Diurnal variations refer to the fluctuations or changes that occur over a 24-hour period, typically on a daily basis. This research area focuses on studying and understanding how various biological, environmental, and atmospheric processes exhibit patterns or rhythms throughout the day. Diurnal variations can impact a wide range of factors including weather patterns, biological processes such as human sleep-wake cycles, and environmental conditions like air quality. Researchers in this area often collect and analyze data over a period of time to identify and analyze these diurnal patterns in order to gain insights into the underlying mechanisms and potential impacts.