17 research outputs found
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Does localized recharge occur at a discharge area within the ground-water flow system of Yucca Mountain, Nevada?
Studies done in 1984, at a central site on Franklin Lake playa (also known as Alkali Flat, a major discharge area of the ground-water flow system that includes Yucca Mountain, Nevada, the potential site of a high-level nuclear-waste repository) yield limited hydraulic-head and hydrochemical data from a 3-piezometer nest which indicated a slightly downward hydraulic gradient ({minus}0.02) and decreasing concentration of dissolved solids with increasing depth. Hydraulic-head measurements in June, 1989 made at the piezometer nest showed a substantially larger downward gradient ({minus}0.10) and a 0. 83{minus}meter higher water level in the shallowest piezometer (3.29 meters deep), indicating the possibility of localized recharge. during the period of September-November, 1989, a multilevel sampler was used to obtain detailed hydrochemical profiles of the uppermost 1. 5 m of the saturated zone
Drizzle formation in stratocumulus clouds: effects of turbulent mixing
The mechanism of drizzle formation in shallow stratocumulus clouds and the
effect of turbulent mixing on this process are investigated. A
Lagrangian–Eularian model of the cloud-topped boundary layer is used to
simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The model contains ~ 2000 air parcels that are advected in a
turbulence-like velocity field. In the model all microphysical processes are
described for each Lagrangian air volume, and turbulent mixing between the
parcels is also taken into account. It was found that the first large drops
form in air volumes that are closest to adiabatic and characterized by high
humidity, extended residence near cloud top, and maximum values of liquid
water content, allowing the formation of drops as a result of efficient
collisions. The first large drops form near cloud top and initiate drizzle
formation in the cloud. Drizzle is developed only when turbulent mixing of
parcels is included in the model. Without mixing, the cloud structure is
extremely inhomogeneous and the few large drops that do form in the cloud
evaporate during their sedimentation. It was found that turbulent mixing can
delay the process of drizzle initiation but is essential for the further
development of drizzle in the cloud
Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing
Evolution of monodisperse and polydisperse droplet size distributions (DSD)
during homogeneous mixing is analyzed. Time-dependent universal analytical
expressions for supersaturation and liquid water content are derived. For an
initial monodisperse DSD, these quantities are shown to depend on a sole
non-dimensional parameter. The evolution of moments and moment-related
functions in the course of homogeneous evaporation of polydisperse DSD is
analyzed using a parcel model.<br><br>It is shown that the classic conceptual scheme, according to which
homogeneous mixing leads to a decrease in droplet mass at constant droplet
concentration, is valid only in cases of monodisperse or initially very
narrow polydisperse DSD. In cases of wide polydisperse DSD, mixing and
successive evaporation lead to a decrease of both mass and concentration, so
the characteristic droplet sizes remain nearly constant. As this feature is
typically associated with inhomogeneous mixing, we conclude that in cases of
an initially wide DSD at cloud top, homogeneous mixing is nearly
indistinguishable from inhomogeneous mixing
The sources of extreme precipitation predictability; the case of the ‘Wet’ Red Sea Trough
Extreme precipitation events inflict detrimental socio-economic impacts in the Eastern Mediterranean. These are mainly associated with Mediterranean cyclones or the ‘Wet’ Red Sea Trough (WRST). The region's weather forecasters consider the second challenging to forecast, even just a few days in advance. Here, we study the dynamic and thermodynamic factors influencing the intrinsic predictability of WRST events. With this aim, we combine insights from traditional atmospheric analysis techniques, Lagrangian air-parcel backward trajectories, and dynamical systems theory. The latter describes atmospheric states via their local dimension (d) and inverse persistence (θ), which inform us of the intrinsic predictability of the atmosphere in phase space. We compare WRST events of low (upper decile of d and θ) with high (lower decile of d and θ) predictability. We argue that low-predictability events display a significantly different atmospheric pattern. Moreover, the low-predictability events show significantly higher daily precipitation rates, more extensive spatial spread, and greater precipitation variability among events than more predictable ones. On average, low predictability events are initiated by two distinct moisture sources with different water vapor content. We conclude that the dynamical systems framework may become a valuable tool to improve the forecast of extreme precipitation events associated with the WRST by providing a priori information on their intrinsic predictability. We foresee successfully implementing such a framework for other extreme weather events and regions