Final answer:
Low specific humidity values along the western coast of South America are primarily due to the cold Humboldt or Peru Current, which cools the air and reduces its capacity to retain moisture.
Step-by-step explanation:
A possible explanation for why specific humidity values are relatively low in the ocean adjacent to the western coast of South America is the presence of a cold ocean current, known as the Humboldt or Peru Current. This cold current flows northward along the western coast of South America, cooling the air above the ocean surface and reducing its ability to hold moisture, thus leading to lower specific humidity. Additionally, the phenomenon of upwelling, which is common in this region due to the Subtropical Convergence, brings cool, nutrient-rich water to the surface, further lowering the temperature and reducing the humidity of the overlying air. Factors such as wind systems, ocean currents, and latitude are crucial in influencing the climate and weather patterns in this area.