Atmósfera <h3>Focus and Scope</h3> <p dir="ltr">Atmosfera is an international, peer-reviewed journal published quarterly since 1988, devoted to original research in the atmospheric sciences and climate change, and interactions with the hydrosphere, cryosphere, biosphere and human systems. </p> <p>It is published by the Universidad Nacional Autónoma de México, through the Instituto de Ciencias de la Atmósfera y Cambio Climático.</p> <p>All papers published are Open Access for readers and there are no publication fees for authors. The journal is indexed in Scopus, SCimago, Science Citation Index, LatinIndex, SciELO, among other databases. It has continuously increased its visibility and impact, with an Impact Factor of 2.063 (2022), as determined by the Journal Citation Report (Clarivate/ Web of Science).</p> <!-- WIDGET SCImago - Open Access --> <p><a title="SCImago Journal &amp; Country Rank" href=";tip=sid&amp;exact=no"><img src="" alt="SCImago Journal &amp; Country Rank" border="0" /></a> <img style="float: right; width: 256px; height: 93px;" src="" alt="Atmósfera - CCA UNAM" /></p> <!-- WIDGET SCImago - Open Access --> Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México en-US Atmósfera 0187-6236 <p>Once an article is accepted for publication, the author(s) agree that, from that date on, the owner of the copyright of their work(s) is Atmósfera.</p><p>Reproduction of the published articles (or sections thereof) for non-commercial purposes is permitted, as long as the source is provided and acknowledged.</p><p>Authors are free to upload their published manuscripts at any non-commercial open access repository.</p> Relationship between rainfall and streamflow in the La Plata Basin: Annual cycles, interdecadal and multidecadal variability <p class="p1">The aim of this study is to understand the interaction between rainfall and streamflow variability in the La Plata basin (LPB) along a wide range of timescales. The LPB is divided in six sub-basins associated to the main regional rivers (Paraguay, Paraná, Uruguay and Iguazú). The amplification of the streamflow response is addressed in order to evaluate to what extent river discharges variability can be explained by precipitation fluctuations. Mean annual cycles corresponding to the period 1931-2010 and to each decade of this interval are analyzed. Streamflow interdecadal changes are observed in most of the gauging stations. In addition, an 11-year moving-average filter is applied to the normalized annual time series. Results exhibit a considerable higher percentage of explained variance in the streamflow filtered series, highlighting the predominance of medium and low frequencies variability present in these compared to those of precipitation. Consistently, river discharges show higher spectral density in the interdecadal/multidecadal frequencies compared to precipitation analysis. A simple statistical approach to advance in the understanding of the complex rainfall-streamflow physical relationship is addressed with promising results: streamflow spectrums are derived directly from the precipitation spectrum, transformed by a “basin” operator, characteristic of the basin itself. It is assumed that watersheds act on precipitation as spatiotemporal integrators operating as low-pass filters, like a moving average. Streamflow power spectrums are simulated assuming that the underlying process is an autoregressive moving average. Considering the sub-basin areal-averaged precipitation time series as the only input, results show that simulated streamflow spectrums fit effectively the observations at the sub-basin scale.<span class="Apple-converted-space"> </span></p> Carla Gulizia Inés Camilloni Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 183 205 10.20937/ATM.53013 Cyclonic circulation and climatology of SST, CHL and wind stress curl in a semi-enclosed bay (Bahía de La Paz, Gulf of California, Mexico) <p class="p1">The first direct current observations (with the Lowering Acoustic Doppler Current Profiler [LADCP] and surface drifters) in Bahía de La Paz, in the southwestern Gulf of California (GC), concur with previous reports that the main dynamical feature during summer is a closed cyclonic circulation. However, we found that geostrophic calculations overestimate the speed of the orbital velocity: actual speeds (0.20-0.25 m s<sup>–1</sup>) were ~25-40% lower than those estimated from geostrophic balance (0.25-0.35 m s<sup>–1</sup>). The reason is that the centrifugal force cannot be neglected in this case. The mean rotation period during ship-borne observations