Showing papers in "Atmosfera in 2020"

Impact of fossil fuels, renewable energy consumption and industrial growth on carbon emissions in Latin American and Caribbean economies

Abstract: This study examines the impact of fossil fuels consumption, renewable energy use and industrial growth on carbon emissions in the developing economies of Latin America and the Caribbean. An industrial growth index is developed using competitive industrial indicators, and a two-step system generalized method of moments robust estimator is employed, involving a panel of 16 middle- and lower-middle-income economies for the period 1990 to 2015. The empirical results show an Inverted-U shaped relationship between economic growth and carbon emissions and confirm the existence of the environmental Kuznets curve for the region. The results indicate that industrial growth and consumption of fossil fuels are significantly contributing to carbon emissions in the region. The results highlight that, based on competitiveness in manufacturing and the transition from simple to sophisticated technologies, advance technology-based industrial growth increases the potential to produce goods competitively with lower carbon emissions. The findings suggest that such advanced industrial growth is unavoidable to attain sustainable economic growth. Thus, technological advancement and consumption of renewable energies have the potential to both meet the rising demand for goods and energy and to control carbon emissions in the developing countries of Latin America and the Caribbean.

Spatio-temporal analysis of the droughts in Cali, Colombia and their primary relationships with the El Niño-Southern Oscillation (ENSO) between 1971 and 2011

Abstract: This paper analyzed the spatio-temporal variability of droughts in Cali, Colombia and their primary relations to the El Nino Southern Oscillation (ENSO). The Standardized Precipitation Index (SPI) was used to detect drought events from monthly rainfall data of 24 stations well spread over Cali during 1971-2011. The SPI provided the drought intensity, magnitude, frequency, and the minimum rainfall thresholds, mainly on an annual scale (SPI-12). Eighty percent of the stations reported four events with dry conditions in Cali: 1976-1977, 1983-1984, 1990-1992 and 2009-2010. The ENSO influence was evaluated using the correlation and wavelet transform analyses. Significant (non-significant) negative correlations between SPI-12 in the northern (southern) part of Cali, the multivariate ENSO Index (MEI), and Sea Surface Temperature (SST) Nino 3.4 and Nino 4 indices were observed. The wavelet coherence analysis showed significant coherencies between ENSO and SPI-12: at interannual scale (4-6 years), the phase difference of –135o generates a lag of 6-9 months between the minimum peak of the SPI-12 and the maximum peak of the indices. On the quasi-biennial scale (2-3 years), the phase difference of –180o suggests that the maximum wet (dry) conditions coincide with the mature stage of the La Nina (El Nino) event; and on the decadal scale (8-16 years), the decreases (increases) in rainfall precede the El Nino (La Nina) mature stage by approximately 10-18 months. These results are relevant for seasonal forecasting, since changes in SST in the equatorial Pacific may take place 6-18 months ahead of the dry conditions in Cali.

Air pollution and daily mortality in the Mexico City Metropolitan Area

Abstract: We utilize a time-series semi-parametric Poisson regression approach, incorporating natural cubic splines for temperature, to study the short-term associations between PM 10 and daily mortality due to cardiovascular, respiratory, and cardiorespiratory events for seven municipalities in Mexico City Metropolitan Area (2001-2013). Our results demonstrate that assessing seasonality, along with temperature variability, is vital in understanding the relationship between air pollution and mortality events. Additionally, our findings support the World Health Organization’s morbidity and mortality threshold for PM 10 within the assessed municipalities. We were able to identify associations between different meteorological seasons and air pollutions effects on mortality. Lastly, we demonstrate that geographical differences are modulating the relationship between air pollutants and mortality for models with and without distributed lagged. Our findings highlight the need for policy-driven approaches that take into consideration the dynamics of meteorological influences and geographic variability in terms of mitigating future deleterious health impacts of air pollutants in facilitating mortality risk.

