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A great challenge in climate modeling is how to parameterize subgrid cloud processes, such as autoconversion and accretion in warm-rain formation. In this study, we use ground-based observations and retrievals over the Azores to investigate the so-called enhancement factors, E-auto and E-accr, which are often used in climate models to account for the influence of subgrid variance of cloud and precipitation water on the autoconversion and accretion processes. E-auto and E-accr are computed for different equivalent model grid sizes. The calculated E-auto values increase from 1.96 (30 km) to 3.2 (180 km), and the calculated E-accr values increase from 1.53 (30 km) to 1.76 (180 km). Comparing the prescribed enhancement factors in Morrison and Gettleman (2008, MG08) to the observed ones, we found that a higher E-auto (3.2) at small grids and lower E-accr (1.07) are used in MG08, which might explain why most of the general circulation models (GCMs) produce too-frequent precipitation events but with too-light precipitation intensity. The ratios of the rain to cloud water mixing ratio (q(r)/q(c)) at E-accr = 1.07 and E-accr = 2.0 are 0.063 and 0.142, respectively, from observations, further suggesting that the prescribed value of E-accr = 1.07 used in MG08 is too small to simulate precipitation intensity correctly. Both E-auto and E-accr increase when the boundary layer becomes less stable, and the values are larger in precipitating clouds (CLWP > 75 gm(-2)) than those in non-precipitating clouds (CLWP < 75 gm(-2)). Therefore, the selection of E-auto and E-accr values in GCMs should be regime- and resolution-dependent.