Correct Option
Assertion (A) states that anticyclonic conditions are formed in the winter season when atmospheric pressure is high and air temperatures are low. Anticyclones are high-pressure systems characterized by subsiding cold, dense air, leading to clear skies and stable atmospheric conditions. In winter, particularly over northern India, radiative cooling at night significantly lowers surface temperatures. This cold, dense air increases atmospheric pressure, thereby creating and reinforcing anticyclonic conditions. Thus, Assertion (A) is correct.
Reason (R) states that winter rainfall in northern India causes the development of anticyclonic conditions with low temperatures. Winter rainfall in northern India is primarily associated with Western Disturbances. These are temperate low-pressure systems that bring moisture. After the passage of a Western Disturbance and the associated rainfall, the skies often clear, and the air becomes colder and denser due to radiative cooling and atmospheric subsidence. This subsequent cooling and increase in air density lead to a rise in atmospheric pressure, fostering the development or intensification of anticyclonic conditions characterized by low temperatures. Thus, Reason (R) is correct.
Reason (R) provides a direct explanation for the formation and intensification of anticyclonic conditions in winter. The cooling effect following winter rainfall, especially from Western Disturbances, contributes to increased air density and a subsequent rise in atmospheric pressure, which are the defining characteristics of anticyclones with low temperatures. Therefore, Reason (R) correctly explains Assertion (A).
Incorrect Options
Option (b) is incorrect because Reason (R) directly explains a mechanism contributing to the formation of anticyclonic conditions in winter, establishing a causal link with Assertion (A).
Options (c), (d), and (e) are incorrect because both Assertion (A) and Reason (R) are factually correct statements regarding meteorological phenomena observed in northern India during the winter season.