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1.
Louise Nuijens Kerry Emanuel Hirohiko Masunaga Tristan L’Ecuyer 《Surveys in Geophysics》2017,38(6):1257-1282
Space-borne observations reveal that 20–40% of marine convective clouds below the freezing level produce rain. In this paper we speculate what the prevalence of warm rain might imply for convection and large-scale circulations over tropical oceans. We present results using a two-column radiative–convective model of hydrostatic, nonlinear flow on a non-rotating sphere, with parameterized convection and radiation, and review ongoing efforts in high-resolution modeling and observations of warm rain. The model experiments investigate the response of convection and circulation to sea surface temperature (SST) gradients between the columns and to changes in a parameter that controls the conversion of cloud condensate to rain. Convection over the cold ocean collapses to a shallow mode with tops near 850 hPa, but a congestus mode with tops near 600 hPa can develop at small SST differences when warm rain formation is more efficient. Here, interactive radiation and the response of the circulation are crucial: along with congestus a deeper moist layer develops, which leads to less low-level radiative cooling, a smaller buoyancy gradient between the columns, and therefore a weaker circulation and less subsidence over the cold ocean. The congestus mode is accompanied with more surface precipitation in the subsiding column and less surface precipitation in the deep convecting column. For the shallow mode over colder oceans, circulations also weaken with more efficient warm rain formation, but only marginally. Here, more warm rain reduces convective tops and the boundary layer depth—similar to Large-Eddy Simulation (LES) studies—which reduces the integrated buoyancy gradient. Elucidating the impact of warm rain can benefit from large-domain high-resolution simulations and observations. Parameterizations of warm rain may be constrained through collocated cloud and rain profiling from ground, and concurrent changes in convection and rain in subsiding and convecting branches of circulations may be revealed from a collocation of space-borne sensors, including the Global Precipitation Measurement (GPM) and upcoming Aeolus missions. 相似文献
2.
Toshimichi Ito Arata Kaneko Hiroyuki Tsubota Noriaki Gohda 《Journal of Oceanography》1994,50(4):465-477
The localized near-bottom water with silica content higher than that in the adjacent shelf water was observed to exist at the eastern margins of the East China Sea continental shelf. The core of the high silica water possessed the silica content corresponding to that in the Kuroshio at depths greater than on the shelf. The mixing analysis of water masses using temperature (T) and silica (Si) showed that the core water can be produced through the vertical mixing of intermediate water of the Kuroshio deeper than 100 m. This study provides us a conclusion that the intermediate water of the Kuroshio is strongly mixed on the shelf slope and then upwelled to form the ridge-like distribution of water masses with low temperature and high silica content at the shelf edge. 相似文献
3.
4.
Noriaki Kimura 《Journal of Oceanography》2007,63(4):685-694
This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea
ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special
Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic
processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and
sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important
role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both
advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift.
Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind
speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge. 相似文献
5.
The Kuroshio East of Taiwan and in the East China Sea and the currents East of Ryukyu Islands during early summer of 1996 总被引:6,自引:0,他引:6
Yaochu Yuan Arata Kaneko Jilan Su Xiaohua Zhu Yonggang Liu Noriaki Gohda Hong Chen 《Journal of Oceanography》1998,54(3):217-226
Using hydrographic data and moored current meter records and the ADCP observed current data during May–June 1996, a modified
inverse method is applied to calculate the Kuroshio east of Taiwan and in the East China Sea and the currents east of Ryukyu
Islands. There are three branches of the Kuroshio east of Taiwan. The Kuroshio in the East China Sea comes from the main (first)
and second branches of the Kuroshio east of Taiwan. The easternmost (third) branch of the Kuroshio flows northeastward to
the region east of Ryukyu Islands. The net northward volume transports of the Kuroshio through Section K2 southeast of Taiwan and Section PN in the East China Sea are 44.4×106 and 27.2×106 m3s−1, respectively. The western boundary current east of Ryukyu Islands comes from the easternmost branch of the Kuroshio east
of Taiwan and an anticyclonic recirculating gyre more east, making volume transports of 10 to 15×106 m3s−1. At about 21°N, 127°E southeast of Taiwan, there is a cold eddy which causes branching of the Kuroshio there. 相似文献
6.
