Luiz F. Sapucci

The Chuva Project: How Does Convection Vary across Brazil?

CHUVA, meaning “rain” in Portuguese, is the acronym for the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (GPM). The CHUVA project has conducted five field campaigns; the sixth and last campaign will be held in Manaus in 2014. The primary scientific objective of CHUVA is to contribute to the understanding of cloud processes, which represent one of the least understood components of the weather and climate system. The five CHUVA campaigns were designed to investigate specific tropical weather regimes. The first two experiments, in Alcantara and Fortaleza in northeastern Brazil, focused on warm clouds. The third campaign, which was conducted in Belem, was dedicated to tropical squall lines that often form along the sea-breeze front. The fourth campaign was in the Vale do Paraiba of southeastern Brazil, which is a region with intense lightning activity. In addition to contributing to the understanding of clo...

Intercomparison of Integrated Water Vapor Estimates from Multisensors in the Amazonian Region

Water vapor is an atmospheric component of major interest in atmospheric science because it affects the energy budget and plays a key role in several atmospheric processes. The Amazonian region is one of the most humid on the planet, and land use change is able to affect the hydrologic cycle in several areas and consequently to generate severe modifications in the global climate. Within this context, accessing the error associated with atmospheric humidity measurement and the validation of the integrated water vapor (IWV) quantification from different techniques is very important in this region. Using data collected during the Radiation, Cloud, and Climate Interactions in Amazonia during the Dry-to-Wet Transition Season (RACCI/DRY-TO-WET), an experiment carried out in southwestern Amazonia in 2002, this paper presents quality analysis of IWV measurements from RS80 radiosondes, a suite of GPS receivers, an Aerosol Robotic Network (AERONET) solar radiometer, and humidity sounding from the Humidity Sounder for Brazil (HSB) aboard the Aqua satellite. When compared to RS80 IWV values, the root-mean-square (RMS) from the AERONET and GPS results are of the order of 2.7 and 3.8 kg m 2 , respectively. The difference generated between IWV from the GPS receiver and RS80 during the daytime was larger than that of the nighttime period because of the combination of the influence of high ionospheric activity during the RACCI experiment and a daytime drier bias from the RS80.

Analysis of Relative Humidity Sensors at the WMO Radiosonde Intercomparison Experiment in Brazil

Abstract The quality of the vertical distribution measurements of humidity in the atmosphere is very important in meteorology due to the crucial role that water vapor plays in the earth’s energy budget. The radiosonde is the humidity measurement device that provides the best vertical resolution. Also, radiosondes are the operational devices that are used to measure the vertical profile of atmospheric water vapor. The World Meteorological Organization (WMO) has carried out several intercomparison experiments at different climatic zones in order to identify the differences between the available commercial sensors. This article presents the results of an experiment that was carried out in Brazil in 2001 in which major commercial radiosonde manufacturers [e.g., Graw Radiosondes GmbH & Co., KG (Germany); MODEM (France); InterMet Systems (United States); Sippican, Inc. (United States); and Vaisala (Finland)] were involved. One of the main goals of this experiment was to evaluate the performance of the different...

The Amazon Dense GNSS Meteorological Network: A New Approach for Examining Water Vapor and Deep Convection Interactions in the Tropics

AbstractThe complex interactions between water vapor fields and deep atmospheric convection remain one of the outstanding problems in tropical meteorology. The lack of high spatial–temporal resolution, all-weather observations in the tropics has hampered progress. Numerical models have difficulties, for example, in representing the shallow-to-deep convective transition and the diurnal cycle of precipitation. Global Navigation Satellite System (GNSS) meteorology, which provides all-weather, high-frequency (5 min), precipitable water vapor estimates, can help. The Amazon Dense GNSS Meteorological Network experiment, the first of its kind in the tropics, was created with the aim of examining water vapor and deep convection relationships at the mesoscale. This innovative, Brazilian-led international experiment consisted of two mesoscale (100 km × 100 km) networks: 1) a 1-yr (April 2011–April 2012) campaign (20 GNSS meteorological sites) in and around Manaus and 2) a 6-week (June 2011) intensive campaign (15 G...

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).

Avaliação de perfis atmosféricos de rádio ocultação GPS do satélite CHAMP sobre a América do Sul

With the advent of Global Positioning System (GPS), together with Low Earth Orbit (LEO) satellites, the Radio Occultation GPS (RO GPS) technique appears as a possibility of obtaining atmospheric profiles remotely, with positive perspectives of applications in atmospheric numerical modeling. The LEO satellite mission denominated Challenging Minisatellite Payload of Geophysical Research and Application (CHAMP), although with the main objective being in the area of geophysical studies, it has also allowed studies about the potential of RO-GPS. This study is related to the evaluation of the atmospheric profiles quality obtained by the LEO CHAMP satellites over South America, comparing them to radiosondes profiles and of regional reanalysis of five years from CPTEC/INPE. The results of the comparisons between RO GPS and RSO profiles pointed out a mean temperature difference below 1 K and a standard deviation of up to 3 K, distributed in altitudes from 9 to 18 km. The comparisons of temperature profiles from RO GPS and CPTECs reanalysis between 9 and 13 km showed that the bias is almost null and the standard deviation is around 1 K.

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.

