Waveshapes of continuing currents and properties of M-components in natural positive cloud-to-ground lightning     

Leandro Z.S. Campos  Marcelo M.F. Saba  Osmar Pinto Jr.  Maurício G. Ballarotti   《Atmospheric Research》2009,91(2-4):416-424

This work analyses the waveshapes of continuing currents and parameters of M-components in positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos. The dataset is composed of only long continuing currents (with duration longer than 40 ms) and was selected from more than 800 flashes recorded in São José dos Campos (45.864°W, 23.215°S) and Uruguaiana (29.806°W, 57.005°S) in Southeast and South of Brazil, respectively, during 2003 to 2007 summers. The videos are compared with data obtained by the Brazilian Lightning Location System (BrasilDAT) in order to determine the polarity of each flash and select only positive cases. There are only two studies of waveshapes of continuing currents in the literature. One is based on direct current measurements of triggered lightning, in which four different types of waveshapes were observed; and the other is based on measurements of luminosity variations in high-speed videos of CG negative lightning, in which besides the four types above mentioned two additional types were observed. The present work is an extension of the latter, using the same method but now applied to obtain the waveshapes of positive CG lightning. As far as the authors know, this is the first report on M-components in positive continuing currents. We also have used the luminosity-versus-time graphs to observe their occurrence and measure some parameters (duration, elapsed time and time between two successive M-components), whose statistics are presented and compared in detail to the data for negative flashes. We have plotted a histogram of the M-components elapsed time over the total duration of the continuing current for positive flashes, which presented an exponential decay (correlation coefficient: 0.83), similar to what has been observed for negative flashes.  相似文献   

Decadal predictability and prediction skill of sea surface temperatures in the South Pacific region     

Ramiro I. Saurral  Javier Garc&#;a-Serrano  Francisco J. Doblas-Reyes  Leandro B. D&#;az  Carolina S. Vera 《Climate Dynamics》2020,54(9):3945-3958

The South Pacific Ocean is a key driver of climate variability within the Southern Hemisphere at different time scales. Previous studies have characterized the main mode of interannual sea surface temperature (SST) variability in that region as a dipolar pattern of SST anomalies that cover subtropical and extratropical latitudes (the South Pacific Ocean Dipole, or SPOD), which is related to precipitation and temperature anomalies over several regions throughout the Southern Hemisphere. Using that relationship and the reported low predictive skill of precipitation anomalies over the Southern Hemisphere, this work explores the predictability and prediction skill of the SPOD in near-term climate hindcasts using a set of state-of-the-art forecast systems. Results show that predictability greatly benefits from initializing the hindcasts beyond the prescribed radiative forcing, and is modulated by known modes of climate variability, namely El Niño-Southern Oscillation and the Interdecadal Pacific Oscillation. Furthermore, the models are capable of simulating the spatial pattern of the observed SPOD even without initialization, which suggests that the key dynamical processes are properly represented. However, the hindcast of the actual phase of the mode is only achieved when the forecast systems are initialized, pointing at SPOD variability to not be radiatively forced but probably internally generated. The comparison with the performance of an empirical prediction based on persistence suggests that initialization may provide skillful information for SST anomalies, outperforming damping processes, up to 2–3 years into the future.  相似文献   

Analysis of physical quality of soil using the water retention curve: Validity of the S-index     

Glenio Guimares Santos  Euzebio Medrado da Silva  Roblio Leandro Marcho  Pedro Marques da Silveira  Ary Bruand  Francois James  Thierry Becquer 《Comptes Rendus Geoscience》2011,343(4):295-301

  相似文献   

Food web structure of sandy beaches: Temporal and spatial variation using stable isotope analysis     

Leandro Bergamino  Diego Lercari  Omar Defeo 《Estuarine, Coastal and Shelf Science》2011,91(4):2751

  相似文献   

The consequences of Brazil’s lack of transport planning is written in the blood of sparrows     

Fabio Angeoletto  Deleon da Silva Leandro  Mark D. E. Fellowes 《Urban geography》2013,34(8):1191-1197

