Hisashi Yoshikoshi

Large, unique radar echoes in a new, self-enhancing cloud seeding

1999 . The total number of ice crystals with the nucleant remains essentially constant after the moment of the nucleation. The horizontally laid ice crystal thermal in the cloud, like cumulus convection, rolls up in the form of twin cylinders and turbulently spreads with the help of the buoyant motion caused by the heat of ice crystal growth or phase . change Fukuta, 1973 . The supercooled cloud volume, slowly and continually taken into the ice thermal during the ascent, sustains the condition and time for crystal growth, the heat generation, and the buoyancy to a maximum extent in feedback. When the enlarging thermal reaches the temperature inversion, which often exists at the cloud top, the thermal spreads horizontally in an anvil shape, but the crystals there have already acquired sufficient size to fall through the supercooled cloud volume below, grow, and generate heat. The heating induces lifting of the underlying cloudy, as well as moist air,

Water and salt movement in soil driven by crop roots: a controlled column study

Water deficit and salt accumulation in soil presents serious problems to crop production in semi-arid regions. These problems depend on the active transpiration stream and the selective absorption of ions by crop roots. In this study, a large sized soil column system was used to examine the dynamics of water and ion transport and salt accumulation in soil layers. Special reference was placed on the effects of the active and selective absorption by roots of different crops (i.e., corn plants, sunflower plants and no plants). The column system was equipped with on-line systems for the control of groundwater level. Soil water content sensors enabled time-course evaluations of the volumetric water content and hence upward flux of the groundwater in the soils at different depths. Furthermore, the distribution and accumulation of ions in soil layers, plant organs and xylem sap were analyzed using ion chromatography. In this column experiment, diurnal and longer term changes in water movement and ion accumulation in soil, affected by root absorption characteristics of plants, were evaluated quantitatively. The results demonstrated that the column system was applicable for the quantitative analysis of the effects of root absorption by different crops on water deficit and salinization in soils.