Atmósfera (Journal)
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A new index to assess meteorological drought: the Drought Exceedance Probability Index (DEPI)
Get PDFThis paper presents a new index to determine meteorological drought conditions, the Drought Exceedance Probability Index (DEPI), derived from monthly precipitation time series. Its formulation is simple and undemanding in terms of baseline information requirements. This makes the DEPI suitable for routine application to any climate, similar to the well-known Standardized Precipitation Index (SPI). The index is based on the calculation of cumulative rainfall anomalies and their subsequent standardization, similarly to other indices. The hallmarks of the DEPI, and its main comparative advantages, are the process of accumulating anomalies and their standardization process. The paper compares the DEPI with the SPI in several different climates across the world and in all cases the results show the complementarity of both indices. The DEPI shows an excellent ability to reflect the actual severity and duration of droughts, without requiring application on different time scales, unlike the SPI. It is also valid for all types of climates, including arid and semiarid or Mediterranean, for which the literature has shown that using the SPI is problematic
Long-term measurements of aerosol optical properties and radiative forcing (2011-2017) over Central Amazonia
Get PDFThe Amazon region is one of the most pristine continental areas whose concentrations of atmospheric trace gases and aerosol particles are very low, mainly in the wet season. This study provides observational results of aerosol optical and radiative characteristics in situ as well as atmospheric columnar at a pristine forest in Central Amazonia. Spectral variation of the aerosol properties (aerosol optical depth [AOD], single scattering albedo [SSA], and asymmetry parameter [AP]) was evaluated using the AErosol RObotic NETwork (AERONET) data. The SSA values under natural atmospheric column conditions (AERONET) were compared to the SSA values calculated with in situ measurements. The values of shortwave aerosol radiative forcing (SWARF) on top of the atmosphere (TOA) and the surface (SUR) were estimated using the SBDART model and were validated with the AERONET values with regression analysis. SWARF had a high correlation to TOA (0.97) and SUR (0.92), including dry and wet seasons. Monthly, seasonal and annual mean values of SWARFTOA and SWARFSUR were negative while SWARFATM values were positive. SWARFTOA was –9.18 ± 2.80 W m–2 and SWARFSUR was –20.77 ± 5.04 W m–2 in the dry season, inducing a heating rate (HR) of 0.37 ± 0.13 K.day–1. This study showed that, for a long series of measurements, the effects caused by aerosols on the radiative flux in the pristine forest of Central Amazonia were of the order of SWARFTOA of –3.66 ± 1.59 W m–2 and SWARFSUR of –11.86 ± 2.35 W m–2 during the wet season
The anomalous wet 2020 southeast Brazil austral summer: Characterization and possible mechanisms
Get PDFThis paper analyzed the anomalous rainy austral summer of 2020 over the southeastern region of Brazil (SEB), investigating its possible mechanisms. The SEB experienced dry summers in the years before 2020; however, the austral summer of 2020 in this region was the wettest since 1991. A wave train starting from the Indian Ocean to the Pacific Ocean, plus a wave train from the tropical north (U-shape), and another from the western equatorial Pacific (PSA-like) contributed to an anomalous anticyclonic circulation at high levels southward South America. This merged wave train continued its path with an anomalous cyclonic circulation over the southern region of Brazil and the state of Sao Paulo, and anticyclonic northward, enhancing (inhibiting) convection over SEB (southern Brazil). Besides, the Southern Annular Mode (SAM) pattern was in a positive phase, and there were negative sea surface temperature (SST) anomalies near SEB and Argentina, contributing for the configuration over the continent. Comparisons of the main differences between the austral summer of 2019 (dry) and the summer of 2020 show there was no anomalous divergence at high levels over the Indian Ocean in 2019, triggering a wave train from this region to the Pacific. The two wave trains from the Pacific merged in an anomalous anticyclonic circulation over the southeastern Pacific, near the South American coast. The SAM pattern was neutral in 2019; however, there were positive SST anomalies near SEB, southern Brazil and Argentina coastal. The South Atlantic SST and the wave trains generated an anticyclonic anomalous circulation over the southern Region of Brazil and cyclonic northward, in opposition to the 2020 configuration
Letter from the Editor
