scholarly journals Increasing Weekend Effect in Ground-Level O3 in Metropolitan Areas of Mexico during 1988–2016

2018 ◽  
Vol 10 (9) ◽  
pp. 3330 ◽  
Author(s):  
Iván Hernández-Paniagua ◽  
Rodrigo Lopez-Farias ◽  
José Piña-Mondragón ◽  
Juan Pichardo-Corpus ◽  
Olivia Delgadillo-Ruiz ◽  
...  
Keyword(s):  
Total Population ◽  
Metropolitan Areas ◽  
Ground Level ◽  
Weekend Effect ◽  
Monitoring Site ◽  
Lower Growth ◽  
Urban Core ◽  
Long Term Trends ◽  
Increasing Trends

Here, we present an assessment of long-term trends in the O3 weekend effect (WE) occurrences and spread within the Mexico City (MCMA), Guadalajara (GMA), and Monterrey (MMA) metropolitan areas, which are the three largest metropolitan areas (MAs) of Mexico and concentrate around 33% of the total population in the country. Daytime averages and peak differences in O3 concentrations from weekdays to weekends were used as a proxy of WE occurrence. All MAs exhibited the occurrence of WE in all years at least in one monitoring site. Substantial differences in O3 daytime averages and peaks from weekdays to weekends have decreased over time in all MAs, and since 1998 and 2013 for the MCMA and GMA, respectively, higher O3 levels during weekends are typical during most of the year. The largest variations in the O3 WE were observed at downwind and urban core sites of the MCMA and GMA. Significant increasing trends (p < 0.05) in the O3 WE magnitude were observed for Sundays at all sites within the MCMA, with trends in annual averages ranging between 0.33 and 1.29 ppb O3 yr−1. Within the GMA, for Sundays, fewer sites exhibited increasing trends in the WE occurrence and at lower growth rates (0.32 and 0.48 ppb yr−1, p < 0.1) than within the MCMA, while within the MMA no apparent trends were observed in marked contrast with the MCMA and GMA. Our findings suggest that policies implemented have been successful in controlling weekday ground-level O3 within the MCMA and GMA, but further actions must be introduced to control the increases in the O3 WE magnitude and spread.

Considerations on Ambient Levels of Ozone Concentrations and Relationship with NOx in an Urban Environment

2017 ◽  
Vol 68 (4) ◽  
pp. 824-829
Author(s):  
Cornel Ianache ◽  
Laurentiu Predescu ◽  
Mirela Predescu ◽  
Dumitru Dumitru
Keyword(s):  
Nitrogen Oxides ◽  
Urban Areas ◽  
Road Traffic ◽  
Temporal Distribution ◽  
Ground Level ◽  
Distinct Pattern ◽  
Weekend Effect ◽  
Monitoring Site ◽  
Ground Level Ozone ◽  
Ozone Concentrations

The serious air pollution problem has determined public concerns, worldwide. One of the main challenges for countries all over the world is caused by the elevated levels of ground-level ozone (O3) concentrations and its anthropogenic precursors. Ploiesti city, as one of the major urban area of Romania, is facing the same situation. This research aims to investigate spatial and temporal distribution characteristics of O3 in relationship with nitrogen oxides (NOx) using statistical analysis methods. Hourly O3 and NOx measurements were collected during 2014 year in Ploiesti. The results obtained showed that the ozone spatial distribution was non-normal for each month in 2014. The diurnal cycle of ground-level ozone concentrations showed a mid-day peak, while NOx diurnal variations presented 2 daily peaks, one in the morning (7:00 a.m.) and one in the afternoon (between 5:00 and 7:00 p.m.). In addition, it was observed a distinct pattern of weekly variations for O3 and NOx. Like in many other urban areas, the results indicated the presence of the �ozone weekend effect� in Ploiesti during the 2014 year, ozone concentrations being slightly higher on weekends compared to weekdays. For the same monitoring site, the nitrogen oxides were less prevalent on Saturdays and Sundays, probably due to reducing of road traffic and other pollution-generating activities on weekends than during the week.

scholarly journals Trends in the Frequency of Intense Precipitation Events in Southern and Southeastern Brazil during 1960–2004

2011 ◽  
Vol 24 (7) ◽  
pp. 1913-1921 ◽  
Author(s):  
Mateus da Silva Teixeira ◽  
Prakki Satyamurty
Keyword(s):  
Extreme Rainfall ◽  
Southeastern Brazil ◽  
Extreme Rainfall Event ◽  
Southern Brazil ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Annual Frequency ◽  
Long Term Trends ◽  
Increasing Trends

