Atmósfera (Journal)
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CO2 variability in the Mexico City region from in situ measurements at an urban and a background site
Get PDFUrban areas are important contributors to the increase of global CO2 levels due to human activities, but continuous records of CO2 concentration in cities are scarce, especially in the developing world. In this study we present five years of simultaneous, in-situ measurements at a university campus in the south of Mexico City (UNAM) and at a high-altitude station, the Altzomoni atmospheric observatory (ALTZ), 60 km apart from the first site. The characteristics of the daily cycles, seasonality, and long-term trends were extracted from both time series. The features of the daily and seasonal cycles at UNAM are dominated by the dynamics of the boundary layer growth, while the seasonality at Altzomoni is determined by both the local meteorology and the photosynthetic activity of the vegetation. Annual CO2 growth rates of 2.4 and 2.6 ppm yr–1 were estimated for UNAM and Altzomoni, respectively, in close agreement with reported global growth rates and with previous estimates of total column CO2 trends. The simultaneous monitoring at the urban and the mountain sites revealed a regular exchange of air masses between the city and its vicinities. The annual cycle at UNAM shows a secondary CO2 maximum at the end of the dry season, the source of which is yet to be determined, but likely due to incoming air parcels enriched with emissions from agricultural burnings. Likewise, the daily CO2 cycle at ALTZ during the dry season shows evidence of a daily afternoon arrival of polluted air masses from the neighboring urban areas. This study lays the foundation of an upcoming expansion in the CO2 measurement sites and capabilities in the metropolitan area of Mexico City
Friction velocity estimation using a 2D sonic anemometer in coastal zones
Get PDFFriction velocity (u*) is an important velocity scale used in the study of engineering and geophysical flows. The widespread use of 2D sonic anemometers in modern meteorological stations makes the estimation of u* from just the horizontal components of the velocity a very attractive possibility. The presence of different wind regimes (such as sea breezes in or near coastal zones) causes the turbulent parameters to be dependent on the wind direction. Additionally, u* depends on atmospheric stability, whch makes the estimation of u* from 2D measurements very difficult. A simple expression is proposed, and then tested with data from six independent experiments located in coastal zones. The results show that it is possible to estimate friction velocity from 2D measurements using the turbulence intensity as a proxy for u*, reducing substantially the sensitivity to the wind direction or atmospheric stability, with small root mean squared errors (0.06 < RMSE < 0.097) and high correlation coefficients (0.77 < r2 < 0.95)
Evaluation of the WRF-ARW model during an extreme rainfall event: Subtropical storm Guará
Get PDFThis study simulates an unusual extreme rainfall event that occurred in Salvador city, Bahia, Brazil, on December 9, 2017, which was named subtropical storm Guará and had precipitation of approximately 24 mm within less than 1 h. Numerical simulations were conducted using the Weather Research and Forecasting (WRF) model over three domains with horizontal resolutions of 9, 3, and 1 km. Different combinations of seven microphysics, three cumulus, and three planetary boundary layer schemes were evaluated based on their ability to simulate the hourly precipitation during this rainfall event. Statistical indices (MB = –0.69; RMSE = 4.11; MAGE = 1.74; r = 0.55; IOA = 0.66; FAC2 = 0.58) and time series plots showed that the most suitable configurations for this weather event were the Mellor-Yamada-Janjić, Grell-Freitas, and Lin formulations for the planetary boundary layer, cumulus, and microphysics schemes, respectively. The results were compared with the data measured at meteorological stations located in Salvador city. The WRF model simulated well the arrival and occurrence of this extreme weather event in a tropical and coastal region, considering that the region already has intense convective characteristics and is constantly influenced by sea breezes, which could interfere in the model results and compromise the performance of the simulations
Characterization of particulate matter in the iron ore mining region of Itabira, Minas Gerais, Brazil
