How does the ELR change during the night in terms of stability?

The change in the Environmental Lapse Rate (ELR) during the night is typically characterized by a stabilization of the atmosphere. At night, the ground cools due to the loss of solar radiation, which leads to a decrease in the temperature of the air immediately near the surface. This process enhances the stability of the atmosphere, as cooler air sinks and alters the vertical temperature gradient.

In general, a stable atmosphere means that the ELR is lower than the adiabatic lapse rates, making it less likely for air to rise and form clouds or storms. The cooling of the surface at night leads to a temperature inversion, where the temperature increases with height at lower levels, further contributing to atmospheric stability. Thus, the night-time conditions promote a stable environment, reducing turbulence and convection.

This behavior is contrasted with daytime conditions, where solar heating often leads to a more unstable atmosphere as the surface warms and the ELR increases. The stabilization process at night is important for understanding various meteorological phenomena, including fog formation and the development of low-level clouds.