in August 2004 was ~1.4 days, but it varied in the time that surface drifters were inside the bay, from ~1-2 days in June-July to ~2.5-3 days in September-October. The analysis of satellite data (wind velocity, sea surface temperature and chlorophyll) shows that from May to September the wind stress curl is strong and cyclonic, and the surface of the bay is cooler and richer than the adjacent Gulf of California waters, which could be attributed to the positive wind stress curl. This positive wind stress curl on the bay is part of a larger-scale positive wind stress curl distribution that surrounds the southern part of the Baja California Peninsula during summer, probably enhanced in the bay by local topography features. Although there is an exchange of water between the bay and the GC, its effect on the dynamics is poorly known.<span class="Apple-converted-space"> </span></p> Emilio Beier Rubén Castro Victor M. Godínez Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 207 224 10.20937/ATM.53093 Understanding convective storms in a tropical, high-altitude location with in-situ meteorological observations and GPS-derived water vapor <p class="p1">We investigate convective storms over the Sabana de Bogotá, a high-altitude and densely populated area in the Colombian tropical Andes. Convective events are identified using infrared satellite images and in-situ precipitation data. As expected, convection shows a strong early-afternoon peak during the two rainy seasons. Previous studies hypothesize that early-afternoon westerly winds and their moisture advection from the warmer Magdalena valley are the main explanatory mechanism for intense storms. We find that early-afternoon westerlies are present in 78% of rainy season days, but convective events develop in only 26% of them. Thus, although westerlies seem necessary for convection due to the convergence they generate, they only occasionally generate storms and are therefore not a good predictor. Furthermore, reanalysis data indicate that precipitable water vapor (PWV) at the Magdalena valley is anomalously low during convective days, suggesting that moisture converges locally instead of being advected from the west. Based on composites of surface wind speed, air temperature, surface pressure, and GPS-derived PWV, we identify the most prominent signals associated with deep convection: a weaker than average wind speed throughout the morning, higher than normal values of surface air temperature towards noon, followed by an anomalous steep increase of PWV and wind speed. These features indicate that convection results from a strong diurnal forcing facilitated by convergence of westerly winds, combined with sufficient water vapor convergence, with a timescale of about 3 h. This highlights the relevance of high temporal resolution monitoring of PWV offered by Global Navigational Satellite System stations.</p> Alejandro Casallas-García Daniel Hernández-Deckers Héctor Mora-Páez Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 225 238 10.20937/ATM.53051 Regional flow climatology for central Mexico (Querétaro): A first case study <p class="p1">A flow climatology was established for the Metropolitan Area of Querétaro (MAQ) in central Mexico, by analyzing four years (2014-2017) of back-trajectories generated using the HYSPLIT model. Two flow regimes were found: one from June until September (rainy regime); the other from December to May (dry regime). October and November were considered transition months. Northeasterly flows were present throughout the year; in contrast, trajectories from the southwest were much less frequent and observed mainly during the dry regime. An analysis of the wind fields from the North American Regional Reanalysis (NARR) database for a longer period of time (1979-2019) suggests that these results are representative of the average conditions of the atmosphere at the study site. Some of the northeasterly trajectories observed originate within a dessert region of the state of Querétaro, where several limestone mines are located. During the dry regime and transition months some clusters originate at the industrial area in Guanajuato, which includes the Salamanca refinery. As air transport of pollutants follow these paths, this analysis could be useful for identifying regional sources that affect the MAQ and possibly increase its air pollution load. In fact, the variability of criteria pollutants concentrations matched the flow regimes described above.