What does "WS" signify in relation to METAR wind reports?

In METAR wind reports, "WS" signifies wind shear, which refers to a change in wind speed or direction with altitude. Wind shear can occur in various atmospheric conditions and is particularly significant during takeoff and landing phases of flight, as it can impact aircraft performance. Identifying wind shear in METAR reports alerts pilots and air traffic controllers to potential turbulence or unexpected changes in wind patterns, crucial for safety during flight operations.

Understanding wind shear is essential for pilots because it can lead to challenging flying conditions, including turbulence or sudden shifts in lift, which must be anticipated for safe maneuvers. In contrast, the other options do not accurately describe the meaning of "WS" in a wind report, as they relate to different aspects of weather and wind measurement.