Abstract A new approach to define heavy and extreme rainfall events based on cluster analysis and area-average rainfall series is presented. The annual frequency of the heavy and extreme rainfall events is obtained for the southeastern and southern Brazil regions. In the 1960–2004 period, 510 (98) and 466 (77) heavy (extreme) rainfall events are identified in the two regions. Monthly distributions of the events closely follow the monthly climatological rainfall in the two regions. In both regions, annual heavy and extreme rainfall event frequencies present increasing trends in the 45-yr period. However, only in southern Brazil is the trend statistically significant. Although longer time series are necessary to ensure the existence of long-term trends, the positive trends are somewhat alarming since they indicate that climate changes, in terms of rainfall regimes, are possibly under way in Brazil.

scholarly journals Analysis of Long-Term Trends of Annual and Seasonal Rainfall in the Awash River Basin, Ethiopia

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1498 ◽  
Author(s):  
Solomon Mulugeta ◽  
Clifford Fedler ◽  
Mekonen Ayana
Keyword(s):  
Climate Change ◽  
River Basin ◽  
Summer Rainfall ◽  
Seasonal Rainfall ◽  
Winter Rainfall ◽  
Adaptation Measures ◽  
Awash River Basin ◽  
Long Term Trends ◽  
Increasing Trends

With climate change prevailing around the world, understanding the changes in long-term annual and seasonal rainfall at local scales is very important in planning for required adaptation measures. This is especially true for areas such as the Awash River basin where there is very high dependence on rain- fed agriculture characterized by frequent droughts and subsequent famines. The aim of the study is to analyze long-term trends of annual and seasonal rainfall in the Awash River Basin, Ethiopia. Monthly rainfall data extracted from Climatic Research Unit (CRU 4.01) dataset for 54 grid points representing the entire basin were aggregated to find the respective areal annual and seasonal rainfall time series for the entire basin and its seven sub-basins. The Mann-Kendall (MK) test and Sen Slope estimator were applied to the time series for detecting the trends and for estimating the rate of change, respectively. The Statistical software package R version 3.5.2 was used for data extraction, data analyses, and plotting. Geographic information system (GIS) package was also used for grid making, site selection, and mapping. The results showed that no significant trend (at α = 0.05) was identified in annual rainfall in all sub-basins and over the entire basin in the period (1902 to 2016). However, the results for seasonal rainfall are mixed across the study areas. The summer rainfall (June through September) showed significant decreasing trend (at α ≤ 0.1) over five of the seven sub-basins at a rate varying from 4 to 7.4 mm per decade but it showed no trend over the two sub-basins. The autumn rainfall (October through January) showed no significant trends over four of the seven sub-basins but showed increasing trends over three sub-basins at a rate varying from 2 to 5 mm per decade. The winter rainfall (February through May) showed no significant trends over four sub-basins but showed significant increasing trends (at α ≤ 0.1) over three sub-basins at a rate varying from 0.6 to 2.7 mm per decade. At the basin level, the summer rainfall showed a significant decreasing trend (at α = 0.05) while the autumn and winter rainfall showed no significant trends. In addition, shift in some amount of summer rainfall to winter and autumn season was noticed. It is evident that climate change has shown pronounced effects on the trends and patterns of seasonal rainfall. Thus, the study contribute to better understanding of climate change in the basin and the information from the study can be used in planning for adaptation measures against a changing climate.

scholarly journals Global Tropopause Altitudes in Radiosondes and Reanalyses

2018 ◽  
Author(s):  
Tao Xian ◽  
Cameron R. Homeyer
Keyword(s):  
Coordinate System ◽  
Lapse Rate ◽  
Vertical Resolution ◽  
Relative Coordinate ◽  
Relative Coordinates ◽  
Long Term Trends ◽  
The Tropics ◽  
Increasing Trends

