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1.
Abstract

A three-dimensional Environmental Fluid Dynamics Code model was developed for a 17-km segment of the Mobile River, Alabama, USA. The model external forcing factors include river inflows from upstream, tides from downstream, and atmospheric conditions. The model was calibrated against measured water levels, velocities, and temperatures from 26 April to 29 August 2011. The Nash-Sutcliffe coefficients for water levels were greater than 0.94 and for water temperatures ranged from 0.88 to 0.99. The calibrated model was extended approximately 13 km upstream for simulating unsteady flow, dye, and temperature distributions in the Mobile River under different upstream inflows and downstream harmonic tides. Velocity profiles and distributions of flow, dye, and temperature at various locations were analyzed and show that flow recirculation could only occur under small inflow (50 m3 s-1) when downstream tides control the flow pattern in the Mobile River. The model results reveal complex interactions among discharges from a power plant, inflows, and tides.
Editor D. Koutsoyiannis; Associate editor D. Yang  相似文献   

2.
Rainfall–runoff modelling was conducted to estimate the flows that Latonyanda River contribute to Luvuvhu River downstream of Albasini Dam. The confluence of Latonyanda and Luvuvhu Rivers is ungauged. The contributed flows compensate for upstream water abstractions and periodic lack of releases from Albasini Dam. The flow contributions from tributaries to Luvuvhu River are important for ecosystem sustenance, meeting downstream domestic and agricultural water demand and ecological water requirements particularly in Kruger National Park. The upper Latonyanda River Quaternary Catchment (LRQC), with streamflow gauging station number A9H027 was delineated and used for rainfall–runoff modelling. The simulation was done using Mike 11 NAM rainfall–runoff model. Calibration and verification runs of Mike 11 NAM rainfall–runoff model were carried out using data for periods of 4 and 2 years, respectively. The model was calibrated using shuffled complex evolution optimizer. The model efficiency was tested using coefficient of determination (R2), root mean square error (RMSE), overall water balance error (OWBE) and percentage bias (PBIAS). The model parameters obtained from the upper LRQC were transferred and used together with rainfall and evaporation data for 40 years period in the simulation of runoff for the LRQC. The flows that Latonyanda River contribute to Luvuvhu River were computed by subtracting irrigation abstractions and runoff drained to Tshakhuma Dam from the simulated runoff time series of the LRQC. The observed and the simulated runoff showed similar trends and measures of performances for both calibration and verification runs fell within acceptable ranges. The pairs of values obtained for R2, RMSE, OWBE and PBIAS for calibration and verification were 0.86 and 0.73, 0.21 and 0.2, 2.1 and 1.3, and 4.1 and 3.4, respectively. The simulated runoff for LRQC correlated well with the areal rainfall showing that the results are reasonable. The mean and maximum daily flow contributions from the Latonyanda River are 0.91 and 49 m3/s respectively. The estimation of these ungauged flows makes it possible to plan and manage the water requirements for the downstream users.  相似文献   

3.
This study focused on the effects of upstream reservoir thermal dynamics and downstream tidal influences on temperatures in a 25-km reach of Alouette River (coastal British Columbia, Canada) below a control dam and upstream of its confluence with Pitt River. Temperature was monitored during summer 2013 using 25 sensors. Water was released from the reservoir through a low level outlet at approximately 2.7 m3 s−1, except during late spring when a higher flow was released over the dam spillway. Temperature variations in the lowest section of Alouette River, and in the lower portion of a tributary, were distinct from those further upstream due to backwatering effects associated with a semi-diurnal tide, which can cause flow reversals in Pitt River. An internal seiche was identified in the reservoir during mid-summer that resulted in oscillating releases of warmer and cooler water with an amplitude of up to 6°C and a period of approximately 12 hr. Wavelet analysis and band-pass filtering indicated that the 12-hr signal declined in strength with downstream distance, but remained detectable about 15 km below the dam. In contrast, the 24-hr diel signal increased in strength with distance below the dam. Travel times computed via cross-correlation of the 12-hr signals with that at the low level outlet were within ±10% of those estimated from measured mean velocities. Lagrangian tracking of water parcels using the derived travel times indicated that the cooling effect of periodic releases of cold water during the seiching period persisted to the lower extent of the non-tidal reach. The tidally influenced locations experienced higher temperatures than those recorded in the non-tidal portion of Alouette River, although the relative roles of heating in the upstream tidal reach versus upstream advection of water associated with tide-driven flow reversals in Pitt River require further study.  相似文献   