Trends and variability of temperature and evaporation over the African continent: Relationships with precipitation

Abstract: This study analyzes changes in the long-term (1901-2015) monthly values of potential evapotranspiration (PET), precipitation, and minimum (T min ) and maximum (T max ) temperatures across Africa to quantify trends and assess covariability between these climatic variables. Both warming and drying trends were observed across the continent. The 1979-2015 warming was stronger than that from 1901 to 1940. Some cooling occurred from 1941 to the mid-1970s. The 1901-2015 annual T max , T min , and PET averaged over Africa exhibited increasing or drying trends across the continent at rates of 0.18 oC, 0.22 oC, and 3.5 mm per decade, respectively. The 1961-1990 annual precipitation averaged over the whole continent showed that Africa experienced drying at a rate of about –28 mm per decade. When considering the period 1961-2015, the rate of precipitation decrease was about –8 mm per decade. From 1901 to 1915, areas around Lake Victoria in East Africa and along the western coastline south of the equator experienced wetting rates of up to 36 mm per decade. Significant (p 0.01). Because the sensitivity of T min to local influences is higher than that of T max , areas with strong negative correlation were larger in coverage for T max than those of T min . These results call for planned measures to tackle food insecurity in sub-Saharan Africa.

Spatial and temporal variability of sea breezes and synoptic influences over the surface wind field of the Yucatán Peninsula

Abstract: The balance between synoptic and sea breeze atmospheric phenomena can profoundly influence atmospheric circulation in coastal regions. In this paper, a comprehensive study to understand the quasi-permanent patterns of such variability over the surface wind field of the Yucatan Peninsula is described. We performed a Complex Empirical Orthogonal Function (CEOF) analysis on 10 years (May 2007-May 2017) of modeled surface winds from the North American Mesoscale Forecast System (hereafter, NAM). High-pass/low-pass filtering was applied to the time series obtained from the CEOF analysis, to study the high and low-frequency temporal behavior that can be associated with the modes. Results show that for the period from October to March, cold fronts dominate in two different patterns (first two modes), which damp the local winds that show higher amplitude during the nighttime (land breezes) than during the daytime (sea breezes). By the end of this season, the influence of tropical systems, although smaller, is noticeable (third mode). From April to September the peninsula is dominated by sea breezes accentuated at the western shelf (first mode) while land breezes exhibit lesser dominance than sea breezes (third mode). In this period cold fronts and tropical systems (mode 2) exert milder influence over local winds. A distinctive phenomenon seen in the high frequencies of the second mode during this period is the occurrence of peninsula-wide sea breeze. The results of this work have important implications for atmospheric pollutant dispersion, wind wave generation and coastal erosion, among others.

Investigating the performance of SWAT and IHACRES in simulation streamflow under different climatic regions in Iran

Abstract: It is often reported that simpler models, due to their low parameter requirements, perform better than more complex models. To test this, the current study compared a simple rainfall-runoff model (IHACRES) with a complex watershed model (SWAT). Based on these two approaches, six models were developed for three climatically distinct (arid, semi-arid and semi-humid) watersheds in Iran. The coefficient of determination (R 2 ) and the Nash-Sutcliffe model efficiency coefficient (NS) were calculated in each case. In arid, semi-arid, and semi-humid watersheds the SWAT model (R 2 = 0.52, 0.68, 0.66; NS = 0.54, 0.63, 0.64, respectively) outperformed the IHACRES model (R 2 = 0.37, 0.70, 0.57; NS = 0.22, 0.57, 0.56, respectively) for the same respective climate zones. Overall, SWAT performed better than IHACRES, although both models had acceptable performances in the semi-arid and semi-humid watersheds. In the arid watershed, the IHACRES model performed poorly compared to SWAT.

Trends and rainfall tropicalization in Paraná State, south of Brazil

Abstract: In order to detect areas and periods of rainfall reduction and increase in Parana State, south of Brazil, the objective of this manuscript is to analyze, spatially and temporally, rainfall trends from 1976 to 2011. Monthly data were collected on accumulated rainfall (mm) from 63 pluviometric stations distributed throughout the study area. The data were grouped into quarterly (autumn, winter, spring, and summer), seasonal (dry and rainy season), and annual values. All values were evaluated for homogeneity and trends using the Mann-Whitney-Pettitt, Mann-Kendall, and linear regression tests. The results indicate a rainfall transition detected in the period 1991 to 1999, with a maximum change point in 1993. The trends indicate an average increase of 4.03 mm in the rainy season, mainly in the sectors that are predominately subtropical and coastal climates. These results corroborate in a better explanation rainfall patterns and variability in the tropical regions and the Southern Hemisphere, and imply a moderate process of rainfall tropicalization in the subtropical climate of Parana State.

