Robert Oscar David

• Motos, Ghislain; Freitas, Gabriel; Georgakaki, Paraskevi; Wieder, Jörg; Li, Guangyu & Aas, Wenche [Vis alle 15 forfattere av denne artikkelen] (2023). Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 23(21), s. 13941–13956. doi: 10.5194/acp-23-13941-2023. Fulltekst i vitenarkiv
• Hofer, Stefan; Hahn, Lily; Shaw, Jonah; McGraw, Zachary; Bruno, Olimpia & Hellmuth, Franziska [Vis alle 11 forfattere av denne artikkelen] (2023). Realistic representation of mixed-phase clouds increases future climate warming. Research Square. ISSN 2693-5015. doi: 10.21203/rs.3.rs-2981113/v1. Vis sammendrag

  Clouds are the main source of uncertainties when projecting climate change. Mixed-phase clouds (MPCs) that contain ice and supercooled-liquid particles are especially hard to constrain, and climate models neither agree on their phase nor their spatial extent. This is problematic, as models that underestimate contemporary supercooled-liquid in MPCs will underestimate future warming. Furthermore, it has recently been shown that supercooled-liquid water in MPCs is not homogeneously-mixed, neither vertically nor horizontally. However, while there have been attempts at observationally constraining MPCs to constrain uncertainties in future warming, all studies only use the phase of the interior of MPCs. Using novel satellite observations, and contrary to current knowledge, we show that MPCs are more liquid at the cloud top globally. We use these observations to constrain, for the first time, the cloud top phase in addition to the interior of MPCs in a global climate model, leading to +1C more 21st century warming in NorESM2 SSP5-8.5 climate projections. We anticipate that the difference between cloud top and interior phase in MPCs is an important new target metric for future climate model development, because similar MPC-related biases in future warming are likely present in many climate models.

• Pasquier, Julie T.; Henneberger, Jan; Korolev, Alexei; Ramelli, Fabiola; Wieder, Jörg & Lauber, Annika [Vis alle 12 forfattere av denne artikkelen] (2023). Understanding the History of Two Complex Ice Crystal Habits Deduced From a Holographic Imager. Geophysical Research Letters. ISSN 0094-8276. 50(1). doi: 10.1029/2022GL100247. Fulltekst i vitenarkiv
• Pasquier, Julie Thérèse; Henneberger, Jan; Ramelli, Fabiola; Lauber, Annika; David, Robert Oscar & Wieder, Jörg [Vis alle 10 forfattere av denne artikkelen] (2022). Conditions favorable for secondary ice production in Arctic mixed-phase clouds. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 22(23), s. 15579–15601. doi: 10.5194/acp-22-15579-2022. Fulltekst i vitenarkiv
• Pasquier, Julie T.; David, Robert Oscar; Freitas, Gabriel; Gierens, Rosa; Gramlich, Yvette & Haslett, Sophie [Vis alle 44 forfattere av denne artikkelen] (2022). The Ny-Ålesund Aerosol Cloud Experiment (NASCENT) Overview and First Results. Bulletin of The American Meteorological Society - (BAMS). ISSN 0003-0007. 103(11), s. E2533–E2558. doi: 10.1175/BAMS-D-21-0034.1. Fulltekst i vitenarkiv
• Carlsen, Tim & David, Robert Oscar (2022). Spaceborne Evidence That Ice-Nucleating Particles Influence High-Latitude Cloud Phase. Geophysical Research Letters. ISSN 0094-8276. 49(14). doi: 10.1029/2022GL098041. Fulltekst i vitenarkiv
• Ramelli, Fabiola; Henneberger, Jan; David, Robert Oscar; Bu¨hl, Johannes; Radenz, Martin & Seifert, Patric [Vis alle 13 forfattere av denne artikkelen] (2021). Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 21(9), s. 6681–6706. doi: 10.5194/acp-21-6681-2021. Fulltekst i vitenarkiv
• Vâjâiac, Sorin Nicolae; Calcan, Andreea; David, Robert Oscar; Moaca, Denisa-Elena; Iorga, Gabriela & Storelvmo, Trude [Vis alle 8 forfattere av denne artikkelen] (2021). Post-flight analysis of detailed size distributions of warm cloud droplets, as determined in situ by cloud and aerosol spectrometers. Atmospheric Measurement Techniques. ISSN 1867-1381. 14(10), s. 6777–6794. doi: 10.5194/amt-14-6777-2021. Fulltekst i vitenarkiv
• Miller, Anna J.; Brennan, Killian P.; Mignani, Claudia; Wieder, Jörg; David, Robert Oscar & Borduas-Dedekind, Nadine (2021). Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard. Atmospheric Measurement Techniques. ISSN 1867-1381. 14(4), s. 3131–3151. doi: 10.5194/amt-14-3131-2021. Fulltekst i vitenarkiv
• Hellmuth, Franziska; Engdahl, Bjørg Jenny Kokkvoll; Storelvmo, Trude; David, Robert Oscar & Cooper, Steven J. (2021). Snowfall Model Validation Using Surface Observations and an Optimal Estimation Snowfall Retrieval. Weather and forecasting. ISSN 0882-8156. 36(5), s. 1827–1842. doi: 10.1175/WAF-D-20-0220.1. Fulltekst i vitenarkiv Vis sammendrag

