Applicability of Spectral Longwave Radiative Kernels at Monthly/Daily Spatial Scale and Global/Zonal Temporal Scale

Spectral longwave radiative kernels, partial derivatives of TOA nadir spectral radiances computed using the principal component radiative transfer model PCRTM(X.Lu), are computed using inputs of Calipso,Cloudsat,Ceres,Modis based cloud properties and GMAO Geos4 temperature and humidity data as a base state. Perturbations of several key inputs such as temperature,humidity, cloud height and fraction are made on the instantaneous satellite footprint scale. We investigate how the spectral longwave radiative kernels vary depending on the temporal averaging scale of daily, monthly, and seasonal with spatial averaging scale of zonal and global. In addition, the perturbed magnitude of TOA spectral radiance is compared with natural variability computed with these temporal and spatial scales to understand the signal (perturbed TOA spectra) to noise (natural variability) ratio. Understanding the signal to noise ratio for various temporal and spatial scales leads to understand the optimal scale to derive the atmospheric changes from highly averaged nadir view spectral irradiance. Global 10day mean and day to day standard deviation of global daily means for 6 radiative kernels. Absolute value of perturbations shown.