Dust induced radiative perturbations during an episode of long-range dust transport over Delhi, India: a high-resolution
- PDF / 11,268,015 Bytes
- 25 Pages / 595.276 x 790.866 pts Page_size
- 8 Downloads / 208 Views
ORIGINAL PAPER
Dust induced radiative perturbations during an episode of long‑range dust transport over Delhi, India: a high‑resolution regional NWP model study Timmy Francis1 · A. Jayakumar1 · Jisesh Sethunadh1 · Saji Mohandas1 · Sumit Kumar1 · E. N. Rajagopal1 Received: 4 May 2019 / Accepted: 18 August 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Dust-induced modifications to the radiative fluxes/heating during a light-blocking haze episode over Delhi, India, 7–9th Nov 2017—triggered by long range transport from a severe Saudi Arabian dust storm—have been investigated with a regional NWP model, NCUM-R with prognostic dust-radiation feedbacks. The study employs ‘Double Radiation Calls’, wherein parallel runs of the radiation scheme ‘with’ (prognostic) and ‘without’ (diagnostic) dust radiative effects—while prognostic fields drive the forecast—isolate the dust-induced perturbations. The forecasted dust optical depth agreed spatially with the AOD from MODIS with Angstrom Exponent > 0.5, indicating that the dust was well mixed with the fine mode anthropogenic aerosols upwind. The ‘downward shortwave (SW) flux’ was diminished (upto − 12.9 W m−2) in layers sampling (i) near-surface (L1Avg), (ii) well-mixed layer within the planetary boundary layer (PBL, L 2Avg) and (iii) free-troposphere (FT, L3Avg). Dust-induced ‘Solar heating’ dominated in FT (upto 9.5 × 10–7 Ks−1) and the patches below (in L2Avg) exhibited a cooling, leading to thermal dipoles. The ‘upward longwave (LW) flux’ in FT was reduced and ‘LW heating’ prevailed in all levels—peak (2.5 × 10–6 Ks−1) in L 2Avg—along with well-defined cooling zones in L1Avg. The dust–radiation interaction in turn influenced the boundary layer meteorology, manifested as (i) shallow PBLs that spatially correlate with dust-induced cooling of the boundary layer column, (ii) enhanced surface humidity and (iii) reduced visibility. The study is an instance of prognostic dust-radiation feedbacks improving the skill of NWP models in dust-laden regions.
1 Introduction Mineral dust, one of the main constituents of the atmospheric aerosols, exerts more complex perturbations in radiation transfer than purely scattering aerosols via scattering as well as absorption of solar and infrared radiation (the direct aerosol effect) (Alpert et al. 1998), with many model studies projecting the radiative forcing by dust comparable or even exceeding those by anthropogenic aerosols
Responsible Editor: Clemens Simmer. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00703-020-00760-3) contains supplementary material, which is available to authorized users. * Timmy Francis [email protected] 1
National Centre for Medium Range Weather Forecasting, Ministry of Earth Sciences, A‑50, Sector 62, Noida 201 309, India
(Tegen and Fung 1995; Li et al. 1996; Sokolik and Toon 1996; Tegen et al. 1996). Dust aerosols can modify the vertical profile of radiative heating, with implications to altering the atmospheric s
Data Loading...
