Changes in satellite retrievals of atmospheric composition over eastern China during the 2020 COVID-19 lockdowns

We examined daily level-3 satellite retrievals of Atmospheric Infrared Sounder (AIRS) CO, Ozone Monitoring Instrument (OMI) SO2 and NO2, and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) over eastern China to understand how COVID-19 lockdowns affected atmospheric composition. Changes in 2020 were strongly dependent on the choice of background period since 2005 and whether trends in atmospheric composition were accounted for. Over central east China during the 23 January–8 April lockdown window, CO in 2020 was between 3 % and 12 % lower than average depending on the background period. The 2020 CO was not consistently less than expected from trends beginning between 2005 and 2016 and ending in 2019 but was 3 %–4 % lower than the background mean during the 2017–2019 period when CO changes had flattened. Similarly for AOD, 2020 was between 14 % and 30 % lower than averages beginning in 2005 and 14 %–17 % lower compared to different background means beginning in 2016. NO2 in 2020 was between 30 % and 43 % lower than the mean over different background periods and between 17 % and 33 % lower than what would be expected for trends beginning later than 2011. Relative to the 2016–2019 period when NO2 had flattened, 2020 was 30 %–33 % lower. Over southern China, 2020 NO2 was between 23 % and 27 % lower than different background means beginning in 2013, the beginning of a period of persistently lower NO2. CO over southern China was significantly higher in 2020 than what would be expected, which we suggest was partly because of an active fire season in neighboring countries. Over central east and southern China, 2020 SO2 was higher than expected, but this depended strongly on how daily regional values were calculated from individual retrievals and reflects background values approaching the retrieval detection limit. Future work over China, or other regions, needs to take into account the sensitivity of differences in 2020 to different background periods and trends in order to separate the effects of COVID-19 on air quality from previously occurring changes or from variability in other sources.

The effects of human movements on urban climate over Eastern China

We live on an urban planet with unprecedented human mobility. In this study, we collectively analyze ten large cities over densely populated Eastern China, and detect that mass people outflows during Spring Festival (SF) holiday significantly cool down urban climate expressed as urban heat island intensity variation particularly at the nighttime after minimizing the effects of other factors. We estimate that the average nighttime cooling effects of the ten large cities over Eastern China during the SF holiday relative to the nearby background period are 0.63 °C stronger during the 2000s than during the 1990s. The attribution analysis points to that the urban cooling effects are primarily caused by mass people outflows during the SF holiday. Our findings help to better understand the complex interactions of human population dynamics, urban development, and the environment, and may have important implications for promoting sustainable, people-centered, and resilient development of our urban planet.

Chemical composition of ultrafine aerosol particles in central Amazonia during the wet season

Central Amazonia serves as an ideal location to study atmospheric particle formation, since it often represents nearly natural, pre-industrial conditions but can also experience periods of anthropogenic influence due to the presence of emissions from large metropolitan areas like Manaus, Brazil. Ultrafine (sub-100 nm diameter) particles are often observed in this region, although new particle formation events seldom occur near the ground despite being readily observed in other forested regions with similar emissions of volatile organic compounds (VOCs). This study focuses on identifying the chemical composition of ultrafine particles as a means of determining the chemical species and mechanisms that may be responsible for new particle formation and growth in the region. These measurements were performed during the wet season as part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) field campaign at a site located 70 km southwest of Manaus. A thermal desorption chemical ionization mass spectrometer (TDCIMS) characterized the most abundant compounds detected in ultrafine particles. Two time periods representing distinct influences on aerosol composition, which we label as “anthropogenic” and “background” periods, were studied as part of a larger 10 d period of analysis. Higher particle number concentrations were measured during the anthropogenic period, and modeled back-trajectory frequencies indicate transport of emissions from the Manaus metropolitan area. During the background period there were much lower number concentrations, and back-trajectory frequencies showed that air masses arrived at the site predominantly from the forested regions to the north and northeast. TDCIMS-measured constituents also show distinct differences between the two observational periods. Although bisulfate was detected in particles throughout the 10 d period, the anthropogenic period had higher levels of particulate bisulfate overall. Ammonium and trimethyl ammonium were positively correlated with bisulfate. The background period had distinct diurnal patterns of particulate cyanate and acetate, while oxalate remained relatively constant during the 10 d period. 3-Methylfuran, a thermal decomposition product of a particulate-phase isoprene epoxydiol (IEPOX), was the dominant species measured in the positive-ion mode. Principal component analysis (PCA) was performed on the TDCIMS-measured ion abundance and aerosol mass spectrometer (AMS) mass concentration data. Two different hierarchical clusters representing unique influences arise: one comprising ultrafine particulate acetate, hydrogen oxalate, cyanate, trimethyl ammonium and 3-methylfuran and another made up of ultrafine particulate bisulfate, chloride, ammonium and potassium. A third cluster separated AMS-measured species from the two TDCIMS-derived clusters, indicating different sources or processes in ultrafine aerosol particle formation compared to larger submicron-sized particles.