4.
Abstract

The Colorado River is one of the most highly regulated and extensively utilized rivers in the world. Total reservoir storage is approximately four times the mean annual runoff of ?17 × 109 m3 year?1. Reservoir storage and regulation have decreased annual peak discharges and hydroelectric power generation has increased daily flow variability. In recent years, the incidental impacts of this development have become apparent especially along the Colorado River through Grand Canyon National Park downstream from Glen Canyon Dam and caused widespread concern. Since the completion of Glen Canyon Dam, the number and size of sand bars, which are used by recreational river runners and form the habitat for native fishes, have decreased substantially. Following an extensive hydrological and geomorphic investigation, an experimental flood release from the Glen Canyon Dam was proposed to determine whether sand bars would be rebuilt by a relatively brief period of flow substantially greater than the normal operating regime. This proposed release, however, was constrained by the Law of the River, the body of law developed over 70 years to control and distribute Colorado River water, the needs of hydropower users and those dependent upon hydropower revenues, and the physical constraints of the dam itself. A compromise was reached following often difficult negotiations and an experimental flood to rebuild sand bars was released in 1996. This flood, and the process by which it came about, gives hope to resolving the difficult and pervasive problem of allocation of water resources among competing interests.  相似文献   

5.
Hydrodynamic flow fields affect the ecological processes such as the water diversity and the distribution of organisms. Understanding the hydrodynamic and ecological processes is critical for the restoration and protection of especially fragile ecological habitats in river systems. This study uses turbulent flow to characterize the ecological behaviour of Chinese Sturgeon (Acipenser sinensis) in the Yangtze River. The Delft3D‐Flow model, which is first validated with field‐measured data, is used to simulate the flow field within spawning habitats of Chinese Sturgeon, downstream of Gezhouba Dam. The model‐simulated turbulent kinetic energy (TKE) and its distribution pattern are then used to characterize the hydraulic environment of the fish's spawning habitat. For the spawning habitat, downstream of Gezhouba Dam, the lower limit of TKE for the Chinese Sturgeon egg mass field is 0.025 m2/s2, which occurs at a velocity less than 1.7 m/s. Chinese Sturgeon prefers habitats with TKE range of 0.010 ~ 0.015 m2/s2 for resting. This suggests that discharge regimes provide the basis for ecological regulation of the Three Gorges Reservoir and the scientific reference for river management. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

6.
“The Ekman Drain”: a conduit to the deep ocean for shelf material   总被引：1，自引：1，他引：0  
A long (167 days) acoustic Doppler current profiler time series from the European continental slope west of Scotland has been analysed to investigate the influence of bathymetric steering on the slope current and the extent of down-slope transport in the bottom boundary layer. Within an interior region between the surface and bottom boundary layers, the direction of the flow is found to be remarkably consistent as required by the Taylor-Proudman theorem for geostrophic flow. The mean value of this interior flow direction is taken to be the effective direction of the bathymetry in controlling the geostrophic flow and so defines the rotation of coordinates required to determine along and cross-flow transports. Within a bottom boundary layer (BBL) of thickness ~100 m, the direction of the flow was deflected increasingly to the left with the mean veering angle ~12.5° at 12 mab and a down-slope speed of 2.6 cm s?1. The corresponding integrated transport (the “Ekman drain”) had an average value of ~1.6 m2 s?1 over the full observation period. This down-slope flow was significantly correlated (at 0.1 % level), with the stress applied by the along-slope flow although with considerable scatter (r.m.s. ~1 m2 s?1) which suggests the influence of other forcing mechanisms. Combining the BBL volume transport with an estimate of the mean concentration of suspended particulate material indicates an annual down-slope flux of 3.0?±?0.6 tonnes m?1 year?1, of which ~0.36?±?0.1 tonnes m?1 year?1 is carbon. Biogeochemical measurements indicate that the carbon flux in the Ekman drain predominates over settlement of organic material through the water column over the slope and provides for relatively rapid delivery of material to deep water.  相似文献   

7.
Abstract

Mosul Dam is one of the biggest hydraulic structures in Iraq. Its storage capacity is 11.11 × 109 m3 at a maximum operation level of 330 m a.s.l. The dam became operational in 1986 and no survey has been conducted to determine its storage capacity and establish new operational curves since this date. A topographic map of scale 1:50 000 dated 1983 was converted into triangulated irregular network (TIN) format using the ArcGIS program to evaluate the operational curves. Then the reservoir was surveyed in 2011 to establish the reduction in its storage capacity and to develop new operational curves. The results indicated that the reduction in the storage capacity of the reservoir was 14.73%. This implies that the rate of sedimentation within the reservoir was 45.72 × 106 m3 year?1. These results indicate that most of the sediment was deposited within the upper zone of the reservoir where the River Tigris enters the reservoir.

