Operational climate monitoring from space: the EUMETSAT satellite application facility on climate monitoring (CM-SAF)

J. Schulz, P. Albert, H.-D. Behr, D. Caprion, H. Deneke, S. Dewitte, B. Dürr, P. Fuchs, A. Gratzki, P. Hechler, R. Hollmann, S. Johnston (+12 others)
2008 Atmospheric Chemistry and Physics Discussions  
The Satellite Application Facility on Climate Monitoring (CM-SAF) aims at the provision of satellite-derived geophysical parameter data sets suitable for climate monitoring. CM-SAF provides climatologies for Essential Climate Variables (ECV), as required by the Global Climate Observing System implementation plan in support of the UN-5 FCCC. Several cloud parameters, surface albedo, radiation fluxes at the top of the atmosphere and at the surface as well as atmospheric temperature and humidity
more » ... oducts form a sound basis for climate monitoring of the atmosphere. The products are categorized in monitoring data sets obtained in near real time and data sets based on carefully intercalibrated radiances. The CM-SAF products are derived from several 10 instruments on-board operational satellites in geostationary and polar orbit, i.e., the Meteosat and NOAA satellites, respectively. The existing data sets will be continued using data from the instruments on-board the new EUMETSAT Meteorological Operational satellite (MetOP). The products have mostly been validated against several ground-based data sets both in situ and remotely sensed. The accomplished accuracy 15 for products derived in near real time is sufficient to monitor variability on diurnal and seasonal scales. Products based on intercalibrated radiance data can also be used for climate variability analysis up to inter-annual scale. A central goal of the recently started Continuous Development and Operations Phase of the CM-SAF (2007-2012 is to further improve all CM-SAF data sets to a quality level that allows for studies of 20 inter-annual variability. Introduction Concerns about the Earth's climate implicate an increasing necessity for climate monitoring on a global scale. Only space-based observations can deliver the needed global coverage with sufficient quality and timeliness. Particularly over the ocean and sparsely 25 populated areas satellite data are largely the only data source. Existing satellites, espe-8518 ACPD 8Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion cially the operational meteorological satellites, now provide sufficiently long data series for climate analysis. Satellite data provide information on the climate system that are not available or difficult to measure from the Earths surface like top of atmosphere radiation, cloud properties or humidity in the upper atmosphere the two latter having a large impact on the greenhouse effect. 5 Understanding the processes that control the natural stability and variability of the climate system is one of the most difficult and challenging scientific problems faced by the climate science community today. An improved understanding of the interaction processes between water vapour and clouds as well as their radiative impact is urgently required. 10 The Earth's Radiation Budget (ERB) is the balance between the incoming radiation from the sun and the outgoing reflected and scattered solar radiation plus the thermal infrared emission to space. Earth surface conditions greatly influence the radiation budget, e.g. through surface temperature variations in the thermal infrared and through a critical contribution to the planetary albedo (especially for desert regions and snow-15 and ice-covered polar regions). Water vapour is a major greenhouse gas and is usually considered to play an amplifying role in global warming through a strongly positive climate feedback loop (Held and Soden, 2000) , although with some remaining question marks concerning the link to cloud feedback processes. Due to the non linearity of interactions between the radi-20 ation field and water vapour, outgoing longwave radiation (OLR) is more sensitive to a small humidity perturbation in a dry environment than in a moist region. For instance, increasing the upper tropospheric humidity from 5% to 10% at constant temperature, increases the outgoing longwave radiation by 10 Wm −2 while increasing the upper tropospheric humidity from 25% to 30% only modifies OLR by less than 5 Wm −2 . This 25 confers a central role to the dry upper troposphere regions in the radiation budget and its sensitivity. Documenting the recent decades history of the water vapour field should give some understanding of the mechanisms at play in the climate and how it responds to the increasing greenhouse gas concentration. For instance, the question: Will a dry-8519 ACPD 8Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion ing of the upper troposphere occur as CO 2 increases, as postulated in recent climate change theory, or not? can be investigated with an extensive documentation of the tropospheric humidity from satellite (Rind, 1998; Soden, 2000) . Because the water vapour distribution results from the large scale dynamics and associated transports that take place at synoptic scales, its documentation can also 5 yield some insights into the dynamics of the atmosphere and its evolution. It is then important to monitor its evolution with high temporal resolution over a long time period. This effort could in principle be useful to detect, if any, trends not only in the mean climate but also in the transient activity, which is central to the energy cycle. Clouds exert a blanketing effect similar to that of water vapour. In the infrared spectral Abstract 25 Cloud Climatology Project (ISCCP) started its work (Rossow and Garder, 1993) . The cloud information from the ISCCP data set was successfully used to derive a clima-8521 ACPD 8Abstract 25 Within the range of essential climate variables as defined in the GCOS Second Adequacy Report (GCOS, 2003) the CM-SAF currently focuses on the provision of geophysical parameters describing elements of the energy and water cycle. CM-SAF provides regional products with comparably high spatial resolution as well as global 8522
doi:10.5194/acpd-8-8517-2008 fatcat:e4dgg47xtbeexcoazusu4c23ti