Luis Gustavo de Gonçalves

Toward global drought early warning capability: Expanding international cooperation for the development of a framework for monitoring and forecasting

Drought is a global problem that has far-reaching impacts, especially on vulnerable populations in developing regions. This paper highlights the need for a Global Drought Early Warning System (GDEWS), the elements that constitute its underlying framework (GDEWF), and the recent progress made toward its development. Many countries lack drought monitoring systems, as well as the capacity to respond via appropriate political, institutional, and technological frameworks, and these have inhibited the development of integrated drought management plans or early warning systems. The GDEWS will provide a source of drought tools and products via the GDEWF for countries and regions to develop tailored drought early warning systems for their own users. A key goal of a GDEWS is to maximize the lead time for early warning, allowing drought managers and disaster coordinators more time to put mitigation measures in place to reduce the vulnerability to drought. To address this, the GDEWF will take both a top-down approach...

Análise climatológica da precipitação e do transporte de umidade na região da ZCAS através da nova geração de reanálises

The knowledge of the reanalysis performance and the systematic errors associated with them is extremely important in the acknowledgement of the physical processes occurring in the atmosphere. The goal of this study is to document the main characteristics of precipitation over the South Atlantic Convergence Zone (SACZ), based on six atmospheric reanalysis (MERRA, ERA-Interim, ERA-40, NCEP 1, NCEP 2 and NCEP CFSR) and five observed precipitation data products (SALDAS, CPC, CMAP, GPCP and GLDAS). Using the aforementioned available datasets the transport of moisture over SACZ was evaluated for the period of 1979 through 2007. In summary, the new generations of reanalyses show an improvement in the representation of the rainfall patterns and their magnitude. Taylor diagrams show that the observational products tend to be tightly grouped and close to the reference (CPC) point, whereas most of reanalyses show correlation coefficients below 0.6. NCEP CFSR reanalysis however, presented higher correlation coefficients relative to the others. Atlantic Ocean is the main moisture flux source to SACZ, which decreases towards the continent. Topography has an important role in moisture convergence over SE Region of Brazil. Over Amazon region, the convergence must be associated with thermodynamic processes.

Ensemble Evaluation of Hydrologically Enhanced Noah-LSM: Partitioning of the Water Balance in High-Resolution Simulations over the Little Washita River Experimental Watershed

Abstract The ability of two versions of the Noah land surface model (LSM) to simulate the water cycle of the Little Washita River experimental watershed is evaluated. One version that uses the standard hydrological parameterizations of Noah 2.7 (STD) is compared another version that replaces STD’s subsurface hydrology with a simple aquifer model and topography-related surface and subsurface runoff parameterizations (GW). Simulations on a distributed grid at fine resolution are compared to the long-term distribution of observed daily-mean runoff, the spatial statistics of observed soil moisture, and locally observed latent heat flux. The evaluation targets the typical behavior of ensembles of models that use realistic, near-optimal sets of parameters important to runoff. STD and GW overestimate the ratio of runoff to evapotranspiration. In the subset of STD and GW runs that best reproduce the timing and the volume of streamflow, the surface-to-subsurface runoff ratio is overestimated and simulated streamfl...

The South American Land Data Assimilation System (SALDAS) 5-Yr Retrospective Atmospheric Forcing Datasets

Abstract The definition and derivation of a 5-yr, 0.125°, 3-hourly atmospheric forcing dataset that is appropriate for use in a Land Data Assimilation System operating across South America is described. Because surface observations are limited in this region, many of the variables were taken from the South American Regional Reanalysis; however, remotely sensed data were merged with surface observations to calculate the precipitation and downward shortwave radiation fields. The quality of this dataset was evaluated against the surface observations available. There are regional differences in the biases for all variables in the dataset, with volumetric biases in precipitation of the order 0–1 mm day−1 and RMSE of 5–15 mm day−1, biases in surface solar radiation of the order 10 W m−2 and RMSE of 20 W m−2, positive biases in temperature typically between 0 and 4 K depending on the region, and positive biases in specific humidity around 2–3 g kg−1 in tropical regions and negative biases around 1–2 g kg−1 farth...

Is the data collection period of the large-scale biosphere-atmosphere experiment in amazonia representative of long-term climatology?

[1] The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) sampled surface-atmosphere flux exchanges and related ecohydrometeorological processes at several flux tower sites in the Amazonian region between 1999 and 2006. This extensive database is now being analyzed to investigate, for example, the carbon balance of the Amazon basin and the effect of land use change in the basin on climate. It is therefore important to establish whether the period during which these data were collected is representative of the long-term climatology for the region. This study analyzed long-term climate station data for stations located nearby the LBA eddy flux tower sites. Measurements taken during the period of data collection were compared with the longterm station climatology using the Kolmogorov-Smirnov test and analysis of histogram from random samples from the long-term climatological record. In terms of precipitation, the LBA data collection period is statistically consistent with the climatology for all LBA study sites. In terms of temperature, the same result is true for most flux station sites; the main exception being the Bananal Island site where the temperature during the LBA period is significantly warmer by about 1C. There were some short periods when temperature in the region of other LBA flux sites was also statistically different (higher) during the LBA data collection period and an average but not statistically significant tendency toward higher temperatures across the whole region during the LBA period relative to previous years. This is probably because there has been significant land cover change near some of the LBA study sites, but a contribution from climate warming cannot be ruled out.

