Xueshun Shen Minghuan Wang Chinese Academy of Meteorological Sciences China Meteorological Administration Feng Xiao Tokyo Inst. of Tech.

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1 Application of a high-resolution conservative advection scheme to GRAPES meso-scale scale model Xueshun Shen Minghuan Wang Chinese Academy of Meteorological Sciences China Meteorological Administration Feng Xiao Tokyo Inst. of Tech. Outline Brief introduction of background PRM & its application to GRAPES_Meso Forecast experiments

Necessity in accurate representation of sharp gradients in moisture field Unique feature of summer weather

variances Discontinuity along boundary of cloud band Sharp gradient of moisture Discontinuities of Cloud

structures, cloud boundary over the East Asian monsoon region in meso-scale NWP model, of course in much

2 Necessity in accurate representation of sharp gradients in moisture field Unique feature of summer weather over the East Asia: Mei-yu Sharp horizontal gradient of lower-level level moist field Small-scale moisture variances Discontinuity along boundary of cloud band Sharp gradient of moisture Discontinuities of Cloud boundary To better represent sharp-gradient of low-level moisture, small scale moisture variances & cloud structures, cloud boundary over the East Asian monsoon region in meso-scale NWP model, of course in much higher resolution model (say ~km resolution) because the discontinuity or sharp gradient in moist fields becomes much more obvious.

3 GRAPES_Meso Non-hydrostatic -time-level semi-implicit semi-lagrangian (SISL) time-stepping Quasi-monotone semi-lagrangian scheme for scalar advection Too diffusive revolution 0 revolution 3

4 Forecast QMSL 4 hour accumulated rainfall Rainfall intensity is weak 00 mm/day heavy rainfall is difficult to forecast Obs. Application of PRM to SL model ^ ^ q u v w qu qv q w q z z t z z z z z q u qu z q t z q v qv z q t z z z z q w qw q t z z z Volume remapping Multi-dimensional time-splitting Rancic,, 99 4

5 PRM: High-order reconstruction with 3 degrees of freedom f (x) i/ F(x i i F(x i i Δx F i i f i/ xi/ x i x i/ x ) i x i ) f n i F(x)dx ρ i n fi n i Given one cell average & two interface values f i/, f i / Find piecewise function Piecewise Parabolic (PPM) F ( x) c i 0 c F ( x) i 0 c ( x x c ( x x i ) c ( x x Extension of PPM Piecewise Rational (Present) i [ c ( x x ) c c ( x x i )] i ) i i ) PRM: Piece-wise Rational Method (Xiao et al., 004) PRM: a simple and practical alternative to the PPM PRM: do not need modifications of monotonicity Straightforward convexity / monotonicity preserving by using the nature of rational function More accurate numerical dispersion than PPM PRM provides sub-grid resolution Better numerical properties shown in various numerical experiments J.Comp.Phys.,vol.98/, pp 389, 004 5

6 QMSL QMSL revolution 0 revolution PRM PRM revolution 0 revolution PRM Forecast QMSL 4 hour accumulated rainfall Obs. 6

7 July average of 4-hr accumulated rainfall QMSL Obs. PRM PRM can keep more reasonable moisture gradient 7

8 score of 4hr accumulated rainfall GRAPES- 5km TS 4小时降水预报t s评分 nom3dv中雨 nom3dv_pr m中雨 nom3dv大雨 nom3dv_pr m大雨 >5mm >50mm July 年7月 Aug 年8月 8km 6km km One-way nesting 8

Fine-scale GRAPES_Meso Piecewise Rational Method for scalar advection (high accuracy conserved monotonic) Raymond filter to remove the unresolved topo.

9 Fine-scale GRAPES_Meso Piecewise Rational Method for scalar advection (high accuracy conserved monotonic) Raymond filter to remove the unresolved topo.. & mitigate the steepness Vertical velocity damping to prevent the grid-point storm 4 th -order horizontal diffusion with orographic flux limiting Relaxation boundary condition Mixed phase microphysics by CAMS & WSM6 Complicated land surface process Gradient & Orientation of topography on surface radiation Higher-order PBL with moist effect; non-local PBL Shallow convection dynamics physics Severe flood occurred over Huai River basin during Jun.9-Jul.6/007 Jul.6/007 since ~800 mm 年的流域性大洪水安徽五河毫米河南鸡公山 84.3 毫米安徽固镇 85. 毫米河南信阳 83.5 毫米淮河流域今年 6 月 9日进入多雨期, 至 7 月 6日结束, 持续 38天 ; 持续性强降水集中在 6 月 9日至 7 月 6 日期间 9

10 obs-000 stations 6km resolution obs-000 stations km resolution 0

11 obs-000 stations 6km obs-000 stations km

12 Rainfall forecast of GRAPES km on opening ceremony day of BJ08 GRAPES km hourly rainfall forecast Fcst. Rainfall forecast of GRAPES km on opening ceremony day of BJ08 4 o N 30' 0 Aug.8 obs model 40 o N 8 30' 5 o E 6 o E 7 o E 8 o E :00 6:00 0:00 00:00 04:00 08:00

13 dbz Radar echo Hourly rainfall forecast By improving the advection algorithm of water substances, forecast of heavy, torrential and storm rainfall are improved to a large extent. 3

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Techniques of Severe Convective Weather Comprehensive Monitoring

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