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Abstract Tropical cyclones (TCs) are often generated from preexisting “seed” vortices. Seeds with higher persistence might have a higher chance to undergo TC genesis. What controls seed persistence remains unclear. This study proposes that planetary Rossby wave drag is a key factor that affects seed persistence. Using recently developed theory for the response of a vortex to the planetary vorticity gradient, a new parameter given by the ratio of the maximum wind speed (V_max) to the Rhines speed at the radius of maximum wind (R_max), here termed “vortex structural compactness” (C_υ), is introduced to characterize the vortex weakening by planetary Rossby wave drag. The relationship between vortex compactness and weakening rate is tested via barotropicβ-plane experiments. The vortex’s initialC_υis varied by systematically varying their initialV_maxandR_maxin idealized wind profile models. Experiments are also conducted with real-world seed vortices from reanalysis data, which possess natural compactness variability. The weakening rate depends strongly on the vortex’s initialC_υacross both idealized and real-world experiments, and the initial axis-asymmetry introduces minor differences. Experiments doubling the size of seed vortices cause them to weaken more rapidly, in line with other experiment sets. The dependence of the weakening rate on initial compactness can be predicted from a simple theory, which is more robust for more compact vortices. Our results suggest that a seed’s structure strongly modulates how long it can persist in the presence of a planetary vorticity gradient. Connections to real seeds on Earth are discussed. Significance StatementThis study explores the evolution of tropical cyclone (TC) seeds, which are preexisting weakly rotating rainstorms, in a simple setting that isolates the dynamical effects of the rotating sphere. It is not clear why some seeds can persist for a longer duration and might have a higher chance to eventually undergo genesis. We proposed that a factor called “planetary Rossby wave drag” plays a crucial role in this process. To investigate this, we introduce a new parameter called “compactness” to describe how the size and intensity of a seed vortex determines how quickly it will weaken due to this drag. We conducted experiments with numerical simulations and real-world TC seeds to test our ideas. Our findings show that the initial compactness of seeds strongly influences how quickly they weaken. We have developed a formula to predict how quickly these seeds weaken based on their compactness, which is especially accurate for more compact seeds. This research helps us understand how planetary Rossby wave drag affects the persistence of a TC seed and, ultimately, how it might impact the frequency of TCs. 

Abstract Tropical cyclones are known to expand to an equilibrium size on thefplane, but the expansion process is not understood. In this study, an analytical model for tropical cyclone outer-size expansion on thefplane is proposed. Conceptually, the storm expands because the imbalance between latent heating and radiative cooling drives a lateral inflow that imports absolute vorticity. Volume-integrated latent heating increases more slowly with size than radiative cooling, and hence, the storm expands toward an equilibrium size. The predicted expansion rate is given by the ratio of the difference in size from its equilibrium valuer_t,eqto an environmentally determined time scaleτ_rtof 10–15 days. The model is fully predictive if given a constantr_t,eq, which can also be estimated environmentally. The model successfully captures the first-order size evolution across a range of numerical simulation experiments in which the potential intensity andfare varied. The model predictions of the dependencies of lateral inflow velocity and expansion rate on latent heating rate are also compared well with numerical simulations. This model provides a useful foundation for understanding storm size dynamics in nature. 

ABSTRACT Reactive small-molecule probes are widely used for RNA structure probing, however current approaches largely measure average RNA transcript dynamics and do not resolve structural differences that occur during folding or transcript maturation. Here, we present SNIPER-seq, an RNA structure probing method relying upon metabolic labeling with 2’-aminodeoxycytidine, structure-dependent 2’-amino reaction with an aromatic isothiocyanate, and high-throughput RNA sequencing. Our method maps cellular RNA structure transcriptome-wide with temporal resolution enabling determination of transcript age-dependent RNA structural dynamics. We benchmark our approach against known RNA structures and investigate the dynamics of human 5S rRNA during ribosome biogenesis, revealing specific structural changes in 5S rRNA loops that occur over the course of several hours. Taken together, our work sheds light on the maturation and coordinated conformational changes that take place during ribosome biogenesis and provides a general strategy for surveying evolving RNA structural dynamics across the transcriptome. 

Abstract A model for tropical cyclone (TC) potential size (PS), which is capable of predicting the equilibrium outer radius of a TC solely from environmental parameters, is proposed. The model combines an updated Carnot cycle model with a physical model for the wind profile, which serve as energetic and dynamic constraints, respectively, on the minimum pressure. Physically, the Carnot cycle model defines how much the surface pressure can be dropped energetically, and the wind profile model defines how large the steady-state storm needs to be to yield that pressure drop for a given maximum wind speed. The model yields an intrinsic length scale V Carnot / f , with f the Coriolis parameter, V Carnot similar to the potential intensity V p , but without a dependence on the surface exchange coefficients of enthalpy C k and momentum C d . Analytic tests with the theory varying outflow temperature, sea surface temperature (SST), and f demonstrate that the model predictions are qualitatively consistent with the V p / f scaling for outer size found in past work. The model also predicts a weak dependence of outer size on C d , C k , and horizontal mixing length l h of turbulence, consistent with numerical simulation results. Idealized numerical simulation experiments with varied tropopause temperature, SST, f , C d , C k , and l h show that the model performs well in predicting the simulated outer radius. The V Carnot / f scaling also better captures the dependence of simulated TC size on SST than V p / f . Overall, the model appears to capture the essential physics that determine equilibrium TC size on the f plane. 

High-temperature poling eliminates light-scattering domain walls in a relaxor ferroelectric.