Atmósfera (Journal)
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Changes to tropical eastern North Pacific intraseasonal variability under global warming, implications for tropical cyclogenesis
Get PDFChanges to the tropical eastern North Pacific Intraseasonal Oscillation (ISO) at the end of the 21st century and implications for tropical cyclone (TC) genesis are examined in the Shared Socioeconomic Pathways (SSP585) scenario of the Coupled Model Intercomparison Project phase 6 (CMIP6) data set. Multimodel mean composite low-level wind and precipitation anomalies associated with the leading intraseasonal mode indicate that precipitation amplitude increases while wind amplitude weakens under global warming, consistent with previous studies for the Indo-Pacific warm pool. The eastern North Pacific intraseasonal precipitation/wind pattern also tends to shift southwestward in a warmer climate, associated with weaker positive precipitation anomalies near the coast of Mexico and Central America during the enhanced convection/westerly wind phase. Implications for the modulation of TC genesis by the leading intraseasonal mode are then explored using an empirical genesis potential index (GPI). In the historical simulation, GPI shows positive anomalies in the eastern North Pacific in the convectively enhanced phase of the ISO. The ISO’s modulation of GPI weakens near the coast of Mexico and Central America with warming, associated with a southward shift of GPI anomalies. Further examination of the contribution from individual environmental variables that enter the GPI shows that relative humidity and vorticity changes during ISO events weaken positive GPI anomalies near the Mexican coast with warming and make genesis more favorable to the southwest. The impact of vertical shear anomaly changes is also to favor genesis away from the coast. These results suggest a weaker modulation of TCs near the Mexican Coast by the ISO in a warmer climate
Partial COVID-19 lockdown effect in atmospheric pollutants and indirect impact in UV radiation in Rio Grande do Sul, Brazil
Get PDFThe COVID-19 pandemic introduced a significant decrease in industrial activities and other anthropogenic interventions on the environment, followed by a reduction of the emission of pollutant gases and aerosols. Monitoring of air quality is commonly performed through automatic stations, which can provide nearly real-time, accurate information. However, stations located in urban areas are subject to maintenance problems and extensive coverage for large areas is not feasible. As an alternative approach, data from orbital sensors can provide useful information for large areas at a low cost. Consequently, this study aimed to analyze the partial COVID-19 lockdown effect in atmospheric pollutants and its indirect impact in UV radiation in Rio Grande do Sul, Brazil. Data on concentrations of nitrogen dioxide (NO2), total ozone (O3), and ultraviolet index (UVI) acquired by the OMI sensor aboard the Aura satellite were accessed for May, for the entire period 2010 to 2018, 2019, and 2020. Differences between these time series were calculated. Results showed significant reductions in NO2 in most of the study area by as much as 33.9%, followed by increases in total ozone of up to 3.5% and the UVI by up to 4.8%. Although NO2 plays a fundamental role in stratospheric chemistry, our results suggest that its decrease in 2020 was not directly responsible for the increase in total O3; however, NO2 was partially the cause for the increase in UVI, which in turn led to the heating of the stratosphere, generating an increase in O3
Surface shortwave cloud radiative effect of cumulus and stratocumulus-cumulus cloud types in the Caribbean area (Camagüey Cuba, 2010-2016)
Get PDFThe effects of cumulus (Cu) clouds and the combination of stratocumulus-cumulus (Sc-Cu) clouds on solar radiation at the Earth’s surface were evaluated at Camagüey, Cuba, during a 6-yr period (from June 2010 to May 2016). Two methods to calculate the cloud radiative effect (CRE) were employed. The first method (CREm) uses solar irradiances in cloudy conditions from actinometric observations, where cloud information was also reported by visual observation. In the second method (CRE0) surface solar irradiances were estimated for both cloudy and clear sky conditions using a 1-D radiative transfer model, and cloud optical depth (COD) retrieved from an AERONET sun-photometer as the main input. A temporal correspondence criterion between COD retrievals and actinometric observations was performed in order to classify the COD of each cloud type. After the application of this criterion, the COD belonging to the optically thin clouds was removed. Finally, 255 and 732 COD observations for Cu and Sc-Cu, respectively, were found. Results show a statistically significant difference at the 95% confidence level between CRE calculated for Sc-Cu and Cu, using both methods. Mean values of CREm and CRE0 for Cu (Sc-Cu) were −442 (−390) and −460 (−417) Wm–2, respectively. CRE0 shows a linear relation with ln(COD), with stronger correlation at a lower solar zenith angle. The shortwave cloud effect efficiency (CEE) for the two cloud types sharply decreases with the increase of the COD value up to 20. For larger COD, the CEE is less sensitive to the increase of COD
Analysis of an extreme precipitation event in the Atacama desert in January 2020 and its relationship to humidity advection along the Southeast Pacific
