From weak to intense downslope winds: origin, interaction with boundary-layer turbulence and impact on CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; variability

Arrillaga, Jon A.; Yagüe, Carlos; Román‐Cascón, Carlos; Sastre, Mariano; Jiménez, María A.; Maqueda, Gregorio; Arellano, Jordi Vilà‐Guerau de

doi:10.5194/acp-19-4615-2019

Cited by 10 publications

(6 citation statements)

References 61 publications

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“…The triggering of a specific NOE event requires the mixing of ozone-rich air from the nighttime residual layer to the surface or the horizontal transport of ozone-rich air from adjacent regions. Active nighttime transport and vertical mixing of air are associated with increasing atmospheric instability, which can be quantitatively indicated by the friction velocity (U * ), the planetary boundary layer height (PBLH), and vertical profiles of temperature (Su et al, 2018;Arrillaga et al, 2019;Wang et al, 2019;Shao et al, 2020). The U * and PBLH are widely applied to assess the atmospheric turbulence capacity for the vertical mixing, transport, and diffusion of air pollutants.…”

Section: Frequent Noe Events Associated With High Ozone Inmentioning

confidence: 99%

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Wang

et al. 2022

Atmos. Chem. Phys.

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Abstract. Surface ozone concentrations typically peak during the daytime, driven by active photochemical production, and decrease gradually after sunset, due to chemical destruction and dry deposition. Here, we report that nocturnal ozone enhancement (NOE, defined as an ozone increase of more than 5 ppbv h−1 in 1 of any 2 adjacent hours between 20:00 and 06:00 LT, local time) events are observed at multiple monitoring sites in China at a high frequency, which has not been recognized in previous studies. We present an overview of the general characteristics of NOE events in China and explore the possible mechanisms based on 6 years of observations from the national monitoring network. We find that the mean annual frequency of NOE events is 41±10 % (i.e., about 140 d would experience an NOE event per year) averaged over all 814 Chinese sites between 2014 and 2019, which is 46 % larger than that over Europe or the United States. The NOE event frequency is higher in industrialized city clusters (>50 %) than in regions with lighter ozone pollution, and it is higher in the warm season (46 %) than in the cold season (36 %), consistent with the spatiotemporal evolution of ozone levels. The mean ozone peak during NOE events reaches 37±6 ppbv in the warm season. The ozone enhancements are within 5–15 ppbv h−1 during 85 % of the NOE events; however, in about 10 % of cases, the ozone increases can exceed 20 ppbv h−1. We propose that high photochemistry-induced ozone during the daytime provides a rich ozone source in the nighttime residual layer, determining the overall high frequency of NOE events in China, and that enhanced atmospheric mixing then triggers NOE events by allowing the ozone-rich air in the residual layer to mix into the nighttime boundary layer. This is supported by our analyses which show that 70 % (65 %) of the NOE events are associated with increases in friction velocity (planetary boundary layer height), indicative of enhanced atmospheric mixing, and also supported by the observed sharp decreases in surface NO2 and CO concentrations with ozone increases in NOE events, a typical signal of mixing with air in the residual layer. Three case studies in Beijing and Guangzhou show that synoptic processes such as convective storms and low-level jets can lead to NOE events by aggravating vertical mixing. Horizontal transport of ozone-rich plumes may also be a supplementary driver of NOE events. Our results summarize, for the first time, the characteristics and mechanism of NOE events in China based on nationwide and long-term observations, and our findings emphasize the need for more direct measurements and modeling studies on the nighttime ozone evolution from the surface to the residual layer.

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Section: Frequent Noe Events Associated With High Ozone Inmentioning

confidence: 99%

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Wang

et al. 2022

Atmos. Chem. Phys.

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“…Climate research requires accurate characterization of atmospheric CO 2 , which is closely affected by both atmospheric transport and terrestrial sources and sinks (Bauska et al, 2015; Keenan et al, 2016). Our current knowledge largely comes from interpreting ground-or space-based measurements and model simulations.…”

Section: Introductionmentioning

confidence: 99%

Analysis of CO<sub>2</sub> spatio-temporal variations in China using a weather–biosphere online coupled model