Contribuição de diversos sistemas de observação na previsão de tempo no CPTEC/INPE

Experimentos utilizando sistemas de observacao global, foram realizados excluindo um ou mais tipos de observacao do esquema global de assimilacao de dados/previsao de tempo do Centro de Previsao de Tempo e Estudos Climaticos do Instituto Nacional de Pesquisas Espaciais - CPTEC/INPE (Global Physical-space Statistical Analysis System - GPSAS). Estes experimentos indicam como efetivamente as observacoes sao usadas no GPSAS. Os sistemas de observacao testados foram o conjunto de dados convencionais, que incluem informacoes de superficie (estacoes em superficie, boias, navios e plataformas oceânicas) e de ar superior (radiossondagem, aeronaves e baloes piloto), os sistemas de sondagem Advanced TIROS-N/NOAA Operational Vertical Sounder (ATOVS) e AQUA, composto pelos sensores Atmospheric Infrared Sounder e Advanced Microwave Sounding Unit (AIRS/AMSU), dados de vento de satelite, estimados a partir do deslocamento de nuvens (Cloud Track Wind), dados de vento em superficie sobre o oceano (QuikScat) e agua precipitavel (Total Precipitation water - TPW). Todos os sistemas testados mostram um impacto positivo na qualidade da previsao. Os dados convencionais tem um maior impacto na regiao do Hemisferio Norte devido a maior disponibilidade dessas informacoes sobre esta regiao. Por outro lado, as sondagens AIRS/AMSU sao fundamentais para uma boa previsao sobre o Hemisferio Sul. Sobre a America do Sul, os perfis inferidos pelo sistema de sondagem AQUA contribuem com a mesma ordem de grandeza dos dados convencionais e apresentam um impacto positivo para todos os periodos de previsoes analisados. Dados de vento e agua precipitavel estimados por satelites tem maior impacto nas regioes tropical e da America do Sul, nas primeiras horas de previsao (1-3 dias). Todavia, a utilizacao de um conjunto completo de observacoes e crucial para se obter, operacionalmente, uma boa condicao inicial do estado atmosferico para ser utilizada nos modelos de previsao numerica de tempo do CPTEC/INPE.

Os últimos avanços na previsibilidade dos campos de umidade no sistema global de assimilação de dados e previsão numérica de tempo do CPTEC/INPE

Two important implementations, directly related to the prediction of atmospheric humidity fields, have been introduced during in the recent years in the weather forecast model and its data assimilation system at CPTEC/INPE. The first is the inclusion of Integrated Water Vapor (IWV) data in the assimilation scheme. The second is the improvement of the weather forecast model along with an increase in the grid resolution. The goal of this paper is to characterize the impact of these implementations in the prediction of humidity fields. To achieve this goal four experiments were conducted using the T126L28 (without the improvement) and T213L42 (with the improvement) versions of the CPTECs global model, with and without assimilation of IWV. The results show that the impact of IWV assimilation is larger in the first hours of forecast. On the other hand, the larger impacts produced by the improvements in the weather forecast model occur from the 60th h of forecast onward. Consequently the combined impact of both implementations represent an improvement throughout the integration period or the period at which predictions of IWV present an acceptable skill (above 60%) were extended in up to 25 hours over the global tropical regions and up to 18 hours over South America.

AVALIAÇÃO ROBUSTA DA MODELAGEM NEUTROSFÉRICA SOBRE O TERRITÓRIO BRASILEIRO BASEADA EM MODELOS DE PREVISÃO NUMÉRICA DE TEMPO DA AMÉRICA DO SUL

O posicionamento com o sistema GNSS (Global Navigation Satellite System) e atualmente a tecnica mais utilizada para se obter a localizacao sobre a superficie terrestre ou proxima a essa. Depois dos efeitos causados pela ionosfera, a refracao que o sinal sofre ao ultrapassar a neutrosfera pode ser considerada como uma das maiores fontes de erro no sinal, a qual gera um atraso, que rebatida na direcao zenital e denominado atraso zenital neutrosferico (ZND), ou ainda atraso zenital troposferico (ZTD – Zenithal Tropospheric Delay). Esse atraso gera erros no posicionamento GNSS quando o mesmo nao e devidamente modelado. Os modelos de Previsao Numerica de Tempo (PNT) sao boas alternativas para a modelagem do ZND, pois como sao alimentados diariamente por observacoes da atmosfera, os mesmos, geram previsoes do ZND capazes de captar suas oscilacoes espaciais e temporais. No CPTEC/INPE sao desenvolvidos e operacionalizados modelos de PNT globais e regionais, sendo os ultimos dedicados ao melhor detalhamento sobre a America do Sul. No Brasil esta operacional no CPTEC/INPE um processo que gera tais previsoes com resolucao espacial de 15 km e temporal de 3 horas, alem de outras versoes que contemplam outras sofisticacoes. Para determinar o impacto dessas melhorias na qualidade das previsoes do ZND, o presente trabalho apresenta uma avaliacao robusta das versoes disponibilizadas, utilizando como referencia os valores de ZND estimados a partir dos dados GNSS coletados pelas estacoes da RBMC (Rede Brasileira de Monitoramento Continuo), levando em consideracao: a variacao sazonal, a continentalidade e a variacao da altitude e latitude.