How is wind direction expressed in surface observations?

Wind direction in surface observations is expressed in degrees from true north because this method provides a clear and standardized way to understand which direction the wind is coming from. In meteorology, wind is described by the direction from which it originates, not the direction it is blowing toward. Measuring this in degrees allows for precise communication among meteorologists and simplifies the interpretation of wind patterns.

True north is a fixed reference point; therefore, stating wind direction in degrees (0° being north, 90° east, 180° south, and 270° west) offers an unambiguous understanding of the wind's source direction. This also facilitates the plotting of wind data on maps and helps in various analyses such as weather forecasting and aviation.

The other options are measurements or units that pertain to other aspects of wind: miles per hour and knots are both units of speed, measuring how fast the wind is moving, while centimeters per second, although a valid measure of speed, is not commonly used in meteorological contexts. Thus, they do not provide information about the direction from which the wind is blowing.