Editor D. Koutsoyiannis

Citation Issa, E.I., Al-Ansari, N., and Knutsson, S., 2013. Sedimentation and new operational curves for Mosul Dam, Iraq. Hydrological Sciences Journal, 58 (7), 1456–1466.  相似文献   

8.
We assessed the effectiveness of pulse flows in facilitating the upstream migration of an imperiled summer-run Chinook salmon (Oncorhynchus tshawytscha) stock in the Puntledge River, BC, Canada. During July and August, over 3 years, we tracked radio-tagged fish (n = 100) in a reach of the Puntledge River where water is diverted for power generation, resulting in stable low flows that are believed to impede migration. Over the course of  13 pulse flows, we measured migration rate, passage rate at natural barriers that are difficult to pass during low flows, movement away from the turbine outlet pool that creates distracting flows, and locomotor activity. Mean river flow during the peak of the pulses varied from 12.1 to 42.5 m3 s?1 and was at least 6.1 m3 s?1 above residual base flows. Typically, the pulse flows lasted 48 h. Migration rate was higher during some pulse flows, but results varied among pulses. Passage at natural barriers was only higher during an abnormal pulse where flows reached twice that of the prescribed flow (i.e., 24+ m3 s?1). Some fish moved away from the turbine outlet pool during pulse flows. Pulse flows did not affect fish activity levels, as measured by electromyogram telemetry. Although the effect of pulsed flows on the migration of the Puntledge River summer-run Chinook salmon was unclear, no negative impacts, such as hyperactivity or downstream displacement were observed. The use of pulse flows as a management tool still requires further research.  相似文献   

9.
Motivated by field studies of the Ems estuary which show longitudinal gradients in bottom sediment concentration as high as O(0.01 kg/m4), we develop an analytical model for estuarine residual circulation based on currents from salinity gradients, turbidity gradients, and freshwater discharge. Salinity is assumed to be vertically well mixed, while the vertical concentration profile is assumed to result from a balance between a constant settling velocity and turbulent diffusive flux. Width and depth of the model estuary are held constant. Model results show that turbidity gradients enhance tidally averaged circulation upstream of the estuarine turbidity maximum (ETM), but significantly reduce residual circulation downstream, where salinity and turbidity gradients oppose each other. We apply the condition of morphodynamic equilibrium (vanishing sediment transport) and develop an analytical solution for the position of the turbidity maximum and the distribution of suspended sediment concentration (SSC) along a longitudinal axis. A sensitivity study shows great variability in the longitudinal distribution of suspended sediment with the applied salinity gradient and six model parameters: settling velocity, vertical mixing, horizontal dispersion, total sediment supply, fresh water flow, and water depth. Increasing depth and settling velocity move the ETM upstream, while increasing freshwater discharge and vertical mixing move the ETM downstream. Moreover, the longitudinal distribution of SSC is inherently asymmetric around the ETM, and depends on spatial variations in the residual current structure and the vertical profile of SSC.  相似文献   

10.
The response of tidal and residual currents to small-scale morphological differences over abrupt deep-sea topography (Seine Seamount) was estimated for bathymetry grids of different spatial resolution. Local barotropic tidal model solutions were obtained for three popular and publicly available bathymetry grids (Smith and Sandwell TOPO8.2, ETOPO1, and GEBCO08) to calculate residual currents from vessel-mounted acoustic Doppler current profiler (VM-ADCP) measurements. Currents from each tidal solution were interpolated to match the VM-ADCP ensemble times and locations. Root mean square (RMS) differences of tidal and residual current speeds largely follow topographic deviations and were largest for TOPO8.2-based solutions (up to 2.8 cm?s?1) in seamount areas shallower than 1,000 m. Maximum RMS differences of currents obtained from higher resolution bathymetry did not exceed 1.7 cm?s?1. Single depth-dependent maximum residual flow speed differences were up to 8 cm?s?1 in all cases. Seine Seamount is located within a strong mean flow environment, and RMS residual current speed differences varied between 5 % and 20 % of observed peak velocities of the ambient flow. Residual flow estimates from shipboard ADCP data might be even more sensitive to the choice of bathymetry grids if barotropic tidal models are used to remove tides over deep oceanic topographic features where the mean flow is weak compared to the magnitude of barotropic tidal, or baroclinic currents. Realistic topography and associated flow complexity are also important factors for understanding sedimentary and ecological processes driven and maintained by flow–topography interaction.  相似文献   