Climatic variation in the high mountains of central Mexico: Temperature and precipitation indices at Nevado de Toluca volcano

Abstract: The Nevado de Toluca weather station (4283 masl, 19 oN) has recorded meteorological data for over half a century, and this combination of elevation and duration provides a rare opportunity to study climate trends in a tropical high-mountain environment. The climatic variability during the period 1965-2015 at the Nevado de Toluca volcano was analyzed. Nine standard climate indices for temperature and seven for precipitation were calculated from daily data from its weather station. The results, with a high level of statistical significance, show an increase in the number of days with night frost and cold periods; likewise, results indicate an increase in the diurnal thermal oscillation. Total accumulated precipitation shows an increasing tendency over time, although the periods with precipitation are increasingly isolated. This suggests that seasonal snow on the summit of the volcano will be increasingly isolated but, at the same time, the snowpack will persist longer. This work is expected to serve as a reference for other high-mountain tropical environmental studies, where air temperature and precipitation are crucial issues.

Crop yield simulations in Mexican agriculture for climate change adaptation

Abstract: Climate change is considered a serious threat to food security worldwide. In this study, yields of maize, beans, wheat, soybean, sorghum, barley and potato were modeled with 28 future climate change scenarios. Our results reduce the information gap that is frequently reported for Mexico and will contribute to better knowledge on spatial impact of climate change. We applied FAO AquaCrop model for 22 case studies located in 14 states of Mexico. Climate change scenarios were: CNRM, GFDL, HADGEM, MPI and Ensemble REA, with two radiative forcing concentrations (4.5 and 8.5 W m –2 ) and three time horizons (2015-2039, 2045-2069, and 2075-2099). The results show decreases in yields of most of the case studies as a consequence of a decrease in the amount and distribution of precipitation. Maize yield in warm dry climates could decrease up to 84% in the most severe scenarios. Beans could decrease from 10 to 40% in the north of the country, while in the northwest a 15% decrease in wheat yield is predicted. Soybeans could benefit, with increases from 15 to 40%. Sorghum and potatoes are expected to decrease for all the case studies, while barley would have increases and decreases. The results suggest differentiated impacts according to crops and regions studied. We concluded that agriculture requires better focused strategies and policies (attention on crop and spatial distribution).

Modeling photosynthetically active radiation: A review

Abstract: Photosynthetically active radiation (PAR) is important in applications related to plant physiology or the carbon cycle However, despite its importance, a global network for its measurement has not yet been established This work consists of the revision of a series of works related to the development of empirical models for the estimation of PAR in places where it is not regularly measured, using for this purpose measurements of meteorological and radiation parameters available in weather stations A list of the models developed, the study site, the results obtained, and the nomenclature used in each of them is made The most common way to develop empirical estimation models is by studying spatio-temporal changes in the relationship between PAR and global solar radiation Other estimation methods include the use of satellite-derived products such as MODIS-derived products and the use of artificial neural networks Despite being more efficient for estimating PAR, the use of artificial neural networks is not as widespread because its use is more complex than the development of empirical models The PAR to global solar radiation ratio reached its maximum in the summer months and the minimum in the winter months; in addition, the daily values per hour reached their maximum at sunrise and sunset, and their minimum around noon

Potential sources and measured concentrations of VOCs in Balikesir ambient atmosphere

Abstract: The assessment of volatile organic compounds (VOCs) has become an important field of interest in atmospheric pollution. This study quantifies and characterizes the ambient levels and spatial distribution of VOCs in urban and rural areas of Balikesir city, Turkey. For these assessments, passive sampling of VOCs performed at approximately 50 locations in and around the city of Balikesir. Twenty-five VOCs were regularly monitored and analyzed with the GC-FID system. The sampling periods were carried out for seven-day periods during March and August 2010. In the study, mean ∑VOC concentrations were found to be as high 67 and 51 µg m –3 for the winter and summer seasons, respectively. Median concentrations of benzene, toluene, ethylbenzene, m,p-xylene and o-xylene were 2.6, 11, 1.30, 1.80 and 0.73 μg m -3 , respectively. Although there were some changes between concentrations of VOC groups between the summer and winter campaigns, differences were not dramatic. Winter-to-summer ratios of the target compounds ranged from 0.2 (1,2,4-trimethylbenzene) to 9 (hexane). Most of the target compounds have higher concentrations in winter. Only few VOCs, including n-propylbenzene, 1,2,4- trimethylbenzene, 1-undecene and 1,2,4- trichlorobenzene have higher concentrations in summer. Spatial distribution of VOCs demonstrated that the roads are hot spots for measured VOC concentrations. The drinking water treatment plant, industrial solvent emissions from pesticide and insecticide applications in agriculture, and emissions from traffic were the sources that contribute to total VOC load in the Balikesir atmosphere.

