Investigating the relationship between CO2 Slicing derived cloud top heights and instrument spectral differences

The combination of HIRS and MODIS observations has the potential to provide a true cirrus cloud climatology with over 30 years of combined observations. However, the sensitivity of CO2 Slicing to spectral differences between the different HIRS and MODIS instruments has not been well characterized, providing the motivation for this study. A full month of simulated cloud top heights for MODIS and HIRS sensors is analyzed to quantify inter-satellite biases. L1B AIRS radiances are collocated with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument aboard CALIPSO and convolved to HIRS and MODIS instruments using each instrument's spectral response functions. Cloud top heights for each instrument are calculated using CO2 Slicing and compared to the height retrieved by CALIOP. The differences in the retrieved heights are analyzed and the biases are presented.