et al. 2021

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Abstract. The dynamics of atmospheric CO2 has received considerable attention in the literature, yet significant uncertainties remain within the estimates of contribution from the terrestrial flux and the influence of atmospheric mixing. In this study we apply the WRF-Chem model configured with the Vegetation Photosynthesis and Respiration Model (VPRM) option for biomass fluxes in China to characterize the dynamics of CO2 in the atmosphere. The online coupled WRF-Chem model is able to simulate biosphere processes (photosynthetic uptake and ecosystem respiration) and meteorology in one coordinate system. We apply WRF-Chem for a multi-year simulation (2016–2018) with integrated data from a satellite product, flask samplings, and tower measurements to diagnose the spatio-temporal variations of CO2 fluxes and concentrations in China. We find that the spatial distribution of CO2 was dominated by anthropogenic emissions, while its seasonality (with maxima in April 15 ppmv higher than minima in August) was dominated by the terrestrial flux and background CO2. Observations and simulations revealed a consistent increasing trend in column-averaged CO2 (XCO2) of 2.46 ppmv (0.6 % yr−1) resulting from anthropogenic emission growth and biosphere uptake. WRF-Chem successfully reproduced ground-based measurements of surface CO2 concentration with a mean bias of −0.79 ppmv and satellite-derived XCO2 with a mean bias of 0.76 ppmv. The model-simulated seasonality was also consistent with observations, with correlation coefficients of 0.90 and 0.89 for ground-based measurements and satellite data, respectively. Tower observations from a background site at Lin'an (30.30∘ N, 119.75∘ E) revealed a strong correlation (−0.98) between vertical CO2 and temperature gradients, suggesting a significant influence of boundary layer thermal structure on the accumulation and depletion of atmospheric CO2.

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“…In this work, the main wind directions of the satellite's overpassed time were taken into account when selecting the pixels for the study. This footprint estimation approach was done due to the location of the flux tower, which is influenced by mesoscale thermally driven flows (mountain breezes) due to the presence of the Guadarrama Mountains, located quite close to the station [48,49]. According to these studies, the dynamics of the planetary boundary layer and these breezes influenced the CO 2 mixing ratio of the study area.…”

Section: Overall Discussionmentioning

confidence: 99%

“…In the study site, there is an eddy covariance flux tower that belongs to the Guadarrama Meteorological Network [47][48][49].…”

Section: Flux Tower Datamentioning

confidence: 99%

Modeling Gross Primary Production (GPP) of a Mediterranean Grassland in Central Spain Using Sentinel-2 NDVI and Meteorological Field Information

Cicuéndez,

Inclán,

Sánchez-Cañete

et al. 2024

Agronomy

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Mediterranean grasslands provide different ecosystems and social and economic services to the Mediterranean basin. Specifically, in Spain, pastures occupy more than 55% of the Spanish surface. Farmers and policymakers need to estimate the Gross Primary Production (GPP) to make sustainable management of these ecosystems and to study the role of grasslands acting as sinks or sources of Carbon in the context of climate change. High-frequency satellites, such as Sentinel-2, have opened the door to study GPP with a higher spatial and lower revisit time (10 m and 5 days). Therefore, the overall objective of this research is to estimate an ecosystem light use efficiency (eLUE) GPP model for a Mediterranean grassland in central Spain using Sentinel-2 NDVI Normalized Difference Vegetation Index (NDVI), complemented with meteorological information at the field scale for a relatively long period (from January 2018 to July 2020). The GPP models studied in this research were the MODIS GPP product, as well as the four eLUE models built with MODIS or Sentinel-2 NDVI and complemented by the inclusion of minimum temperature (Tmin) and soil water content (SWC). The models were validated through the GPP obtained from an eddy-covariance flux tower located in the study site (GPP_T). Results showed that the MODIS GPP product underestimated the GPP_T of the grassland ecosystem. Besides this, the approach of the eLUE concept was valid for estimating GPP in this Mediterranean grassland ecosystem. In addition, the models showed an improvement using Sentinel-2 NDVI compared to MODIS GPP product and compared to the models that used MODIS NDVI due to its higher spatial and temporal resolution. The inclusion of Tmin and SWC was also a determinant in improving GPP models during winter and summer periods. This work also illustrates how the main wind directions of the study area must be considered to appropriately estimate the footprint of the eddy covariance flux tower. In conclusion, this study is the first step to efficiently estimating the GPP of Mediterranean grasslands using the Sentinel-2 NDVI with complementary meteorological field information to make the management of these ecosystems sustainable.

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From weak to intense downslope winds: origin, interaction with boundary-layer turbulence and impact on CO<sub>2</sub> variability

Cited by 10 publications

References 61 publications

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Analysis of CO<sub>2</sub> spatio-temporal variations in China using a weather–biosphere online coupled model

Modeling Gross Primary Production (GPP) of a Mediterranean Grassland in Central Spain Using Sentinel-2 NDVI and Meteorological Field Information

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From weak to intense downslope winds: origin, interaction with boundary-layer turbulence and impact on CO&lt;sub&gt;2&lt;/sub&gt; variability

Cited by 10 publications

References 61 publications

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Analysis of CO&lt;sub&gt;2&lt;/sub&gt; spatio-temporal variations in China using a weather–biosphere online coupled model

Modeling Gross Primary Production (GPP) of a Mediterranean Grassland in Central Spain Using Sentinel-2 NDVI and Meteorological Field Information

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From weak to intense downslope winds: origin, interaction with boundary-layer turbulence and impact on CO<sub>2</sub> variability

Analysis of CO<sub>2</sub> spatio-temporal variations in China using a weather–biosphere online coupled model