11.
Dam removals with unmanaged sediment releases are good opportunities to learn about channel response to abruptly increased bed material supply. Understanding these events is important because they affect aquatic habitats and human uses of floodplains. A longstanding paradigm in geomorphology holds that response rates to landscape disturbance exponentially decay through time. However, a previous study of the Merrimack Village Dam (MVD) removal on the Souhegan River in New Hampshire, USA, showed that an exponential function poorly described the early geomorphic response. Erosion of impounded sediments there was two‐phased. We had an opportunity to quantitatively test the two‐phase response model proposed for MVD by extending the record there and comparing it with data from the Simkins Dam removal on the Patapsco River in Maryland, USA. The watershed sizes are the same order of magnitude (102 km2), and at both sites low‐head dams were removed (~3–4 m) and ~65 000 m3 of sand‐sized sediments were discharged to low‐gradient reaches. Analyzing four years of repeat morphometry and sediment surveys at the Simkins site, as well as continuous discharge and turbidity data, we observed the two‐phase erosion response described for MVD. In the early phase, approximately 50% of the impounded sediment at Simkins was eroded rapidly during modest flows. After incision to base level and widening, a second phase began when further erosion depended on floods large enough to go over bank and access impounded sediments more distant from the newly‐formed channel. Fitting functional forms to the data for both sites, we found that two‐phase exponential models with changing decay constants fit the erosion data better than single‐phase models. Valley width influences the two‐phase erosion responses upstream, but downstream responses appear more closely related to local gradient, sediment re‐supply from the upstream impoundments, and base flows. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

12.
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13.
Temperature plays an essential role in the ecology and biology of aquatic ecosystems. The use of dams to store and subsequently re-regulate river flows can have a negative impact on the natural thermal regime of rivers, causing thermal pollution of downstream river ecosystems. Autonomous thermal loggers were used to measure temperature changes downstream of a large dam on the Macquarie River, in Australia’s Murray-Darling Basin to quantify the effect of release mechanisms and dam storage volume on the downstream thermal regime. The magnitude of thermal pollution in the downstream river was affected by different release mechanisms, including bottom-level outlet releases, a thermal curtain (which draws water from above the hypolimnion), and spill-way release. Dam storage volume was linked to the magnitude of thermal pollution downstream; high storage volumes were related to severe thermal suppressions, with an approximate 10 °C difference occurring when water originated from high and low storage volumes. Downstream temperatures were 8 ̶ 10 °C higher when surface releases were used via a thermal curtain and the spillway to mitigate cold water pollution that frequently occurs in the river. Demonstrating the effectiveness of engineering and operational strategies used to mitigate cold water pollution highlight their potential contribution to fish conservation, threatened species recovery and environmental remediation of aquatic ecosystems.  相似文献   

14.
Abstract

Theory and experiments are presented for critically controlled flow of a layer of inviscid rotating fluid. Flow is controlled by a level passage. For a wide upstream channel of fixed depth (i.e. constant potential vorticity) the volume flux on the right-hand wall is unaffected by passage flow. This suggests that specifying Bernoulli potential on the right-hand passage wall produces a physically well-posed condition. The specification results in one less dimensionless number than was required by previous formulations to specify flow in the controlled passage. The upstream flow needs the same number as before, so that a range of upstream conditions produce exactly the same passage flow. A laboratory study is conducted using a thin layer of water under air. This is pumped in steadily at various locations in a deep rotating upstream basin, with fluid leaving through a level passage. All currents in the upstream basin cross to the left-hand wall as the current approaches the passage over a sloping bottom. The current crosses back to the right-hand wall within the passage. Velocity profiles of currents agree reasonably well with constant potential vorticity theory. To the right of the detached upstream current is a closed gyre that connects the upstream flows (that have different patterns depending on source location) with the unique passage flows. The results suggest that gyres upstream of critically controlling passages in the ocean might serve as adjustment regions between the relatively unconstrained upstream flows and the tightly controlled passage flows.  相似文献   

