Coupled Land/Atmosphere Data Assimilation in NOAA's Global NWP System

Clara Draper

NOAA Physical Sciences Laboratory

Tuesday, Feb 25, 2025, 2:00 pm MT
DSRC Room GC402

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Abstract

As a part of a major upgrade to our global Numerical Weather Prediction (NWP) system, NOAA is developing a new land data assimilation system. This seminar will present these developments, focussing on an upgrade to our snow depth analysis, and the introduction of our first global soil moisture and soil temperature analysis. The new snow depth analysis will be a variational data assimilation of station snow depth and satellite snow cover, using the JEDI software platform. Compared to our current snow depth analysis, the variational snow analysis improves both the initial snow states, and low-level atmospheric temperatures over land. The new soil analysis will expand the current GSI Hybrid 4DEnVar assimilation of atmospheric observations to also assimilate screen-level temperature and humidity observations, and to also update the soil moisture and soil temperature states. This system improves the 6-hour low-level atmospheric forecasts, as measured by the data assimilation observation minus forecast statistics for the screen-level variables, while having a minimal, but positive, impact higher in the atmosphere. The above developments are a part of a long-term effort to unify our land and atmospheric data assimilation to use the same methods, allowing more information to be shared between the land and atmosphere updates, and introducing the possibility of strongly coupled land/atmosphere data assimilation. The potential advantages and challenges of strongly coupled land and atmospheric data assimilation will then also be discussed.