Being a good observer leads to being an excellent learner. To know and understand the wind direction in the layer adjacent to the earth is the first step to understanding the weather. One needs to start somewhere and starting at the ground level is a good as any. The planetary boundary layer (PBL) is the lowest part of the atmosphere and is controlled by interactions with the earth - temperature, moisture, turbulence, vertical motion.
If the PBL is stable there is apt to be no wind. Stability means that air parcels are resistant to being shoved around. If they are pushed, they are likely to return to where they started.
If the PBL is unstable there is likely to be a lot of wind. Any air parcel that is shoved is likely to keep going until it encounters an even warmer layer of air and the breaks are put on like with a hot air balloon cooler than its surroundings.
With wind in an unstable PBL, cloud streets form along interacting helical circulations. Individual cloud streets parallel the wind direction in the PBL. Cloud streets themselves are parallel to each other and separated by clear distance related to the height of the PBL above the ground - the height of the capping inversion. The separation of the cloud streets increase with the height of the PBL.
If the PBL is stable there is apt to be no wind. Stability means that air parcels are resistant to being shoved around. If they are pushed, they are likely to return to where they started.
If the PBL is unstable there is likely to be a lot of wind. Any air parcel that is shoved is likely to keep going until it encounters an even warmer layer of air and the breaks are put on like with a hot air balloon cooler than its surroundings.With wind in an unstable PBL, cloud streets form along interacting helical circulations. Individual cloud streets parallel the wind direction in the PBL. Cloud streets themselves are parallel to each other and separated by clear distance related to the height of the PBL above the ground - the height of the capping inversion. The separation of the cloud streets increase with the height of the PBL.