15.
This study assessed the effect of the largest flood since dam regulation on geomorphic and large wood (LW) trends using LW distributions at three time periods on the 150 km long Garrison Reach of the Missouri River. In 2011, a flood exceeded 4390 m3/s for a two‐week period (705% above mean flow; 500 year flood). LW was measured using high resolution satellite imagery in summer 2010 and 2012. Ancillary data including forest character, vegetation cover, lateral bank retreat, and channel capacity. Lateral bank erosion removed approximately 7400 standing trees during the flood. Other mechanisms, that could account for the other two‐thirds of the measured in‐channel LW, include overland flow through floodplains and islands. LW transport was commonly near or over 100 km as indicated by longitudinal forest and bank loss and post‐flood LW distribution. LW concentrations shift at several locations along the river, both pre‐ and post‐flood, and correspond to geomorphic river regions created by the interaction of the Garrison Dam upstream and the Oahe Dam downstream. Areas near the upstream dam experienced proportionally higher rates of bank erosion and forest loss but in‐channel LW decreased, likely due to scouring. A large amount of LW moved during this flood, the chief anchoring mechanism was not bridges or narrow channel reaches but the channel complexity of the river delta created by the downstream reservoir. Areas near the downstream dam experienced bank accretion and large amounts of LW deposition. This study confirms the results of similar work in the Reach: despite a historic flood longitudinal LW and channel trends remain the same. Dam regulation has created a geomorphic and LW pattern that is largely uninterrupted by an unprecedented dam regulation era flood. River managers may require other tools than infrequent high intensity floods to restore geomorphic and LW patterns. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

16.
We have used a suite of remotely sensed data, numerical lava flow modeling, and field observations to determine quantitative characteristics of the 1995 Fernandina and 1998 Cerro Azul eruptions in the western Galápagos Islands. Flank lava flow areas, volumes, instantaneous effusion rates, and average effusion rates were all determined for these two eruptions, for which only limited syn-eruptive field observations are available. Using data from SPOT, TOPSAR, ERS-1, and ERS-2, we determined that the 1995 Fernandina flow covers a subaerial area of 6.5×106 m2 and has a subaerial dense rock equivalent (DRE) volume of 42×106 m3. Field observations, ATSR satellite data, and the FLOWGO numerical model allow us to determine that the effusion rate declined exponentially from a high of ~60–200 m3 s-1 during the first few hours to <5 m3 s-1 prior to ceasing after 73 days, with a mean effusion rate of 4–16 m3 s-1. Integrating the ATSR-derived, exponentially declining effusion rate over the eruption duration produces a total (subaerial + submarine) DRE volume of between 27 and 100×106 m3, the range in values being due to differing assumptions about heat loss characteristics; only values in the higher part of this range are consistent with the independently derived subaerial volume. Using SPOT, TOPSAR, ERS-1, and ERS-2 data, we determine that the 1998 Cerro Azul flow is 16 km long, covers 16 km2, and has a DRE volume of 54×106 m3. FLOWGO produces at-vent velocity and effusion rate values of 11 m s-1 and ~600 m3 s-1, respectively. The velocity value agrees well with the 12 m s-1 estimated in the field. The mean effusion rate (total DRE volume/duration) was 7–47 m3 s-1. Dike dimensions, fissure lengths, and pressure gradients along the conduit based on magma chamber depth estimates of 3–5 km produce mean effusion rates for the two eruptions that range over nearly four orders of magnitude, the range being due to uncertainty in the magma viscosity, dike dimensions, and pressure gradient between magma chamber and vent. Although somewhat consistent with mean effusion rates from other techniques, their wide range makes them less useful. The exponentially declining effusion rates during both eruptions are consistent with release of elastic strain being the driving mechanism of the eruptions. Our results provide independent input parameters for previously published theoretical relationships between magma chamber pressurization and eruption rates that constrain chamber volumes and increases in volume prior to eruption, as well as time constants of exponential decay during the eruption. The results and theoretical relationships combine to indicate that at both volcanoes probably 25–30% of the volumetric increase in the magma chamber erupted as lava onto the surface. In both eruptions the lava flow volumes are less than 1% of the magma chamber volume.  相似文献   