The medium-sized cities of Brazil are those with populations of between 100,000 and 500,000 inhabitants. These cities are growing rapidly, and are characterized by poor urban planning, a loss of biodiversity and decreasing health prospects for residents. Historically, urbanization in Brazil has been associated with incentives to increase the use of private vehicles for local transport. The air pollution resulting from this “car dependency” has been quantified in some major cities in Brazil, such as the megacity of São Paulo. In this paper, we demonstrate through a bioindication study carried out in the Brazilian city of Rondonópolis, that atmospheric pollution resulting from vehicular emissions is also a measurable reality for medium-sized cities. Most Brazilian cities lack air quality measurement equipment, and we used an inexpensive and easy to apply bioindication assay to measure air pollution, and this approach could be easily implemented in those cities and beyond.  相似文献   

Do the recent severe droughts in the Amazonia have the same period of length?     

Yong Zou  Elbert E. N. Macau  Gilvan Sampaio  Antônio M. T. Ramos  Jürgen Kurths 《Climate Dynamics》2016,46(9-10):3279-3285

  相似文献   

Changes in precipitation extremes in Brazil (Paraná River Basin)   总被引：2，自引：1，他引：1  

Leandro Zandonadi  Fiorella Acquaotta  Simona Fratianni  João Afonso Zavattini 《Theoretical and Applied Climatology》2016,123(3-4):741-756

  相似文献   

Variations in annual snowline and area of an ice-covered stratovolcano in the Cordillera Ampato,Peru, using remote sensing data (1986–2014)     

Bijeesh Kozhikkodan Veettil  Ulisses Franz Bremer  Sergio Florêncio de Souza  Éder Leandro Bayer Maier  Jefferson Cardia Simões 《国际地球制图》2016,31(5):544-556

This research focuses on the recent variations in the annual snowline and the total glaciated area of the Nevado Coropuna in the Cordillera Ampato, Peru. Maximum snowline altitude towards the end of dry season is taken as a representative of the equilibrium line altitude of the year, which is an indirect measurement of the annual mass balance. We used Landsat and IRS LISS3 images during the last 30 years due to its better temporal coverage of the study site. It is found that there was a decrease of 26.92% of the glaciated area during 1986–2014. We calculated the anomalies in precipitation and temperature in this region and also tried to correlate the changes in glacier parameters with the combined influence of El Niño – Southern Oscillation (ENSO) and pacific decadal oscillation (PDO). It is concluded that the snowline of Nevado Coropuna has been fluctuated during ENSO, and maximum fluctuations were observed when ENSO and PDO were in phase.  相似文献   

New ICP‐MS Results for Trace Elements in Five Iron‐Formation Reference Materials          下载免费PDF全文

Geraldo Magela Santos Sampaio  Jacinta Enzweiler 《Geostandards and Geoanalytical Research》2015,39(1):105-119

Iron formations (IFs) typically contain low mass fractions of most trace elements, including the rare earth elements (REE), and few publications describe analytical methods dedicated to this matrix. In this study, we used bomb and table‐top acid dissolution procedures and ICP‐MS to determine the mass fractions of trace elements in IF reference materials FER‐1, FER‐2, FER‐3, FER‐4 and IF‐G. The full digestion of the IF samples with the bomb procedure required the addition of a small amount of water together with the acids. The results obtained by this method mostly agreed statistically with published values. The most remarkable exception was the higher values obtained for the heavy REE in FER‐3. The recoveries of the REE obtained with the table‐top procedure were slightly higher than those of the bomb digestion, except for the values of the heavy REE in FER‐3 and FER‐4, which were up to 30% lower than published values. Sintering of the samples with sodium peroxide was performed to determine the REE, but the results tended to be lower than those derived following acid digestion. On the whole, the recoveries showed dependence on the conditions of digestion, but subtle differences in trace mineral composition between samples also exerted influence on the analytical results for trace elements.  相似文献   

Comparisons of the Noah-MP land surface model simulations with measurements of forest and crop sites in Amazonia     

Isabel L. Pilotto  Daniel A. Rodríguez  Javier Tomasella  Gilvan Sampaio  Sin Chan Chou 《Meteorology and Atmospheric Physics》2015,127(6):711-723

  相似文献