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<p>Fog is a common occurrence during the winter season in the Indo-Gangetic plains, often causing hazardous disruptions in daily life. Accurately predicting the intensity and spread of fog with sufficient lead time is a challenging task. Most available techniques rely on continuous remote sensing observations to fill data gaps. To enhance our fog forecasting precision, it’s crucial to validate fog intensity and spatial extent both during the day and night. This study primarily focuses on monitoring nighttime fog using satellite-derived fog products. Nighttime fog information is obtained from the difference of Mid-Infrared and Thermal Infrared (MIR-TIR1) channels of the INSAT-3DR satellite. The conventional threshold for channel differencing to identify fog pixels has been set at 2.5&#xa0;°C or K. However, this research reveals that this threshold isn’t consistent across the entire Indo-Gangetic plains or the broader Indian region, especially when dealing with radiation fog. This study examines the relationship between Brightness Temperature Difference (BTD) and visibility conditions at four key locations within the Indo-Gangetic Plains—Amritsar, Varanasi, Delhi, and Lucknow. Focusing on the winter season of 2020–21 (December–January), various fog events were analyzed using different BTD threshold values. Findings indicate that in Delhi, the majority of fog events in January (58%) occurred when BTD was less than − 2.5. A similar pattern was observed in Amritsar during December, with 30% of cases falling within this BTD range. In Varanasi, 33% of foggy events in January also aligned with BTD &lt; -2.5. However, in contrast, Lucknow showed a different trend, with 28% of fog events occurring when BTD ranged between 0 and 2.5. These results underscore the importance of accounting for temporal variability, as BTD thresholds for fog detection can differ significantly by month and location. Additionally, the research presents a time-series analysis of visibility occurrences at these locations as part of the case study.</p>

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Analysis of Fog Occurrence During Night time Over the Indo-Gangetic Plain with INSAT-3DR Data Channel Difference Method

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • Neeti Singh,
  • Kalash Sharma,
  • Shailesh Parihar,
  • R. K. Giri

摘要

Fog is a common occurrence during the winter season in the Indo-Gangetic plains, often causing hazardous disruptions in daily life. Accurately predicting the intensity and spread of fog with sufficient lead time is a challenging task. Most available techniques rely on continuous remote sensing observations to fill data gaps. To enhance our fog forecasting precision, it’s crucial to validate fog intensity and spatial extent both during the day and night. This study primarily focuses on monitoring nighttime fog using satellite-derived fog products. Nighttime fog information is obtained from the difference of Mid-Infrared and Thermal Infrared (MIR-TIR1) channels of the INSAT-3DR satellite. The conventional threshold for channel differencing to identify fog pixels has been set at 2.5 °C or K. However, this research reveals that this threshold isn’t consistent across the entire Indo-Gangetic plains or the broader Indian region, especially when dealing with radiation fog. This study examines the relationship between Brightness Temperature Difference (BTD) and visibility conditions at four key locations within the Indo-Gangetic Plains—Amritsar, Varanasi, Delhi, and Lucknow. Focusing on the winter season of 2020–21 (December–January), various fog events were analyzed using different BTD threshold values. Findings indicate that in Delhi, the majority of fog events in January (58%) occurred when BTD was less than − 2.5. A similar pattern was observed in Amritsar during December, with 30% of cases falling within this BTD range. In Varanasi, 33% of foggy events in January also aligned with BTD < -2.5. However, in contrast, Lucknow showed a different trend, with 28% of fog events occurring when BTD ranged between 0 and 2.5. These results underscore the importance of accounting for temporal variability, as BTD thresholds for fog detection can differ significantly by month and location. Additionally, the research presents a time-series analysis of visibility occurrences at these locations as part of the case study.