149 Interaction of dietary protein and endophyte- infected Tall Fescue seed in stocker steers on finishing phase performance and carcass traits

Fescue toxicosis is a multifaceted disease that negatively impacts cattle. It was hypothesized that exposure to endophyte-infected fescue during the stocker phase affects finishing phase growth and carcass characteristics. Eight-month-old steers were sorted by weight and randomly assigned to receive one of four treatments for 56 days in confinement: endophyte-free seed (0 ug/ kg ergovaline) with either 18% (EF-18; n = 9) or 14% dietary protein (EF-14; n = 9) and endophyte-infected seed (500 ug/kg ergovaline) with 18% (EI-18; n = 9) or 14% dietary protein (EI-14; n = 9). Following fescue exposure calves were backgrounded on novel endophyte fescue pastures for 8 mo. At 18 mo, all steers were vaccinated, implanted, and reentered the feedlot for a 112 d growing phase and 52 d finishing phase. Body weight was recorded every 28 d and carcass data was collected at slaughter. Data were analyzed using the MIXED procedure of SAS for effects of BW, ADG, dressing percentage (DP), HCW, backfat, ribeye area (REA), KPH, USDA Yield grade (YG), and USDA Quality grade (QG). Statistical significance was determined at P > 0.05) HCW, BW, backfat, REA, DP, or QG. TheEI-14 had a greater ADG (1.69 kg/d) during the feedlot growing phase compared to the other treatment groups (1.53, 1.47, 1.55 for EI-18, EF-14, EF-18, respectively; P > 0.05). Steers stockered on 18% dietary protein had greater BW compared to steers previously fed at 14% (501.3±3.8 vs. 489.7±3.8; P = 0.0339). In addition, 18% protein in stocker diet resulted in greater KPH (2.3±0.2 vs. 1.78±0.2; P = 0.0129) and YG (3.4±0.1 vs. 3.0±0.1; P = 0.0168) compared with steers fed 14% dietary protein. Finishing growth and carcass characteristics were not affected by exposure to ergot alkaloids at weaning as much as dietary protein when cattle had a background period prior to feedlot entry

47 Interaction of dietary protein and endophyte- infected Tall Fescue seed in stocker steers on finishing phase performance and carcass traits

Fescue toxicosis is a multifaceted disease that negatively impacts cattle. It was hypothesized that exposure to endophyte-infected fescue during the stocker phase affects finishing phase growth and carcass characteristics. Eight-month-old steers were sorted by weight and randomly assigned to receive one of four treatments for 56 days in confinement: endophyte-free seed (0 ug/kg ergovaline) with either 18% (EF-18; n = 9) or 14% dietary protein (EF-14; n = 9) and endophyte-infected seed (500 ug/kg ergovaline) with 18% (EI-18; n = 9) or 14% dietary protein (EI-14; n = 9). Following fescue exposure calves were backgrounded on novel endophyte fescue pastures for 8 mo. At 18 mo, all steers were vaccinated, implanted, and reentered the feedlot for a 112 d growing phase and 52 d finishing phase. Body weight was recorded every 28 d and carcass data was collected at slaughter. Data were analyzed using the MIXED procedure of SAS for effects of BW, ADG, dressing percentage (DP), HCW, backfat, ribeye area (REA), KPH, USDA Yield grade (YG), and USDA Quality grade (QG). Statistical significance was determined at P > 0.05) HCW, BW, backfat, REA, DP, or QG. TheEI-14 had a greater ADG (1.69 kg/d) during the feedlot growing phase compared to the other treatment groups (1.53, 1.47, 1.55 for EI-18, EF-14, EF-18, respectively; P > 0.05). Steers stockered on 18% dietary protein had greater BW compared to steers previously fed at 14% (501.3±3.8 vs. 489.7±3.8; P = 0.0339). In addition, 18% protein in stocker diet resulted in greater KPH (2.3±0.2 vs. 1.78±0.2; P = 0.0129) and YG (3.4±0.1 vs. 3.0±0.1; P = 0.0168) compared with steers fed 14% dietary protein. Finishing growth and carcass characteristics were not affected by exposure to ergot alkaloids at weaning as much as dietary protein when cattle had a background period prior to feedlot entry

