The impact of changes in soil moisture in subtropical Argentina in rainfall distribution and low level circulation is studied with a state-of-the art regional model in a downscaling mode, with different scenarios of soil moisture for a 10 day period. The selected case (starting January 29, 2003) was characterized by a Northwestern Argentina Low event associated with well defined low level northerly flow that extended east of the Andes over subtropical latitudes. Four tests were conducted at 50 km horizontal resolution with 31 sigma levels, decreasing and increasing the soil moisture initial condition by 50% over the entire domain, 50 % reduction over northwest Argentina and 50% increase over South East South America. A control run with NCEP/GDAS initial conditions was used to assess the impact of the different soil moisture configurations.It was found that land-surface interactions are stronger when soil moisture is decreased, with a coherent reduction of precipitation over southern south America.Enhanced northerly winds result form an increase in the zonal gradient of pressure at low levels. In contrast, when soil moisture is increased, no circulation changes are found, though there appears to be a local feedback effect between the land and precipitation The combined effects of changes in the circulation and in local stratification induced by soil wetness modifications, through variations in evaporation and CAPE, are in agreement with what has been found by other studies, resulting in coherent modifications of precipitation when variations of CAPE and moisture flux convergence mutually reinforce.INPE ePrint: sid.inpe.br/mtc-m18@80

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NCEP short-range operational forecast and Limited Area HIBU (Federal Hydrometeorological Institute and Belgrade University) Model (LAHM) regional model performance during a 2-month period over the southern part of South America are evaluated through the analysis of bias and rmse's. While spatial structure of errors could be only examined using gridded operational analyses as the ''ground truth,'' observed data have been used at two radiosonde stations to have an independent control of forecast and analysis quality. LAHM precipitation forecast error has been also determined using observed 24-h accumulated precipitation over a subregion of interest.Bias and rmse are, in general, lower for Medium-Range Forecast Model (MRF) 24-h forecasts than for the regional model, though MRF errors appear to be larger than those reported by other studies carried out over the whole Southern Hemisphere, suggesting the necessity to perform regional verification analysis whenever gridded analyses and/or forecasts are being used. This recommendation particularly holds over data-void regions like South America.While geopotential and wind biases do not exhibit a particular pattern in either forecast, there is a clear tendency to cold biases over the whole troposphere, and for the MRF in particular, growing with height.The results obtained from LAHM evaluation suggest that continuous development is needed to keep this regional forecast system as a plausible counterpart of available global model products for fulfillment of local requirements.

Antico et al. (2018, https://doi.org/10.1002/2017WR020897) made available the longest hydrometric record (1875–2017) of the Paraná River of South America, one of the 10 largest rivers in the world. The oldest part of this record (1875–1883) has low accuracy because it was obtained from a hand‐drawn plot of the time series of daily water levels at Rosario City, Argentina. Here we overcame this data limitation by digitizing more accurate typewritten daily water levels observed at Rosario in 1875–1883. The digitized levels were referenced to the modern datum, subjected to quality checks, and corrected for errors caused by a gradual gauge sinking. A rating curve was used to convert water levels into discharges. Interestingly, our data capture the extreme Paraná flood associated with the very strong 1877–1878 El Niño.