An exploration of the aerosol indirect effects in East Asia using a regional climate model

Abstract: In this study, the aerosol direct, semi-direct and indirect effects on the East Asia climate are investigated using the International Center for Theoretical Physics Regional Climate Model v. 4 (RegCM4.1.1), by focusing on the East Asian Summer Monsoon temperature and precipitation. The externally mixed aerosols, including sulfate (SO 4 2– ), black carbon and organic carbon, reduced the solar flux reaching the surface directly by scattering solar radiation, and indirectly by increasing the cloud droplet concentration and cloud liquid water path over East China. The combined aerosol effects (direct and indirect) decreased the temperature on the continent and increased it over the oceans, leading to the reduction of rainfall in the central regions of China and an enhancement of rainfall in the adjacent ocean regions.

Performance of the WRF model with different physical parameterizations in the precipitation simulation of the state of Puebla

Abstract: In Mexico, intense rains generated by tropical cyclones, cold fronts, and mesoscale convective systems can cause floods and landslides, causing damage to social, service, economic and financial sectors, among others, leaving the population with fewer resources and in greater vulnerability. Given this scenario, disaster prevention has relevance in the civil protection agenda, which recognizes that it is essential to establish long-range strategies and programs focused on preventing and reducing their effects, beyond only paying attention to emergencies and disasters. The objective of this work is to evaluate the performance of the WRF model for the simulation of accumulated pluvial precipitation in 24 hours in the state of Puebla, considering 768 different combinations of physical parameters, compared to rain records of weather stations for the period from June 1 to August 20, 2017. In addition, as part of the research, optimal configurations are defined to obtain the best performance of the model at local and state levels.

Relationship between precipitation anomalies and multivariate ENSO index through wavelet coherence analysis

Abstract: A better understanding of the local and regional spatio-temporal variability of past precipitation is needed to contextualize climate change research. Monthly precipitation data from 59 stations in the state of Zacatecas, Mexico were transformed into standardized monthly precipitation anomalies for the period 1976-2010 (34 years). Cluster analysis of the new time series was used to identify regions with similar precipitation regimes. Power spectrum analysis was carried out to identify important frequencies. Wavelet coherence analysis was performed to detect significant relations between each of the regional mean standardized anomalies of the monthly precipitation (SAMP) time series and the Multivariate El Nino Southern Oscillation Index (MEI). Three regions were identified: semi-arid, highlands and canyons. In all the three regional SAMP series, the 0.5-, 1-, 2- and 3-year frequencies are present in the power spectrum; the highlands and canyons regions showed important frequencies of 13 and 12 years, respectively. The 3-year frequencies may be linked to El Nino Southern Oscillation phenomenon. Three periods with significant correlation between regional SAMP time series and the MEI were identified: 1993 to 2003 for the semi-arid region, 1995 to 2003 for the highlands region and 1988 to 2003 for the canyons region. The results suggest that precipitation anomalies vary over time and according to regions. The results also strongly indicate that precipitation is modulated by the MEI.

Evaluation of clearness index and cloudiness index using measured global solar radiation data: A case study for a tropical climatic region of Nigeria

Abstract: This study uses a two-year dataset (January 2016-December 2017) on global solar radiation to model the clearness and cloudiness indices at Ile-Ife, Nigeria, a tropical location. Analysis of the daily variations showed that most days at the location are uniform in cloudiness, with scarcely any day either extremely cloudy or extremely clear. On a monthly basis, the clearness index ranged from 0.27 to 0.51, while cloudiness index ranged from 0.44 to 0.72, confirming that the variations of both ratios are influenced by changes in the position of the sun, turbidity and clouds. The seasonal variations of the two parameters were observed to be inverse, so that increases in the clearness index induced by cloudless sky and dry months correspond to decreases in the cloudiness index values and vice versa. The minimum values (0.10 and 0.28) of the clearness index at the location are observed to be higher than the minimum value of 0.05 stipulated for the clearness index in cloudy conditions. Two empirical equations for estimating the maximum clearness index in terms of the average clearness index and the cloudiness index in terms of the clearness index are developed and recommended for other locations with climatological conditions similar to those of the study site. It was furthermore observed from the evaluation of formulated empirical equations that the Hollands and Huget and the Saunier et al. models performed well and improved by about 23.62 and 3.66%, respectively, after calibration, to make the models suitable for their application at other tropical areas.

