WRF-NMM Nesting for Advanced Hurricane Forecasting and other

WRF-NMM Nesting for Advanced Hurricane Forecasting and other Mesoscale Modeling Applications S. G. Gopalakrishnan and Dusan Jovic Environmental Modeling Center SAIC/NCEP/NOAA/NWS, Washington, DC

Acknowledgements Naomi Surgi Robert Tuleya Thomas Black Zavisa Janjic Brad Ferrier John Michalakes* NCEP/EMC/NOAA, Washington D. C. *NCAR, Boulder, Colorado

WRF-NMM: The Mesoscale Model Real cases: Standard Initialization (WRF-NMM SI) Because. /WRFSI/srcroot/src/mod/wrfsi_static WRF 2. 0 in. /dyn_nmm/NMM_NEST_UTILS 1. F is used in reading high resolution land use data in. /Registry the netcdf format, compilation of HWRF is. /inc dependent on the WRF-NMM SI, in WRFV 2. 0 However this. /Main case in the release is not the version!! . /dyn_nmm . /phys. /frame. /share. /external Post Processor: NCEP WRFPOST (& diffwrf)

External Data Used In Nested WRF-NMM Modeling System • WRF NMM SI may use GFDL or GFS or Eta model grib files for initializing the parent domain, as usual. Bottom Line: • HWRF uses GFDL grib files for initial and boundary Same WRF-NMM SI but used with conditions. changes to grib_prep. nl, Vtables and call-script level changes to • Because GFDL grib files do not have soil moisture (SM 000010 & SM 010200) and soil temperature accommodate the GFDL (ST 000010 & ST 010200) over land we use the GFS Initialization data as surrogate. grib_prep. pl is run twice and the Vtables are modified accordingly. (HWRF users please refer to. /RUN/wrfsi_nmm. scr and. /RUN/grib_prep. nl for more details.

STATIC/MOVING NEST SPECIFIC EXTERNAL DATA • The only external data that the nested domain requires at this time is the static. wrfsi. rotlat which contains topography and other terrain related parameters (such as the land sea mask). Bottom Line: • For a 3: 1 parent: nest ratio, simply run the domain localization part in the wrfsi with the wfsi. nl have all the static field Now you set to: at high resolution all over the parent XDIM=3*parent_xdim – 2 ! Factor 2 takes care of staggering domain and this is important for YDIM=3*parent_ydim – 2 ! Factor 2 takes care of staggering nested grid motion! MOAD_DELTA_X=PARENT_X_RESOLUTION/3. 0 MOAD_DELTA_Y=PARENT_Y_RESOLUTION/3. 0 • Create static. wrfsi. rotlat and put that in a subdirectory. /nest 1/static/ (that has to be created) along with the other data files (like VEGPARM. TBL) required to run the model.

The WRF-NMM Modeling System • Regional-Scale, Moving Nest, Atmospheric Modeling System. • Non-Hydrostatic system of equations formulated on a rotated latitude-longitude, Arakawa E-grid and a vertical, pressure hybrid (sigma_p-P) coordinate. • Advanced HWRF, 3 D Variational analysis that includes vortex reallocation and adjustment to actual storm intensity. • Uses SAS convection scheme, GFS surface, boundary layer physics, GFDL/GFS radiation and Ferrier Microphysical Scheme. • Ocean coupled modeling system.

☞ Nonhydrostatic model equations; for simplicity, inviscid, adiabatic, sigma: ● Φ, w and ε not independent, watch for overspecification! ● BC: at the top, Janjic, et al. , Mon. Wea. Rev. , 2001; at the bottom. Janjic, Meteor. Atmos. Phys. , 2002)

Some Numerical Details Time stepping method fast waves: forward-backward vertically propagating sound waves: implicit Advection: horizontal: Adams-Bashforth for U, V and T (and Coriolis) vertical: Crank-Nicholson for U, V and T forward, flux-corrected for q and water species Horizontal diffusion forward, 2 nd order “Smagorinsky-type” http: //www. mmm. ucar. edu/mm 5/workshop/ws 04/Session 7/Janjic. Zavisa. pdf

Salient Features: Telescopic E-Grid • All interpolations are done on a rotated lat-lon, E-grid with the reference lat-lon located at the centre of the parent domain. • Consequently the nested domain can be freely moved anywhere within the grid points of the parent domain, yet the nested domain lat-lon lines will coincide with the lat-lon lines of the parent domain at integral parent-to-nest ratio. • This coincidence of grid points between the parent and nested domain eliminates the need for more complex, generalized remapping calculations in the WRF Advanced Software Framework and is expected to aid better distributed memory performance, and portability of the modeling system.

Salient Features: Telescopic E-Grid • Large Scale portion of the flow may be easily separated from the small scale structure which may be advantageous for Hurricane analysis. • However, as pointed out by Zhang et al. (1986; MWR), for the sake of smooth solutions across the interfaces it may be necessary to sacrifice mass and energy conservation across the interface in this approach. Nevertheless, for short-term numerical forecasts in which the use of appropriate model physics and the patterns to be forecast may be important than exact mass and energy conservation, as long as the mass (or energy) discrepancy at the interface is small.

