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Sensitivity of convective precipitation to model grid spacing and land‐surface resolution in ICON
Author(s) -
Singh Shweta,
Kalthoff Norbert,
Gantner Leonhard
Publication year - 2021
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.4046
Subject(s) - precipitation , environmental science , meteorology , atmospheric sciences , numerical weather prediction , convection , orographic lift , forcing (mathematics) , climatology , geology , physics
The impact of model grid spacing and land‐surface resolution (LSR) on convective precipitation are investigated for areas with different orographic complexities. ICOsahedral Nonhydrostatic (ICON) model simulations were performed for six days having weak large‐scale forcing using six model grid spacings (in metres): Numerical Weather Prediction (NWP) (Δ 5000,Δ 2500) and Large‐Eddy Simulation (LES) physics simulations (Δ 1250,Δ 625,Δ 312, andΔ 156) in a nested set‐up. Concerning LSR, we focused on simulations with LSRs of 1,250 and 5,000 m, keeping the model grid spacing at 156 m. The onset of precipitation inΔ 1250is earlier by 0.5–2 hr, while LSR modifications show a similar onset compared withΔ 156. The relative percentage difference (RPD) of areal mean daily precipitation across LES physics simulations decreases consistently with model grid spacing for most of the cases. The RPD of precipitation inΔ 1250is considerably higher (75th percentile: ≈155%) than that of the LSR runs at resolutions of both 1,250 and 5,000 m, with 75th percentiles of ≈7% and ≈22%, respectively. To investigate the processes causing the differences in precipitation characteristics, like onset time and amount, the heat and moisture budgets ofΔ 1250andΔ 156were compared. The results show that, at the initial stage of cloud formation, a higher number of smaller clouds are formed inΔ 156compared withΔ 1250. The small clouds inΔ 156are subject to considerable evaporative cooling at their edges and shell regions, due to entrainment processes. As a result, these clouds often dissolve before they can grow deep. Later on, cloud aggregation inΔ 156also enables precipitation. The delayed onset of precipitation and reduced areas of aggregated clouds having low precipitation rates are the main reasons for less precipitation inΔ 156than inΔ 1250.