Relationship between daily atmospheric circulation patterns and South Atlantic Convergence Zone (SACZ) events

Abstract: This study presents the daily atmospheric circulation patterns at surface and altitude related to the South Atlantic Convergence Zone (SACZ) events that occurred between 2007 and 2017. For this analysis, Principal Pattern Sequence Analysis (PPSA) and sea level pressure and geopotential height reanalysis were used. Four typical atmospheric circulation patterns associated with SACZ episodes were identified. Three of them are related to the propagation of a cold front toward southeastern Brazil with a post-frontal anticyclone moving over the Atlantic Ocean. The fourth pattern is associated with the presence of a cut-off low centered over the Central-South region of Brazil that induces moisture transport from the Atlantic Ocean and from the Amazon Basin to most of southeastern Brazil. Considering the first three patterns, they represent, respectively, a frontal wave, a classical cold front and a slow-moving cold front. All of these patterns provides permanent northwesterly winds in the lower troposphere over southeastern Brazil from two days before the SACZ occurrence.

Evapotranspiration flux partitioning at a multi-species shrubland with stable isotopes of soil, plant, and atmosphere water pools

Abstract: Evapotranspiration is the second largest component of the hydrological cycle after rainfall precipitation in semiarid regions such as northwestern Mexico. In this study, we partitioned the evapotranspiration (ET) flux using stable isotopes of water in the soil-plant-atmosphere continuum in combination with eddy covariance flux measurements. We considered three methods for determining the isotopic composition of transpiration ( δ T ): (1) isotopic steady state, (2) non-steady state, and (3) non-steady state weighting the relative importance of dominant species cover and accounting for the relative values of stomatal conductance. Three approaches of T/ET partitioning were estimated during several wet and dry days at the study site in Sonora, Mexico. The total ET flux was variable across years due to differences in precipitation amount between years. ET was lower during the drier-year and reached higher values during the wetter-year. Soil evaporation (E) dominated ET soon after large rain events (40 to 70 mm d –1 [DOY-196 and DOY-197] in 2008) but showed a rapid decrease in dominance as the soil surface dried. Estimated values of T/ET based on an isotopic mass balance were in the same range independent of three methods used. The mean T/ET ratio across all the periods studied was in the range of other studies in semiarid ecosystems and global trends with values of ~0.67 ± 0.02. This work contributes to a better understanding of the surface atmosphere interactions in semi-arid regions.

Building adaptation to extreme rain effects in San Francisco de Campeche, Mexico

Abstract: An integrated coastal zone management approach was used towards building adaptation strategies for the city of San Francisco de Campeche, Mexico. Large interannual variability in precipitation extremes have led to city-wide flooding in numerous occasions, threatening the population and city infrastructure. A special steering committee was appointed to coordinate an integrated coastal management plan within the three levels of government (federal, state and municipal) and to review the legal framework for water management. The municipal administration designed the blueprint for the project and an associated environmental education campaign. A pluvial drainage system was built to separate pluvial from domestic wastewater. Moreover, the wastewater drainage system was strengthened, and the city water treatment plants improved. As a result, water quality in the coastal zone improved and the city of San Francisco de Campeche was able to build its plan for adaptation to extreme rain events, which are increasingly frequent due to climate change.

Seasonal precipitation in South Central Chile: trends in extreme events since 1900