Get PDFItabira has in its territory the largest complex of opencast mining in the world, located close to residential areas of the city. The air quality monitoring network installed in the city is the main source of particulate matter (PM) emission data. However, these air quality stations only cover the areas near the mines and do not measure fine particulate matter (PM2.5). Thus, a first field campaign was carried out to characterize PM in the city and to compare high volume data from air quality stations with the dichotomous air sampler data. Results of trajectories’ cluster analysis showed a long-range transport of aerosols during the sampling days from northeast (84% of the trajectories), east-southeast (12%), and south-southwest (3%) directions. Regarding the meteorological conditions during the sampling days, negative correlations were seen between coarse particulate matter (PM10) from mostly air quality stations and all meteorological parameters (but temperature). Results of the X-ray fluorescence and principal component analyses showed that the main trace elements in the coarse (PM2.5-10) and fine modes (PM2.5) are iron and sulfur, associated with emissions from mining activities, air mass transport from regional iron and steelmaking industry activities, vehicle emissions, local and regional biomass burning, and natural biogenic emissions. This work is the first assessment of source apportionment done in the city. Comparisons with other studies, for some large metropolitan areas, showed that Itabira has comparable contributions of sulfur, iron and elements such as copper, selenium, chromium, nickel, vanadium and lead
Application of network theory to study the spatio-temporal evolution in the ozone weekend effect in urban areas
Get PDFThe occurrence of higher ground-level O3 concentrations on weekends rather than on weekdays, despite reduced anthropogenic activity in urban areas, is known as the O3 weekend effect (OWE). We present here an approach to analyse OWE spatio-temporal variations in urban areas, integrated by the trend, prediction and network representation. We used data from ten monitoring sites geographically distributed within the Mexico City Metropolitan Area (MCMA) recorded during 1994-2018. The OWE occurrence within the MCMA ranged typically between 40 and 60 % of the total weeks per year. The annual differences between weekday and weekend O3 peaks (magnitudes) showed were most significant on Sundays. Naive, Linear and Auto-regressive Integrated Moving Average models were tested for predicting the OWE annual occurrences and magnitudes. There was no single model that outperformed significantly for predicting OWE at all sites. The proposed concept of generalised OWE (GOWE) implies that at least half of the sites under study exhibited simultaneous OWE occurrence. GOWE is represented as a network and its integration with prediction models is useful to determine the OWE spread over the MCMA in the following years. The GOWE occurrence showed an increasing trend interpreted as the spread of VOC-limited conditions over most of the MCMA. Predicted data suggest that, with the current emission control policies, the GOWE will continue occurring. The integrated methodology presented provides valuable insight into the design of potential air quality control strategies
Domestic electricity consumption in Mexican metropolitan areas under climate change scenarios
Get PDFThe following estimates analyse human bioclimatic conditions due to climate change in three time horizons, as suggested by Article 2 of the Paris Agreement. Each scenario corresponds to an increase in the global average temperature (∆T) of 1 ºC, 1.5 ºC and 2 ºC, respectively. The measurements of residential electricity consumption for air conditioning were made in 30 metropolitan areas of Mexico with at least half a million inhabitants in 2010. Bioclimatic conditions also included estimates of the effects of urban heat islands (UHI). Use of heating will decrease and, in some cases, disappear, while the need for cooling will increase. Electricity consumption due to cooling is expected to increase in Mexicali, Reynosa-Río Bravo (on the border with the United States), Cancún, Villahermosa, and Veracruz (on the shores of the Caribbean Sea and the Gulf of Mexico). Urban areas like Toluca, Pachuca, Xalapa, San Luis Potosí, and Puebla-Tlaxcala used little or no energy for cooling in the second decade of the 21st century but will need to do so halfway through the centur
Stratospheric temperature features over Saudi Arabia and their relationship to Atlantic SSTs and surface temperatures in winter
Get PDFStratospheric temperature is an important climatic factor regionally and globally. This paper investigates temperature trends in the lower stratosphere at 50 hPa (T50), the mid-stratosphere at 30 hPa (T30), and the upper stratosphere at 10 hPa (T10), as well as their impacts on Atlantic Ocean sea surface temperature (SST) and Saudi Arabian surface air temperature (SAT) during the entire winter seasons of 1979-2019. The results show significant cooling for the T50 linear trend, progressive cooling for the T30 linear trend, and cooling for the T10 linear trend during the study period over Saudi Arabia. The results also indicate a significant nonlinear cooling trend for stratospheric temperature at T50 and T30, while a weak cooling at T10 is observed. Abrupt climatic changes towards warmth exist at all three levels of stratospheric temperature, which occur in 1992 for T50 and T30 and in 1983 for T10. These abrupt climate changes may be related to volcanic eruptions. Our results also indicate that a strong negative relationship exists between T50 and the SST of the tropical South Atlantic (TSA) and the Atlantic Multi-Decadal Oscillation (AMO), while T30 indicates a statistically negative relationship with the AMO. The lead-lag cross-correlation suggests that the SST of the Atlantic Ocean (tropical North Atlantic [TNA], TSA, and AMO) are linked to stratospheric temperatures at three lead winters. As a result of the teleconnection between SAT and stratospheric temperature over Saudi Arabia, the coupling of these two features occurs in winter, especially in the lower to mid-stratosphere layers
