Development of the Regional Arctic Climate System Model (RACM) ---

Initial Implementation of VIC within CCSM System through CPL7Chunmei Zhu1, Dennis Lettenmaier1, Juanxiong He2, Tony Craig3, Gabriele Jost4, Wieslaw Maslowski5

1Department of Civil and Environmental Engineering, Box 352700, University of Washington, Seattle, WA 981952International Arctic Research Center, Fairbanks, AK; 3National Center for Atmospheric Research; 4Texas Advanced Computing Center; 5Naval Postgraduate School

Coupling Guideline

As part of the development of a state-of-the-art Regional Arctic Climate system Model (RACM) including high-resolution atmosphere, ocean, sea ice, and land hydrology components, we implemented the macroscale hydrologic model VIC (Variable Infiltration Capacity) within CCSM (Community Climate System Model) system through the new coupling architecture CPL7. Currently, VIC runs for 5 days in the CCSM system in an all data (I) configuration at global 4x5 resolution. The fields sent to the coupler by VIC model at the end of the 5 day run were compared with the standard CCSM land model CLM (Community Land Model) run in the same configuration. The fields produced by VIC agree with CLM in most areas. Ongoing work is testing the cam/vic/camdom/cice configuration (F), run of VIC in the CCSM system in fully coupled mode. We are also parrallelizing VIC and implementing the VIC stream routing model in RACM.

1 Introduction

Model Description2

3

4

Sensible Heat Comparison 6

The spatial pattern of surface skin temperature sent by VIC – CCSM4 are quite similar with CLM – CCSM4.

VIC Land Component Fields -> Atmosphere Component 10

• Macroscale hydrologic model VIC

has been implemented within CCSM

system through CPL7.

• VIC – CCSM4 successfully runs 5

days in all data (I) configuration at

global 4x5 resolution.

• The spatial distribution of state and

flux fields sent by VIC land model are

mostly similar to CLM, aside from

South America for latent heat flux.

Net solar radiation values for both

models are unrealistic over Africa and

Eurasia.

8

Model features:

• multiple vegetation classes in each cell

• energy and water budget closure at each time step

• subgrid infiltration and runoff variability

• non-linear baseflow generation

• critical elements relevant to high latitude implementations: a snow model, a frozen soil algorithm, a lake/wetland model, and a blowing snow model.

In CCSM4, the communication process is separated from the component integration process. All communication processes are taken over by Cpl7 and the components run by themselves. Our coding work therefore is mainly focused on replacing CLM with VIC. Most of the coding doesn’t involve Cpl7 directly. Key aspects of the work:

● Extract VIC as run in an existing MM5-VIC coupling system for interaction with the flux coupler (because VIC in MM5 is in image mode, i.e., runs at all space for a given time step).

● Current versions of VIC don’t have the capacity for parallel operation.

● VIC and the flux coupler exchange fields hourly (the time step at which VIC runs). This allows WRF and VIC to run at different time steps.

● The current VIC version in MM5 is VIC4.0.4. We plan to update VIC to a newer version after the coupling finished

land -> atmosphere state variables structure!----------------------------------------------------

type lnd2atm_state_type real(r8), pointer :: t_rad(:) !radiative temperature (Kelvin) real(r8), pointer :: t_ref2m(:) !2 m height surface air temperature (Kelvin) real(r8), pointer :: q_ref2m(:) !2 m height surface specific humidity (kg/kg) real(r8), pointer :: h2osno(:) !snow water (mm H2O) real(r8), pointer :: albd(:,:) !(numrad) surface albedo (direct) real(r8), pointer :: albi(:,:) !(numrad) surface albedo (diffuse)end type lnd2atm_state_type

!----------------------------------------------------

land -> atmosphere flux variables structure!----------------------------------------------------

type lnd2atm_flux_type real(r8), pointer :: taux(:) !wind stress: e-w (kg/m/s**2) real(r8), pointer :: tauy(:) !wind stress: n-s (kg/m/s**2) real(r8), pointer :: eflx_lh_tot(:) !total latent heat flux (W/m8*2) [+ to atm] real(r8), pointer :: eflx_sh_tot(:) !total sensible heat flux (W/m**2) [+ to atm] real(r8), pointer :: eflx_lwrad_out(:) !emitted infrared (longwave) radiation (W/m**2) real(r8), pointer :: qflx_evap_tot(:) !qflx_evap_soi + qflx_evap_veg + qflx_tran_veg real(r8), pointer :: fsa(:) !solar radiation absorbed (total) (W/m**2)end type lnd2atm_flux_type

5

7

Latent Heat Comparison

CLM VIC

VIC and CLM exhibit generally similar spatial patterns globally. The biggest differences are over

eastern South America where VIC produces much higher latent heat fluxes (about 60 W/M^2). This is

likely related to the much higher shortwave radiation produced in VIC-CCSM in this region (see

section 8).

CLM

VIC

Surface Skin Temperature

CLM

VIC

Net Shortwave Radiation

Rout surface and subsurface

runoff into rivers

Implement VIC routing model into RACM

9 Longwave Radiation

Future Work

Testing the cam/vic/camdom/cice configuration (F). Running VIC in CCSM system in fully coupled mode.

Parrellizing VIC land model in CCSM system to improve computing performance.

Summary

CLM

VIC

VICCLM

VIC – CCSM shortwave radiation extends much further into eastern South America and eastern United States than CLM. Values for both models are unrealistic over Africa and Eurasia.

Longwave radiation patterns are similar to surface skin temperature (section 7). Spatial patterns of longwave radiation for VIC and CLM are quite similar.

● The sensible heat difference over South America is explained by the shortwave radiation difference (Section 8) and surface skin temperature in section 7.

● Africa shows reverse pattern between VIC and CLM, also the Arctic region has larger area with upward sensible heat for CLM than VIC. These may be related to differences in model physics.