Get PDFI have the pleasure to introduce this new issue of Atmósfera which this year, its 33rd since being founded by Dr. Julian Adem, has once again started publishing systematically 8 papers per number. In particular, in this issue we have the great fortune to share editing responsibilities with Dr. Luisa Molina, a well renowned and much celebrated scientist and editor. The papers edited by her relate to issues associated with emissions of greenhouse gases and to methodologies to estimate them in Latin America. These papers provide methods that are very relevant to accurately measure emissions that aid in the estimates of national inventories and provide better tools for designing mitigation strategies. We are very grateful to Dr. Molina for her time and expertise in editing the manuscripts received on the topic
Application of several data-driven techniques to predict a standardized precipitation index
Get PDFClimate modeling and prediction is important in water resources management, especially in arid and semi-arid regions that frequently suffer further from water shortages. The Maharlu-Bakhtegan basin, with an area of 31 000 km2 is a semi-arid and arid region located in southwestern Iran. Therefore, precipitation and water shortage in this area have many problems. This study presents a drought index modeling approach based on large-scale climate indices by using the adaptive neuro-fuzzy inference system (ANFIS), the M5P model tree and the multilayer perceptron (MLP). First, most of the climate signals were determined from 25 climate signals using factor analysis, and subsequently, the standardized precipitation index (SPI) was predicted one to 12 months in advance with ANFIS, the M5P model tree and MLP. The evaluation of the models performance by error parameters and Taylor diagrams demonstrated that performance of the MLP is better than the other models. The results also revealed that the accuracy of prediction increased considerably by using climate indices of the previous month (t – 1) (RMSE = 0.802, ME = –0.002 and PBIAS = –0.47)
Etesian winds outbursts over the Greek Seas and their linkage with larger-scale atmospheric circulation features: Two real time data case studies
Get PDFThere are significant differences in the way that researchers have defined “Etesian wind days”. An attempt is made here to establish common definitions of the various types of Etesian winds from the weather forecaster’s viewpoint. These definitions are based on objective criteria adopted from the frequency of atmospheric circulation features associated with the occurrence of the Etesian winds and their physical characteristics. The presence of fairly constant northerly winds over the Greek Seas in summer are called Etesian winds. When a new spell of Etesian winds is established with no diurnal variation of the wind direction for consecutive days (maximum of seven), these winds are called “type B” Etesian winds or “Etesian outbursts”. The atmospheric circulations associated with the occurrence, origin and evolution of the type B Etesian winds and the accompanying weather are revealed utilizing data for the period 1975-2015 and focusing on two case studies on July 21-22, 1983 and July 3-4, 2017. The presence of the Subtropical Jet Stream (SJS) over the Greek territory and its interaction with the Polar Jet Stream (PJS) are dominant factors. Large-scale atmospheric circulations are studied to identify simultaneous direct links to the Indian Summer Monsoon (ISM), El Niño-Southern Oscillation (ENSO), Madden-Julian Oscillation (JMO), deep convective activity in the Hadley circulation in the tropics, and West Africa Monsoon (WAM)
Assessment of the accuracy of open-circuit respiration chambers for measuring enteric methane emissions in cattle
Get PDFRuminants are the main source of methane emissions from the agricultural sector. Emission inventories and mitigation strategies require reliable technics of measurement. The respiration chamber methodology is a precise approach for measuring enteric methane emissions in cattle. A set of experiments was carried out to validate two respiration chambers for measuring enteric methane emissions of cattle. The chambers were calibrated considering three main components: the methane analyzer, the air duct and air extraction system, and the chamber itself, by evaluating linearity and response time of the analyzer, plateau variability and high purity methane recoveries in chambers. Recovery test calculations carried out after releasing high purity methane into the chambers gave calibration factors of 0.95 ± 0.05 and 1.03 ± 0.03 for the complete system of respirations chambers one and two, respectively, with corresponding uncertainties of 4.87 and 2.49%. Thus, the respiration chambers for enteric methane measurements of cattle at the University of Yucatan, Mexico function with precision and accuracy. This technique can be used to establish methane inventories and methane mitigation strategies in cattle.Los rumiantes son la principal fuente de emisiones de metano del sector agropecuario. Los inventarios de emisiones y las estrategias de mitigación requieren técnicas confiables de medición. La metodología de la cámara de respiración de circuito abierto es un enfoque preciso para medir las