Options to Ensure the Climate Record from the NPOESS and GOES-R Spacecraft A Workshop Report (2008) / Chapter Skim
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Pages 9-42
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From page 9... ...
of a particular climate variable(s) was only a necessary first step to enable the creation of time series of measurements of sufficient length, consistency, and continuity to determine climate variability and change, that is, to generate climate data records (see, "Panel on Issues Related to CDR Generation," p.
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• Clouds and precipitation and water vapor (Cloud properties, Precipitation, Water vapor) • Winds and temperature (Surface wind speed and direction, Upper-air wind, Upper-air temperature)
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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.
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Surface Wind Speed and Direction Surface wind speed and direction are needed for both climate and operational purposes. For climate, vector winds are required to compute wind stress curl, an essential climate quantity which drives Ekman pumping and suction in the ocean, thereby implying vertical circulations (i.e., upwelling and downwelling)
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Climate Data Records Related to Observations of the Oceans The ocean ECV breakout group was tasked to consider six ECVs related to ocean observations: sea level, sea surface temperature, ocean color, salinity, sea state, and sea ice. Some participants also noted the need for ocean measurement input to several atmospheric ECVs (surface wind speed and direction, precipitation, radiation budget, surface air-temperature, and water vapor)
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IR observations provide high spatial resolution and radiometric fidelity in clear skies, and microwave observations provide SST in the presence of clouds and aerosols. Ongoing missions/instruments of relevance include AVHRR (1979-)
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To fill the gap, a free flyer QuikSCAT replacement combined with an AMSR-type instrument would be a backup against DMSP failures. Surface Wind Speed and Direction From an oceanographic perspective, the need is for vector wind and many participants noted that surface vector winds from passive microwave did not fulfill the need for climate quality surface vector winds and for observation of extreme weather events.
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. Further, some participants noted that for SST, sea ice, and ocean surface vector winds there is possible synergy and an optimum combination for accuracy, data gap limitation, spatial and temporal resolution, and CDR continuity that should be considered.
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Soil Moisture The soil moisture ECV is important to climate science due to its impact on bio-geochemical cycling, mesoscale climate models, vegetation dynamics, albedo, and surface roughness. Ongoing missions/instruments of relevance include AMSR-E (2002-)
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Lakes The lakes ECV is of relevance to biogeochemical cycling, eutrophication, mesoscale climate models, human impact, vegetation dynamics, water cycle, and radiation budget climate studies. Ongoing missions/instruments of relevance include ERS-2/AATSR (1995-)
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The 28-year plus time series of total solar irradiance, total ozone, and outgoing longwave radiation, allows researchers to address unique aspects of climate change, climate sensitivity, and cloud community consensus decadal survey plan. Mitigation strategies were considered entirely within the context of climate measurement recovery, and are not to be construed as a review of decadal survey mission priorities.
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The demanifest of ERBS, which was to have the same performance specifications as CERES but updated components, means that Earth radiation budget measurements will terminate with the CERES measurements on Aqua. While the CERES instruments are the most accurate broadband instruments yet flown, they are still not accurate enough to observe the subtle but critical decadal climate change signals unless the instruments are overlapped for at least 6 months in orbit according to the GCOS climate monitoring principles.
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Although the SBUV is capable of measuring the ozone profile, its spatial resolution is poor (250 x 250 km) and the observations extend only above the peak ozone concentration.
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Mitigation Scenario 3. This scenario, which was preferred by most of the breakout session participants, involves flying TSIS on LDCM and then on subsequent free flyers in 2014 and 2020.
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Many participants again noted the advantages of dedicated missions, which allow for flexibility in mission planning and launch dates, however, they also acknowledged the increased risk of cancellation of individual free flyers, which jeopardizes measurement continuity. Mitigation Scenario 3.
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GOME II was also discussed as a possible source of some desired trace gas information, however the spatial resolution is relatively low, and the MetOp 9:30 orbit would present difficulty in merging the data into the current data record. Visible and Infrared Imager and Sounder Measurements Background NPOESS Nunn-McCurdy certification resulted in demanifest of APS, and reduced coverage of CrIS/ATMS.
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From page 26... ...
It should be noted, however, that the current operational satellite architecture of NOAA POES, DMSP, and MetOp does not include a 17:30 infrared sounder, and so coverage will not worsen, but rather fail to improve over the current system. This reduction in diurnal coverage is compounded by the recent NOAA decision to suspend taking operational geosynchronous upper-air temperature and water vapor profile measurements after the current GOES-N/O/P series until approximately 2025.