Salient features: Initial Conditions • Simple bi-linear interpolation is used for initializing all the meteorological fields along the horizontal. • Nearest neighbor approach is adopted for prescribing most of the land state variables. • High-resolution topography and land-sea mask are redefined over the nested domain using the wrfsi dataset. • To be consistent with the NMM model numerics, quasi-hydrostatic mass balancing is carried out after introducing the high resolution topography. Cubic spline interpolation is used to interpolate data back and forth from standard pressure surfaces on to the hybrid surfaces.

Salient features: WRF-NMM Nested Boundary Conditions Because of the E-grid structure and the fact that the input interface (where the external boundary conditions are prescribed) is well separated from dynamic interface (where the model integration is carried out), boundaries are updated at every time step of the parent domain in a very similar manner as the parent domain is updated at the mass point from the external data source.

LBCs: WRF-NMM Nest Specific! § Along the horizontal direction, bi-linear interpolation is used for all progonostic variable (u, v, t, q, cwm, pd). However, geopotential height field (z 3 d), temperature (t) and moisture (q) are vertically interpolated (using cubic spline) from the hybrid surfaces on to standard pressure levels in the parent domain. Using interpolated information of the height fields from the parent domain, and high resolution topography over the nested domain, mass is adjusted and the new hybrid surfaces are reconstructed. Temperature and moisture which are available after horizontal interpolation from the parent domain at standard pressure levels are interpolated on to the new hybrid surfaces. The approach seem to be involved yet, as seen later, produces an effective way of updating the interface without much distortion or noise even while moving the teslesopic nest.

WRF-NMM namelist. input: nest specific!. /frame/LOGICAL FUNCTION nests_to_open &domains max_dom grid_id parent_id = 2, = 1, = 0, 2, 1, &time_control start_year start_month start_day start_hour start_minute start_second end_year end_month end_day end_hour end_minute end_second = 2005, = 07, = 06, = 00, = 2005, = 07, = 11, = 06, = 00, 2005, 07, 06, 00, 2005, 07, 11, 06, 00, CALL nl_get_max_dom ( 1, max_dom ) DO nestid = 2, max_dom IF (. NOT. active_domain( nestid ) ) THEN CALL nl_get_parent_id ( nestid, parent_id ) IF ( parent_id. EQ. parent%id ) THEN CALL nl_get_start_year (nestid, s_yr) CALL nl_get_end_year (nestid, e_yr) CALL nl_get_start_month (nestid, s_mm) CALL nl_get_end_month (nestid, e_mm) CALL nl_get_start_day (nestid, s_dd) CALL nl_get_end_day (nestid, e_dd) CALL nl_get_start_hour (nestid, s_h) CALL nl_get_end_hour (nestid, e_h) CALL nl_get_start_minute (nestid, s_m) CALL nl_get_end_minute (nestid, e_m) CALL nl_get_start_second (nestid, s_s) CALL nl_get_end_second (nestid, e_s) …………. ENDDO

WRF-NMM : Setting up multiple domains Option 1: Both grid 2 and grid 3 are children of grid 1. &domains max_dom grid_id parent_id = 3, = 1, = 0, 2, 1, 3, 1, Possible only with one-way nests! Option 1: Both grid 2 and grid 3 are children of grid 1. &domains max_dom grid_id parent_id = 3, = 1, = 0, 2, 1, 3, 2,

namelist. input: history file for the nest &time_control history_interval frames_per_outfile = 360, = 1, 360, 1, WRF model produces nested domain outputs very similar to those of the parent domain. The history outputs are called as wrfout_d 02_? ? as against wrfout_d 01_? ? for the parent domain. As a rule of the thumb, look at the rconfig entry in the Registry file and if is set to max_domains then you may set the corresponding column for the nest with a vaild entry in the namelist !!!

Domain configuration for the nest &domains time_step = 60, time_step_fract_num = 0, time_step_fract_den = 1, s_we = 1, e_we = 160, s_sn = 1, e_sn = 310, s_vert = 1, e_vert = 43, parent_grid_ratio = 1, parent_time_step_ratio= 1, dx =. 18, dy =. 18, . /share/MODULE module_integrate RECURSIVE SUBROUTINE integrate DO WHILE ( nests_to_open( grid , nestid , kid ) ) 1, 60, 1, 100, 1, 43, 3, 3, 0. 06, a_nest_was_opened =. true. CALL med_pre_nest_initial ( grid , nestid , config_flags ) & CALL alloc_and_configure_domain ( domain_id = nestid , grid = new_nest , & parent = grid , & kid = kid ) & & CALL Setup_Timekeeping (new_nest) CALL med_nest_initial( grid , new_nest , config_flags ) END DO Dummy for the nested domain

WRF-NMM: ISTART, JSTART AND GRID MOTION &domains grid_id i_parent_start j_parent_start num_moves move_id move_interval move_cd_x move_cd_y = 1, 5, = 0, ISTART 1, = 0, JSTART 1, = -99, = 2, = 0, = 0/ Option for automatic grid motion, specifically for Hurricanes; For locating the initial grid based on storm center, we are providing an utility. . /UTILS/SET_IJSTART/swcorner_dynamic. F. However this code has to be re-compiled independent of the WRF model.