Chemical composition of ultrafine aerosol particles in central Amazonia during the wet season

Central Amazonia serves as an ideal location to study atmospheric particle formation since it often can be characterized as representing natural, pre-industrial conditions but can also experience periods of anthropogenic influence due to the presence of emissions from large metropolitan areas like Manaus, Brazil. Ultrafine (sub-100 nm diameter) particles are often observed in this region, although new particle formation events seldom occur near the ground despite being readily observed in other forested regions with similar emissions. This study focuses on identifying the chemical composition of ultrafine particles as a means of determining the chemical species and mechanisms that may be responsible for new particle formation and growth in the region. These measurements were performed during the wet season as part of the GoAmazon2014/5 field campaign at a site located 70 km southwest of Manaus. A Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) measured the concentrations of the most abundant compounds detected in ultrafine particles. Two time periods representing distinct influences on aerosol composition, which we label as anthropogenic and background periods, were studied as part of a larger ten-day period of analysis. The anthropogenic period saw higher particle number concentrations and modeled back-trajectories indicate transport of emissions from the Manaus metropolitan area. The background period saw much lower number concentrations and back-trajectories showed that air masses arrived at the site predominantly from the forested regions to the north and northeast. TDCIMS-measured constituents also show distinct differences between the two observational periods. Although bisulfate was detected in particles during the ten-day period, the anthropogenic period had increased levels of particulate bisulfate overall. Additionally, with larger fractions of bisulfate observed, increased fractions of ammonium and trimethyl ammonium were observed. The background period had distinct diurnal patterns of particulate organic nitrogen species and acetate, while oxalate remained relatively constant during the ten-day period. 3-Methylfuran, a thermal decomposition product of particulate phase isoprene epoxydiol (IEPOX), was the dominant species measured in the positive ion mode. Principal Component Analysis (PCA) was performed on the TDCIMS-measured ion abundance and Aerosol Mass Spectrometer (AMS) mass concentration data. Two different hierarchical clusters representing unique influences arise: one relating ultrafine particulate acetate, hydrogen oxalate, organic nitrogen species, trimethyl ammonium and 3-methylfuran with each other and ultrafine particulate bisulfate, chloride, ammonium and potassium. A third cluster separated AMS-measured species from the two TDCIMS-derived clusters, indicating different sources or processes in ultrafine aerosol particle formation compared to submicron-sized particles.

Comparing indicators of recreational fishing in Port Phillip Bay, Australia, from 2008 to 2011 with variability from a background period (2003–07)

Understanding the effects of anthropogenic disturbances on marine environments that support recreational fisheries requires suitable monitoring data. Although catch rates are frequently considered to inform resource status for commercial fisheries, similar time series data are generally unavailable for recreational fisheries. This study is based on 9 years of data from boat-based recreational fishing surveys in Port Phillip Bay, Australia. Harvest rates and length distributions of the retained catches for three target species were statistically compared over 4 years following commencement of shipping channel dredging (2008–11) with variability from a background period (2003–07). Mean harvest rates were generally within historical ranges, with increases for snapper (Chrysophrys auratus) and King George whiting (Sillaginodes punctatus) and decreases for sand flathead (Platycephalus bassensis). Length–frequency distributions were not significantly different to the background period, except for increased mean length of snapper and King George whiting in 2011. This study demonstrates that data obtained from sampling recreational fishers can provide valuable information to monitor harvested resources and maintain social amenity for recreational fisheries during periods of anthropogenic disturbance. Trends in harvest rates from recreational fishing surveys may also complement catch rates from commercial fisheries for assessments of multisector fisheries or stand-alone assessments for recreational-only fisheries.

30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

There are only four lidar stations in the world which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufrière Hills, Rabaul, Merapi, Nabro, and Kelut and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallajökull, and Grímsvötn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in the cases of the Okmok, Kasatochi, and Eyjafjallajökull eruptions, the HYSPLIT air mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanic eruptions in volcanogenic aerosol loading of the midlatitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e., the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that the Kelut volcanic eruption (Indonesia, February 2014) could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015.

