2026-06-29 カリフォルニア大学サンディエゴ校（UCSD）
＜関連情報＞
- https://today.ucsd.edu/story/scientists-identify-houston-power-plant-as-dominant-source-of-cloud-forming-aerosols
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JD044628
- https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2025JD045547
- https://www.science.org/doi/10.1126/sciadv.aeb6751
海洋エアロゾルから製油所排出物へ：ヒューストン都市圏における雲凝結核（CCN）の輸送と変化、および雲形成への影響 Marine Aerosol to Refinery Emissions: Transport and Evolution of CCN in the Houston Metropolitan Area and Their Impact on Cloud Formation
G. C. Roberts, K. Ranjbar, L. Nichman, M. Wolde, C. S. McCluskey, A. Takeishi, R. Patnaude, S. Patil, G. M. McFarquhar, P. Kollias
Journal of Geophysical Research: Atmospheres Published: 28 June 2026
DOI:https://doi.org/10.1029/2025JD044628
Abstract
The Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) campaign aimed to untangle the impacts of contrasting aerosol sources on cloud microphysical properties within deep convective cells using airborne observations with the National Research Council Canada (NRC) Convair CV-580 research aircraft. Horizontal and vertical gradients of aerosol number size distributions, total aerosol concentrations and cloud condensation nuclei (CCN) spectra were measured in the lower troposphere to quantify the impact of different aerosol sources on aerosol-cloud interactions. This study focuses on a research flight dedicated to characterizing the aerosol and CCN properties in the Houston Metropolitan region and identifies five main categories of aerosols based on characteristics of aerosol number size distributions, their CCN properties and meteorological conditions. These categories encompassed more than two orders of magnitude differences in aerosol and CCN concentrations, yet their hygroscopic properties remained similar. Aerosol number size distributions and effective hygroscopicity parameters are used to generate continuous CCN spectra to represent the major aerosol types. The different CCN spectra are then incorporated into a 1-D aerosol-cloud parcel model using a large range of updrafts selected in the range of those observed during the ESCAPE campaign to assess the impact of the major aerosol sources in Houston on deep convective cloud microphysical properties.
Plain Language Summary
The ESCAPE (Experiment of Sea Breeze Convection, Aerosols, Precipitation, and Environment) campaign identified the different sources of air pollution in and around Houston and how these sources impact cloud formation and rain. Scientists used an instrumented research aircraft to fly over the metropolitan area and identified five main categories of polluted air, which varied widely in concentration and cloud-forming ability. Using these findings, we show how a simple cloud model predicts the impact of aerosols on cloud growth in deep convection. These findings contrast how clean marine and polluted air impacts weather and climate.
準定常状態の過飽和度：ESCAPEから得られた高い値は、実際の高い過飽和度と凝縮活性化の可能性を表しているのだろうか？ Quasi-Steady State Supersaturation: Do High Values Derived From ESCAPE Represent Real High Supersaturations and the Potential for Condensational Invigoration?
Saurabh Patil, Greg McFarquhar, Yongjie Huang, Gregory Roberts, Mengistu Wolde, Leonid Nichman, Cuong M Nguyen, Keyvan Ranjbar, Natalia Bliankinshtein, Amanda Richter, Pavlos Kollias, and Daniel Rosenfeld
Journal of Geophysical Research: Atmospheres Published: 10 June 2026
DOI:https://doi.org/10.1029/2025JD045547
Abstract
Deep convective clouds were intensively sampled during the Experiment of Sea Breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE) with coordinated flights of the NRC Convair-580 and SPEC Learjet. A total of 219 updraft core segments were sampled over coastal Texas and Louisiana under diverse meteorological conditions. Median updraft properties included widths of ∼1 km, velocities of 4.8 m s−1, droplet number concentrations of ∼400 cm−3, and liquid water contents of 0.9 g m−3. The limitations of using the quasi-steady state approximation to derive supersaturations were explored. Supersaturation (SQSS) estimated from in situ observations under a quasi-steady state assumption averaged 0.4% but occasionally exceeded 2%, with values >1% (high supersaturations) identified as statistical outliers. Two case studies illustrated the conditions linked to high supersaturations. In a storm over the Gulf, median core SQSS reached 2.46% in the developing stage compared to 2.17% in the mature stage under similar thermodynamic conditions. In a storm over coastal Louisiana, SQSS peaked near 11% within a 13.7-m s−1 updraft, accompanied by predominantly supercooled liquid droplets at −13°C and exceptionally low diameter concentrations of 0.29 mm cm−3. Bootstrap analysis of all sampled cores showed that high supersaturations are most probable in cold and mixed-phase regimes with moderate to strong updrafts and are strongly influenced by vertical velocity and droplet number concentrations. While extreme supersaturations (∼10%) were rare, their occurrence underscores the need for targeted multiplatform observations to resolve their spatiotemporal variability and assess their potential role in deep convective invigoration.
Plain Language Summary
Scientists studied thunderstorms along the Texas and Louisiana coasts using research aircraft. They found that most of the rising air currents, or updrafts, were about a kilometer wide and carried large amounts of water upward at average speeds near 5 m per second. Most updrafts showed only slightly higher humidity than saturation, known as supersaturation, but a few cases revealed much higher excesses. In one Gulf storm, a developing cell contained higher supersaturation than a nearby mature cell. In a Louisiana storm, supersaturation briefly reached 11 percent within a strong updraft, allowing liquid water to persist at very low temperatures. Although rare, these brief but extreme conditions may play an important role in storm intensification in polluted environments. Because they are short-lived and difficult to measure, more coordinated aircraft and instrument observations are needed to better understand their impact on extreme weather.
雲における乾燥空気の巻き込みによって生じる不均一混合の支配的な特徴の解釈 Interpreting the dominant signature of inhomogeneous mixing resulting from dry-air entrainment in clouds
Nithin Allwayin, Gregory Roberts, Elise Rosky, Kenny Bala, […] , and Raymond A. Shaw
Science Advances Published:20 May 2026
DOI:https://doi.org/10.1126/sciadv.aeb6751
Abstract
How cloud droplets evaporate when mixed with the dry surrounding air is fundamental to cloud optical properties and lifetime. We find from observations in cumulus clouds made during the ESCAPE field campaign that this mixing process appears strongly inhomogeneous-like, where a subset of droplets evaporate completely as mixing proceeds, rather than all droplets partially evaporating. We visualize the microphysical properties in a two-dimensional evaporation-phase-relaxation space and find that a diffusive turbulent-evaporation model is able to capture the dynamic evolution of the entrainment process. The results indicate that the first evaporating droplets humidify the region around the cloud so that the unmixed dry air rarely reaches the core, explaining why most mixing events appear inhomogeneous. A mixing slope parameter also confirms the nature of the mixing process. On the basis of the inhomogeneous mixing model, we propose a simple parameterization of cloud optical properties suitable for coarse-resolution models.
