Assessment of fog conditions over capital city Delhi (India) during December 2023–January 2024
摘要
This research examines the fog conditions in Delhi, India, for the winter season of December 2023–January 2024 (D–J). Known for its severe air quality challenges, Delhi experiences frequent and intense fog episodes during winter season, significantly affecting transportation, public health, and daily routines. The analysis is mainly based on data from ground-based observations at the Palam and Safdarjung meteorological stations, focusing on the frequency, duration, and intensity of fog events in winter months. The data reveals that Delhi encountered periods of dense to very dense fog (DDF) during the winter season, particularly in the last week of December 2023 and from the second week to the end of January 2024. This study examined various meteorological factors including temperature inversion, relative humidity, dew point depression, wind patterns and synoptic systems. The analysis reveals that relative humidity exceeds 95% on 78% of the days with DDF conditions. In December, minimum temperatures over Delhi were in the range from 5 to 16 °C, while in January, these were in the range from 3 to 10 °C. Wind speeds generally ranged from 0 to 6 knots, with westerly and northwesterly directions prevailing during most periods of DDF conditions. The dew point depression was ≤ 1.0 °C, observed 75–100% of the time over Delhi during DDF conditions. Temperature inversions and DDF conditions coincided in 87% of cases, while 24% of DDF events occurred without an inversion. Synoptically, 17 Western Disturbances (WDs) moved eastward towards Delhi, during December 2023–January 2024, with 16 reaching within a 1000 km radius of the city. Although DDF events in Delhi are typically associated with the presence of a WD, there were also notable instances of DDF occurring without any WD in the region. This study may be useful for understanding and management of fog conditions in urban areas like Delhi, focusing on improving preparedness and response strategies.