roll convection within an arctic cold air outbreak interpretation of in situ aircraft measurements and spaceborne sar imagery by a three dimensional atmospheric model abstract atmospheric roll convection within an arctic cold air outbreak was observed over the greenland sea during the arktis 1993 experiment on 24 march 1993 by in situ aircraft measurements and synthetic aperture radar sar imagery from the first european remote sensing satellite ers 1 inside a boundary layer heated from below two kinds of rolls were observed one aligned parallel and the other perpendicular to the mean wind direction the wind parallel rolls occupied the entire boundary layer whereas the wind perpendicular rolls were confined to a region around the top of the boundary layer where a strong vertical shear in the downstream wind component was observed a three dimensional numerical model has been applied to simulate the observed convective pattern it is shown that the model does not reproduce the observed pattern when using a height constant geostrophic wind profile however when adjusting the vertical wind profile to the one measured from the aircraft the model reproduces buoya

coupled ice ocean dynamics in the marginal ice zones upwelling downwelling and eddy generation this study is aimed at modeling mesoscale processes such as upwelling downwelling and ice edge eddies in the marginal ice zones a two dimensional coupled ice ocean model is used for the study the ice model is coupled to the reduced gravity ocean model through interfacial stresses the parameters of the ocean model were chosen so that the dynamics would be nonlinear the model was tested by studying the dynamics of upwelling winds parallel to the ice edge with the ice on the right produce upwelling because the air ice momentum flux is much greater than air ocean momentum flux thus the ekman transport is greater under the ice than in the open water the stability of the upwelling and downwelling jets is discussed the downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence a constant wind field exerted on a varying ice cover will generate vorticity leading to enhanced upwelling downwelling regions i e wind forced vortices steepening and strengthening of vortices are provided by the nonlinear terms when forcing is time varying the advection terms will also redistribute the vorticity the wind reversals will separate the vortices from the ice edge so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice

reply to comments on how much does the upward advection of the supergradient component of boundary layer wind contribute to tropical cyclone intensification and maximum intensity

slab and height resolving models of the tropical cyclone boundary layer part ii why the simulations differ depth averaged or slab models of the tropical cyclone boundary layer have had important practical uses in engineering design and climatological risk assessment studies and as components of tropical cyclone potential intensity models in part i of this article such models were compared with a fully height resolving model and it was shown that there are substantial differences in the simulations this second part determines the reasons for these differences the main tool used is a new model which parametrizes the vertical structure of the boundary layer and thereby allows more accurate calculation of the surface drag and nonlinear terms it is more accurate than the slab model but of similar computational cost this model and hybrids of it and the slab model are used to determine the consequences of the approximations in slab models it was indicated in part i and is confirmed here that the excessively strong inflow and too great departure of the boundary layer mean winds from gradient balance in the slab model are due to excessive surface drag the tendency of slab models to produce quasi inertial oscillations is shown to be due to the inaccurate treatment of the vertically averaged nonlinear terms in the momentum equations in particular these oscillations are shown not to be due to the improper specification of the upper boundary condition as has recently been argued by smith and vogl the considerable deficiencies of slab models of the tropical cyclone boundary layer are therefore inherent to their formulation it is further shown that the dynamics leading to supergradient flow are different in the slab model and in the height resolving model the possible uses of linearized versions of the slab model are briefly considered copyright 2010 royal meteorological society

the kinematic structure of hurricane gloria 1985 determined from nested analyses of dropwindsonde and doppler radar data abstract a set of three dimensional filtered multiply nested objective analyses has been completed for the wind field of hurricane gloria for 0000 utc 25 september 1985 at this time gloria was one of the most intense hurricanes ever observed in the atlantic basin with a minimum sea level pressure of 919 mb the nested analyses based on observations from airborne doppler radar and omega dropwindsondes simultaneously describe eyewall and synoptic scale features and are the most comprehensive analyses of a single hurricane constructed to date the analyses have been used to document the multiscale kinematic structure of gloria and to investigate the relationship between the kinematic fields and the motion of the vortex the analyses indicate that the vortex was unusually barotropic the radius of maximum wind rmw was nearly vertical below 500 mb with a slight inward slope with height between 750 and 550 mb the strongest azimuthal mean tangential winds were found well above the boundary layer near

