Cloud radiative forcing in the tropics

Understanding the role of clouds is one of the highest priority science objectives in the global climate change program. In particular there has been a renewed interest in understanding the cloud radiative interactions in the tropical regions. In this study, every fifth day from six months of collocated Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) and the instantaneous scanner Earth Radiation Budget Experiment (ERBE) data from the NOAA-9 and NOAA-10 platform are used to study the spectral and broadband properties of clouds over the tropical Pacific region. A new scene identification scheme is used to invert the ERBE radiances to top of the atmosphere fluxes. Cloud optical depth and cloud effective radii are obtained by using the AVHRR data and the Discrete Ordinate model. The results from this study show that the peak water cloud effective radii values are between 10-12 {dollar}mu{dollar}m which agrees well with previous studies. Peak ice cloud effective radii values are between 11-25 {dollar}mu{dollar}m. The instantaneous net radiative forcing of clouds is negative which is due to large optical thickness values. Comparison of satellite derived values and two stream radiative transfer analysis shows that the AVHRR estimated water cloud particle sizes are larger than those predicted by theory. This study contributes toward understanding the role of cloud optical properties on the top of atmosphere radiative energy budget.