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. 2021 Feb 18;11(1):4104.
doi: 10.1038/s41598-021-83467-8.

Performance of high resolution (400 m) PM2.5 forecast over Delhi

Chinmay Jena  1 , Sachin D Ghude  2 , Rajesh Kumar  3 , Sreyashi Debnath  4   5 , Gaurav Govardhan  4   6 , Vijay K Soni  7 , Santosh H Kulkarni  8 , G Beig  4 , Ravi S Nanjundiah  4   9 , M Rajeevan  10
Affiliations

Performance of high resolution (400 m) PM2.5 forecast over Delhi

Chinmay Jena et al. Sci Rep. .

Abstract

This study reports a very high-resolution (400 m grid-spacing) operational air quality forecasting system developed to alert residents of Delhi and the National Capital Region (NCR) about forthcoming acute air pollution episodes. Such a high-resolution system has been developed for the first time and is evaluated during October 2019-February 2020. The system assimilates near real-time aerosol observations from in situ and space-borne platform in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to produce a 72-h forecast daily in a dynamical downscaling framework. The assimilation of aerosol optical depth and surface PM2.5 observations improves the initial condition for surface PM2.5 by about 45 µg/m3 (about 50%).The accuracy of the forecast degrades slightly with lead time as mean bias increase from + 2.5 µg/m3 on the first day to - 17 µg/m3 on the third day of forecast. Our forecast is found to be very skillful both for PM2.5 concentration and unhealthy/ very unhealthy air quality index categories, and has been helping the decision-makers in Delhi make informed decisions.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Averaged surface PM2.5 simulated by the model before (red) and after (green) assimilation at 0900 UTC assimilation cycle and its comparison with observed mean PM2.5 over Delhi during 21 October 2019 to 01 February 2020. The model output is averaged over the observational locations across Delhi.
Figure 2
Figure 2
(a) Spatial distribution of averaged PM2.5 concentrations at 400 m horizontal grid-spacing (from day 1 forecast) overlaid with mean PM2.5 observed at different monitoring stations across Delhi during 21 October 2019 to 01 February 2020, (b) Comparisons between daily mean PM2.5 forecast (red) and daily mean PM2.5 observations (blue) over Delhi during 21 October 2019 to 01 February 2020 (vertical bar shows the standard deviation).
Figure 3
Figure 3
(a) Comparisons between hourly mean PM2.5 forecast (red) and hourly mean PM2.5 observations (blue) on day one forecast at 400 m horizontal grid spacing over Delhi during 21 October 2019 to 01 February 2020 (vertical bar shows the standard deviation) and (b) diurnal plots of hourly mean PM2.5 observations and hourly mean PM2.5 forecast on day one (red), day two (blue) and day three (green).
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