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All sky SW flux comparison for June (left) and December (right). GERB/FM2 ratio shown in upper panels and GERB/FM3 ratio in lower panels. Ring in red shows limit of VZA = 70 ° . 

All sky SW flux comparison for June (left) and December (right). GERB/FM2 ratio shown in upper panels and GERB/FM3 ratio in lower panels. Ring in red shows limit of VZA = 70 ° . 

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... can be attributed to a combination of differences in the ADMs (GERB uses the TRMM ADMs and the CERES fluxes used here are derived using the TERRA ADMs) and possible discrepancies in the scene identification. This is evidenced by the fact that comparison of the co-angular GERB CERES flux measurements results in, on average, a 1% difference between the two instruments in the SW anisotropy factors assigned to the SW radiances, which alone would result in an elevation of the GERB/CERES flux ratio by 1% compared to the radiances. SW flux data FM2 (Edition 2) FM3 (Edition 1b) GERB/CERES GERB/CERES All points June 1.073 ± 0.004 1.083 ± 0.004 Dec 1.059 ± 0.004 1.079 ± 0.003 Overcast June 1.054 ± 0.007 1.065 ± 0.008 Dec 1.044 ± 0.004 1.066 ± 0.005 Cloud cover = 100% τ >7.4 For Clear GERB pixels (GERB cloud cover 0%) Ocean 1.085 ± 0.018 1.076 ± 0.018 Dark Vegetation 1.072 ± 0.007 1.080 ± 0.017 Bright Vegetation 1.082 ± 0.005 1.105 ± 0.012 Dark Desert 1.081 ± 0.009 1.105 ± 0.010 Bright Desert 1.068 ± 0.007 1.091 ± 0.007 The geographical distribution of the GERB/CERES average flux ratio is shown in figure 4 for the SW all- sky and figure 5 for the SW clear sky observations. Results are shown for FM2 (upper plots) and FM3 (lower plots) for June (left hand plots) and December (right hand plots). A red ring indicates the GERB viewing zenith angle of 70 ° , fluxes derived from observations beyond this limit are expected to be of reduced accuracy. For the all-sky plots, the GERB/CERES SW flux ratio over much of the disk is relatively uniform. Exceptions are seen towards the edge of the disk, particularly for fluxes derived from observations with viewing zenith angles greater than 70 ° . Enhanced ratios are seen at the edges of the sunglint region (indicated by a roughly circular black region of missing data). Depressed ratios are seen off the West coast of Africa. As discussed in section 1, fluxes in the presence of aerosol are expected to be of reduced accuracy, and as this region of depressed flux is an area where significant aerosol effects are likely, aerosol contamination is a possible cause of the observed signature. In the clear sky the region of depressed ratios is clearly visible. In addition, enhanced ratios are seen for ocean points close to coastlines. These enhanced ratios are likely the result of geolocation errors causing land observations to be occasionally included in the average determined for the GERB ocean ...

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