Showing papers by "Ivan Ortega published in 2023"

Intercomparison of long-term ground-based tropospheric ozone measurements

Abstract: Ground-based observations are indispensable for the long-term monitoring of atmospheric constituents. In this work, we take advantage of multiple collocated instruments to analyze potential biases and drifts in ground-based ozone observations, within the context of the HEGIFTOM (Harmonization and Evaluation of Ground-based Instruments for Free Tropospheric Ozone Measurements) working group in the Tropospheric Ozone Assessment Report, Phase II (TOAR-II). This work is performed at Lauder (New Zealand), Boulder (Colorado), and Mauna Loa (Hawaii) where comparisons are made between Fourier Transform Infrared (FTIR) spectroscopy, Dobson Umkehr, and ozonesonde observations. The validation is performed with respect to FTIR as arbitrary reference, while considering the differences between the a priori profile information for the techniques that employ these as well as accounting for the different vertical resolution of each measurement technique. Such intercomparison is done for a handful discrete altitude partial columns, defined to have independent pieces of information also in the case of the low vertical resolution techniques (FTIR and Umkehr). This leads to 4 independent vertical layers to be compared, including one in the troposphere where ozone plays an important role as a greenhouse gas and as a risk to human health. In this tropospheric layer we compare the FTIR, Dobson Umkehr and ozonesonde techniques and derive a consistent bias from the FTIR data of about 5%, which we attribute in part to the assumed spectroscopy. Fitting the time series of the relative measurement differences using multiple linear regression, we obtain a linear trend, which quantifies the drift between pairs of techniques. Within the uncertainties, we find no significant drift between FTIR and Umkehr or ozone sonde data in the troposphere.

:Il Mediterraneo occidentale dalla fase fenicia all’egemonia cartaginese: Dinamiche insediative, forme rituali e cultura materiale nel V secolo a.C.

Abstract: Previous articleNext article FreeBook reviewIl Mediterraneo occidentale dalla fase fenicia all’egemonia cartaginese: Dinamiche insediative, forme rituali e cultura materiale nel V secolo a.C., edited by Andrea Roppa, Massimo Botto, and Peter van DommelenIván Fumadó OrtegaIván Fumadó Ortega Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmailPrint SectionsMoreDetailsFiguresReferencesCited by American Journal of Archaeology Ahead of Print The journal of the Archaeological Institute of America Views: 32Total views on this site Article DOIhttps://doi.org/10.1086/725314 Views: 32Total views on this site Copyright 2023 by Archaeological Institute of America. All rights reserved.PDF download Crossref reports no articles citing this article.

Anomalies of O3, CO, C2H2, H2CO, and C2H6 detected with multiple ground-based Fourier-transform infrared spectrometers and assessed with model simulation in 2020: COVID-19 lockdowns versus natural variability

Abstract: Anomalies of tropospheric columns of ozone (O3), carbon monoxide (CO), acetylene (C2H2), formaldehyde (H2CO), and ethane (C2H6) are quantified during the 2020 stringent COVID-19 world-wide lockdown using multiple ground-based Fourier-transform infrared spectrometers covering urban and remote conditions. We applied an exponential smoothing forecasting approach to the data sets to estimate business-as-usual values for 2020, which are then contrasted with actual observations. The Community Atmosphere Model with chemistry (CAM-chem) is used to simulate the same gases using lockdown-adjusted and business-as-usual emissions. The role of meteorology, or natural variability, is assessed with additional CAM-chem simulations. The tropospheric column of O3 declined between March and May 2020 for most sites with a mean decrease of 9.2% ± 4.7%. Simulations reproduce these anomalies, especially under background conditions where natural variability explains up to 80% of the decline for sites in the Northern Hemisphere. While urban sites show a reduction between 1% and 12% in tropospheric CO, the remote sites do not show a significant change. Overall, CAM-chem simulations capture the magnitude of the anomalies and in many cases natural variability and lockdowns have opposite effects. We further used the long-term record of the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument to capture global anomalies of CO. Reductions of CO vary highly across regions but North America and Europe registered lower values in March 2020. The absence of CO reduction in April and May, concomitant with reductions of anthropogenic emissions, is explained by a negative anomaly in the hydroxyl radical (OH) found with CAM-chem. The implications of these findings are discussed for methane (CH4), which shows a positive lifetime anomaly during the COVID-19 lockdown period. The fossil fuel combustion by-product tracer C2H2 shows a mean drop of 13.6% ± 8.3% in urban Northern Hemisphere sites due to the reduction in emissions and in some sites exacerbated by natural variability. For some sites with anthropogenic influence there is a decrease in C2H6. The simulations capture the anomalies but the main cause may be related to natural variability. H2CO declined during the stringent 2020 lockdown in all urban sites explained by reductions in emissions of precursors.

The diurnal variation of pollutant distributions over Asia using observations from the Geostationary Environment Monitoring Spectrometer (GEMS)

Abstract: Over the last 20 years, low-Earth orbit (LEO) atmospheric composition observations have provided amazing satellite measurements of atmospheric pollutants, mainly at continental-to-global, weekly-to-seasonal scales. The new-generation geostationary (GEO) satellite perspective, with high spatial resolution and hourly measurements, represents a major step forward in capability for understanding how air quality processes change diurnally at the local scale. South Korea's Geostationary Environment Monitoring Spectrometer (GEMS) was launched in February 2020 over Asia and is the first member of the GEO constellation that will eventually include the Tropospheric Emissions: Monitoring Pollution (TEMPO) mission over North America, and Sentinal-4 over Europe. The measurement hourly time resolution is truly the new perspective that the GEO platform provides, and in this presentation, we use a combination of satellite observations from GEMS and chemical transport model simulations to investigate the diurnal variation of pollution over several Asian regions. When considering the GEMS whole-Asia field-of-regard, the most striking impression of the NO2 diurnal variation is of how large it is in magnitude as well as how much the spatial distribution changes hour-by-hour. This questions our understanding of the distributions of reactive species based on the representativeness of once-a-day LEO observations. To help understand daily differences in diurnal patterns at regional and local scales, we use the Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA-V0). This uses a global modeling framework with regional grid refinement to resolve chemistry at emission and exposure relevant scales. The model shows reasonable agreement with the GEMS data and captures the different diurnal patterns at the different spatial scales and the degree of day-to day variability. The model also allows the drivers of variability due to emissions, meteorology, and photochemistry to be considered separately. The results of this analysis are further compared with the NO2 diurnal variability observed by PANDORA sun spectrometer measurements at polluted and less-polluted Korean and other Asian sites. We investigate spatial scale, including the city-scale within Seoul, at which GEMS captures the differences in diurnal variability between the PANDORAs.