A condition in the atmosphere where air parcels are heated and therefore are warmer than the surrounding atmosphere resulting in unstable weather conditions such as heavy rains and hailstorms. See Atmospheric Stability & Instability
River Long Profile
The long profile shows the river from source to mouth with changing gradient and landforms along the course.
The upper course where the river starts is characterised by steep gradient.These steep gradients give the river more velocity and therefore energy to erode and transport.Erosion is mainly vertical creating V-Shaped Valleys . Transportation is mainly traction and saltation as large boulders and cobbles dominate in the bed. During or after heavy storms velocities are high that even boulders can be lifted and transported considerable distances. Flows are turbulent with eddies. This is because boulders causes flowing water to bump and diverge creating irregular turbulent flows. Landforms which dominate the upper course are: waterfalls, rapids, interlocking spurs,gorges and terraces.
In the middle course gradients are relatively gentler. Erosion is mainly diverted to lateral caused by hydraulic action or cavitation (vertical erosion also happens). Channels are now wide and relatively shallow compared to the upper course and the cross section is U-Shaped. Sediment is transported in suspension as it is now small. Flows are less violent or turbulent. Main landforms are meanders, ox-bow lakes, floodplains, incised meanders, terraces, point bars and cliffs.
The lower course is mostly dominated by deposition. Erosion is less pronounced but channels are very wide.The load is now big as many tributaries have deposited their load in the main channel causing river velocity to be overpowered to carry the load anymore. Landforms such as deltas, braids, levees, meanders, ox-bow lakes and floodplains are dominate. NB: Some landforms can be found in more than one course such as terraces which are a result of vertical and lateral erosion or meanders which are a result of erosion and deposition.