Abstract: We study a regional precipitation time series, built upon seven meteorological records from South Central Chile (SCC; 37° - 42°S), which together cover the period 1900 - 2019. As a first objective, we investigated changes in the return period (RP) of dry ( P80) seasonal extreme events of precipitation (SEE), for each season. We observed a reduction in the RP of wet SEE during 1900 - 1950 in all seasons. Contrarily, the dry SEE RP shows a reduction from 1950 to the present in all seasons. This phenomenon is noteworthy since 1900 for summer and winter, and since 1930 for autumn. Spring registers a constant RP value from 1990 onwards. As a second objective, we study possible relationships between seasonal precipitation variability and climate modes, such as the Southern Annular Mode (SAM) and the Tripolar Index (TPI) of sea surface temperature (SST) over the Pacific Ocean. Summer and autumn precipitation register a significant negative correlation with SAM activity at interannual and decadal scales, while winter and spring precipitation show a significant positive correlation with SST variability over multiple regions of the Pacific Ocean (including the tropics and New Zealand) and the Southern Ocean (Amundsen-Bellingshausen Sea). Finally, we confirm that SAM strongly modulates precipitation in SCC, especially in autumn, and that SEE variability in SCC is considerably characterized by climate modes of tropical and extra-tropical origin.

Is the energy balance in a tropical lowland rice paddy perfectly closed

Abstract: A two-year (2015 and 2016) field experiment was carried out to study the surface energy budget and energy balance closure (EBC) in a tropical lowland rice paddy in Cuttack, India. Maintenance of a standing water layer in lowland irrigated rice ecosystem makes it unique and this strongly influences the surface energy balance which may alter the surface runoff, ground water storage, water cycle, surface energy budget, and possibly microclimate of the region. To study this, an experiment was conducted using eddy covariance system to measure the surface energy balance components during two cropping seasons (dry season, DS and wet season, WS) and two consecutive fallow periods (dry fallow, DF and wet fallow, WF). The rice was grown in puddled wet lands in DS and WS and the ground was left fallow (DF and WF) during the rest of the year. Results displayed that daily average latent heat flux at surface (LE) and at canopy height (LEc) dominated over sensible heat flux at surface (H) and canopy height (Hc), respectively due to the presence of water source coming from the standing water in the rice field. The EBC was evaluated by ordinary least square (OLS), energy balance ratio (EBR) and residual heat flux (RHF). In OLS, the slope ranged 0.38-0.89 (2015) and 0.28-0.99 (2016) during the study period. Average RHF was 10.3-12.0% higher in WS as compared to DS. It was concluded that the EBC estimated using RHF is the most suitable way to calculate closure for lowland rice paddy since it can distinguish different seasons distinctively, followed by OLS. Much variation was not observed in EBR after inclusion of storage terms (water, soil, photosynthesis, canopy) to the classical EBR.

Analysis and selection of optimal sites for wind farms: case study, region north of Mexico

Abstract: The analytic hierarchy analysis process allowed establishing a hierarchical model of a target function under a set of criteria aimed at choosing the best sites for the installation of wind farms in the north of Mexico. In this study, a large number of known and estimated criteria of diverse types (technical, economic, environmental, and social) were used, based on preliminary studies and information that allowed for the identification of the most relevant variables. The process simplifies a complex problem into simpler ones that can be analyzed independently, facilitating the efforts of decision takers since it allows envisaging the feasible alternatives. Once the most weighty and relevant variables were obtained, each variable was transformed into feasibility maps, and through the technique of map algebra coupled to a geographic information system, the sites were assessed in feasibility percentages in a general map fulfilling the set of imposed variables. The best scenarios for the location of a wind farm corresponded to the southern part of the state of Coahuila. The multicriteria analyses focused on decision-making within the planning process and characterization of feasible sites for a wind farm, are tools that optimize the selection of different variables, favoring the most relevant for the project by considering decision elements that are difficult to assess or quantify.

Statistical analysis of building-induced turbulence at an airport

Abstract: Building-induced turbulence may affect aviation safety, e.g. when the aircraft is about to land at an airport. Observations of such flow have been conducted at the Hong Kong International Airport using short-range LIDAR (SRL). Statistical analysis of the radial velocity, namely, the longitudinal structure function, is described herein. It is found that the classical Kolmogorov theory for homogeneous turbulence applies to LIDAR observations of building-disrupted airflow. Some distinctive features of the turbulent flow are also discussed, notably velocity streaks and tiny anticyclones at the hectometer scale. The potential impact on a landing aircraft is examined and compared to flight data. The results in this paper could be useful for studying building-induced turbulence at other airports around the world.