Energy Partitioning and Evapotranspiration over a Rice Paddy in Southern Brazil

AbstractDuring approximately 80% of its growing season, lowland flooded irrigated rice ecosystems in southern Brazil are kept within a 5–10-cm water layer. These anaerobic conditions have an influence on the partitioning of the energy and water balance components. Furthermore, this cropping system differs substantially from any other upland nonirrigated or irrigated crop ecosystems. In this study, daily, seasonal, and annual dynamics of the energy and water balance components were analyzed over a paddy rice farm in a subtropical location in southern Brazil using eddy covariance measurements. In this region, rice is grown once a year in low wetlands while the ground is kept fallow during the remaining of the year. Results show that the energy budget residual corresponded to up to 20% of the net radiation during the rice-growing season and around 10% for the remainder of the year (fallow). The energy and water balance analysis also showed that because of the high water table in the region, soil was near sat...

An early freeze in southern Brazil in April 1999 and its NWP guidance

A cold air outbreak occurred in the third week of April 1999 in southern Brazil. A synoptic study of this rare event is undertaken. A surface high pressure cell in the Pacific Ocean off the coast of Chile slowly built up and moved eastward on 14 April. It started crossing the Andes, acquiring the characteristic shape of a bean on 15th, and separated into two cells later in the day. The cell on the lee side of the mountains moved gradually northwards over central South America affecting northern Argentina, Paraguay, Uruguay, Bolivia and southern Brazil. The temperature fell in the state of Mato Grosso (about ). In southern Brazil temperatures below freezing were registered in some places on the 17th and 18th and frost occurred in many states. There was snowfall in the uplands of Santa Catarina on the 17th, and such an early snow had not been recorded for 30 years. Baroclinic synoptic wave intensification followed by surface low development in association with a cut-off low formation in the middle and upper troposphere were responsible for strong surface southerlies over Argentina on the 16th and 17th. Cold air advection by the southerlies in the eastern sector of the high-pressure centre was responsible for the northward projection of the high pressure cell east of the Andes. The whole event was well predicted by the Centro de Previsao de Tempo e Estudos Climaticos/Instituto Nacional de Pesquisas Espaciais (CPTEC/INPE) operational global and regional models with lead times of 120 and 60 hours respectively. Copyright

Seasonality of soil water exchange in the soybean growing season in southern Brazil

The processes of water transfer in the soil-plant-atmosphere system are strongly affected by soil use and management. Differences in the dynamics of soil water transfer between no-tillage (NT) and conventional tillage (CT) practices during a soybean (Glycine max) growing season in southern Brazil were assessed in this study. All the water balance components were analyzed during the soybean growing season (2009/2010). Rainfall, runoff, soil water storage and hydro-physical soil properties were analyzed under two tillage systems. The land-atmosphere water vapor exchanges, obtained from eddy covariance stations, were analyzed with regard to the soybean agroecosystem. Characterizations of soil water storage were also formulated in the 2006/2007 and 2008/2009 soybean growing seasons under the NT system. During the periods without rain, the soil water content under NT was greater than under CT. The soil superficial layer, more porous under NT, contributed to less runoff during rainy events. Moreover, under NT conditions the water supply was always high, between 0.2 - 0.5 m. The total evapotranspiration in the soybean agroecosystem growing season was 410.8 mm.

Quantitative Precipitation Estimation Integrated by Poisson’s Equation Using Radar Mosaic, Satellite, and Rain Gauge Network

AbstractHigh-resolution quantitative precipitation estimation (QPE) from radar and satellite combined with rain gauges is one of the most important guides for hydrological forecasts. Whereas rain gauges provide accurate measurement at a point, remote sensing helps to retrieve the spatial pattern. An algorithm, named Siprec, has been used to blend rain gauges, radar mosaic data, and satellite Eumetsat/MPE estimates by using Poisson’s equation over two basins in Brazil. The results indicated that Siprec decreased the root mean square error (RMSE) when compared to radar and satellite estimates as well as improved the correlation. Most of the errors were related to precipitation above 10  mm h−1, due to large spatial variability, typical of deep convection. The solution of Poisson’s equation acts directly on the data received at a certain time, converging the amplitude to the rain gauge values and keeping the spatial distribution of the radar or satellite measurement without a priori adjustments. This is an i...

INFLUENCE OF SOIL PROPERTIES IN DIFFERENT MANAGEMENT SYSTEMS: ESTIMATING SOYBEAN WATER CHANGES IN THE AGRO-IBIS MODEL

AbstractThe water balance in agricultural cropping systems is dependent on the physical and hydraulic characteristics of the soil and the type of farming, both of which are sensitive to the soil management. Most models that describe the interaction between the surface and the atmosphere do not efficiently represent the physical differences across different soil management areas. In this study, the authors analyzed the dynamics of the water exchange in the agricultural version of the Integrated Biosphere Simulator (IBIS) model (Agro-IBIS) in the presence of different physical soil properties because of the different long-term soil management systems. The experimental soil properties were obtained from two management systems, no tillage (NT) and conventional tillage (CT) in a long-term experiment in southern Brazil in the soybean growing season of 2009/10. To simulate NT management, this study modified the top soil layer in the model to represent the residual layer. Moreover, a mathematical adjustment to th...