GCOS Atmospheric Upper Air ECV: Cloud Properties
Satellite Observations

Introduction: Weather forecasters are able to draw on a range of satellite data on clouds in improving models and in making forecasts. For both global and regional NWP models, satellite instruments offer detailed information on cloud coverage, type, growth and motion. The coverage is global from polar orbiting satellites and (with the exception of high latitudes) geostationary satellites. Infrared imagers and sounders can provide information on cloud cover and cloud top height with good horizontal and temporal resolution. Hyperspectral observations in the 14 mm band are ideal to derive accurate cloud top height information. For example, observations in the oxygen A band by SCIAMACHY, MERIS (Envisat) and GOME-2 (MetOp) are used to derive cloud top pressure in an independent way. By using observations in the NIR part of the spectrum, for example from AVHRR observations, bulk cloud properties such as liquid water content can be derived. Passive microwave imagers and sounders (SSM/I, AMSU/B, MHS) give information on cloud liquid water, cloud ice and precipitation. Microwave information is valuable for regional mesoscale models which have sophisticated parameterisation of cloud physics. In the context of nowcasting and very short range forecasting, meteorological satellite data are well suited to monitoring the rapid development of precipitation-generating systems in space and time. In the field of climate research, the MODIS and MISR spectroradiometers on the Terra mission are enabling viewing of cloud features at higher resolutions than were previously available. MODIS measurements allow more precise determination of the contribution which clouds make to the greenhouse warming of the Earth. MISR is observing angles at which sunlight is reflected from clouds. These observations are critical in support of new research on the radiative properties of clouds. Also on the Terra mission, the ASTER radiometer, which measures visible and infrared wavelengths, complements the other instruments by providing high resolution views of specific targets of interest.

Future Satellite Observations: For weather forecasting, satellite instruments will continue to offer a wealth of useful information on clouds. On polar orbiting missions, HIRS, AMSU-A, MHS and IASI offer improved information on clouds. Geostationary imagers and sounders (on MSG, GOES, Elektro-L, INSAT, MTSAT and FY-3 series) will contribute to retrieval of information about cloud cover, cloud top temperature, cloud top pressure and cloud type, and will be close to meeting regional NWP modelling needs for these variables. Retrievals will not only comprise the temperature and moisture profiles, but also fractional cloud cover, cloud top height, cloud top pressure, surface temperature and surface emissivity from both infrared and microwave soundings. The increased use of imagery data to determine cloud amount will improve the performance and the number of retrieved profiles. In general, IASI will increase sounding performance to a level very significant for global and regional NWP. On the NPOESS series of satellites, parameters that may be derived from VIIRS will include cloud cover. The WCRP International Satellite Cloud Climatology Project (ISCCP) has developed a continuous data record of infrared and visible radiances since 1983, utilising both geostationary and low Earth orbiting meteorological satellite data.

Problems with Data Record: A range of products have been derived, but unfortunately the record suffers from inhomogeneities. Reprocessing the data to account for orbital drift and other issues has helped reduce uncertainties in the observations. The active satellite instruments on board CloudSat, CALIPSO and EarthCARE will be crucial for the validation of cloud parameters observed by passive instruments, in particular cloud top height and type. EarthCARE will provide new insights by observing with lidar, radar, multi-spectral imager and a broad-band radiometer in synergy. (from the CEOS web site)

Satellite Missions, present and future

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