  In the winter, orographic precipitation falls as snow in the mid to high latitudes where it causes avalanches, affects local infrastructure, or leads to flooding during the spring thaw. We present a technique to validate operational numerical weather prediction model simulations in complex terrain. The presented verification technique uses a combined retrieval approach to obtain surface snowfall accumulation and vertical profiles of snow water at the Haukeliseter test site, Norway. Both surface observations and vertical profiles of snow are used to validate model simulations from the Norwegian Meteorological Institute’s operational forecast system and two simulations with adjusted cloud microphysics. Retrieved surface snowfall is validated against measurements conducted with a double-fence automated reference gauge (DFAR). In comparison, the optimal estimation snowfall retrieval produces + 10.9% more surface snowfall than the DFAR. The predicted surface snowfall from the operational forecast model and two additional simulations with microphysical adjustments (CTRL and ICE-T) are overestimated at the surface with +41.0 %, +43.8 %, and +59.2 %, respectively. Simultaneously, the CTRL and ICE-T simulations underestimate the mean snow water path by -1071.4% and -523.7 %, respectively. The study shows that we would reach false conclusions only using surface accumulation or vertical snow water content profiles. These results highlight the need to combine ground-based in-situ and vertically-profiling remote sensing instruments to identify biases in numerical weather prediction.

• Ramelli, Fabiola; Henneberger, Jan; David, Robert Oscar; Lauber, Annika; Pasquier, Julie T. & Wieder, Jorg [Vis alle 11 forfattere av denne artikkelen] (2021). Influence of low-level blocking and turbulence on the microphysics of a mixed-phase cloud in an inner-Alpine valley. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 21(6), s. 5151–5172. doi: 10.5194/acp-21-5151-2021. Fulltekst i vitenarkiv
• David, Robert Oscar; Fahrni, Jonas; Marcolli, Claudia; Mahrt, Fabian; Brühwiler, Dominik & A. Kanji, Zamin (2020). The role of contact angle and pore width on pore condensation and freezing. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 20(15), s. 9419–9440. doi: 10.5194/acp-20-9419-2020.
• P. Brennan, Killian; David, Robert Oscar & Borduas-Dedekind, Nadine (2020). Spatial and temporal variability in the ice-nucleating ability of alpine snowmelt and extension to frozen cloud fraction. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 20(1), s. 163–180. doi: 10.5194/acp-20-163-2020.
• McGraw, Zachary; Storelvmo, Trude; David, Robert Oscar & Sagoo, Navjit (2020). Global Radiative Impacts of Mineral Dust Perturbations Through Stratiform Clouds. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(23). doi: 10.1029/2019JD031807. Fulltekst i vitenarkiv
• Cascajo-Castresana, María; David, Robert Oscar; Iriarte-Alonso, Maiara A.; Bittner, Alexander M. & Marcolli, Claudia (2020). Protein aggregates nucleate ice: The example of apoferritin. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 20(6), s. 3291–3315. doi: 10.5194/acp-20-3291-2020. Fulltekst i vitenarkiv
• Mahrt, Fabian; Kilchhofer, Kevin; Marcolli, Claudia; Grönquist, Philippe; David, Robert Oscar & Rösch, Michael [Vis alle 8 forfattere av denne artikkelen] (2020). The Impact of Cloud Processing on the Ice Nucleation Abilities of Soot Particles at Cirrus Temperatures. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(3), s. 1–23. doi: 10.1029/2019JD030922.

Se alle arbeider i Cristin

• Motos, Ghislain; Freitas, Gabriel; Georgakaki, Paraskevi; Wieder, Jörg; Aas, Wenche & Lunder, Chris Rene [Vis alle 13 forfattere av denne artikkelen] (2023). Linking aerosol size distribution and hygroscopicity to cloud droplet formation at an Arctic mountain site.

Se alle arbeider i Cristin