A rare winter thunderstorm event near Hong Kong

Abstract: A rare winter thunderstorm event near Hong Kong is documented in this paper. The thunderstorm occurrence was confirmed by the observation of one of the authors and lightning location information systems (both regional and global). It developed over the frontal cloud band associated with the winter monsoon. Observing the upper air measurements, however, the thermodynamic conditions did not seem favorable to the occurrence of the thunderstorm. The convective available potential energy could not be determined in the cool and dry lower troposphere. There was only a moister layer in the middle troposphere. The weather forecaster did not anticipate the occurrence of thunder and lightning. However, some features could have changed dynamically, which suggested the possibility that a thunderstorm would take place. For instance, waves could be identified in the middle troposphere and a broad troughing flow could be analyzed in the lower troposphere. The integrated wave vapor was also of a rather high level. It is hoped that this paper can serve as a useful reference for forecasters in assessing the possibility of thunderstorms occurring during winter over subtropical latitudes in association with frontal cloud bands.

The UNAM-Droplet Freezing Assay: An Evaluation of the Ice Nucleating Capacity of the Sea-Surface Microlayer and Surface Mixed Layer in Tropical and Subpolar Waters (edited by Dr. Michel Grutter)

Abstract: Ice nucleating particles (INPs) in the atmosphere are necessary to generate ice crystals in mixed-phase clouds, a crucial component for precipitation development. The sources and composition of INPs are varied: from mineral dust derived from continental erosion to bioaerosols resulting bubble bursting at the ocean surface. The performance of a home-built droplet freezing assay (DFA) device for quantificatying of the ice nucleating abilities of water samples via immersion freezing has been validated against both published results and analyses of samples from sea surface microlayer (SML) and bulk surface water (BSW) from the Gulf of Mexico (GoM) and Saanich Inlet, off Vancouver Island (VI), Canada. Even in the absence of phytoplankton blooms, all the samples contained ice nucleating particles at moderate concentrations, ranging from 6.0x101 to 1.1x105 L-1 water. The freezing temperatures (i.e., T50, the temperature at which 50% of the droplets freeze) of the samples decreased in order of VI SML > GoM BSW > GoM SML, indicating that the higher-latitude coastal waters have a greater potential to initiate cloud formation and precipitation.

Changes in the flooding area due to storm surge under climate change in an extensive wetland area in the southern Gulf of Mexico

Abstract: RESUMEN Se estudian, mediante el analisis de observaciones y simulaciones numericas, las inundaciones causadas por frentes frios intensos y como estas podrian cambiar en diferentes escenarios de aumento del nivel del mar en la Laguna de Terminos, Mexico. El modelo numerico de circulacion oceanica utilizado es el Finite-Volume Community Ocean Model (el forzamiento meteorologico proviene de simulaciones de alta resolucion con el modelo Weather Research and Forecasting (WRF). Las simulaciones oceanicas se llevaron a cabo utilizando mallas no estructuradas y configuraciones con la posibilidad de inundacion y secado en las celdas. Los resultados de las simulaciones numericas se compararon con observaciones. Teniendo en cuenta el nivel del mar actual, un evento intenso de Norte inunda un area de 940 km 2 , que actualmente esta cubierta por manglares. Esto indica que los Nortes son importantes en la irrigacion de extensas areas de manglar. Para los escenarios de aumento del nivel del mar de 0.25, 0.50 y 0.75 m, las areas inundadas se incrementan en 297, 1062 y 2152 km 2 , respectivamente, lo cual implica un aumento considerable en las areas inundadas en Isla del Carmen. Se sugiere considerar estos resultados en la planificacion a largo plazo. ABSTRACT Floods caused by intense cold fronts and how they could change under different scenarios of sea level rise in the Terminos Lagoon, Mexico, are studied through the analysis of observations and numerical simulations. The numerical ocean model used is the Finite-Volume Community Ocean Model (FVCOM) of the Marine Ecosystem Dynamics Modeling Laboratory of the University of Massachusetts-Dartmouth, and the meteorological forcing comes from high-resolution simulations with the Weather Research and Forecasting model (WRF). The ocean simulations were carried out using unstructured meshes with the possibility of flooding and drying in their cells. Results of the numerical simulations were compared against observations. Considering the current mean sea level, an intense northern cold front event (or Norte) floods an area of 940 km 2 that is currently covered by mangroves. This indicates that Nortes are important in the irrigation of extensive mangrove areas. Under scenarios of sea level rise of 0.25, 0.50 and 0.75 m the flooded areas increase by 297, 1062 and 2152 km 2 , representing a considerable increase in the areas flooded at Isla del Carmen. It is suggested to consider this situation in long-term planning.

