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Mid-Holocene climate change over China: model–data discrepancy

The mid-Holocene has been an excellent target for comparing models and data. This work shows that, over China, all the ocean–atmosphere general circulation models involved in PMIP3 show a very large discrepancy with pollen data reconstruction when comparing annual and seasonal temperature. It demonstrates that to reconcile models and data and to capture the signature of seasonal thermal response, it is necessary to integrate non-linear processes, particularly those related to vegetation changes.

Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption

We performed seven physical experiments to explore terrace formation and sediment export from a braided alluvial river system that is perturbed by changes in water discharge, sediment supply, or base level. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace formation, and (3) the transient response of sediment discharge. Our findings provide guidelines for interpreting fill terraces and sediment export from fluvial systems.

Contrail cirrus radiative forcing for future air traffic

The climate impact of air traffic is to a large degree caused by changes in cirrus cloudiness resulting from the formation of contrails. We use an atmospheric climate model with a contrail cirrus parameterization to investigate the climate impact of contrail cirrus for the year 2050. The strong increase in contrail cirrus radiative forcing due to the projected increase in air traffic volume cannot be compensated for by the reduction of soot emissions and by improvements in propulsion efficiency.

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

This research project assesses biases in traditional, filter-based, aerosol absorption measurements by comparison to state-of-the-art, non-filter-based, or in situ, measurements. We assess biases in traditional absorption measurements for three main aerosol types, including dust and fresh and aged biomass burning aerosols. The main results of this study are that the traditional and state-of-the-art absorption measurements are well correlated and that biases in the former are up to 45 %.

Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: hourly results from EPIC/DSCOVR in deep space

Detecting aerosol layer height from space is challenging. The traditional method relies on active sensors such as lidar that provide the detailed vertical structure of the aerosol profile but is costly with limited spatial coverage (more than 1 year is needed for global coverage). Here we developed a passive remote sensing technique that uses backscattered sunlight to retrieve smoke aerosol layer height over both water and vegetated surfaces from a sensor 1.5 million kilometers from the Earth.

Technical note: A microcontroller-based automatic rain sampler for stable isotope studies

Most commercial automatic rain samplers are costly and do not prevent evaporation from the collection bottles. Hence, we have developed a microcontroller-based collector enabling timer-actuated integral rain sampling. The simple, low-cost device is robust and effectively minimizes post-sampling evaporation. The excellent performance of the collector during an evaporation experiment in a lab oven suggests that even multi-week field deployments in warm climates are feasible.

Induced seismicity in geologic carbon storage

To meet the goal of the Paris Agreement to limit temperature increase below 2 ºC, geologic carbon storage (GCS) will be necessary at the gigatonne scale. But to successfully deploy GCS, seismicity induced by CO₂injection should be controlled and maintained below a threshold that does not generate nuisances to the population. We conclude that felt induced seismicity can be minimized provided that a proper site characterization, monitoring and pressure management are performed.

Aerosol pH and its driving factors in Beijing

Aerosol acidity plays a key role in secondary aerosol formation. To provide a more comprehensive reference for aerosol pH and a basis for controlling secondary aerosol generation, this study used the latest data covering four seasons and different particle sizes to obtain the characteristics of aerosol pH and explore the main factors affecting aerosol pH and gas–particle partitioning in the Beijing area.

Including the efficacy of land ice changes in deriving climate sensitivity from paleodata

Processes causing the same global-average radiative forcing might lead to different global temperature changes. We expand the theoretical framework by which we calculate paleoclimate sensitivity with an efficacy factor. Applying the revised approach to radiative forcing caused by CO₂and land ice albedo perturbations, inferred from data of the past 800 000 years, gives a new paleo-based estimate of climate sensitivity.

A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles

Volatile organic compound (VOC) emissions influence air quality and particulate distributions, particularly in major source regions such as the Amazon. A sampler for collecting VOCs from an unmanned aerial vehicle (UAV) is described. Field tests of its performance and an initial example data set collected in the Amazon are also presented. The low cost, ease of use, and maneuverability of UAVs give this method the potential to significantly advance knowledge of the spatial distribution of VOCs.

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