Atmospheric convection is called "deep" when it extends from near the surface to above the 500 hPa level, generally stopping at the tropopause at around 200 hPa. Most atmospheric deep convection occurs in the tropics as the rising branch of the Hadley circulation; and represents a strong local coupling between the surface and the upper troposphere which is largely absent in winter midlatitudes. Its counterpart in the ocean (deep convection downward in the water column) only occurs at a few locations. While less dynamically important than in the atmosphere, such oceanic convection is responsible for the worldwide existence of cold water in the lowest layers of the ocean.