Physics Options &physics chem_opt = 0, mp_physics = 5, cu_physics = 2, ra_lw_physics = 99, ra_sw_physics = 99, sf_sfclay_physics = 2, sf_surface_physics = 99, bl_physics = 3, nphs = 5, ncnvc = 5, nrads = 60, nradl = 60, 0, 5, 2, 99, 3, 3, 3, 180, Ferrier Microphysics BMJ/ SAS convection (option 4) GFDL long wave GFDL short wave MYJ/ GFDL sfclayer (option 88) NOAA LSM/ GFDL SLAB (opt 88) MYJ/ GFS PBL (option 3) In model time step unit **** For Hurricane WRF we are constantly working in updating the parameterization schemes more consistent with the GFDL model which appears to have good skills in hurricane predictions. Not in repository.

One-Way Static Nest: Test Case of DC snow storm Parent domain Nested domain (BMJ+MYJ physics)

Two-Way Interactive Static Nest For the two-way interactive technique, a 13 -point averaged mass, momentum and scalar fields from the high resolution nest are weighed and fed-back into the parent domain. Currently, the weighting Factor is 0. 5.

Metro-Watch

The WRF-NMM Moving Nest* For Hurricane Forecasting *Not available in the repository

Multi-Scale Interactions weak subsiding motion upper level divergence Warm Core Vortex= Latent Heat –Cooling by W PBL Mois ture Conv ergence over warm ocean While organized convection occurs at the cloud scale, boundary layer convergence and subsidence, for instance, takes place in the warm core system over larger scales. In order to create the right scale interactions, a large domain as well as high resolution are pivotal requirements of a hurricane modeling system. Consequently, a moving nest becomes a back -bone structure for hurricane forecasting at this time

WRF-NMM GRID MOTION • While data was exchanged between the region of nest before and after grid motion, bilinear interpolation code that was earlier developed for the one-way static nest was still applied, but this time with masking of the leading edge of the moving nest. • The nest is "set to sail" on the parent domain using a simple criterion based on variations in dynamic pressure. The so called “stagnation point” was chosen to be the center of the storm (Gopalakrishnan et al 2002, MWR. )

GFDL IDEAL* VORTEX INITIALIZATION Parent domain of the size of about 60 o x 60 o at 36 km resolution * The Nested domain of the size of about 20 o x 20 o at 12 km resolution initial condition for this idealized case did not include topography and land, however, as in the case of static, one-way nest the code is general enough to take care of topography.

Moving domain of size of about 70 x 70 at about 12 km resolution Despite the small size of the nested domain, as long as the vortex is located in the center of the nest, we see the effect of lateral boundary diffusion to be limited and we are indeed able to hold on to the intensities!

HWRF Moving nested runs • • WRF-NMM V 2. 0 using HWRF 5 days of forecasts at 06 and 18 UTC 55 mins w/ 72 tasks 9 km moving nest w/in 27 km parent domain of about 600 x 600 • 42 levels • Initialized with 1/6 degree GFDL Pressure grids • Ferrier Microphysics; SAS convection scheme • GFS PBL and GFDL slab

HWRF DENNIS

HURRICANE EMILY

HWRF Hurricane Katrina

HWRF Hurricane Wilma

On Going Efforts… Ø Advanced Vortex Initialization for HWRF Ø HWRF-Wavewatch coupling Ø HWRF-Ocean Coupling (HYCOM) Ø Use of static nest for Urban and dispersion applications Ø Two-way interaction is now available in NMM-HWRF 2. 0 and has to be migrated into the repository version (i. e. WRFV 2. 1)

References (1) NCEP's Two-way-Interactive-Moving-Nest WRF-NMM modeling system for Hurricane Forecasting. 27 th Conference on Hurricanes and Tropical Meteorology, Monterey, CA, April 24 -29, 2006. S. G. Gopalakrishnan, N. Surgi, R. Tuleya, and Z. Janjic. (http: //ams. confex. com/ams/27 Hurricanes/techprogram/paper_107899. htm) (2) An Operational Multiscale Hurricane Forecasting System. Monthly Weather Review, 2002, Vol. 130, No. 7, pp. 1830– 1847. S. G Gopalakrishnan et al. (3) HWRF: An intorduction to the NMM-WRF modeling system. Hurricane WRF (HWRF) Tutorial - October 26 & 27, 2004. S. G. Gopalakrishnan (http: //www. emc. ncep. noaa. gov) (4) Nesting in WRF 2. 0, WRF/MM 5 Joint Workshop, Boulder, June 22 -25, 2004. David Gill, John Michalakes, Jimy Dudhia, William Skamarock and S. G. Gopalakrishnan,