Abstract. Accurate depictions of the tropopause and its changes are important for studies such as stratosphere-troposphere exchange and climate change.Here, the fidelity of primary lapse-rate tropopause altitudes and double tropopause frequencies in four modern reanalyses (ERA-Interim, JRA-55, MERRA-2, and CFSR) is examined using global radiosonde observations. In addition, long-term trends (1981–2015) in these tropopause properties are diagnosed in both the reanalyses and radiosondes. It is found that ERA-Interim, JRA-55, and CFSR reproduce observed tropopause altitudes with little bias and error comparable to the model vertical resolution, while MERRA-2 tropopause altitudes are biased 500–600 m high. All reanalyses underestimate the double tropopause frequency (up to 30 % lower than observed), with the largest biases found in JRA-55 and the smallest in CFSR. The underestimates in double tropopause frequency are primarily attributed to the coarse vertical resolution of the reanalyses. Significant increasing trends in both tropopause altitude (40–120 m per decade) and double tropopause frequency (≥ 3 % per decade) were found in both the radiosonde observations and reanalyses over the 35-year analysis period. ERA-Interim, JRA-55, and MERRA-2 broadly reproduce the patterns and signs of observed significant trends, while CFSR is inconsistent with the remaining datasets. These trends were diagnosed in both the native Eulerian coordinate system of the reanalyses and in a relative latitude coordinate system where the tropopause break (the discontinuity in tropopause altitude between the tropics and extratropics) was used as the reference latitude in each hemisphere. The tropopause break-relative coordinate facilitates the evaluation of tropopause behavior within the tropical and extratropical reservoirs and revealed significant differences in trend estimates compared to the traditional Eulerian analysis. Notably, increasing tropopause altitude trends were found to be of greater magnitude in tropopause break-relative coordinates and increasing double tropopause frequency trends were found to occur primarily poleward of the tropopause break in each hemisphere.

scholarly journals Long-term trends of climate change and its impact on crop growing season on Montreal Island

2016 ◽  
Vol 8 (1) ◽  
pp. 78-88
Author(s):  
Erika Bouchard ◽  
Zhiming Qi
Keyword(s):  
Climate Change ◽  
Daily Rainfall ◽  
Growing Season ◽  
Annual Rainfall ◽  
Climate Trends ◽  
Growing Season Length ◽  
Mk Test ◽  
Long Term Trends ◽  
Increasing Trends

Long-term trends in air temperature and precipitation under climate change were analyzed for two meteorological stations on the Island of Montreal: McGill (1872–1986) and Pierre-Elliott-Trudeau (P-E-T, formerly Dorval) Airport (1942–2014). A linear trendline analysis, the Mann–Kendall (MK) test and the two-sample Kolmogorov–Smirnov (KS) test were conducted to assess specific climate trends. On a 100-year basis, temperature increased 1.88°C (34%) and 1.18°C (19%) at the McGill and P-E-T Airport sites, respectively, while annual rainfall increased 23.9 mm y−1 (2.3%) and 138.8 mm y−1 (15%) over the same period. The frequency of 50% (every other year) and 95% (every year) annual maximum daily rainfall events showed decreasing trends for the McGill station, but increasing trends for the P-E-T Airport station. Growing degree-days and growing season length are prone to being influenced by climate change and are critical to managing agricultural activities in the Montreal region; both showed increasing trends. At the same time, the onset of the growing season occurred earlier as time progressed.

scholarly journals Trend Analysis of Urban Heat Island Intensity According to Urban Area Change in Asian Mega Cities

2019 ◽  
Vol 12 (1) ◽  
pp. 112 ◽  
Author(s):  
Kyungil Lee ◽  
Yoonji Kim ◽  
Hyun Chan Sung ◽  
Jieun Ryu ◽  
Seong Woo Jeon
Keyword(s):  
Urban Heat Island ◽  
Urban Area ◽  
Anthropogenic Heat ◽  
Heat Island ◽  
Individual Factor ◽  
Long Term Trends ◽  
Urban Heat ◽  
Increasing Trends ◽  
Mega Cities

Urban heat island (UHI) is a phenomenon that occurs in cities worldwide. Therefore, there is an increasing need for studies on the changes in UHI intensity and long-term trends based on macroscopic characteristics related to urbanization. In this study, changes in seasonal UHI intensity based on urban area were analyzed for eight Asian mega cities from 1992–2012. The results indicate that the change in pattern of UHI intensity varies for different cities and seasons. UHI intensity increased as the urban area size increased. Furthermore, the dependency of UHI intensity on the economic situation was also demonstrated. With respect to the seasons, significantly increasing trends appeared during the summer. Moreover, depending on urban characteristics such as geography and climate, increasing trends appeared during other seasons. Population was also found to affect UHI intensity by generating anthropogenic heat; however, its effect as an individual factor appeared to be insignificant. This is a macroscale study that analyzes the effect of urban area size on UHI intensity. Future studies on urbanization factors and levels influencing the UHI intensity using higher resolution materials are required

An assessment of long-term trends in hydrologic components and implications for water levels in Lake Superior

2009 ◽  
Vol 40 (6) ◽  
pp. 564-579 ◽  
Author(s):  
Homayoun Motiee ◽  
Edward McBean
Keyword(s):  
Lake Superior ◽  
Water Levels ◽  
Annual Average ◽  
Hydroelectric Energy ◽  
Regression Modelling ◽  
Long Term Trends ◽  
Lake Evaporation ◽  
Changes Over Time ◽  
Increasing Trends

