Changes in soil moisture conditions at LPB: impact over

1. - - - - + - - + Ctrl SMOIS GDAS/NCEP Exp1 -%50 SMOIS GDAS/NCEP Exp2 -%50 SMOIS GDAS/NCEP at NOA Exp3 +%50 SMOIS GDAS/NCEP Exp4 +%50 SMOIS GDAS/NCEP at SESA 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 andJuan Ruiz2,3 1 Servicio Meteorológico Nacional, Buenos Aires, Argentina2DCAO FCEyN-UBA Buenos Aires, Argentina3Centro de Investigaciones del Mar y la Atmósfera, CONICET, Buenos Aires, Argentina,4University of Utah, Salt Lake City, Utah ferreira@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/eta12tpb). 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 NOAHLand 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 WRF GDAS E1 W:vertically integrated atmospheric water (precipitable water). E: evapotranspiration P: Precipitation Q: vertically integrated moisture flux 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. In general, the WRF model represents satisfactorily the synoptic situation during the 10 days simulation. In some cases, it underestimates the horizontal pressure gradients. • 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, 3077–3107 • 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, 263–280 • 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-468+STR. • 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, 741–762 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 P>E. 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.