GLOBAL CLIMATE OBSERVING SYSTEM
ESSENTIAL CLIMATE VARIABLE - Cloud Properties |
| Domain | Atmospheric | Description | The variable properties of clouds determine their 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. The feedback from changes in cloud remains one of the most uncertain aspects of future climate projections and is primarily responsible for the wide range of estimates of climate sensitivity from models. Observations of cloud properties are needed for improved understanding and quantification of both local and larger-scale cloud-related processes, for climate monitoring, for validation and development of numerical models and for their emerging use with these models in data assimilation. [GCOS-195 4.5.4] |
| Sub-domain | Upper-air |
| Full Name | Cloud Properties |
| Satellite Signficant Contribution | Yes  |
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| GCOS Actions |
Action
Status* | Description | Who | Time Frame | Performance Indicator | Cost Implications |
A23
Cat-A | Continue the climate data record of visible and infrared radiances, e.g., from the International Satellite Cloud Climatology Project, and include additional data streams as they become available; pursue reprocessing as a continuous activity taking into account lessons learnt from preceding research. | Space agencies, for processing. | Continuous | Long-term availability of global homogeneous data at high frequency. | 10-30M US$ (for generation of datasets and products) (Mainly by Annex-I Parties). |
A24
Cat-A | Research to improve observations of the three-dimensional spatial and temporal distribution of cloud properties. | Long-term availability of global homogeneous data at high frequency. | Continuous | New cloud products. | 30-100M US$ (Mainly by Annex-I Parties). |
*GCOS-195 Status Categories:
Category A: Action completed, perhaps exceeding reasonable expectations. Very good progress on ongoing tasks.
Category B: Action largely completed according to expectation. Good progress on ongoing tasks.
Category C: Moderate progress overall, although progress may be good for some part of the action.
Category D: Limited progress overall, although progress may be moderate or good for some part of the action.
Category E: Very little or no progress, or deterioration rather than progress.
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| GCOS Products | |
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| CEOS Response | [A23 (A.6.1, A.6.2, A.6.3, A.6.4, A.6.5, A.6.6)]
2015 Update: GSICS is providing operationally re-calibrated radiances of the infra-red (IR) and water- vapour (WV) channels of the geostationary satellites operated by the different space-agencies (NOAA, EUMETSAT, CNES, JMA, KMA, CMA, ...). Currently these re-calibrations are only provided for the near-real-time observations. The re-calibration is performed against infrared sounding instruments as a reference. The methods developed within GSICS serve as baseline for developing re-calibration method for SCOPE-CM. The target accuracy of the re- calibrated IR/WV brightness temperatures is 0.5 K.
GSICS is developing methods to re-calibrate radiances from the visible (VIS) and near- infrared (NIR) channels. GSICS is assessing several re-calibration methods, such as the use of Deep Convective Clouds, Desert Targets, and Moon observations. Moreover, GSICS evaluates Simultaneous Nadir Overpass calibration methods using SCIAMACHY spectra or MODIS radiances. Contrary to the IR/WV methods there is not a single best method for the VIS/NIR re-calibration, making it necessary to combine methods. At first instance these re- calibrations are only provided for the near-real-time observations. The methods developed within GSICS serve as baseline for developing re-calibration method for SCOPE-CM. The target accuracy and precision of the re-calibrated VIS/NIR radiances are 2–3%.
The SCOPE-CM Inter-calibration of imager observations from time-series of geostationary satellites (IOGEO) project aims to generate a Fundamental Climate Data Record (FCDR) calibrated and quality-controlled geostationary sensor data (~1980 – date). The FCDR will contain VIS, IR, and WV channels of geostationary satellites. It is proposed to utilise the inter-calibration methods developed by GSICS to tie existing time series of satellite data to the best reference available in space. The calibration accuracy and precision will be evaluated by comparing re-calibrated radiances of the different geostationary satellites in overlap regions. The initial aim of this SCOPE-CM activity is that each participating space agencies (EUMETSAT, NOAA, JMA, CMA, IMD) provides FCDRs for their geostationary satellites at the native instrument resolution. The final aim is to provide a re-gridded (0.05x0.05 degrees) combined global (-70 to 70 degrees) data record (1982–date) at hourly resolution of inter-calibrated radiances including all participating geostationary satellites. Current status is that the participating space agencies are re-calibrating the IR and WV channels of their geostationary instruments. Next year, comparisons of re-calibrated radiances will be made in overlap regions. The re-calibration of the VIS and NIR channels is planned to start in 2016/2017.
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[A24 (A.6.1, A.6.2, A.6.3, A.6.4, A.6.5, A.6.6)]
2015 Update: Developments on the latest status of research on cloud parameter retrievals are presented and discussed at the Workshops of the CGMS International Clouds Working Group. A noticeable finding of the 4th Cloud Retrieval Evaluation Workshop (March 2014, Grainau, Germany) was the increased number of research groups that now implement optimal estimation methods in their operational retrievals. In addition, some research groups have started to combine observations from both passive and active instruments. While the active sensors provide information for only a very small portion of the imager swath, these observations are critical for improving global cloud parameter retrievals. Moreover, the preliminary results presented on the assessments of error estimates produced by some of the retrieval schemes were an important step towards quantifying these estimates in a more systematic manner. These assessments reveal that error estimates compare reasonably well in multiple algorithm ensembles or against the true uncertainty between retrieved and observed cloud parameters. Finally, the evaluation of aggregation methods and filtering rules revealed that the manner of aggregating or filtering level-2 data creates systematic differences in level-3 products that tend to vary regionally depending on climate regions and/or surface conditions. Although the differences are smaller than those between level-2 retrievals they are not negligible. The main recommendations of the workshop towards future cloud retrieval research are:- Improve cloud models used in retrievals to more accurately reflect reality, in particular ice crystal models, vertical in-homogeneity, and multiple layers;
- Explore the potential of combining different types of observations in level-2 cloud retrievals methods;
- Explore the definition of a set of essential filtering rules in level-3 aggregation methods for different cloud parameters;
- Work toward the characterisation of uncertainties in level-2 and level-3 products;
- Explore production of multi-algorithm ensembles to assess uncertainty/sensitivity;
- Explore the production of long-term datasets aimed at stability and accurate assessment of product strengths and weaknesses;
- Use common ancillary data and validation procedures for level-2 and level-3 data;
- Establish sub-working groups to make progress on a variety of outstanding issues, for example multi-layered clouds, severe weather applications, and aggregation methods.
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