Foreword

This User’s Guide describes the Advanced Research WRF (ARW) Version 3.9 modeling system, released in April 2017. As the ARW is developed further, this document will be continuously enhanced and updated. Please send feedback to wrfhelp@ucar.edu.

This document is complementary to the ARW Tech Note (http://www2.mmm.ucar.edu/wrf/users/docs/arw_v3.pdf), which describes the equations, numerics, boundary conditions, and nesting etc. in greater detail.

Highlights of updates to WRFV3.9 include:

· WRF model:

Vertical coordinate:

o Hybrid sigma-pressure vertical coordinate: terrain-following near the surface, and gradually transitions to constant pressure at higher levels.

Physics:

o P3 microphysics (contributed by Morrison and Milbrandt);

o Three urban models are added to NoahMP (Salamanca of Arizona State, Yizhou Zhang of IUM/CMA, China, and Barlage of NCAR);

o Physics suite specification via namelist;

o Improvement to RAP/HRRR and other physics;

o Stochastically perturbed parameter scheme and stochastically perturbed physics tendencies (Judith Berner of NCAR)

· WPS:

o Capability to drive WRF from MPAS native grid data;

o 30-seconds BNU soil category dataset (Barlage of NCAR)

· WRF-DA updates:

o New assimilation capability: 4DEnVar (Nils Gustafsson of Swedish Meteorological and Hydrological Institute and Feng Gao of NCAR)

o Cloudy radiance assimilation capability for AMSR-2 (Chun Yang of Nanjing University of Information Science & Technology)

o Radar “null-echo” assimilation (Ki-Hong Min and Yu-Shin Kim; Kyungpook National University, Daegu, South Korea)

· WRF-Chemistry

o Tropospheric Ultraviolet and Visible (TUV) photolysis option (S. Walters, A. Hodzic, and S. Madronich of NCAR);

o Coupled WSM6 microphysics with MOZART gas wet scavenging (Megan Bela of NOAA);

o Modified GOGART dust scheme for SORGAM and MOSAIC chemistry.

For the latest version of this document, please visit the ARW Users’ Web site at http://www2.mmm.ucar.edu/wrf/users/.

Contributors to this guide:

Wei Wang, Cindy Bruyère, Michael Duda, Jimy Dudhia, Dave Gill, Michael Kavulich, Kelly Keene, Ming Chen, Hui-Chuan Lin, John Michalakes, Syed Rizvi, Xin Zhang, Judith Berner, Soyoung Ha and Kate Fossell

Contributors to WRF-Fire chapter:

Jonathan D. Beezley, Janice L. Coen, and Jan Mandel

Special Acknowledgment:

We gratefully acknowledge the late Dr. Thomas T. Warner for his years of research, development, instruction, leadership, and motivation in the field of NWP modeling.