Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8591-2019 8 July 2019 Effects of aerosols on clouds are important for climate studies but are among the largest uncertainties in climate projections. This study evaluates the skill of global models to simulate aerosol, cloud condensation nuclei (CCN) and cloud droplet number concentrations (CDNCs). Model results show reduced spread in CDNC compared to CCN due to the negative correlation between the sensitivities of CDNC to aerosol number concentration (air pollution) and updraft velocity (atmospheric dynamics). Read more
Flood risk in a range of spatial perspectives – from global to local scales Natural Hazards and Earth System Sciences DOI 10.5194/nhess-19-1319-2019 5 July 2019 Considering flood risk composed of hazard, exposure, and vulnerability from global to local scales, this paper reviews and presents increasing observed flood losses and projections of flood hazard and losses. We acknowledge existence of multiple driving factors and of considerable uncertainty, in particular with regards to projections for the future. Finally, this paper analyses options for flood risk reduction from a global framework to regional and local scales. Read more
Description of a formaldehyde retrieval algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS) Atmospheric Measurement Techniques DOI 10.5194/amt-12-3551-2019 4 July 2019 The Geostationary Environment Monitoring Spectrometer (GEMS) will be launched by South Korea in 2019, and it will measure radiances ranging from 300 to 500 nm every hour with a fine spatial resolution of 7 km x 8 km over Seoul in South Korea to monitor column concentrations of air pollutants including O3, NO2, SO2, and HCHO, as well as aerosol optical properties. This paper describes a GEMS formaldehyde retrieval algorithm including a number of sensitivity tests for algorithm evaluation. Read more
Converting snow depth to snow water equivalent using climatological variables The Cryosphere DOI 10.5194/tc-13-1767-2019 4 July 2019 We present a new statistical model for converting snow depths to water equivalent. The only variables required are snow depth, day of year, and location. We use the location to look up climatological parameters such as mean winter precipitation and mean temperature difference (difference between hottest month and coldest month). The model is simple by design so that it can be applied to depth measurements anywhere, anytime. The model is shown to perform better than other widely used approaches. Read more
Emission of trace gases and aerosols from biomass burning – an updated assessment Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8523-2019 4 July 2019 Biomass burning is one of the largest sources of atmospheric pollutants worldwide. This paper presents an up-to-date compilation of emission factors for over 120 trace gas and aerosol species from the different forms of open vegetation fires and domestic biofuel use, based on an analysis of over 370 published studies. Using these emission factors and current global burning activity data, the annual emissions of important species released by the various types of biomass burning are estimated. Read more
Mid-Holocene climate change over China: model–data discrepancy Climate of the Past DOI 10.5194/cp-15-1223-2019 2 July 2019 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. Read more
Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption Earth Surface Dynamics DOI 10.5194/esurf-7-609-2019 1 July 2019 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. Read more
Contrail cirrus radiative forcing for future air traffic Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8163-2019 27 June 2019 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. Read more
Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy Atmospheric Measurement Techniques DOI 10.5194/amt-12-3417-2019 27 June 2019 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 %. Read more
Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: hourly results from EPIC/DSCOVR in deep space Atmospheric Measurement Techniques DOI 10.5194/amt-12-3269-2019 20 June 2019 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. Read more