The combination of climate change and natural periodicities in meteorological variables are demonstrating significant impacts on the water resources of Lake Superior within the Laurentian Great Lakes system of North America. Statistical analyses of long-term records are used to demonstrate how changes over time may be interpreted very differently, depending upon the timeframe over which the analyses are made. Non-linear regression modelling shows that, while increasing trends in overland and overlake precipitation, flows and runoff occurred during the first decades of the twentieth century, very different trends are apparent for the period 1970–2005. For this latter period, increasing rates of air overlake temperature and lake evaporation are occurring but all other parameters are demonstrating decreasing trends. The result is a decline in water levels in Lake Superior at the rate of approximately 1 cm per year over the last 35 years. The results are used to show that to avoid decreasing water levels in Lake Superior, the discharge through St Mary's River must be decreased to approximately one-half the long-term annual average, the results of which will have dramatic implications for ships' cargo levels and hydroelectric energy generation.

scholarly journals Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests

2016 ◽  
Vol 13 (19) ◽  
pp. 5567-5585 ◽  
Author(s):  
Marta Camino-Serrano ◽  
Elisabeth Graf Pannatier ◽  
Sara Vicca ◽  
Sebastiaan Luyssaert ◽  
Mathieu Jonard ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Atmospheric Deposition ◽  
Soil Solution ◽  
Surface Waters ◽  
N Deposition ◽  
Icp Forests ◽  
Level Ii ◽  
Long Term Trends ◽  
Increasing Trends

Abstract. Dissolved organic carbon (DOC) in surface waters is connected to DOC in soil solution through hydrological pathways. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site studies have failed so far to establish consistent trends in soil solution DOC, whereas increasing concentrations in European surface waters over the past decades appear to be the norm, possibly as a result of recovery from acidification. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physico-chemical and biological controls. We applied trend analysis at two levels: (1) to the entire European dataset and (2) to the individual time series and related trends with plot characteristics, i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC concentrations in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC. The rate change in soil solution DOC ranged between −16.8 and +23 % yr−1 (median  = +0.4 % yr−1) across Europe. The non-significant trends (40 %) outnumbered the increasing (35 %) and decreasing trends (25 %) across the 97 ICP Forests Level II sites. By means of multivariate statistics, we found increasing trends in DOC concentrations with increasing mean nitrate (NO3−) deposition and increasing trends in DOC concentrations with decreasing mean sulfate (SO42−) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO42− deposition could be confirmed in low to medium N deposition areas, in agreement with observations in surface waters, this was not the case in high N deposition areas. In conclusion, long-term trends of soil solution DOC reflected the interactions between controls acting at local (soil and vegetation properties) and regional (atmospheric deposition of SO42− and inorganic N) scales.

scholarly journals Spatial and temporal characteristics of evaporation trends over India during 1971-2000

MAUSAM ◽  
2021 ◽  
Vol 59 (2) ◽  
pp. 149-158
Author(s):  
A. K. JASWAL ◽  
G. S. PRAKASA RAO ◽  
U. S. DE
Keyword(s):  
Spatial Analysis ◽  
Cloud Cover ◽  
Sunshine Duration ◽  
Post Monsoon ◽  
Rainfall Trends ◽  
Long Term Trends ◽  
Two Parameters ◽  
Increasing Trends ◽  
Spatial And Temporal Characteristics

Evaporation and rainfall data for the period 1971-2000 for 58 well distributed stations over India were selected for this study. Trends of these two parameters for the country as a whole and for individual stations for annual (January – December), winter (December, January and February), summer (March – May), monsoon (June – September) and post-monsoon (October, November) period were analysed and tested for significance at 95% level of confidence. The analysis shows that for the country as a whole, the evaporation has significantly decreased in all seasons while there is no significant trend in rainfall. Out of 58 stations, numbers of stations having significant decrease in evaporation are 45 (annual), 30 (winter), 42 (summer) and 35 (monsoon and post monsoon seasons). Decadal analysis of trends shows that the variability of evaporation towards the decreasing trend is steadily maintained throughout the period but more in the decade 1991-2000. Spatial analysis of the seasonal trends of evaporation indicates the decreasing trends over all parts of India except northeast where it is increasing. Regions of significant decrease in evaporation viz., North, Southwest and Southeast and increase in evaporation viz., Northeast emerge from the spatial analysis of trends over the country. Spatial analysis of seasonal rainfall trends indicates the increasing trends in southern parts and decreasing trends in central and northeastern parts of the country. Evaporation trends of nearly 50% stations (mostly in southern parts of India) show complimentary relation with rainfall of the same period. Rest of the long term trends in evaporation may be due to the variation in other parameters like wind speed, cloud cover, sunshine duration etc. which needs further examination.

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