Dirceu Luis Herdies

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.

The atmospheric water cycle over South America as seen in the new generation of global reanalyses

In this study the main features of the hydrological cycle over the South American region are documented with three reanalysis datasets and two observation-derived precipitation products. Rather than attempting to “close the water balance” that requires additional terms, many model dependent, we focus on the individual terms of the water cycle. An additional analysis is also presented in this work to investigate the role of the transport of moisture over the La Plata Basin (LPB) and South Atlantic Convergence Zone (SACZ) in the precipitation regimes from 1979 to 2007.

Assimilação do IWV-GPS no Brasil: otimização das estimativas do atraso zenital troposférico em tempo real

IWV (Integrated Water Vapor) values from the Brazilian Network for Continuous Monitoring (RBMC) of GPS (Global Positioning System) signals are additional sources of humidity information available for being used in Numerical Weather Prediction (NWP) models operating in the Brazilian meteorological centers. In order to obtain IWV-GPS values in an efficient approach, an optimization of the GPS data processing for estimating the ZTD values (Zenithal Tropospheric Delay) is involved, which should search for the best result with lowest computational cost. In this optimization process it is necessary to determine the ideal size of the so called sliding-window data involved in the real time data processing, which must be the as small as possible but providing results with the required quality. In this paper is investigated the ideal size of such sliding-window. An experiment was carried out in which GPS sliding-windows of different sizes were evaluated using simulations of a real time data processing. Comparing the obtained results with those from post-processed GPS data, it is observed that a sliding-window containing 7 hours of GPS data generated the best results from the operational point of view (rms of 1.61 and 1.82 kg m −2 for latency of 60 and 120 minutes, respectively).

Impacto de perfis de rádio ocultação GNSS na qualidade das Previsões de tempo do CPTEC/INPE

Studies about the sensibility of numerical weather prediction (NWP) model to uncertainty in the initial conditions have revealed the actual contribution of the data assimilation on the description of future atmosphere state. Among other data sources, the atmospheric profiles obtained by radio occultation Global Navigation Satellite System (GNSS) have become an additional tool in the reduction of the meteorological data base deficiencies. In order to explore the benefits of that additional data source in the NWP generated by the CPTEC/INPE general circulation model, some experiments were carried out by assimilating geopotencial height and humidity atmospheric profiles obtained by Constellation Observing System for Meteorology Ionosphere & Climate (COSMIC) constellation data. The period of these experiments were the months of January and July of 2009. The results show that this data assimilation exhibits a significant positive impact during the summer on all the state variables. Results also show a positive improvement during the summer for all state variables, with expressive improvements in the valid forecasts time range (anomaly correlation above 60%), which were in some cases greater than 48 hours. This impact was still greater over South America with positive results even during the winter.

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...

Análise de um Vórtice Ciclônico e Mesoescala Associado a ZCAS em Janeiro de 2009

This study shows, from the mesoscale analysis perspective that Mesoscale Cyclonic Vortex (MCV) is associated to the South Atlantic Convergence Zone (SACZ) through a feedback process. This system, simulated by the BRAMS regional model, is generated embedded in a stratiform environment within the SACZ region, during the January 2009 austral summer. MCVs present similar characteristics which could be considered as a “signature” for such systems. The case study also presents a lifetime shorter than 24 h and spatial scale of approximately 200 km2 in addition to intense precipitation, shifting in the flow direction in the lower troposphere. In the case occurred in the Mato Grosso State, the presence of this system was associated with heavy rain, relative vorticity of the same order as the Coriolis parameter (10−4 s−1), warm core above the level of maximum intensity and rapid growth of the cyclonic vorticity center mostly in the lower levels. The simulated precipitation is compared against the Hidroestimador precipitation product. The results suggest that the BRAMS model, configured with high spatial and temporal resolutions improves the representation of the MCVs when compared to the NCEP CFSR reanalysis.