Get PDFAn extreme precipitation event took place during the second half of January 2020 in the Atacama Desert. From Tacna, Peru to Iquique, Chile (18-21ºS) rainfall extended for several days producing floods, major damage to infrastructure, and affecting population in one of the driest deserts of the world. Analysis of surface-weather stations and reanalysis suggests that the most intense precipitation occurred in the Precordillera (2000 to 3600 m.a.s.l) on the western foothills of the Andes. The analysis based on surface observations, upper-air sounding, reanalysis and satellite data, suggests that at least four major factors were present to produce record-breaking precipitation: (i) a low-level circulation off-shore the Atacama Desert, potentially generated by the southward displacement of the Bolivian High and a trough located to the west over subtropical southeast Pacific, (ii) humidity advection via an atmospheric river-like structure, trapped along the coast ahead of the low-level cyclonic circulation, leading to increases in precipitable water vapor over the Atacama Desert, (iii) above-normal sea surface temperatures favoring moist conditions in the boundary layer and (iv) a strengthened local circulation, with low-level eastward moisture advection leading to forced orographic ascent along the Precordillera. These factors triggered thunderstorm development and precipitation mostly in the Precordillera, but also in the Lowlands, Pampas and Altiplano regions. Analysis of days with extreme precipitation in previous austral summers over the period (2008-2020) suggests that this combined thermodynamic-dynamic mechanism is present in the majority of such events in Southern Peru and Northern Chile, providing valuable guidance to predict future extreme precipitation events in the Atacama Desert
Evaluating the Global Forecast System (GFS) for energy management over Minas Gerais State (Brazil) against in-situ observations
Get PDFSeveral regions of Brazil have experienced periods of intense drought in the last decades. Hydropower plants produce most of the country’s energy and a reduction in reservoir flow can compromise the energy sector. Therefore, the Brazilian government has sought the diversification of energy production with other renewable sources. The introduction of new renewable sources, such as wind and solar, requires detailed studies of the local weather conditions usually through historical data analysis. However, several areas in Brazil lack weather stations. In this context, this study aims to assess the ability of the Global Forecast System (GFS) reanalysis product to represent wind, in the state of Minas Gerais (MG) which has 79.5% of energy production associated with water resources. Although the study considers a specific region, it presents a methodology that can be replicated in regions where data is not available. Over most areas, 10 m wind speed values of the GFS reanalysis were similar to those registered by weather stations. Results at 10 and 100 m of altitude show high wind speed values in the north of the state, a region where the highest power densities are also recorded (approximately 150 W m–2 during winter and spring). In conclusion, the GFS reanalysis product, albeit with the biases reported here, can be used in regions with scarce meteorological data to estimate the potential for wind energy production as a complementary source of hydroelectricity
Classification of the flood severity of the Guadalquivir River in the Southwest of the Iberian Peninsula during the 13th to 19th centuries
Get PDFThis study estimates the flood severity between the 13th and 19th centuries on the southwestern Iberian Peninsula based on the historic records of impacts of the Guadalquivir River flooding on the city of Seville (Spain). The main documentary source was Historia crítica de las riadas o grandes avenidas del Guadalquivir en Sevilla (Critical history of the floods of the Guadalquivir in Seville) (1878), which compiles news from different observers that were contemporaries of each flood. Regarding the methodology, it was necessary to transfer the information from different documentary sources to ordinal indices, which required developing allocation criteria per flood impact. From the annual severity index assigned to the different floods, an interannual series was generated. Through interannual weighing of the flooding indices, it was possible to deduce the durations and intensities of sequences of flood periods between 1250 and 1850. Of the 10 floods classified as most destructive during the five centuries analyzed (i.e., from 1280 to 1880), five occurred during little more than a century (1598-1701). The obtained results contribute to knowledge on regional rainfall, as well as to historical climatology and hydrology, over multiple centuries
Economic disparities in pollution-related mortality in three municipalities of the Metropolitan Area of the Valley of Mexico
Get PDFThis study explored the nature of health risks in the population of three municipalities within the Metropolitan Area of the Valley of Mexico (MAVM) by means of an empirical analysis of health effects associated with air pollution and temperature variation. Based on the environmental justice theory, we asked whether, in unequal socioeconomic municipalities of the MAVM, the association between PM10 concentrations and mortality depends on socioeconomic disparities. We differ from previous studies that have established a relationship between PM10 and mortality based on a state-space model instead of the Poisson regression model. The state-space model allows estimating the size of the unobserved at-risk population, its hazard rate, the life expectancy of individuals in that population, and the effect of changes in environmental conditions on that life expectancy. Our results show a lower hazard rate in a wealthy municipality, as compared to a higher hazard rate in a poor one. The lower hazard rate of the wealthy municipality extends life expectancy and enhances the likelihood of inhabitants staying long-lasting within the population at risk, thus increasing the size of that population, as compared to the population at risk in the poor municipality, whose members show a lower life expectancy. Thus, the smaller the at-risk population, the sicker its average member and the smaller the impact on long-term mortality. Our study examines how regional health disparities could provide information for public health policy initiatives which might improve living conditions among different communities
