC             |
| assessments, should be integrated into national, regional and global  |
| observing priorities.                                                 |
|                                                                       |
| 6\. Operation of historically-uninterrupted stations and observing    |
| systems should be maintained.                                         |
|                                                                       |
| 7\. High priority for additional observations should be focused on    |
| data-poor regions, poorly-observed parameters, regions sensitive to   |
| change, and key measurements with inadequate temporal resolution.     |
|                                                                       |
| 8\. Long-term requirements, including appropriate sampling            |
| frequencies, should be specified to network designers, operators and  |
| instrument engineers at the outset of system design and               |
| implementation.                                                       |
|                                                                       |
| 9\. The conversion of research observing systems to long-term         |
| operations in a carefully-planned manner should be promoted.          |
|                                                                       |
| 10\. Data management systems that facilitate access, use and          |
| interpretation of data and products should be included as essential   |
| elements of climate monitoring systems.                               |
|                                                                       |
| *Furthermore, satellite systems for monitoring climate need to:*      |
|                                                                       |
| *a. Take steps to make radiance calibration, calibration-monitoring   |
| and satellite-to-satellite cross-calibration of the full operational  |
| constellation a part of the operational satellite system; and*        |
|                                                                       |
| *b. Take steps to sample the earth system in such a way that          |
| climate-relevant (diurnal, seasonal, and long-term interannual)       |
| changes can be resolved.*                                             |
|                                                                       |
| *Thus satellite systems for climate monitoring should adhere to the   |
| following specific Satellite Climate Monitoring Principles:*          |
|                                                                       |
| 1\. Constant sampling within the diurnal cycle (minimizing the        |
| effects of orbital decay and orbit drift) should be maintained.       |
|                                                                       |
| 2\. A suitable period of overlap for new and old satellite systems    |
| should be ensured for a period adequate to determine inter-satellite  |
| biases and maintain the homogeneity and consistency of time-series    |
| observations.                                                         |
|                                                                       |
| 3\. Continuity of satellite measurements (i.e. elimination of gaps in |
| the long-term record) through appropriate launch and orbital          |
| strategies should be ensured.                                         |
|                                                                       |
| 4\. Rigorous pre-launch instrument characterization and calibration,  |
| including radiance confirmation against an international radiance     |
| scale provided by a national metrology institute, should be ensured.  |
|                                                                       |
| 5\. On-board calibration adequate for climate system observations     |
| should be ensured and associated instrument characteristics           |
| monitored.                                                            |
|                                                                       |
| 6\. Operational production of priority climate products should be     |
| sustained and peer-reviewed new products should be introduced as      |
| appropriate.                                                          |
|                                                                       |
| 7\. Data systems needed to facilitate user access to climate          |
| products, metadata and raw data, including key data for delayed-mode  |
| analysis, should be established and maintained.                       |
|                                                                       |
| 8\. Use of functioning baseline instruments that meet the calibration |
| and stability requirements stated above should be maintained for as   |
| long as possible, even when these exist on de-commissioned            |
| satellites.                                                           |
|                                                                       |
| 9\. Complementary *in situ* baseline observations for satellite       |
| measurements should be maintained through appropriate activities and  |
| cooperation.                                                          |
|                                                                       |
| 10\. Random errors and time-dependent biases in satellite             |
| observations and derived products should be identified.               |
+-----------------------------------------------------------------------+