'ध्रुवीय वाताग्र सिद्धांत' (Polar Front Theory) मुख्य रूप से निम्नलिखित में से किस वायुमंडलीय परिघटना से संबद्ध है?

With reference to the Madden-Julian Oscillation (MJO), consider the following statements: I. It is an eastward-moving tropical disturbance rather than a stationary atmospheric trough. II. It is associated with alternating phases of enhanced and suppressed cloudiness, convection and rainfall. III. It generally operates within the tropical belt between 30°N and 30°S latitudes. IV. It can influence monsoon variability as well as tropical cyclone activity. Which of the statements given above are correct?

Which of the following correctly explains the formation of clouds in the atmosphere?