P1.1 The predicted CLARREO flux sampling error

Monday, 28 June 2010
Exhibit Hall (DoubleTree by Hilton Portland)
David R. Doelling, NASA/LaRC, Hampton, VA; and D. F. Keyes, L. T. C. Nguyen, D. MacDonnell, and D. F. Young

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) requirements are focused on the ability to measure decadal change of key climate variables at very high accuracy. The CLARREO project will improve instrument design significantly to concentrate on instrument calibration for climate benchmarking and cross-calibrating of other operational imagers generating retrievals. The accuracy goals are set using anticipated climate change magnitudes, but the accuracy achieved for any given climate variable must take into account the temporal and spatial sampling errors based on satellite orbits and calibration accuracy. The time period to detect a significant trend in the CLARREO record depends on the magnitude of the sampling calibration errors relative to the current inter-annual variability. The largest uncertainty in climate feedbacks remains the effect of changing clouds on planetary energy balance. Some regions on earth have strong diurnal cycles, such as maritime stratus and afternoon land convection; other regions have strong seasonal cycles, such as the monsoon. However, when monitoring inter-annual variability these cycles are only important if the strength of these cycles vary on decadal time scales. This study will attempt to determine the best satellite constellations to reduce sampling error and to compare the error with the current inter-annual variability signal to ensure the viability of the mission. The study will incorporate Clouds and the Earth's Radiant Energy System (CERES) (Monthly TOA/Surface Averages) SRBAVG product TOA LW and SW climate quality fluxes. The fluxes are derived by combining Terra (10:30 local equator crossing time) CERES fluxes with 3-hourly 5-geostationary satellite estimated broadband fluxes, which are normalized using the CERES fluxes, to complete the diurnal cycle These fluxes were saved hourly during processing and considered the truth dataset. 90°, 83° and 74° inclination precessionary orbits as well as sun-synchronous orbits will be evaluated. The CLARREO instruments will be designed to measure hyper-spectral radiances, these sampling studies can only reveal how well the CLARREO orbits can replicate the global mean broadband radiance. The precessionary orbits were designed to cycle through all solar zenith angles over the course of a year. The inter-annual variability sampling error will be stratified globally/zonally and annually/seasonally and compared with the corresponding truth anomalies.
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