Study of the dispersion of AGI emitted from ground-based generators using the WRF-Chem model

Abstract: In studies of cloud seeding by ground-based generators, a dispersion analysis of the silver iodide (AgI) glaciogenic aerosol is a necessary tool to estimate if it reaches seeding heights. A study of the dispersion of AgI emitted by a network of generators with hypothetical locations in the eastern region of Cuba was developed using the WRF-Chem model. Two spatial distributions with different heights and distances between generators were analyzed. Two experiments were undertaken with emission rates of 10 and 30 g h –1 , based on a sample of six days. The activation level was not reached for an emission rate of 10 g h –1 , while for 30 g h –1 static seeding could occur but the area with seeding aerosol was not significant. The distribution in which generators were closer together turned out to be the one with smaller maximum concentrations and bigger areas occupied by the aerosol at a given level. Covered area and seeding aerosol concentrations increased for emission rates of 30 g h –1 . In general, the plume follows the wind direction and its vertical rise is determined by the turbulent kinetic energy for the area where the generator is placed.

Analysis of meteorological droughts in the Sonora River Basin, Mexico

Abstract: Droughts are a complex natural risk that have numerous negative effects on ecosystems, agriculture and the economy. For this reason, it is difficult to determine a precise definition. Nevertheless, different conceptualizations converge in one common denominator: the deficiency of precipitation with respect to an average historical value. Droughts in Mexico have been recurrent and persistent, resulting from complex interactions of the atmosphere with the oceans and the geographic and physiographic characteristics of the country. Several researchers have approached this phenomenon with indexes to characterize it using parameters such as intensity, duration and frequency. In this study we analyze meteorological drought temporally and regionally at scales of 3, 6, 12 and 24 months with SPI and SPEI indexes at 19 weather stations located in the middle and high parts of the Sonora River basin, Mexico, for the period 1974-2013. The regions were defined according to the patterns of mean annual rainfall behavior, applying statistical techniques and analyzing the physiographic characteristics of the study region. The general results indicate that drought intensity increased at the end of the time series analyzed, and important periods were identified in the years 1997, 1999, 2000 and 2011 to 2013. SPEI defined the drought periods and the increasing intensity trend better than SPI, demonstrating the importance of including variables such as evapotranspiration in the balance of available water.

Trend estimation and forecasting of atmospheric pollutants in the Mexico City Metropolitan Area through a non-parametric perspective

Abstract: Trends and forecasts of the main atmospheric pollutants (O 3 , SO 2 , NO 2 , CO, PM 10 , PM 2.5 , NO and NO x ) are estimated by regions in the Mexico City Metropolitan Area (MCMA) with maximum daily data from 2008 to 2018. A non-parametric statistical smoothing controlled technique based on the Hodrick and Prescott filter and estimated through the Kalman filter, is used. Both point and interval estimates, as well as their respective forecasts are generated. Estimates are compared against the environmental standard for Mexico City (NADF-009-AIRE-2017), and it is evident that, in general, they are still distant from good air quality in the MCMA, as opposed to CO and NO 2 . The remaining pollutants have trends and forecasts that are far from the permissible limits.

The anomalous wet 2020 southeast Brazil austral summer: characterization and possible mechanisms

Abstract: This paper analyzed the anomalous rainy austral summer 2020 over the Southeastern Region of Brazil (SEB), investigating the possible mechanisms. The SEB has been experiencing dry summers in the years before 2020. However, the austral summer 2020 in this region was the wettest summer since 1991. A wavetrain started from the Indian Ocean to the Pacific Ocean, plus a wavetrain from tropical north (U-shape), and another from western equatorial Pacific (PSA-like) contributed for an anomalous anticyclonic circulation at high levels southward South America. This merged wavetrain continued its path with an anomalous cyclonic circulation over the Southern region of Brazil and Sao Paulo State 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 for the main differences between austral summer 2019 (dry) from summer 2020 have shown there is no anomalous divergence at high levels over the Indian Ocean in 2019, triggering a wavetrain from this region to Pacific. The two wavetrains from Pacific merged in an anomalous anticyclonic circulation, over the southeastern Pacific, near South America 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 wavetrains generated an anticyclonic anomalous circulation over the Southern Region of Brazil and cyclonic northward, in opposition configuration of 2020.