Summer dry events on synoptic and intraseasonal timescales in the Southeast Region of Brazil
Get PDFThe occurrence of dry events in the Southeast Region of Brazil (SEB) during summer (rainfall season) has been in evidence in the last years, mainly due to previous extreme events in the 2013/14 and 2014/15 seasons. Drought analyses are usually carried out with monthly data. Here our methodology addresses the issue with daily data to generate a thorough analysis. Dry events were evaluated in different homogeneous precipitation sub-regions within the SEB, over 37 December-February (DJF) seasons and with two different timescales of duration: synoptic (5-9 days) and intraseasonal (≥10 days). Two main distinct dynamic patterns were found for dry events in southern and central-northern parts of SEB, respectively, but no significant differences were identified in the different timescales of occurrence. Southern events were characterized by a stationary ridge acting over the whole of southern South America, making the approximation of the transient system to southern SEB difficult. At the same time, this pattern showed a northern-shifted South Atlantic Convergence Zone (SACZ) configuration. In the central-northern events, a high pressure centered between Brazil’s South and Southeast regions was associated with the dryness conditions. An anomalous southward shift of meteorological systems characteristic of the South American summer was also verified for these events. Over the South Atlantic, an opposite SST anomaly configuration was identified between southern and central-northern events
Statistical analysis of the relationship between Quasi-Biennial Oscillation and Southern Annular Mode
Get PDFThe Southern Annular Mode (SAM) is an extratropical pattern that influences the climate of all Southern Hemisphere. However, the variability of this mode is an active area of research. The influence of lower frequency modes on SAM is a path to better knowledge about this pattern. The relationship between Quasi-Biennial Oscillation (QBO) and SAM’s counterpart in the Northern Hemisphere (Northern Annular Mode) has been addressed by previous work. Still, few studies focus on the association between QBO and SAM. The goal of this work was to evaluate the possible QBO-SAM relationship through statistical analyses. This association was investigated by comparing QBO and SAM indices, the latter on different levels of the troposphere and stratosphere, for the 1981-2010 period. The wavelet analysis showed that the SAM indices for troposphere and stratosphere presented variability in many scales, including a two-year band. Cross-wavelets techniques between QBO and SAM ratified that this relation has a complex interaction. There was a significant common high power around the two-year band, with lags varying over the analyzed period, including no lag. Further analysis without lag confirmed previous studies, indicating that the negative (positive) SAM phase is more frequent for easterly (westerly) QBO. However, this was not valid for all months. Some additional analysis suggested that the upward wave propagation to the stratosphere for each QBO phase changes the stratospheric jet and, consequently, the SAM phase
The Role of Sustainable Technological Innovations in the Relationship between Freight Pricing and Environmental Degradation: Evidence from a Panel of 39 R&D economies
Get PDFThis study is in line with the United Nations Framework Convention on Climate Change (UNFCCC) to evaluate the post-Paris Agreement (COP21) through technological innovations and carbon pricing in a panel of 39 R&D economies from 1995 to 2018. The results show that sustainable technological innovations and smart applications of insurance and financial services help decrease GHG emissions in the lowest to highest quantile distribution. In contrast, air transportation freight, air freight pricing, and foreign direct investment (FDI) inflows escalate GHG emissions due to unsustainable logistics activities, inefficient freight pricing, and dirty production, which confirmed the ‘pollution haven’ hypothesis across countries. The impact of air freight revenues has a differential impact on GHG emissions in the different quantiles’ distribution, as in the lowest quantiles (i.e., τ0.2 to τ0.4), air freight revenues increase GHG, whereas, at the highest quantiles’ distribution (i.e., τ0.9) emissions decrease. Thus, the viability of air freight revenues is further assessed using Panel Granger causality and panel innovation matrix. The results show the bidirectional causality between i) air freight pricing and GHG emissions, ii) air transportation freight (and freight pricing, freight revenues, FDI) and technology innovations, iii) FDI and air freight revenues, while there is a unidirectional causality running from i) insurance and financial services to GHG emissions, ii) GHG emissions to technological innovations and FDI inflows, and iii) air transportation freight to FDI inflows