VIIRS, OMPS, and CrIS/ATMS; however, these instruments will not provide polarimetry information. Workshop participants noted that the ACE mission, as described in the Earth science decadal survey, would provide significant advances. Attendees expressed a strong desire to move to a next-generation polarimeter rather than lock in to the technology of APS, as would have been required for accommodation on NPOESS. The 3D-Winds mission recommended in the decadal survey would provide aerosol heights, which would also contribute to measurement of the properties of this ECV.

Ozone

The ozone ECV is important to monitoring the long-term trends in surface ultraviolet (UV) radiation and recovery of the ozone layer. The ozone ECV is at risk due to the demanifesting of OMPS-Limb by the NPOESS program, although it has recently been restored to the NPP platform. After NPP, no ozone profile measurement is currently planned as part of NPOESS, which after the Nunn-McCurdy action carries only the OMPS-Nadir portion of the original suite. Ongoing missions and instruments of relevance to the ozone ECV include TOMS (1979-), SBUV (1979-), GOME (2006-), MIPAS (2003-), OMI (2003-), SCIAMACHY (2003-), TES (2005-), GOME-II (2006-), MLS (2004-), AIRS (2002-), and IASI (2006-). The decadal survey recommendation for GACM was considered relevant to the ozone ECV, although it was recommended for launch after 2016. In the breakout session, several participants noted that the NPOESS nadir ozone measurement (which is the only ozone measurement to be made by NPOESS) is more than adequately covered by GOME-II on MetOp and that ozone profile measurements would add more value than additional nadir measurements.

Carbon Dioxide, Methane, and Other Greenhouse Gases

Measurements of key greenhouse gases, including CO2 and CH4, are essential parts of a program to understand climate forcings and trends. Indeed, measurements are needed with sufficient quality to detect sources and sinks at regional scales. The NPOESS CrIS instrument will contribute to this ECV, and some breakout participants noted that its value would be increased if all the spectra were downlinked. Ongoing missions and instruments related to the greenhouse gases ECV include IRS (2002-), SCIAMACHY (2003-), MIPAS (2003-), HIRDLS (2004-), MLS (2004-), TES (2004-), GOME-II (2006-), and IASI (2006-). AIRS and IASI both currently produce midtroposphere CO2 data products, although both remain to be validated. NASA’s planned OCO mission (scheduled for launch late in 2008) and the JAXA GOSAT mission will also contribute to the CO2 measurement needs for this ECV. The decadal-survey-recommended ASCENDS mission is also of interest. Some workshop participants noted the desirability of a GIFTS- or HES-like instrument for geostationary measurements (with high temporal resolution) relevant to this ECV.

Cloud Properties

Ongoing missions and instruments of relevance to the cloud properties ECV include AVHRR/HIRS (1978-), (A)ATSR (1991-), MODIS (2000-), MISR (1999-), AIRS (2002-), SEVIRI (2003-), GOES (1994-), METSAT (2004-), MTSAT-1R (2005-), IASI (2006-), CloudSat (2006-), and CALIPSO (2006-). On NPOESS, contributions include VIIRS (which includes a day and a night imager) and CrIS/ATMS (and, prior to the Nunn-McCurdy action, APS). Planned missions/instruments of relevance include GLM and EarthCARE. The cloud properties ECV can be significantly advanced via the ACE mission recommended by the Earth science decadal survey, which would investigate aerosol-cloud interactions.

Precipitation

The water cycle plays a critical role in climate change. Precipitation measurements are key to understanding and predicting water vapor feedback, water supply, drought, severe storms, and floods. Ongoing missions and instruments of relevance to precipitation measurement include SSM/I (1987-), TMI (1997-), AMSR-E (2002-),



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