How does the earth surface affect the characteristics of an air mass?

Conduction is the transfer of heat via contact. In the atmosphere this mean only the first 3 meters of the atmosphere usually. After that wind will mix up the air and we have a new first 3 meters of air to be modified.

Additionally the moisture content of the air is directly by the water at the earth's surface. This stands to reason as you need water to get water vapor.

The fact that conduction is a poor transfer of heat is why it takes weeks for a air mass to form.

The Earth's surface affects the characteristics of an air mass by influencing its temperature, moisture content, and stability. Land surfaces absorb and release heat more rapidly than water surfaces, leading to temperature variations between continental and maritime air masses. Additionally, different surface types, such as mountains, forests, deserts, and oceans, can alter air mass properties by modifying surface heating, moisture availability, and atmospheric circulation patterns. These variations influence the temperature, humidity, and stability of air masses as they move across different regions, impacting weather patterns and climate conditions.