why do the winds get calmer at night and morning as opposed to the afternoon during the summer?

Answer 1

Local winds are caused by temperature differentials. If the land is hotter than the sea, for example, air rises over the land and wind blows inland from the sea. Temperatures are highest and thus create the greatest differentials during the afternoon, but are more even when the sun is down or early in the day.

Answer 2

I suspect that you live in the plains or low rolling hill country somewhere or else you would be asking why is it so windy during a clear night and more calm on a bright sunny day.

At night, particularly a nice clear night, with no significant pressure gradient (strong surface low pressure systems around) air will cool most rapidly next to the surface due to radiational cooling. This causes the air to become more dense and settle down next to the ground causing a temperature gradient that is inverse of the normal, "Air gets cooler as you increase height", which is called an inversion. This cool, more dense layer of air next to the surface becomes very stable and doesn't want to move and becomes disconnected (forecasters will use the term decoupled) and any wind will be above this cool layer. In some cases, where there is a significant upper level feature (mid level lows) a night time (nocturnal) low level jet may devleop which results in a possible wind shear problem. I have often seen calm winds at the surface at night with 45 mph winds less than 2000 feet above the surface.

During the day, the heating from the sun will create thermals that mix the air in the lower portion of the atmosphere. There is wind that is caused by the thermals (microscale winds) but also, there often is a momentum transfer of the air flow aloft (where the normally stronger winds are) and those can be mixed down to the surface resulting in stronger breezes. The strongest winds normally is when the deepest mixing of the atmosphere occures which is during the middle part of the afternoon.

In the mountains, this cooler, more dense air will actually slide down the side of mountains and collect in the valleys and even then flow down the valley during the night. These are called down slope and valley winds. They can be quite strong in some cases. The winds reverse in the mountains when during the day, heating of the side of the mountains cause up-slope of up valley winds. The reversal of wind during the morning can cause people fighting forest fires lots of problems and they have to be very wary of this switch.

Answer 3

The heating of the day time sun creates convection and instability. Try to heat up a pan full of water and watch the movement increase when the temperature is hotter. This is resembling daytime conditions. When there is no heat source, just like night time, the water remains still. This is mostly true unless there is an active storm moving in, then the wind is generated from the storm it's self.

Answer 4

The wind at a place is seldom steady.Both the speed and direction vary with time.Sometimes the fluctuations are sudden and short-lived.These are called gusts(sudden increase in speed)and lulls(sudden decrease in speed).These are caused due to turbulence in the atmosphere.
There are generally two types of turbulence.One is mechanical turbulence and the other is the thermal turbulence.The former is caused due to obstruction to wind and the latter is caused due differential heating of the air near the surface.
The thermal turbulence is minimum in the night and morning and maximum during the afternoon and evening.Hence the wind is light and fairly steady in the morning and strong and turbulent in the later part of the day.This phenomena is sometimes called diurnal variation of wind.

Answer 5

because winds are caused from the air in the atmosphere trying to diffuse itself. the sun adds energy to the air and the air starts moving around to equalize itself out. at night the air isn't absorbing the energy of the sun.

Answer 6

I have wondered that myself . I love sleeping with the windows open at night and fall asleep listening to the cricket's . On occasion there will be a breeze but not enough to keep you cool