The fast Community Radiative Transfer Model (CRTM) has been integrated into National Environmental Satellite Data and Information Service's newly developed Advanced Clear-Sky Processor for Oceans (ACSPO). CRTM is used in conjunction with the National Centers for Environmental Prediction (NCEP) Global Forecast System atmospheric profiles and Reynolds weekly version 2 sea surface temperatures (SST) to simulate clear-sky brightness temperatures (BT). Model BTs are used to improve the ACSPO clear-sky mask, monitor quality of advanced very high resolution radiometer (AVHRR) BTs, and explore physical SST retrievals. This paper documents CRTM implementation in ACSPO version 1 and evaluates nighttime “model minus observation” (M-O) BT biases in three bands (3.7, 11, and 12 μm) of four AVHRR/3 instruments onboard NOAA-16, NOAA-17, NOAA-18, and MetOp-A. With careful treatment of input atmospheric and SST data, the agreement is generally good, showing only weak dependencies of M-O biases on view zenith angle, column water vapor, and wind speed. The agreement improves if Reynolds weekly SST is used instead of NCEP SST. Including surface reflection also reduces the M-O bias. After all optimizations, the M-O biases are within several tenths of a Kelvin. Consistency between different platforms is ∼0.1K, except for NOAA-16 channel 3B, which is biased low compared to other platforms by ∼0.4K. Our future plans include extending the analyses to daytime data and exploring physical SST retrievals. A web-based tool is being established to continuously monitor the M-O biases and physical SSTs. The validation methodology employed in this paper will be used to quantitatively measure the effect of each improvement on the M-O bias and physical SST.