Application of a ground-based microwave radiometer in aviation weather forecasting in Indian Air Force
Get PDFTime and intensity-specific very short-term forecasting or nowcasting is the biggest challenge faced by an aviation meteorologist. Ground-based microwave radiometer (MWR) has been used for nowcasting convective activity and it was established that there is a good comparison between thermodynamic parameters derived from MWR and GPS radiosonde observations, indicating that MWR observations can be used to develop techniques for nowcasting severe convective activity. In this study, efforts have been made to bring out the efficacy of MWR in nowcasting thunderstorms and fog. Firstly, the observations of MWR located at Palam, New Delhi, India have been compared with the nearest radiosonde data to ascertain the variation in respective profiles. Large differences were found in relative humidity (RH), whereas temperatures from MWR were found to be close to radiosonde observed temperature up to 3.5 km. Subsequently, the scatter plots and correlation coefficients of thermodynamic indices/parameters indicated that most of the parameters are either not correlated or have moderate correlation only for 12:00 UTC profiles. The superepoch technique of lagged composite for various thermodynamic indices/parameters to obtain a combined picture of all the thunderstorm and dense fog cases on the time series could not determine any pattern to predict thunderstorm and dense fog with lead time of 2-4 hours. MWR profile for a case of occurrence of thunderstorm was analyzed. No significant variation was observed in most of the indices (as calculated from MWR observed parameters) prior to the occurrence of thunderstorm. RH at freezing level and between 950 and 700 hPa levels were the only parameters, which increased four hours prior to the occurrence
A momentum-balance theory for the updraft structure in density currents analogous to squall lines
Get PDFA momentum-balance theory for the orientation of updrafts in density currents is developed for understanding squall-line–shear interactions. The motivation arises from studies showing the diagnostic limitations of the vorticity-balance theory by Rotunno et al. (1988) (RKW theory) under varying shear profiles, together with the flow-force balance constraint (FFB) which determines the shear-layer depth in optimal density currents. Considering that the FFB is derived from the horizontal momentum equation, momentum-balance concepts are explored as an alternative to RKW theory, by assuming that the updraft’s slope is determined by the balance between advective tendencies of inflowing air and the work done by pressure perturbations within the denser fluid. Density currents were simulated under diverse shear and buoyancy profiles. Results show that momentum-balance effectively diagnoses the updraft’s slope at low and mid-levels in experiments contemplating both “classic” c-ΔU variations, as well as changes to the shear and buoyancy vertical profiles. It is also found that cases with stronger system-relative inflow tend to produce deeper lifting of near-surface environmental air, notwithstanding the updraft’s slope. RKW theory’s quantitative criterion (c/ΔU) is not as effective at diagnosing the updraft’s slope nor the depth reached by near-surface parcels, although c/ΔU provides guidance for the updraft’s slope at upper levels. This result justifies a reinterpretation of c/ΔU as a measure of the impacts of wind velocities aloft on the updraft
Connecting heavy precipitation events to outgoing long wave radiation variability scales: Case analysis in Brazil
Get PDFSpatial fields of outgoing long wave radiation (OLR) spectrum variance of the 1979-2016 austral summer months in southern Brazil are analyzed on different timescales: synoptic, sub-monthly, and intra-seasonal. Variability fields differ both in intensity and location and highlight dominant convection cycles in the study area. The results show that the amplitude of sub-monthly variability is greater than that of the other scales in the southeastern region of Brazil, while the synoptic scale prevails in the southern region. The above-mentioned scales show greater amplitudes over the western Pacific Ocean where the Madden-Julian Oscillation plays an important role, along the South Pacific Convergence Zone, and over the storm track areas over the South Pacific Ocean. The influence of spectral OLR scale interaction is also analyzed, associated to the occurrence of two intense rainfall events over the southeastern Brazil in the austral summers of 2011 and 2014 when the South Atlantic Convergence Zone (SACZ) was active in both events. The results obtained suggest that spectral OLR scale interaction takes place in such way that it strengthens the SACZ, since the spatial pattern footprints of the two to eight-day timescale (synoptic), 10 to 30-day timescale (sub-monthly) and 30 to 60-day timescale (intra-seasonal) overlap in the study region