Estudo das condições de tempo e conforto térmico no desempenho esportivo aplicado à maratona da cidade do Rio de Janeiro

The weather condition analysis have proven to be an useful tool when applied specifically to sports. These conditions act as a differential in strategy and training plan, especially for outdoor sports. The main objective of this study is to develop weather forecast and thermal comfort evaluation applied to sports, and it is expected that the obtained results could be used for developing products and weather service to the 2016 Olympic Games in Rio de Janeiro City. The weather forecast applied to sport events showed to be efficient during the Rio de Janeiro City Marathon, especially due to the high spatial resolution. It was concluded that the WRF (Weather Research and Forecasting) model provides, in general, more representative simulations up to 36 hours in advance, an 18 hours forecast is even better, describing efficiently the prevailing synoptic situation. The assessment of the weather conditions and thermal comfort at specific points of the marathon route showed that there are significant differences among the marathon stages, and that there is a relationship between more thermally comfortable (uncomfortable) situation and the best (worst) timing in Rio de Janeiro City Marathon.

Estudo de Caso de um Evento Extremo de Incursão de Ar Frio em Julho de 2013 sobre a Bacia Amazônica Brasileira

The Amazon basin is located in the tropical region whose main characteristics are the high values of temperature and humidity of the air. However, cold and dry air incursions also penetrate the region, as occurred in July 2013. This fourth cold wave that affected the South American continent caused snow in cities of the South region, characterizing an intense polar mass with displacement to the North. The present work analyzed the behavior of meteorological variables in order to investigate the intensity of this effect. The dataset used were observations and reanalyses. The negative anomaly of the maximum temperature in Rio Branco was 15.9 °C, in Manicoré of 6.7 °C and Manaus of 2,0 °C. In this event, the most expressive values occurred at the maximum temperature. Also worth mentioning is a monthly contribution in precipitation rates, whose values were higher than 13.0 mm.day. Thus, it is concluded that the event of July 2013 was a case of intense cold, due to the fact that it moved to the central region of Amazonia and caused abrupt drops, mainly in maximum temperature, favoring rainfall in the tropical regions, as well as changes in surface pressure, humidity and

TREND OF THE INSTABILITY INDICES IN SOUTH AMERICA

The instability indices evaluate the vertical structure of the atmosphere related to temperature and air humidity aiming to identify instability or stability. Where exists instability, these provide an indication of the intensity of precipitation systems. The K index indicates the potential for storms based on the lapse rate and humidity in the lower troposphere and in the extension of the wet layer. The Total Totals (TT) index combines temperature and moisture at low levels with the temperature on middle levels. Due to the importance of these indices in weather forecast and the absence of studies of the tendency of these parameters in South America, this research aimed to determine the K and TT indices for the synoptic hours make a climatology and calculate the seasonal trend of these indices. Results showed that on the continent higher values of the indices K and TT are obtained in the summer, mainly due to seasonal variation of temperature, in addition to rainfall associated with the monsoon particularly in southeastern Brazil. There is an increasing trend in the values of both indices in the northern Amazon and decreasing trend in the northwest of Argentina and southwest Bolivia.

The Inclusion of IWV Estimates from AIRS/AMSU and SSM/I Sensors into the CPTEC/INPE Global Data Assimilation System

AbstractWater vapor plays a crucial role in atmospheric processes and its distribution is associated with cloud-cover fraction and rainfall. The inclusion of integrated water vapor (IWV) estimates in numerical weather prediction improves the vertical structure of the humidity analysis and consequently contributes to obtaining a more realistic atmospheric state. Currently, satellite remote sensing is the most important source of humidity measurements in the Southern Hemisphere, providing information with good horizontal resolution and global coverage. In this study, the inclusion of IWV retrieved from the Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit-A (AIRS/AMSU) and Special Sensor Microwave Imager (SSM/I) were investigated as additional information in the Physical-space Statistical Analysis System (PSAS), which is the operational data assimilation system at the Center for Weather Forecasting and Climate Studies of the Brazilian National Institute for Space Research (CPTEC/INPE). Experimen...