</p> Daniel Atreyu Rozanes-Valenzuela Adolfo Vicente Magaldi Dara Salcedo Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 239 252 10.20937/ATM.53038 Performance evaluation of the WRF model in a tropical region: Wind speed analysis at different sites <p class="p1">In this study, the performance of the mesoscale Weather Research and Forecasting (WRF) model is evaluated using combinations of three planetary boundary layers (PBL) (YSU, ACM2, and MYJ) and three land surface model (LSM) schemes<span class="Apple-converted-space"> </span>(RUC, Noah and Noah-MP) in order to identify the optimal parameters for the determination of wind speed in a tropical region. The state of Bahia in Brazil is selected as the location for the case study and simulations are performed over a period of eight months between 2015 and 2016 (dry and rainy seasons). The results of the simulations are compared with observational data obtained from three towers equipped with anemometers at heights of 80, 100, 120 and 150 m, strategically placed at each site and evaluated with statistical indices: MB, RMSE, MAGE, IOA, R, Fac2 and standard deviation. Overestimation of wind speed is observed in the simulations, despite similarities between the simulated and observed wind directions. In addition, the accuracies of simulations corresponding to sites that are closer to the ocean are observed to be lower. The most accurate wind speed estimates are obtained corresponding to Mucugê, which is located farthest from the ocean. Finally, analysis of the results obtained from each tower accounting for periods with higher and lower precipitation reveals that the combination of the PBL-YSU scheme with the LSM-RUC scheme yields the best results.</p> Noéle B. P. Souza Erick G. S. Nascimento Davidson M. Moreira Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 253 277 10.20937/ATM.52968 Analyzing and forecasting lightning flashes and the related wind gusts at a wind energy power plant in a hilly region of western Greece <p class="p1">Wind power plants are vulnerable to abrupt weather changes caused by thunderstorms associated with lightning activity and accompanying severe wind gusts and rapid wind direction changes. Due to the damages that such phenomena may cause, the knowledge of the relationship between storm systems and the produced wind field is essential during the construction and operation phase of a plant. In the first part of this study, the relationship between severe wind gusts and lightning activity in a power plant in Greece is investigated. Wind data are measured at the wind turbines for a 3-year period (2012-2014); the corresponding lightning data come from the ZEUS lighting detection network. Wind gusts are well correlated to lightning strikes. This correlation is maximized during winter when well organized weather systems affect the area and minimized in summer as a result of local storms due to thermal instability. The second part of the study focuses on the development of an artificial neural network (ANN) model in order to forecast these two parameters in a 1-h ahead horizon based on wind speed, wind direction, and maximum observed wind gust measured at the nacelle of a wind turbine and four other variables, namely CAPE, TTI, wind speed at the 500 hPa isobaric level, and the 0-6 km vertical wind shear. The proposed model could be considered as a promising tool in simulating the occurrence both of wind gusts and lightning flashes, providing a relatively good evidence of the possibility of occurrence of such events.</p> Konstantinos V. Kolokythas Athanassios A. Argiriou Vassiliki Kotroni Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 279 298 10.20937/ATM.53043 Fuzzy cognitive maps to explore the repercussions of less precipitation on the water supply service of the Metropolitan Area of Mexico City <p class="p1">Currently the drinking water supply service system of the Metropolitan Area of Mexico City (MCMA) faces serious problems in its operation, which generate highly negative impacts on the impacts on the environmental, social and provider sectors of this system. Given the presence of climate change, we consider the possible scenario in which a decrease in average annual precipitation occurs in the area. To evaluate its impact on each of the sectors, the fuzzy cognitive map (FCM) associated with each of them was constructed. This framework allowed the study of a system whose available information presented large ranges of uncertainty, in addition to being highly complex. Based on the results obtained, we present a mitigation measure for each sector, in order to provide efficient actions to decisions makers. The mathematical simulation was carried out programming in Python.