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This study investigated rapid intensification (RI, +30 kt in 24 h) and rapid weakening (RW, -20 kt in 24 h) for Typhoon Trami (2018) using the Weather Research and Forecasting V4.2 with the three-dimensional Price-Weller- Pinkel ocean model. As with the previous Typhoon Lan (2017) case study, the three-dimensional relative humidity field reproduced from Tropical Cyclones-Pacific Asian Research Campaign for the Improvement of Intensity Estimations/Forecasts dropsonde data and Himawari-8 satellite imagery was assimilated during every tropical cyclone dynamical initialization process. Specifically, dropsonde data obtained from two aircraft campaigns for Lan and Trami is used. Numerical results showed that compared to without this special data assimilation, Trami’s RI and RW simulations were better improved with this special data assimilation with respect to track and intensity forecasts. Around the RI period, vertical wind shear noticeably decreased and convective bursts (vertical velocity ≥ 3 m s-1 with 30 dBZ at 2 km height) significantly increased during the RI period. With these favorable ambient and storm inner-core environments, Trami quickly formed an eye structure. After RI and slow intensification periods, Trami eventually reached the Category 5 Saffir-Simpson hurricane scale. This maximum intensity was almost maintained until it had turned northwards. After that, as its translation speed significantly decreased, RW occurred with substantial upwelling. This upwelling caused a stable boundary layer and made significant asymmetry of surface heat fluxes and convective clouds. During this significant sea surface cooling period, deep convective cells were significantly suppressed in the eyewall area. As a result, Trami underwent RW during this period. To sum up, Trami’s RI may be associated with the reduction of negative dynamic forcing around the RI period, whereas Trami’s RW may be related to negative thermodynamic forcing by ocean cooling with a very slow translation speed during the RW period. More numerical results and detailed analyses of Trami’s RI and RW will be shown in the 2023 EGU General Assembly. Keywords: dropsonde data assimilation, tropical cyclone dynamical initialization, rapid intensification, rapid weakening, WRF atmosphere and ocean coupled model AcknowledgmentThis work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-00410.

Plasmonic nanoparticles show highly sensitive optical properties upon local dielectric environment changes. Hybridisation of plasmonic nanoparticles with active polymeric materials can allow stimuli-responsive and multiplex sensing over conventional monotonic sensing capacity. Such heterogeneous adlayers around the plasmonic core component, however, are likely to perturb the local refractive index in the nanometre regime and lead to uncertainty in its intrinsic sensitivity. Herein we prepare a series of polystyrene-grafted polyhedral gold nanoparticles, cubic and concave cubic cores, with different edge lengths and polymer thicknesses with precise synthesis control. Their localised surface plasmon resonance (LSPR) spectral changes are monitored to understand the effect of core morphological details in the interplay of nanoscale polymeric shells. Quantitative image analysis of changes in the core and shell shape contours and finite-difference time-domain simulations of the corresponding LSPR spectra and electric field distributions reveal that the magnitude of the LSPR spectral shift is closely dependent on the core morphology, polymer shell thickness and electric field intensity. We also demonstrate that the polystyrene-grafted gold concave cube displays higher sensitivity for nanoscale refractive index change in the polymer shell than the polystyrene-grafted gold cube at different temperatures. Our systematic investigation will help design polymer-composited plasmonic nanosensors for desirable applications.

This study examines the diurnal variation of the convective area and eye size of 30 rapidly intensifying tropical cyclones (RI TCs) that occurred in the western North Pacific from 2015 to 2017 utilizing Himawari-8 satellite imagery. The convective area can be divided into the active convective area (ACA), mixed phase, and inactive convective area (IACA) based on specific thresholds of brightness temperature. In general, ACA tends to develop vigorously from late afternoon to early the next morning, while mixed phase and IACA develop during the day. This diurnal pattern indicates the potential for ACA to evolve into mixed phase or IACA over time. From the 30 samples, RI TCs tend to have at least a single-completed diurnal signal of ACA inside the radius of maximum wind (RMW) during the rapidly intensifying period. In the same period, the RMW also contracts significantly. Meanwhile, more intense storms such as those of category 4 or 5 hurricane intensity are apt to have continuous ACA inside the RMW and maintain eyewall convective clouds. These diurnal patterns of the ACA could vary depending on the impact of large-scale environments such as vertical wind shear, ocean heat content, environmental mesoscale convection, and terrain. The linear regression analysis shows that from the tropical storm stage, RI commences after a slow intensification period, which enhances both the primary circulation and eyewall convective cloud. Finally, after the eye structure appears in satellite imagery, its size changes inversely to the diurnal variation of the convective activity (e.g., the eye size becomes larger during the daytime).

Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts. Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles. However, metal-organic frameworks (MOFs) have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement, although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite. Here, we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework (ZIF) through chemical etching and regrowth, followed by quantitative analysis in the core dimension and curvature. We find the nanorod core shows template-effective behavior in its morphological transformation. In the etching event, the nanorod core is spherically carved from its tips. The regrowth on the spherically etched core inside the ZIF gives rise to formation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition. We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell, intercrystalline gaps in multi-domain ZIF shells, and local structural deformation from the acidic reaction conditions.

Various nanoparticle surface layers allow unique functionalities. We developed a coating method with tetracyanoquinodimethane that forms solid layers through π stacking on gold nanorod surfaces. Its reaction mechanism was investigated with reaction time, aging time and surfactant concentration. Our method could be generalizable to different nanoparticle shapes and crystal facets.

High-resolution numerical experiments for Typhoon Megi (2010) in the western North Pacific are conducted using the Advanced Research version of the Weather Research and Forecasting (WRF) Model to understand the mechanisms of rapid intensification (RI). With a dynamically initialized vortex, sensitivity experiments are carried out focusing on the planetary boundary layer (PBL) and the following microphysics schemes: WRF single-moment 6-class (WSM6) and WRF double-moment 6-class (WDM6) microphysics with Yonsei University, Mellor–Yamada–Janjić (MYJ), and Mellor–Yamada–Nakanishi–Niino (MYNN) 2.5-level (MN2.5) and 3.0-level (MN3) PBL schemes. The largest differences are found between WSM6-MN3 and WDM6-MN3, and we therefore examine RI mechanisms based on the results of these experiments. Prior to RI, WDM6-MN3 shows a drier environment and stronger downdrafts in the lower troposphere than in WSM6-MN3. As a result, during the RI period, WSM6-MN3 (WDM6-MN3) significantly intensifies with the minimum sea level pressure decreasing by 51 (29) hPa and the maximum surface wind increasing by 28 (12) m s−1 in 24 h. In both experiments, the maximum values of surface heat fluxes, potential vorticity (PV), radial absolute angular momentum advection, inertial stability, supergradient wind, and convective bursts inside the radius of maximum winds are frequently observed at each vertex of polygonal eyewalls in the lower troposphere. In particular, WSM6-MN3 exhibits more convective cells inside the inner-core region, a more persistent and thicker polygonal eyewall in the lower troposphere, and a more robust vertical structure of hydrometeors and vertical velocity than WDM6-MN3. This study suggests that within the inner-core region, polygonal eyewalls like WSM6-MN3 provide favorable conditions for RI.