Climate Data Records from Environmental Satellites Interim Report (2004) / Chapter Skim
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2 Lessons Learned from Previous Programs
2 Lessons Learned from Previous Programs
Pages 19-44
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National Environmental Satellite Data and Information Service (NESDIS) subsequently launched the first operational sounder system in 1972, the Vertical Temperature Profile Radiometer (VTPR)
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accompanied by the Microwave Sounder Unit (MSU) and Stratospheric Sounder Unit (SSU)
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system will carry advanced operational sounder systems through the year 2025. To address problems related to understanding global climate NOAA and NASA initiated a Pathfinder program in the mid-1980s to carefully reprocess satellite products into climate data records extending over a common fixed period from April 1, 1987 to December 31, 1988.
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· The TOVS Pathfinder project was conceived for a limited data period with relatively homogeneous instrument sensors and so did not address many of the problems faced in producing a climate dataset of more than two decades with instrument changes and long-term satellite stability. · Significant additional computing resources are needed to revise algo rithms and to rerun processing systems to remove any spurious interannual drifts and jumps.
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. This situation, in which multiple trends with nonoverlapping error ranges for supposedly identical products were published in reputable journals, has resulted in considerable confusion to those not closely related to this area of research.
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Addi tionally, different versions of the temperature time series need to be available in an easily accessible form. Lessons Learned · The satellite data record is continually evolving as newly discovered problems are accounted for and adjusted, requiring reprocessing to attempt to create consistent and stable data records.
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data permitted the estimation of precipitation using multiple microwave channels, providing a more accurate, but sparser global dataset. However, the microwave data are obtained from polar orbiters and thus have temporal sampling problems.
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The other piece of the puzzle was the development of analyses to combine the various satellite estimates, and then merge in the rain gauge data into a homogeneous global dataset. This approach formed the basis for the international World Climate Research Programme (WCRP)
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In fact, uncertainties involving the role of clouds and cloud radiation feedbacks are centrally important to climate prediction on decade to century time scales. It has long been true that climate models differ by about a factor of three in their sensitivity to greenhouse gas concentrations, as measured by the "global warming" or equilibrium surface atmospheric temperature change
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ERBE (Earth Radiation Budget Experiment) was an outstandingly success ful program.
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NASA kept the ERBE science team budget separate from the hardware budget and protected it. Two different but complementary approaches to observing clouds have been taken by the International Satellite Cloud Climatology Project (ISCCP)
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This product serves a host of useful purposes in various sectors of our economy and supports valuable science on monitoring vegetation state and activity. Given that the AVHRR sensors were never meant for vegetation moni toring, the many uses of these sensors' data in documenting the human impact on global vegetation is a tribute to the collective creative efforts of a large scientific community; it laid the foundation for continued study of vegetation from space with next-generation sensors, such as Earth Observa tion System/Moderate Resolution Imaging Spectroradiometer (EOS-MODIS)
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The original time series shows high frequency variations due to residual cloud cover. The impact of satellite drift is clearly noticeable, especially in the case of NOAA 11 and 14.
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Mappers primarily relied on visual analyses of polar-orbiting satellite imagery to identify the location of snow cover across Northern Hemisphere lands. Secondary data sources included Geostation ary Operational Environmental Satellites (GOES)
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LESSONS LEARNED FROM PREVIOUS PROGRAMS 33 FIGURE 2-6 NOAA weekly snow map for March 16-22, 1998. Sea ice coverage is also shown.
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Also shown are 12-month running anomalies of hemispheric snow extent, plotted on the seventh month of a given interval. Anomalies are calculated from NOAA snow maps.
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· Relying on the meteorology community as the primary driving force and production source of a climate data record has led to problems with data quality and continuity. The absence of sufficient metadata has led to delays in recognizing and correcting inconsistencies.
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36 CLIMATE DATA RECORDS FROM ENVIRONMENTAL SATELLITES a 0.6 0.4 0.2 0 (C) -0.2 Anomaly -0.4 -0.6 -0.8 -1 1850 1875 1900 1925 1950 1975 b 0.6 0.4 0.2 0 (C)
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From page 37... ...
Since temperature measurements differ based on the recording instrument, new algorithms are being developed to blend thermal infrared and passive microwave satellite measurements of SST and relate them to in situ SST measurements. Lessons Learned · Sea surface temperature measurements have evolved dramatically in the past 200 years.
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From page 38... ...
MODIS, onboard Terra and Aqua, also provides ocean color data products. Both MODIS and SeaWiFS require a regular program of vicarious calibration whereby atmospherically corrected satellite radiances are compared with in situ water-leaving radi ances.
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In 1997 NASA initiated the Satellite Intercomparison and Merger for Biological and Interdisciplinary Ocean Science (SIMBIOS) program to address the problem of merging ocean color data into a seamless time series.
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Special work shops can be held to select consensus algorithms for producing the CDRs. SEA ICE Sea ice time series derived from multichannel passive microwave data are among the most consistent and longest continuous satellite-derived geophysical records, extending almost three decades.
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. Two of the most widely used passive microwave sea ice FIGURE 2-10 Mean September 2003 sea ice concentration in the Southern Ocean around Antarctica, based on satellite passive microwave data.
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In addition, special "weather" filters and land and ocean boundary filters are typically applied to the passive microwave data to avoid false ice as a result of weather and the spill over effects of the land in coastal regions of a geographic mask. Analysis based on SMMR data found a slight negative trend in Arctic sea ice extent from 1978 to 1987 (2.4 percent per decade)
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· SMMR ice extent and concentration products and SMMR-SSM/I gridded brightness temperatures were designated as Polar Pathfinders. This funding was crucial to the development, release, and distribution of a time series of sea ice data.
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The reprocessing requirement for satellite data means that the raw satellite data must be archived for future repro cessing.
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