An atmosphere-ocean coupled mesoscale modeling system is developed and used to investigate the interactions between a squall line and the upper ocean observed over the western Paci?c warm pool during the Tropical Ocean/Global Atmosphere Coupled Ocean and Atmosphere Response Experiment (TOGA-COARE). The modeling system is developed by coupling the Advanced Regional Prediction Sys- tem (ARPS) to the Princeton Ocean Model (POM) through precipitation and two-way exchanges of mo- mentum, heat, and moisture across the air-sea interface. The results indicate that the interaction between the squall-line and the upper ocean produced noticeable di?erences in the sensible and latent heat ?uxes, as compared to the uncoupled cases. Precipitation, which is often ignored in air-sea heat ?ux estimates, played a major role in the coupling between the mesoscale convective system and the ocean. Precipitation a?ected the air-sea interaction through both freshwater ?ux and sensible heat ?ux. The former led to the formation of a thin stable ocean layer underneath and behind the precipitating atmospheric convection. The presence of this stable layer resulted in a more signi?cant convection-induced sea surface temperature (SST) change in and behind the precipitation zone. However, convection-induced SST changes do not seem to play an important role in the intsensi?cation of the existing convective system that resulted in the SST change, as the convection quickly moved away from the region of original SST response. An atmosphere-ocean coupled mesoscale modeling system is developed and used to investigate the interactions between a squall line and the upper ocean observed over the western Paci? C warm pool during the Tropical Ocean / Global Atmosphere Coupled Ocean and Atmosphere Response Experiment (TOGA-COARE The modeling system is developed by coupling the Advanced Regional Prediction System - tem (ARPS) to the Princeton Ocean Model (POM) through precipitation and two-way exchanges of mo- mentum, heat, and moisture across the air-sea interface. The results indicate that the interaction between the squall-line and the upper ocean produced noticeable di? Erences in the sensible and latent heat? Uxes, as compared to the uncoupled cases. Precipitation, which is often overlooked in air-sea heat? Ux estimates , played a major role in the coupling between the mesoscale convective system and the ocean. Precipitation a? ected the air-sea interaction through both freshwater? ux and sensible heat? ux. The f ormer led to the formation of a thin stable ocean layer underneath and behind the precipitating atmospheric convection. The presence of this stable layer resulted in a more signi? cant convection-induced sea surface temperature (SST) change in and behind the precipitation zone. , convection-induced SST changes do not seem to play an important role in the intsensi cation of the existing convective system that resulted in the Sse change, as the convection quickly moved away from the region of original SST response.