#EGU23: It’s April again, and Vienna is calling.  We share our recent insights from following the energy through the Earth system. @akleidon @s_ghausi @yinglin_tian

Just like in pre-Corona times, April is the month in which Europe’s largest geosciences union convenes for its General Assembly in Vienna, Austria.  We are excited to be there, present our latest research, and look forward to seeing and talking to you there!

Sarosh will be giving his talk on “Determining the radiative and hydrologic controls on the diurnal air-temperature range (DTR) using the thermodynamic limit of maximum power” in the session CL4.1 – Land–atmosphere interactions and climate extremes on Thursday, April 27, 09:05 am in room F1. In his talk, he asks what are the dominant factors that shape the day to day variations in DTR over land. What role does hydrologic cycling play in modulating these variations and to what extent do clouds and surface water availability affect DTR? To answer these questions, he develops a simple estimate for DTR starting with heat accumulation during the day within the lower boundary layer as a predominant control shaping it (based on Annu’s previous work) and combines it with the maximum power approach. He shows that the day-to-day variations in DTR can be predicted reasonably well across a range of climates using this approach forced with observations of the radiative forcing and surface evaporative conditions. He then uses this approach to evaluate the response of DTR to changes in clouds, surface water availability and optical thickness of the atmosphere to quantify the relative importance and to compare this to the expected sensitivity to global warming. To learn more about his work, attend his talk in room F1 or meet him in person – he is there all week, or contact him.

Sarosh and Axel will present Yinglin’s poster on “Understanding variations in downwelling longwave radiation using Brutsaert’s equation” in session CL2.1 – Earth’s radiation budget, radiative forcing and climate change, which is based on a recent manuscript submitted to Earth System Dynamics. Downwelling longwave radiation represents the greenhouse effect of the atmosphere, and it is a highly relevant term in the surface energy balance. We used a semi-emprical parameterization from Brutsaert (1975) and first evaluated it against modern datasets to find that it works really well. The elegance of this parameterization is that it has a physical interpretation and links the flux to an effective emissivity of the atmosphere (mostly affected by water vapor and clouds – using the extension from Crawford and Duchon 1999) and air temperature. With this, we can then identify why the flux of downwelling longwave radiation varies with season and across regions. We found that this is mostly due to heat storage changes within the atmosphere. Why is this useful? Well, for instance, one an use this equation to understand why global warming results in a stronger temperature response on sunny days, which we have already used in the past (see this blogpost). If you want to learn more about this work, visit us at our poster X5.197 on Thursday, April 27, 16:15 – 18:00 in Hall X5.

Jonathan will be presenting his work on the German onshore wind energy potentials as a solicited talk titled “Evaluating the physical limits to technical wind energy potential over onshore Germany in 2050” in the ERE 2.2 – Spatial and temporal modelling of renewable energy systems session. During his talk he asks what the impact of kinetic energy (KE) resource depletion on the onshore technical wind energy potential of Germany is likely to be. He is interested primarily in evaluating the impact of these depletion effects on capacity factors, which is a ratio between actual electrical generation and the installed capacity that is often used in energy scenario analyses. To this end, he has estimated capacity factors using simulations of electrical generation from a range of real and hypothetical wind turbine deployment scenarios using a Weather Research and Forecasting (WRF) model and a simple, momentum balance approach (vKE). WRF incorporates the effects of all atmosphere – turbine interactions while vKE only accounts for the KE resource depletion effects. Despite model biases, WRF estimates show that for a typical planned scenario of ~200 GW deployed over 13.8% of land area, reductions in capacity factor are up to 20%. Comparisons between the comprehensive WRF and physically- based vKE estimates reveal that the KE resource depletion effects are the predominant control on the capacity factor reductions. He concludes that with increased deployment of wind energy in the context of the energy transition, these KE resource depletion effects need to be taken into account in energy scenarios. However, this can be done in a comparatively simple and physical way. To learn more about his work read the abstract here, check out an other interesting preprint, attend the talk in Room 0.96/0.97 on Wednesday, April 26, from 14:05 – 14:25, meet him in person during EGU or just drop him an email.

Axel talks about “How to sustain the terrestrial biosphere in the Anthropocene?” in session CL3.2.6 – Earth resilience, tipping points, and human-Earth system interactions in the Anthropocene. This work is based on a recent paper published in the INSEE journal. He applies, as usual, thermodynamics to this question. The main point is that the biosphere needs energy to maintain metabolisms associated with different organisms. This energy is generated by photosynthesis. In his talk, we will first briefly describe the limits on this form of generating energy from sunlight. This energy is then dissipated by the metabolisms of plants, animals, but also human societies. When human societies increase their need for food, expand and intensify agriculture, then inevitably there is less left for natural consumers to live on, thereby degrading the biosphere. He argues that to sustain the biosphere, it essentially implies that human activity needs to aim at pushing the limits of photosynthesis to higher levels, which can be achieved to expand agriculture into currently unproductive land by the use of technology. If you want to know more, come to his talk on Friday, April 28, from 11:30 to 11:40 in Room 0.31/0.32 or suffer through reading his paper, which will take much more of your time, but also gives you a more in-depth description.

Looking for a Postdoc? We will have an opening shortly, so get in touch with us (e-mail Axel) or meet us in Vienna.


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