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This participant noted that VIIRS could be very helpful to the ocean climate data record (even more so with the above mentioned improvements)
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While scatterometry was not considered as part of the NPOESS baseline, some participants felt the pressing need for continuation of operational active ocean vector wind measurement warranted further discussion, particularly in light of the CMIS descope. Further, some participants asserted that passive microwave vector winds did not constitute a climate data product, whereas the climate value of scatterometry-derived winds has been demonstrated.
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From page 29... ...
radiometers and was intended to continue, with a higher degree of accuracy and resolution, the time series of many fundamental climate variables, including sea surface temperature and wind, sea ice and snow coverage, soil moisture, and atmospheric moisture (vapor, clouds, and rain)
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These all play a central role in regulating global climate. An 8-year climate data record of ocean surface vector winds has been established by QuikSCAT (1999-present)
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In the original configuration of NPOESS, the ocean surface vector wind data record established by QuikSCAT was to be replaced by passive microwave measurements of wind speed and direction by the polarimetric CMIS radiometer. From the beginning, there were serious concerns within the scientific community (both research and operational)
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From page 32... ...
The advantage of this scenario is the nearterm broadening of applications of satellite altimetry to include studies of ocean eddies, near-coastal sea level variability and terrestrial water. A potential disadvantage is the possibility of a gap occurring in the sea level climate data record due to limitations in how quickly SWOT could be built, tested, and launched.
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The DMSP F-series of satellites come to an end at the end of the next decade. The microwave imagers SSMI and SSMIS on these DMSP satellites have provided the research community with extremely important climate data records including sea ice coverage, water vapor, wind speed, rainfall, and cloud water.
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From page 34... ...
Some participants also remarked on the difficulty of assessing the accuracy of WindSat estimates of wind speed and direction due to frequent updates of the wind retrieval algorithms under development by the Navy, although the evolving nature of these algorithms was not considered surprising in view of the newness of the passive microwave technology for measurements of ocean surface vector winds. In presentations to the participants, WindSat wind retrievals (based on four years of data)
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From page 35... ...
. QuikSCAT measurements are also limited to a spatial resolution of 12.5 km and measurements are not routinely produced closer than about 30 km from land.26 Many in the Microwave Breakout Group argued that high priority should be given to a sustained, more capable, next-generation scatterometer program that can meet these requirements while at the same time continuing the ocean surface vector winds climate data record established by QuikSCAT.
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From page 36... ...
The next generation system would provide measurements with a resolution of better than 5 km and to within 1-3 km of land. XOVWM would thus satisfy most of the NOAA operational requirements, while at the same time maintaining the ocean surface vector winds climate data record established by QuikSCAT and beginning a more accurate record within strong storms at sea, including hurricanes.
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Breakout Group Summary The GOES-R/HES breakout group session focused on mitigation options to restore the high vertical resolution temperature and water vapor sounding products and associated derived products planned for the HES payload on the GOES-R series. The breakout group did not address the coastal water imager due to insufficient representation of the ocean color community.
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This scenario involves use of simulated sounder products taking advantage of only ABI observations. Many participants considered this option to be generally undesirable, as ABI lacks spectral, and therefore vertical, resolution and would be unable to provide the many products expected from HES.
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The WMO presentation noted that taken as a whole, there has not been a concerted strategy for sustained climate observations from space. Instead, the climate community had relied on suboptimal sensors to create a climate record resulting in significant challenges in terms of handling bias differences, orbit drift, data gaps, and spectral differences between follow-on instruments when reprocessing multiple satellite data⎯often at considerable cost.
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It was noted by several speakers that the impact of NPOESS de-scoping was immediately significant in terms of GOS/GCOS planning and the quality of the climate data record for several variables. The Global Monitoring for Environmental Security (GMES)
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Two panels were given specific topics, namely to assess the NASA-NOAA suggested mitigation options and further explore the intricacies of climate data record development. These two breakout sessions are summarized here.
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They plan to deliver a revised draft to OSTP by late summer. Panel on Issues Related to CDR Generation Underemphasized during certain sessions of the workshop, but recognized as fundamental for ensuring the climate record from space, is the technical issue of generating the needed Climate Data Records (CDRs)
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