The correct answer is option 1: uniform low pressure.
Doldrums are a region near the equator where the trade winds from the Northern and Southern hemispheres converge. In this region, the warm air rises due to intense solar heating, creating a zone of low atmospheric pressure. This low pressure causes the air to be less dense and rise, leading to calm and light variable winds.
Option 2, uniform high pressure, is incorrect. Doldrums are actually characterized by low pressure rather than high pressure.
Option 3, high wind velocity, is incorrect. As mentioned earlier, doldrums are known for their light and calm winds, not high wind velocity.
Option 4, low humidity, is unrelated to the characteristics of doldrums. Humidity refers to the amount of moisture in the air, which is not directly associated with the formation of doldrums.
In conclusion, doldrums are characterized by uniform low pressure, which leads to calm winds and a lack of strong air movements in the area.