The upper figure shows mean distributions of stratiform and convective rainfall. Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall. A stratocumulus cloud is another type of a cumuliform or stratiform cloud. Wave clouds with clear gaps through which lower stratiform layers may be seen. Warm fronts are usually preceded by stratiform precipitation and fog. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Stratus stratocumulomutatus clouds occur when stratocumulus opacus patches fuse to create a stratiform layer. Convective precipitation is generally more intense, and of shorter duration, than stratiform precipitation. An area of stratiform precipitation develops poleward of the warm front along the conveyor belt. Of the stratiform group, high-level cirrostratus comprises two species. Rainbands can be stratiform or convective, and are generated by differences in temperature. Chromite can be seen in stratiform deposits as multiple layers which consist of chromitite. They are stratiform massive sulfide bodies hosted in Carboniferous black shale and altered carbonates. Nimbostratus clouds are stratiform layers with sufficient vertical extent to produce significant precipitation.