Seasonal-to-Interannual Hydroclimate Variability in Reanalyses and Model Simulations

1
Seasonal-to-Interannual Hydroclimate Variability
in Reanalyses and Model Simulations

• Alfredo Ruiz-Barradas, and
• Sumant Nigam

Department of Atmospheric Oceanic
Science University of Maryland

• Objectives
• Assess seasonal hydroclimate variability over
  North America.
• Investigation of the atmospheric water-balance
  over the Great Plains.
• Interannual variability of summer and winter
  precipitation over
• North America.

2
Regressions of Great Plains Precipitation
Indices on hydroclimate fields during the
warm-season from NARR and CAM3.0s AMIP
simulation
NARR
CAM3.0
Precipitation
Large Precipitation anomalies over the Great
Plains are associated with Large moisture
flux convergence anomalies in NARR
Large evaporation anomalies in
CAM3.0. Those findings suggest different views
of the anomalous atmospheric water budget.
Vertically-integrated Stationary Moisture Fluxes
Evaporation
3

• Conclusions
• NARR successfully assimilates precipitation.
• Unbalanced water budget over the Great Plains in
  NARR
• Large evaporation in spring and summer.
• Weak transient moisture flux convergence.
• Interannual variability of warm-season rainfall
  over the Great Plains indicates
• the importance of remote water sources in nature
  via convergence of moisture fluxes.
• State-of-the-art GCMs vigorously recycle
  precipitation via evaporation, erroneously.
• Underway Work
• Analysis of radiative fluxes and Bowens ratio to
  shed light into the causes of the dominance of
  evaporation over moisture flux convergence in
  accounting for Great Plains precipitation
  variability in many GCMs.
• Analysis of winter precipitation variability over
  North America.