WRF data assimilation (WRFDA) support

Support of WRF and MPAS DA systems fosters effective data assimilation (DA) use across a broad community and with individual university principal investigators and graduate students, enhancing training and accelerating DA and numerical weather prediction for a variety of applications. In 2017 the WRFDA tutorial was held on 24-26 July, with 39 attendees.

WRFDA is a valuable tool for conducting research.  For example, it was demonstrated by Ban et al. (2017) that precipitation DA has improved convective-scale rainfall forecast over US for the first 3 hours. However, precipitation DA has no impact beyond 3 hours.

WRFDA figure

Figure: Aggregate Fractions Skill Score (FSS) of hourly-accumulated precipitation over one-week for the GTS (assimilating only conventional observations) and GTS+RAIN (assimilating both conventional and StageIV data) experiments using 20 km radius of influence. The vertical bars represent the confidence intervals at the 95% confidence level using bootstrap resampling method with 10,000 resamples. (a) 1 mm threshold, (b) 5 mm threshold and (c) 10 mm threshold.

All-sky AMSR2 radiance DA capability was made available to the community from a beta release to official release 3.9. WRFDA V3.9 which also includes other two important new capabilities: hybrid-4DEnVar and null-echo radar data assimilation. The latter was contributed by scientists from the Kyungpook National University of South Korea.

Reference:
Ban, J., Z. Liu, X. Zhang, X.-Y. Huang, and H. Wang, 2017: Precipitation data assimilation in WRFDA 4D-Var: implementation and application to convection-permitting forecasts over United States. Tellus A: Dynamic Meteorology and Oceanography, 69:1, 1368310, DOI: 10.1080/16000870.2017.1368310