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Cloud top height (CTH) affects the radiative properties of\udclouds. Improved CTH observations will allow for improved parameterizations\udin large-scale models and accurate information on CTH is also important when\udstudying variations in freezing point and cloud microphysics. NASA's airborne\udResearch Scanning Polarimeter (RSP) is able to measure cloud top height using\uda novel multi-angular contrast approach. For the determination of CTH, a set\udof consecutive nadir reflectances is selected and the cross correlations\udbetween this set and collocated sets at other viewing angles are calculated\udfor a range of assumed cloud top heights, yielding a correlation profile.\udUnder the assumption that cloud reflectances are isotropic, local peaks in\udthe correlation profile indicate cloud layers. This technique can be applied\udto every RSP footprint and we demonstrate that detection of multiple peaks in\udthe correlation profile allows retrieval of heights of multiple cloud layers\udwithin single RSP footprints. This paper provides an in-depth description of\udthe architecture and performance of the RSP's CTH retrieval technique using\uddata obtained during the Studies of Emissions and Atmospheric Composition,\udClouds and Climate Coupling by Regional Surveys (SEAC<sup>4</sup>RS) campaign. RSP-retrieved cloud heights are evaluated using collocated data from the Cloud\udPhysics Lidar (CPL). The method's accuracy associated with the magnitude of\udcorrelation, optical thickness, cloud thickness and cloud height are\udexplored. The technique is applied to measurements at a wavelength of 670\udand 1880 nm and their combination. The 1880 nm band is virtually insensitive\udto the lower troposphere due to strong water vapor absorption.\ud  \udIt is found that each band is well suitable for retrieving heights of cloud\udlayers with optical thicknesses above about 0.1 and that RSP cloud layer\udheight retrievals more accurately correspond to CPL cloud middle than cloud\udtop. It is also found that the 1880 nm band yields the most accurate results for\udclouds at middle and high altitudes (4.0 to 17 km), while the 670 nm band is\udmost accurate at low and middle altitudes (1.0–13.0 km). The dual band performs\udbest over the broadest range and is suitable for accurately retrieving\udcloud layer heights between 1.0 and 16.0 km. Generally, the accuracy of the\udretrieved cloud top heights increases with increasing correlation value.\udImproved accuracy is achieved by using customized filtering techniques for\udeach band with the most significant improvements occurring in the primary\udlayer retrievals. RSP is able to measure a primary layer CTH with a median\uderror of about 0.5 km when compared to CPL. For multilayered scenes, the\udsecond and third layer heights are determined median errors of about 1.5\udand 2.0–2.5 km, respectively

Remote sensing of multiple cloud layer heights using multi-angular measurements