Mesenbet Yibeltal Atsushi Tsunekawa Nigussie Haregeweyn Enyew Adgo Derege Tsegaye Meshesha Tsugiyuki Masunaga Mitsuru Tsubo Paolo Billi Kindiye Ebabu Mulatu Liyew Berihun 《地球表面变化过程与地形》2021,46(6):1209-1222
Gully erosion is a major cause of soil loss and severe land degradation in sub-humid Ethiopia. The objective of this study was to investigate the role and the effect of subsurface water level change on gully headcut retreat, gully formation and expansion in high rainfall tropical regions in the Ethiopian highlands. During the rainy seasons of 2017–2019, the expansion rate of 16 fixed gullies was measured and subsurface water levels were measured by piezometers installed near gully heads. During the study period, headcut retreats ranged from 0.70 to 2.35 m, with a mean value of 1.49 ± 0.56 m year−1, and average depth of the surface water level varied between 1.12 and 2.82 m, with a mean value of 2.62 m. Gully cross-section areas ranged from 2.90 to 20.90 m2, with an average of 9.31 ± 4.80 m2. Volumetric retreat of gully headcuts ranged from 4.49 to 40.55 m3 and averaged 13.34 ± 9.10 m3. Soil loss from individual gullies ranged from 5.79 to 52.31 t year−1 and averaged 17.21 ± 11.74 t year−1. The headcut retreat rate and sediment yield were closely related over the three study seasons. Elevated subsurface water levels facilitated the slumping of gully banks and heads, causing high sediment yield. When the soil was saturated, bank collapse and headcut retreat were favoured by the combination of elevated subsurface water and high rainfall. This study indicates that area exclosures are effective in controlling subsurface water level, thus reducing gully headcut retreat and associated soil loss. 相似文献
7.
Snowpack dynamics through October 2014–June 2017 were described for a forested, sub‐alpine field site in southeastern Wyoming. Point measurements of wetness and density were combined with numerical modeling and continuous time series of snow depth, snow temperature, and snowpack outflow to identify 5 major classes of distinct snowpack conditions. Class (i) is characterized by no snowpack outflow and variable average snowpack temperature and density. Class (ii) is characterized by short durations of liquid water in the upper snowpack, snowpack outflow values of 0.0008–0.005 cm hr?1, an increase in snowpack temperature, and average snow density between 0.25–0.35 g cm?3. Class (iii) is characterized by a partially saturated wetness profile, snowpack outflow values of 0.005–0.25 cm hr?1, snowpack temperature near 0 °C, and average snow density between 0.25–0.40 g cm?3. Class (iv) is characterized by strong diurnal snowpack outflow pattern with values as high as 0.75 cm hr?1, stable snowpack temperature near 0 °C, and stable average snow density between 0.35–0.45 g cm?3. Class (v) occurs intermittently between Classes (ii)–(iv) and displays low snowpack outflow values between 0.0008–0.04 cm hr?1, a slight decrease in temperature relative to the preceding class, and similar densities to the preceding class. Numerical modeling of snowpack properties with SNOWPACK using both the Storage Threshold scheme and Richards' equation was used to quantify the effect of snowpack capillarity on predictions of snowpack outflow and other snowpack properties. Results indicate that both simulations are able to predict snow depth, snow temperature, and snow density reasonably well with little difference between the 2 water transport schemes. Richards' equation more accurately simulates the timing of snowpack outflow over the Storage Threshold scheme, especially early in the melt season and at diurnal timescales. 相似文献
8.
Chiyoe Koike Hiroichi Hasegawa Noriaki Asada Takeshi Hattori 《Astrophysics and Space Science》1981,79(1):77-85
Extinction measurements were made for some silicate and iron-oxide mineral grains in mid- and far-infrared region. For far-infrared region, high temperature magnesium silicates such as olivine and pyroxenes show the absorption spectra of steep dependence as –3 ( being the wavelength) with some peak structure, but the spectrum of magnetite shows –1 dependence. 相似文献
9.
Observations of synoptic variability from CTD and current meter measurements in Wakasa Bay, Japan in summer of 1980 and 1981 are compared with the results of 1979 reported by Yamagata, Umatani, Masunaga and Matsuura (1984). It is suggested that the speed and direction of propagation can basically be explained in terms of shelf wave dynamics.In the 1980 event, a dense (colder and more saline) water advanced eastward along the north coast at about 10 km day−1. The lateral scale of the phenomenon was about 30 to 40 km, in agreement with the Rossby internal radius of deformation. The T-S and current data suggest that the 1980 cold event was dominated by phase propagation. In the 1981 event, a light (warmer and less saline) water area advanced eastward at the speed similar to the 1980 cold event, but the T-S and current data suggest that Lagrangian drift of water particles associated with strong eddy motions was not negligible. 相似文献
10.
Time-dependent cross-flow was studied around cylinders with circular and noncircular cross-sections. The numerical approach for the analysis was a low-order panel method based on constant source and dipole values along each panel. The method was previously used successfully for several applications, such as calculation of the added mass and damping coefficients. In simulating the viscous time-dependent flow around the cylinder, the time-dependent wake feature of the code was used. For the circular and D-cylinders, the results agreed well with the experiments. Suggestions for improving the results for T-cylinders with angle of attack are included. 相似文献