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

Lidar measurements at Garmisch-Partenkirchen (Germany) have almost continually delivered backscatter coefficients of stratospheric aerosol since 1976. The time series is dominated by signals from the particles injected into or formed in the stratosphere due to major volcanic eruptions, in particular those of El Chichon (Mexico, 1982) and Mt Pinatubo (Philippines, 1991). Here, we focus more on the long-lasting background period since the late 1990s and 2006, in view of processes maintaining a residual lower-stratospheric aerosol layer in absence of major eruptions, as well as the period of moderate volcanic impact afterwards. During the long background period the stratospheric backscatter coefficients reached a level even below that observed in the late 1970s. This suggests that the predicted potential influence of the strongly growing air traffic on the stratospheric aerosol loading is very low. Some correlation may be found with single strong forest-fire events, but the average influence of biomass burning seems to be quite limited. No positive trend in background aerosol can be resolved over a period as long as that observed by lidar at Mauna Loa. We conclude that the increase of our integrated backscatter coefficients starting in 2008 is mostly due to volcanic eruptions with explosivity index 4, penetrating strongly into the stratosphere. Most of them occurred in the mid-latitudes. A key observation for judging the role of eruptions just reaching the tropopause region was that of the plume from the Icelandic volcano Eyjafjallajökull above Garmisch-Partenkirchen (April 2010) due to the proximity of that source. The top altitude of the ash above the volcano was reported just as 9.3 km, but the lidar measurements revealed enhanced stratospheric aerosol up to 14.3 km. Our analysis suggests for two or three of the four measurement days the presence of a stratospheric contribution from Iceland related to quasi-horizontal transport, differing from the strong descent of the layers entering Central Europe at low altitudes. The backscatter coefficients within the first 2 km above the tropopause exceed the stratospheric background by a factor of four to five. In addition, Asian and Saharan dust layers were identified in the free troposphere, Asian dust most likely even in the stratosphere.

35 years of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

The powerful backscatter lidar at Garmisch-Partenkirchen (Germany) has almost continually delivered backscatter coefficients of the stratospheric aerosol since 1976. The time series is dominated by signals from the particles injected into or formed in the stratosphere due to major volcanic eruptions, in particular those of El Chichon (Mexico, 1982) and Mt. Pinatubo (Philippines, 1991). The volcanic aerosol disappears within about five years, the removal from the stratosphere being modulated by the phase of the quasi-biennial oscillation. Here, we focus more on the long-lasting background period since the late 1990s and 2006, in view of processes maintaining a residual lower-stratospheric aerosol layer in absence of major eruptions, as well as the period of moderate volcanic impact afterwards. During the long background period the stratospheric backscatter coefficients reached a level even below that observed in the late 1970s. This suggests that the predicted potential influence of the strongly growing air traffic on the stratospheric aerosol loading is very low. Some correlation may be found with single strong forest-fire events, but the average influence of biomass burning seems to be quite limited. No positive trend in background aerosol can be resolved over a period as long as that observed by lidar at Mauna Loa or Boulder. This suggests being careful with invoking Asian air pollution as the main source as found in the literature. Rather an impact of previously missed volcanic eruptions on the stratospheric aerosol must be taken into consideration. A key observation in this regard was that of the plume from the Icelandic volcano Eyjafjallajökull above Garmisch-Partenkirchen (April 2010) due to the proximity of that source. The top altitude of the ash next to the source was reported just as roughly 9.3 km, but the lidar measurements revealed enhanced stratospheric aerosol up to 14.5 km. Our analysis suggests for two, perhaps three, of the four measurement days the presence of a stratospheric contribution from Iceland related to quasi-horizontal transport, contrasting the strongly descending lower layers entering Central Europe. The backscatter coefficients within the first 2 km above the tropopause exceed the stratospheric background by a factor of three to four. In addition, Asian and Saharan dust layers were identified in the free troposphere, Asian dust most likely even in the stratosphere. The number of minor mid-latitude eruptions has gradually increased during the past ten years. We conclude that, although their stratospheric contribution could not be clearly identified above our site they can sum up for forming some minor background. Clear stratospheric signatures were only seen in the case of eruptions reaching higher altitudes.