emisiones entéricas de metano en el ganado. Se llevaron a cabo una serie de experimentos para validar dos cámaras de respiración, para medir las emisiones entéricas de metano del ganado bovino. Las cámaras de respiración se calibraron teniendo en cuenta tres componentes principales: el analizador de metano, el conducto de aire y el sistema de extracción de aire y la propia cámara, evaluando la linearidad y el tiempo de respuesta del analizador, la estabilidad de la meseta y las recuperaciones de metano de alta pureza en las cámaras. Los cálculos de la prueba de recuperación llevados a cabo después de liberar metano de alta pureza en las cámaras resultaron en factores de calibración de 0.95 ± 0.05 y 1.03 ± 0.03 (para el sistema completo de las dos cámaras de respiración) para las cámaras uno y dos respectivamente, con incertidumbres de 4.87 y 2.49% respectivamente. Se concluyó que las cámaras de respiración para las mediciones de metano entérico del ganado construidas en la Universidad Autónoma de Yucatán, México, funcionan con precisión y exactitud. Esta técnica puede usarse para establecer inventarios de metano y estrategias de mitigación de metano en el ganado bovino
Spatio-temporal analysis of remotely sensed rainfall datasets retrieved for the transboundary basin of the Madeira River in Amazonia
Get PDFRainfall is recognized as the most important driving force of the hydrologic cycle. To accurately represent the spatio-temporal rainfall variability continues to be an enormous hydrological task when using commonly sparse, if available, rain gauges networks. Therefore, the present study devoted a special effort to analyze the robustness of some satellite rainfall products, notably the datasets hereafter named as (i) CHIRP (Climate Hazards Group InfraRed Precipitation), (ii) CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data), (iii) 3B42, and (iv) 3B42RT of the Tropical Rainfall Measuring Mission (TRMM), to adequately represent the pluviometric regime in the Madeira river basin. To assess the accuracy of acquired remotely sensed rainfall products, comparisons to observational available rain gauges usually taken as ground-truth in the literature, despite their well-known limitations, were performed. Wavelet analysis was also used to validate the performance of the referred satellite products by means of extracting the corresponding cycles, frequencies, and tendencies along the available time series across the studied basin. The results showed that the data sources CHIRPS and CHIRP better represent the pluviometric phenomenon by means of their monthly accumulated rainfall in the Madeira river basin when compared to the 3B42 and 3B42RT products taking into account rain gauges as baseline information. The CHIRPS product performed the best among the selected rainfall estimators for the Madeira river basin. Further analysis brought up also another very interesting result related to non-rainfall periods, which is usually not reported. However, such evaluation is quite important in hydrology when examining run sequences of droughts and consequent effects in the water balance at the watershed scale. Highly accurate estimates in the sense of identifying non-rainfall periods by remotely sensed information was achieved, which represents an additional and valuable asset of satellite rainfall products. It is worthwhile to say that this perspective deserves to receive much more attention in the literature in order to deeply discuss the water-energy-food nexus
The tornado of Talavera de la Reina on September 3, 1880
Get PDFOn September 3, 1880 a probable tornado caused significant damage in the city of Talavera de la Reina (Spain). In this work, we analyze the original description made by an observer of that time about this phenomenon and the meteorological conditions for that day. The potential formation of a tornado was possible according to our analysis. This would be the first record of a tornado in the region of Talavera de la Reina prior to 1975. According to the original description, we could estimate the intensity of this tornado as EF2 (in the Enhanced Fujita Scale)
The MAX-DOAS network in Mexico City to measure atmospheric pollutants
Get PDFAn instrument based on the Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique was designed and constructed to measure scattered sunlight in the UV-visible region at different elevation angles. Slant column densities (SCDs) of specific gas absorbers such as nitrogen dioxide (NO2) and formaldehyde (HCHO) are derived from the measured spectra. In this contribution, the technical characteristics and performance of the instruments, their deployment in a newly formed observational network within the metropolitan area of Mexico City, and some results of the retrieved NO2 and HCHO SCDs are presented. These measurements provide more insight on the vertical and spatial distribution of these key atmospheric pollutants and their temporal variability, which also serve as a basis for present and future satellite validation studies