Sensitivity of convective precipitation to model grid spacing and land-surface resolution in ICON,Quarterly Journal of the Royal Meteorological Society

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Sensitivity of convective precipitation to model grid spacing and land-surface resolution in ICON
Quarterly Journal of the Royal Meteorological Society ( IF 3.0 ) Pub Date : 2021-05-02 , DOI: 10.1002/qj.4046
Shweta Singh ₁ , Norbert Kalthoff ₁ , Leonhard Gantner ₁

Affiliation

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}

, and

Δ_{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 in

Δ_{1250}

is earlier by 0.5–2 hr, while LSR modifications show a similar onset compared with

Δ_{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 in

Δ_{1250}

is 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 of

Δ_{1250}

and

Δ_{156}

were compared. The results show that, at the initial stage of cloud formation, a higher number of smaller clouds are formed in

Δ_{156}

compared with

Δ_{1250}

. The small clouds in

Δ_{156}

are 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 in

Δ_{156}

also enables precipitation. The delayed onset of precipitation and reduced areas of aggregated clouds having low precipitation rates are the main reasons for less precipitation in

Δ_{156}

than in

Δ_{1250}

.

中文翻译：

对流降水对 ICON 模型网格间距和地表分辨率的敏感性

针对具有不同地形复杂性的地区，研究了模型网格间距和地表分辨率 (LSR) 对对流降水的影响。ICOsahedral Nonhydrostatic (ICON) 模型模拟使用六个模型网格间距（以米为单位）进行了六天的弱大规模强迫：数值天气预报 (NWP) (