Presentaci

1
Changes in soil moisture conditions at LPB
impact over the atmospheric water Balance and
circulation. Ferreira Lorena 1,2, Saulo
Celeste2,3 , Julia N-Paegle4 and Juan Ruiz 2,3
1 Servicio Meteorológico Nacional, Buenos Aires,
Argentina 2DCAO FCEyN-UBA Buenos Aires, Argentina
3Centro de Investigaciones del Mar y la
Atmósfera, CONICET, Buenos Aires, Argentina, 4
University of Utah, Salt Lake City, Utah
ferreira_at_at.fcen.uba.ar
PURPOSES
MOTIVATION

• To produce several sensitivity studies employing
  different soil moisture (SMOIS) initial
  conditions patterns over South America.
• To evaluate the impact over the precipitation,
  the circulation and the water atmospheric
  storage.
• To evaluate the Model performance in medium range
  experiments.

• In the last time there has been an increasing
  interest to understand the interactions between
  the atmospheric processes and the soil
  characteristics.
• The relationships between lower boundary
  conditions (i.e., land use, soil moisture, soil
  characteristics) and the atmospheric circulation
  that can modify the precipitation patterns in
  South America are not fully understood.
• Several studies as Grimm (2003) , Xue at al
  (2006) and Fu y Li (2004) have focused on the
  Amazon basin showing how the atmosphere exhibits
  strong sensitivity to changes in surface
  conditions. In LPB, only Collini and Berbery
  (2007) and Ferreira(2006) explore these
  interactions.
• There is a clear need to identify land/atmosphere
  linkages which may have some implications for
  atmosphere water balance and precipitation
  over La Plata Basin (LPB).

EXPERIMENTS
Model main features The Weather Research and
Forecasting model (WRF) version 2.0 has been used
(Skamarock et. al. 2005) to perform all the
experiments. The model is run in the
non-hydrostatic mode. The microphysics scheme
utilized is the Eta Grid-scale Cloud and
Precipitation (www.emc.ncep.noaa.gov/mmb/mmbpll/et
a12tpb). Convection is parameterized using
Kain-Fritsch (1993), RRTM (Mlawer et. al., 1997)
and Dudhia (1989) scheme are used to represent
radiative fluxes at long and short waves
respectively. Yonsei University scheme is used in
the boundary layer processes parameterization and
a NOAH Land Surface Model is used to represent
surface processes (Chen and Dudhia,( 2000)).
Horizontal resolution is approximately of 20 km
with 31 vertical sigma levels.
Preliminary Results

• Simulations Characteristics
• Initial Conditions The simulations done using
  the WRF model were initialized on 29 January at
  12UTC with the GDAS (Global Data Assimilation
  System) analyses provided by the National Centers
  for Environmental Predictions (NCEP)
• The simulations were integrated for a 10-day
  period.

Accumulated Precipitation
Continental Experiment
Continental Experiment
Local Experiment
Local Experiment
DOMAIN
Soil Moisture Initial Condition
Exp3
Exp1
NOA
There is a general decrease of precipitation in
the whole continent, with centers concentrated at
LPB and North of Bolivia. The impact is also
present over the adjacent ocean.
Reduction of precipitation is observed at NOA
(Northwestern Argentina) region. The impacts also
show up in the southern portion of the LPB region
and into the Atlantic.
SESA
Increased precipitation at LPB, NOA and
Central Andes. The effects are also evident over
the adjacent Ocean. Lower impact in SACZ
precipitation.
Increased precipitation at LPB and over the
adjacent ocean.
Exp4
Exp2
WRF model topography GDAS/NCEP soil moisture
initial condition
Meridional Wind Component at 850hPa
WRF Performance
E1-Ctrl
E3-Ctrl
Day 5 (3-01-2003 12UTC)
GDAS
WRF
Acceleration of the northerly winds east of the
Andes and of the southerly winds south of NOA and
south of the SACZ. The latter leads to a
divergence region.
Acceleration of the Southerly winds in the whole
domain concentrated not only at NOA region but
also at the southern portion of LPB.
Day 8 (6-01-2003 18UTC)
The accumulated precipitation is reasonably well
simulated with a slight tendency to
overestimation at some areas
Atmospheric Water Balance
GDAS
WRF
E1
W vertically integrated atmospheric water
(precipitable water). E evapotranspiration P
Precipitation Q vertically integrated moisture
flux
In general, the WRF model represents
satisfactorily the synoptic situation during the
10 days simulation. In some cases, it
underestimates the horizontal pressure gradients.
Reduction in moisture flux convergence (also
showed in upper figure) at LPB. Precipitation
tends to be concentrated over the Atlantic ocean
and over the north-northeast regions.

• REFERENCES  
• Anderson J.R., Hardy E.E., Roach J.T. and Witmer
  R.E.,1976 A land use and land cover
  classification system for use with renote sensor
  data U.S. Geological Survey Professional Paper
  964, 28p.
• Chen, S.-H., and J. Dudhia, 2000 Annual report
  WRF physics, Air Force Weather Agency, 38pp.
  Dudhia J., 1989 Numerical Study of Convection
  Observed during the Winter Monsoon Experiment
  Using a Mesoscale Two-Dimensional Model. J. Atmos
  Sci. Vol. 46, 30773107
• Collini, E. A., E. H. Berbery and V. Barros, and
  M. Pyle, 2007 How does Preceding Soil Moisture
  Influence the Onset of the South American
  Monsoon? Submitted to J. Climate.
• Ferreira, L. , C. Saulo, J. Ruiz and M. Seluchi,
  2006 The impact of land use changes over the low
  level circulation related to the Northwestern
  Argentinean low. Extended abstracts (CD) de la
  8th International Conference on Southern
  Hemisphere Meteorology and Oceanography, 24 al 28
  de abril 2006, Foz do Iguazu, Brazil.
• Grimm, A.M, 2003 The El Niño Impact on the
  Summer Monsoon in Brazil Regional Processes
  versus Remote Influences. J. Climate,16, 263280
• Li, W. H., and R. Fu, 2004 Transition of the
  large-scale atmospheric and land surface
  conditions from the dry to the wet season over
  Amazonia as diagnosed by the ECMWF re-analysis.
  J. Climate, 17, 2637-2651
• Kain, J. S. and J. M. Fritsch, 1993. A
  one-dimensional entraining de-training plume
  model and its application in convective
  parameterization. J. Atmos. Sci., 23, 2784-2802.
• Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J.
  Iacono, and S. A. Clough, 1997 Radiative
  trans-fer for inhomogeneous atmosphere RRTM, a
  validated correlated-k model for the long-wave.
  J. Geophys. Res. 102( D14), 16663-16682.
• Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O.
  Gill, D. M. Barker, W. Wang, and J. G. Powers,
  2005 A description of the Advanced Research WRF
  Version 2. NCAR Tech Notes-468STR.
• Yongkang Xue,  F. de Sales,  W.-P. Li,  C. R.
  Mechoso,  C. A. Nobre, and H.-M. Juang, 2006
  Role of Land Surface Processes in South American
  Monsoon Development Journal of Climate. Vol 19,
  741762
• Acknowledgements This research is sponsored by
  the Research Grants UBACyt X155 and for CONICET
  PIP5417 .

Although there is a negative tendency in all the
terms of the water balance equation, no
significant changes are observed in atmospheric
water storage. Nevertheless in some regions a
reduction in atmospheric water storage is
observed associated with lower E and PgtE.
Control
CONCLUSIONES
Intensification in moisture flux convergence
over western LPB and over the oceans, which is in
agreement with enhanced precipitation .
E3
Increased evapotranspiration and precipitation at
LPB.