</p> Norma Elizabeth Olvera-Fuentes Carlos Gay-García Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 299 316 10.20937/ATM.53037 Remote sensing of atmospheric nitrogen dioxide in an urban area in central northern Mexico <p>Nitrogen dioxide (NO<sub>2</sub>) was remotely measured in the urban area of San Luis Potosí (México) using the differential optical absorption spectroscopy (DOAS) technique. Measurements were taken from July to August 2015. In this technique, light scattered by the sun through the atmosphere is focused by a telescope onto a linear array-based spectrometer at ground level. During the measurement period, the maximum NO<sub>2</sub> levels (2.3 x 10<sup>16</sup> molecules/cm<sup>2</sup>) were found at around 11:00 h, whereas NO<sub>2</sub> levels fell on days with wind speeds lower than 1.5 m/s. The NO<sub>2</sub> levels were compared and explained with the behavior of meteorological data such as wind speed, relative humidity, and surface temperature obtained from the Weather Research and Forecasting Model (WRF).</p> Julio César Hernández Clara Rosalía Ávila Luis Felipe Lastras Alfonso Lastras David Enrique Flores Abraham Cárdenas Marcos Algara Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 317 327 10.20937/ATM.53032 Patterns related to pollutant concentrations in the Metropolitan Area of Belo Horizonte, Brazil <p class="p1"><span class="s1">Air pollution from human and industrial activities has been a major concern in recent years. Among the various pollutants found in the atmosphere, particulate matter (PM) and ozone (O<sub>3</sub>) show significant occurrences, with high concentrations in urban centers frequently associated with environmental and public health problems. Therefore, this study uses the analysis of variance (ANOVA) technique and Tukey’s test to investigate patterns related to the variability of maximum daily O<sub>3 </sub>concentrations and mean daily concentrations of PM with a diameter less than 10 μm (PM<sub>10</sub>), registered between 2007 and 2012 through six sites in the Metropolitan Area of Belo Horizonte, Brazil. To this end, the data were analyzed using ANOVA arranged in a factorial scheme (6 × 4 × 2) with four repetitions per treatment, followed by Tukey’s test. In the ANOVA and Tukey’s test, the first factor (A) represents the six air quality monitoring stations, the second (B) represents the seasons, and the third (C), the measurements carried out during working days and weekends. Seasonal variability patterns show higher concentrations of O<sub>3</sub> in spring and of PM<sub>10</sub> in winter. The values were 22.9 and 35.32% higher than the annual averages of O<sub>3</sub> and PM<sub>10</sub> concentrations, respectively. The mean values for working days and weekends showed different patterns for the two pollutants. PM<sub>10</sub> concentrations were 11% higher during working days when compared to weekends. The O<sub>3</sub> weekend effect was found only in one of the stations. The profiles of vehicular and industrial emissions have been identified as a potential factor leading to these results.</span></p> Luiza Maria Marcos Cerqueira Mendes Vanessa Silveira Barreto Carvalho Fabrina Bolzan Martins Taciana Toledo de Almeida Albuquerque Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 329 341 10.20937/ATM.53056 Air pollution and mobility in the Mexico City Metropolitan Area in times of COVID-19 <p class="p1">This paper analyzes the relation between COVID-19, air pollution, and public transport mobility in the Mexico City Metropolitan Area (MCMA). We test if the restrictions to economic activity introduced to mitigate the spread of COVID-19 are associated with a structural change in air pollution levels and public transport mobility. Our results show that mobility in public transportation was significantly reduced following the government’s recommendations. Nonetheless, we show that the reduction in mobility was not accompanied by a reduction in air pollution. Furthermore, Granger-causality tests show that the precedence relation between public transport mobility and air pollution disappeared as a product of the restrictions. Thus, our results suggest that air pollution in the MCMA seems primarily driven by industry and private car usage. In this regard, the government should redouble its efforts to develop policies to reduce industrial pollution and private car usage.</p> J. Eduardo Vera-Valdés C. Vladimir Rodríguez-Caballero Copyright (c) 2021 Atmósfera 2022-09-30 2022-09-30 36 2 343 354 10.20937/ATM.53052