17.
A theory which describes the constant f-plane flow of a steady inviscid baroclinic boundary current over a continental margin with a bathymetry that varies slowly in the alongshore but rapidly in the offshore directions is developed in the parameter regime (LD/L)2 ≤ Ro 1, where LD is the internal deformation radius, L the horizontal length scale, and Ro the Rossby number. To lowest order in the Rossby number the flow is along isobaths with speed qo = Vu(h,z)|Vh|/α, where Vu(h,z) is the upstream speed, α the upstream bottom slope at depth h, and Vh the bottom slope downstream at depth h. The lowest order flow produces a variation in the vertical component of relative vorticity along the isobath as the magnitude and direction of Vh vary in the downstream direction. The variation of vorticity requires a vertical as well as a cross-isobath flow at first order in the Rossby number. The first order vertical velocity is computed from the vorticity equation in terms of upstream conditions and downstream variations of the bathymetry. The density, pressure, and cross-isobath flow at first order in the Rossby number are then calculated. It is shown that in the cyclonic region of current (d/dh(Vu/α) > 0), if the isobaths diverge in the downstream direction ((∂/∂s)|Vh| < 0), then upwelling and onshore flow occur. The theory is applied to the northeastern Florida shelf to explain bottom temperature observations.  相似文献   

18.
Abstract

This paper distinguishes human and climate influences on the Columbia River streamflow disturbance regime, examines how this disturbance regime has changed over the last 150 years, and discusses downstream impacts. Flow management and withdrawal have greatly curtailed exceedence of the natural bankfull level of ～20 000 m3 s-1. The frequency distribution of Columbia River flow has also changed. Sediment transport is positively correlated with streamflow standard deviation, and has been greatly reduced by flow regulation. Three kinds of spring freshet style have been identified; there are also three kinds of winter freshet. Flow regulation and regional climate warming have changed freshet styles and reduced maximum flows during the spring season. Downstream effects of hydrological alterations include increased salinity intrusion length, loss of shallow water habitat area during the freshet season, increased tides throughout most of the year, and a decrease in area of the Columbia River plume during spring and summer. Although climate changes and variations have played a substantial role in changing the hydrological disturbance regime, their influence is still less than that of human manipulation of the flow cycle.

Citation Jay, D. A. & Naik, P. K. (2011) Distinguishing human and climate influences on hydrological disturbance processes in the Columbia River, USA. Hydrol. Sci. J. 56(7), 1186–1209.  相似文献   

19.
ABSTRACT

The impact of climate change on hydrology and water salinity of a valuable coastal wetland (Anzali) in northern Iran is assessed using daily precipitation and temperature data from 19 models of Coupled Model Inter-comparison Project Phase 5. The daily data are transiently downscaled using the Long Ashton Research Station Weather Generator to three climatic stations. The temperature is projected to increase by +1.6, +1.9 and +2.7°C and precipitation to decrease by 10.4%, 12.8% and 12.2% under representative concentration pathway (RCP) scenarios RCP2.6, RCP4.5 and RCP8.5, respectively. The wetland hydrology and water salinity are assessed using the water balance approach and mixing equation, respectively. The upstream river flow modelled by the Soil and Water Assessment Tool is projected to reduce by up to 18%, leading to reductions in wetland volume (154 × 106 m3), area (57.47 km2) and depth (2.77 m) by 34%, 21.1% and 20.2%, respectively, under climate change, while the mean annual total dissolved solids (1675 mg/L) would increase by 49%. The reduced volume and raised salinity may affect the wetland ecology.  相似文献   

20.
ABSTRACT

Knowledge of rainfall characteristics such as drop-size distribution is essential for the development of erosion-mitigation strategies and models. This research used an optical disdrometer to elucidate the relationships between raindrop-size distribution, median volume drop diameter (D50), kinetic energy and radar reflectivity (dBz) of simulated rainfall of different intensities. The D50 values were higher for the simulated rain than for natural rain at almost all rainfall intensities, perhaps due to variations in rainfall types and the turbulence in natural rain that breaks up large drops. The kinetic energy ranged from 26.67 to 5955.51 J m?2 h ?1, while the median volume drop diameter (D50) was in the range 1.94–7.25 mm, for intensities between 1.5 and 202.6 mm h?1. The relationship between radar reflectivity (Z) and the intensity (R) of the simulated rain was best described by a power law function (Z = aRb), with a and b coefficients in the ranges 162–706 and 0.94–2.46, respectively, throughout the range of rainfall intensities (1.5–202.6 mm h?1).  相似文献   

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