• Aditi Singh

      Articles written in Journal of Earth System Science

    • Prediction of fog/visibility over India using NWP Model

      Aditi Singh John P George Gopal Raman Iyengar

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      Frequent occurrence of fog in different parts of northern India is common during the winter months of December and January. Low visibility conditions due to fog disrupt normal public life. Visibility conditions heavily affect both surface and air transport. A number of flights are either diverted or cancelled every year during the winter season due to low visibility conditions, experienced at differentairports of north India. Thus, fog and visibility forecasts over plains of north India become very important during winter months. This study aims to understand the ability of a NWP model (NCMRWF, Unified Model, NCUM) with a diagnostic visibility scheme to forecast visibility over plains of north India. Thepresent study verifies visibility forecasts obtained from NCUM against the INSAT-3D fog images and visibility observations from the METAR reports of different stations in the plains of north India. The study shows that the visibility forecast obtained from NCUM can provide reasonably good indication ofthe spatial extent of fog in advance of one day. The fog intensity is also predicted fairly well. The study also verifies the simple diagnostic model for fog which is driven by NWP model forecast of surface relative humidity and wind speed. The performance of NWP model forecast of visibility is found comparable tothat from simple fog model driven by NWP forecast of relative humidity and wind speed.

    • Analysis of fog and inversion characteristics and prediction of fog and associated meteorological parameters using NWP model over sub-urban Bangalore


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      This is a comprehensive approach for the analysis of fog attributes with high-density intra-hourly data (Oct–Mar) for a period of 11 years from Jan 2009 to Dec 2019 in sub-urban Bengaluru. Also, the characteristics of nocturnal inversion parameters have been examined on the days with/without fog to explore any relationship between the two concurring meteorological phenomena. Lastly, ability of NWP model (NCMRWF, Unified Model, NCUM) was examined for predicting fog over Kempegowda International Airport, Bengaluru. Under the studied time frame, December reported 129 and January 126 fog events, while October, November, February, and March reported 33, 96, 44, 11 events, respectively. Similarly, December and January accounted for maximum fog hours. More than 80% of fog events were reported between 2200 and 0200 UTC with maximum (74) in the 0100–0129 UTC slot and dispersed between 0000 and 0400 UTC. Intensity-wise, shallow fog is most frequent (51%), while moderate, dense, and very-dense have a frequency of 29, 19.6 and 0.4%, respectively. As for atmospheric inversions in Bengaluru, elevated inversions are common occurrences throughout the year, while surface inversions are more frequent in the winter. In the study, it was found that 35% fog events coincided with two elevated inversions (EI) under the 700 hPa ceiling, whereas 25% occurred with a single EI. Surface inversions coinciding with fog events are relatively rare and mostly (71%) occur alongside EI. NWP model predicted reduced visibility during fog events with a hit rate of 42%, false alarm rate of 5% and bias value of 0.76. Model produced mixed results in forecasting of meteorological parameters and visibility. Wind speed and visibility were underestimated, whereas temperature and relative humidity show good agreement with the observed values.

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