Abstract. Vegetation optical depth (VOD) retrievals from passive microwave sensors
provide analog estimates of above-ground canopy biomass.
This study presents the development and analysis of assimilating
VOD retrievals from X-, C-, and L-band passive microwave
instruments within the Noah-MP land surface model over the
Continental U.S.
The results from this study demonstrate that the assimilation of VOD retrievals
have a significant beneficial impact on the simulation of
evapotranspiration and GPP, particularly over the
agricultural areas of the U.S. The improvements in the
water and carbon fluxes from the
assimilation of VOD from X- and C-band sensors are found
to be comparable to those obtained from the assimilation of
vegetation indices from optical sensors.
The study also quantifies the relative and joint impacts of assimilating surface soil moisture and VOD from the Soil Moisture
Active Passive (SMAP) mission.
The utility of soil moisture assimilation for improving evapotranspiration (ET) is more significant over water-limited regions, whereas VOD
DA is more impactful over areas where soil moisture is
not the primary controlling factor on ET.
The results also indicate that the information on
moisture and vegetation states from SMAP can be
simultaneously exploited through the joint assimilation of
surface soil moisture and VOD.
Since passive microwave-based VOD retrievals are available in
nearly all weather conditions, their use within data
assimilation systems offers the ability
to extend and improve the utility obtained from the use of
optical/infrared-based vegetation retrievals.
Assimilation of vegetation optical depth retrievals from passive microwave radiometry