This study focused on an explosive cyclone migrating along the southern periphery of the Kuroshio/ Kuroshio Extension in the middle of January 2013 and examined how those warm currents played an active role in the rapid development of the cyclone using a high-resolution coupled atmosphere-ocean regional model. The evolutions of surface fronts of the simulated cyclone resemble the Shapiro-Keyser model. At the time of the maximum deepening rate, strong mesoscale diabatic heating areas appear over the bent-back front and the warm front east of the cyclone center. Diabatic heating over the bent-back front and the eastern warm front is mainly induced by the condensation of moisture imported by the cold conveyor belt (CCB) and the warm conveyor belt (WCB), respectively. The dry air parcels transported by the CCB can receive large amounts of moisture from the warm currents, whereas the very humid air parcels transported by the WCB can hardly be modified by those currents. The well-organized nature of the CCB plays a key role not only in enhancing surface evaporation from the warm currents but also in importing the evaporated vapor into the bent-back front. The imported vapor converges at the bent-back front, leading to latent heat release. The latent heating facilitates the cyclone's development through the production of positive potential vorticity in the lower troposphere. Its deepening can, in turn, reinforce the CCB. In the presence of a favorable synoptic-scale environment, such a positive feedback process can lead to the rapid intensification of a cyclone over warm currents.
Increases of tropical cyclone intensity with global warming have been demonstrated by historical data studies and theory. This raises great concern regarding future changes in typhoon intensity. The present study addressed the problem to what extent supertyphoons will become intense in the global warming climate of the late 21st century. Very high resolution downscale experiments using a cloud-resolving model without convective parameterizations were performed for the 30 most intense typhoons obtained from the 20 km mesh global simulation of a warmer climate. Twelve supertyphoons occurred in the downscale experiments, and the most intense supertyphoon attained a central pressure of 857 hPa and a wind speed of 88 m s À1. The maximum intensity of the supertyphoon was little affected by uncertainties that arise from experimental settings. This study indicates that the most intense future supertyphoon could attain wind speeds of 85-90 m s À1 and minimum central pressures of 860 hPa.
During three winter seasons from November 2016 to March 2019, 11 gamma‐ray glows were detected at a single observation site of our ground‐based gamma‐ray monitoring network in Kanazawa, Japan. These events are analyzed with observations of an X‐band radar network, a ceilometer, a disdrometer, and a weather monitor. All the detected glows were connected to convective high‐reflectivity regions of more than 35 dBZ, developed up to an altitude of >2 km. They were also accompanied by heavy precipitation of graupels. Therefore, graupels in the lower layer of thunderclouds that correspond to high‐reflectivity regions can form strong electric fields producing gamma‐ray glows. Also, these events are compared with a limited sample of nondetection cases, but no significant differences in meteorological conditions were found between detection and nondetection cases in the present study.
A two-dimensional cloud-resolving model, including a supply of sensible and latent heat fluxes from the surface, is used to study the development of deep convective clouds over a southern region far from the Meiyu front (wet region) of eastern China. Some deep convective clouds were observed during the latter half of the GAME/HUBEX IOP (GEWEX Asian Monsoon Experiment/Huaihe River Basin Experiment Intensive Observation Periods, GEWEX: Global Energy and Water Cycle Experiment) 1998, although there is less large-scale convergence over this region. Numerical simulations reproduce the development of deep convective clouds, and their generating/decaying time. The development process of a convective mixing layer and generation of shallow convective clouds around the top of this layer are also simulated.The results of sensitivity tests on the surface land-use (i.e., the supply of the sensible and latent heat fluxes) and the relative humidity in the middle troposphere, indicate that there are two effective factors in the development of deep convective clouds over this region. One is the large amount of latent heat flux from the surface, and the other is the moist environment in the middle troposphere. The latent heat flux from the surface supplies water vapor to generate convective clouds. Paddy fields can supply a large amount of latent heat flux into the lower atmosphere and are widely distributed over this region. On the other hand, the moist environment in the middle troposphere can cause shallow convective clouds to become deep because the positive buoyancy in the shallow convective clouds is not lost by the evaporation cooling of the entrained air mass. Additionally, this moist environment in the middle troposphere is formed by the development of shallow convective clouds, which transport water vapor from the convective mixing layer.
Stearoyl-coenzyme A desaturase-1 (SCD1) is a rate-limiting enzyme that catalyzes the biosynthesis of monounsaturated fatty acids from saturated fatty acids. Recently, SCD1 down-regulation has been implicated in the prevention of obesity, and the improvement of insulin and leptin sensitivity. In this study, we examined the effect of fucoxanthin, a marine carotenoid, on hepatic SCD1 in obese mouse models of hyperleptinemia KK-A(y) and leptin-deficiency ob/ob. In KK-A(y) mice, providing a diet containing 0.2 % fucoxanthin for 2 weeks markedly suppressed SCD1 mRNA and protein expressions in the liver. The fatty acid composition of liver lipids was also affected by an observed decrease in the ratio of oleic acid to stearic acid. Furthermore, serum leptin levels were significantly decreased in hyperleptinemia KK-A(y) mice after 2 weeks of fucoxanthin feeding. However, the suppressive effects of fucoxanthin on hepatic SCD1 and body weight gain were not observed in ob/ob mice. These results show that fucoxanthin down-regulates SCD1 expression and alters fatty acid composition of the liver via regulation of leptin signaling in hyperleptinemia KK-A(y) mice but not in leptin-deficient ob/ob mice.
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