How well do stratospheric reanalyses reproduce high-resolution satellite temperature measurements? Atmospheric Chemistry and Physics DOI 10.5194/acp-18-13703-2018 27 September 2018 Reanalyses (RAs) are models which assimilate observations and are widely used as proxies for the true atmospheric state. Here, we resample six leading RAs using the weighting functions of four high-res satellite instruments, allowing a like-for-like comparison. We find that the RAs generally reproduce the satellite data well, except at high altitudes and in the tropics. However, we also find that the RAs more tightly correlate with each other than with observations, even those they assimilate. Read more
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation Hydrology and Earth System Sciences DOI 10.5194/hess-22-4959-2018 27 September 2018 Evaporation from wetlands, lakes and irrigation areas needs to be measured to understand water scarcity. So far, this has only been possible for small regions. Here, we develop a solution that can be applied at a very high resolution globally by making use of satellite observations. Our results show that 16% of global water resources evaporate before reaching the ocean, mostly from surface water. Irrigation water use is less than 1% globally but is a very large water user in several dry basins. Read more
World Ocean Circulation Experiment – Argo Global Hydrographic Climatology Ocean Science DOI 10.5194/os-14-1127-2018 27 September 2018 The new gridded WOCE-Argo Global Hydrographic Climatology (WAGHC) is described and compared with the NOAA WOA13 atlas. The monthly fields of temperature and salinity for 65 depth levels have a 1/4° spatial resolution. Two versions of the climatology were produced and differ with respect to the spatial interpolation performed on isobaric or isopycnal surfaces, respectively. The climatology characterizes the thermohaline state of the world ocean for the time period from 2008 to 2012. Read more
Cleaning up our water: reducing interferences from nonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles Atmospheric Measurement Techniques DOI 10.5194/amt-11-5315-2018 24 September 2018 Ice nucleation commonly studied using droplet freezing measurements suffers from artifacts caused by water impurities or substrate effects. We evaluate a series of substrates and water sources to find methods that reduce the background freezing temperature limit. The best performance was obtained from our new microfluidic device and hydrophobic glass surfaces, using filtered HPLC bottled water. We conclude with recommendations for best practices in droplet freezing experiments and data analysis. Read more
Diurnal land surface energy balance partitioning estimated from the thermodynamic limit of a cold heat engine Earth System Dynamics DOI 10.5194/esd-9-1127-2018 21 September 2018 Turbulent fluxes represent an efficient way to transport heat and moisture from the surface into the atmosphere. Due to their inherently highly complex nature, they are commonly described by semiempirical relationships. What we show here is that these fluxes can also be predicted by viewing them as the outcome of a heat engine that operates between the warm surface and the cooler atmosphere and that works at its limit. Read more
Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? The Cryosphere DOI 10.5194/tc-12-2955-2018 20 September 2018 In this paper, we explore the possibility of using locally targeted geoengineering to slow the rate of an ice sheet collapse. We find that an intervention as big as existing large civil engineering projects could have a 30 % probability of stopping an ice sheet collapse, while larger interventions have better odds of success. With more research to improve upon the simple designs we considered, it may be possible to perfect a design that was both achievable and had good odds of success. Read more
Tracing water masses with 129I and 236U in the subpolar North Atlantic along the GEOTRACES GA01 section Biogeosciences DOI 10.5194/bg-15-5545-2018 18 September 2018 The investigation of water mass transport pathways and timescales is important to understand the global ocean circulation. Following earlier studies, we use artificial radionuclides introduced to the oceans in the 1950s to investigate the water transport in the subpolar North Atlantic (SPNA). For the first time, we combine measurements of the long-lived iodine-129 and uranium-236 to confirm earlier findings/hypotheses and to better understand shallow and deep ventilation processes in the SPNA. GEOTRACES GA01 section">Read more
sympl (v. 0.4.0) and climt (v. 0.15.3) – towards a flexible framework for building model hierarchies in Python Geoscientific Model Development DOI 10.5194/gmd-11-3781-2018 18 September 2018 In the same way that the fruit fly or the yeast cell serve as model systems in biology, climate scientists use a range of computer models to gain a fundamental understanding of our climate system. These models range from extremely simple models that can run on your phone to those that require supercomputers. Sympl and climt are packages that make it easy for climate scientists to build a hierarchy of such models using Python, which facilitates easy to read and self-documenting models. Read more
Speculations on the application of foliar 13C discrimination to reveal groundwater dependency of vegetation and provide estimates of root depth and rates of groundwater use Hydrology and Earth System Sciences DOI 10.5194/hess-22-4875-2018 18 September 2018 Groundwater is a significant water resource for humans and for groundwater-dependent vegetation. Several challenges to managing both groundwater resources and dependent vegetation include defining the location of dependent vegetation, the rate of groundwater use, and the depth of roots accessing groundwater. In this study we demonstrate a novel application of measurements of stable isotopes of carbon that can be used to identify the location, the rooting depth, and the rate of groundwater use. Read more
Inverse modelling of CF4 and NF3 emissions in East Asia Atmospheric Chemistry and Physics DOI 10.5194/acp-18-13305-2018 17 September 2018 Emissions of carbon tetrafluoride CF4, NF3 and CHF3 in east Asia have been calculated using atmospheric measurements and an atmospheric transport model. We calculate emissions of CF4 to be quite constant between the years 2008 and 2015 for both China and South Korea, with 2015 emissions calculated at 4.33 ± 2.65 Gg yr-1 and 0.36 ± 0.11 Gg yr-1, respectively. Emission estimates of NF3 from South Korea could be made with relatively small uncertainty at 0.6 ± 0.07 Gg yr-1 in 2015. Read more