rewriting the climatology of the tropical north atlantic and caribbean sea atmosphere abstract the jordan mean tropical sounding has provided a benchmark reference for representing the climatology of the tropical north atlantic and caribbean sea atmosphere for over 50 years however recent observations and studies have suggested that during the months of the north atlantic hurricane season this region of the world is affected by multiple air masses with very distinct thermodynamic and kinematic characteristics this study examined 6000 rawinsonde observations from the caribbean sea region taken during the core months july october of the 1995 2002 hurricane seasons it was found that single mean soundings created from this new dataset were very similar to c l jordan s 1958 sounding work however recently developed multispectral satellite imagery that can track low to midlevel dry air masses indicated that the 1995 2002 hurricane season dataset and likely jordan s dataset as well was dominated by three distinct air masses moist tropical mt saharan air layer sal and midlatit

a coupled ice ocean mixed layer model of the marginal ice zone responding to wind forcing a free drifting thermodynamic sea ice model is coupled with a continuously stratified ocean model whose vertical mixing coefficients are determined by a turbulent closure scheme the system has variability in the cross ice edge direction while two dimensionality along ice edge homogeneity is assumed the model is initially motionless and has no horizontal variability in ocean interior whereas ice covers only a half portion a uniform wind stress is imposed suddenly to drive the coupled system the surface mixed layer is developed as time increases i e a top few tens of meters are well mixed in a day with an initial water temperature above a freezing point the fresh mixed layer forms in the ice covered portion a wind driven ice velocity is oriented to the right from the wind direction a wind with the ice to the right left looking downstream produces upwelling downwelling under the ice edge caused by a difference in ekman transport an off ice on ice wind advects the ice toward the open water ice covered area and makes the ice edge sharper gentler owing partially to faster movement in the region with higher ice concentration in the off ice wind case the mixed layer near the ice edge is shallower under development so that a melt rate is smaller than that estimated by a prescribed depth mixed layer an inertio internal gravity wave is generated by a transient variability in surface stress associated with a moving ice edge most significantly in the case of the off ice wind and enhances sharpness of the ice edge

understanding atypical midlevel wind speed maxima in hurricane eyewalls abstractin tropical cyclones tcs the peak wind speed is typically found near the top of the boundary layer approximately 0 5 1 km recently it was shown that in a few observed tcs the wind s

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

the boundary layer winds in hurricanes danielle 1998 and isabel 2003 abstract this paper describes the boundary layer wind structure and dynamics of hurricanes danielle 1998 and isabel 2003 based on the analysis of high resolution global positioning system dropwindsonde data and simulation of the flow by a three dimensional boundary layer model produced by kepert and wang the observations show that the hurricane boundary layer has a complex three dimensional structure with large variability over small distances the analysis emphasizes three aspects the degree of gradient wind balance the radially varying depth of the boundary layer and the strength of the near surface wind speed relative to that at a higher level each aspect is compared both with results obtained in a simulation of the individual storm by kepert and wang s model and with theoretical predictions the observations show that the boundary layer depth decreases toward the center of the storm consistent with theoretical arguments the strongest azimuthal winds occur near the top of but still within

evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ observations and high resolution simulations of hurricane isabel 2003 part ii inner core boundary layer and eyewall structure this is the second of a two part study of the representation of the planetary boundary layer pbl in highresolutionweatherresearchandforecastmodel wrf simulationsofhurricaneisabel 2003 theyonsei university ysu pbl parameterization and the mellor yamada janjic myj pbl parameterization are evaluated by direct comparison to in situ data obtained by research aircraft the numerical model simulation design details of the pbl schemes and the representation of the boundary layer in the outer core were presented in part i this part presents a detailed study of the inner core pbl including its axisymmetric and asymmetric structures and comparisons to analyses of dropsonde data from previous studies although neither pbl scheme was designed specifically for hurricane conditions their simulated boundary layers are reasonably good representations of the observed boundary layer both schemes reproduce certain unique features of the hurricane boundary layer such as the separate depths of the well mixed layer and the inflow layer and the pronounced wind speed maxima near the top of the inflow layer modification of the original ysu and myj schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes even with these improvements the myj consistently produces larger frictional tendencies in the boundary layer than the ysu scheme leading to a stronger lowlevel inflow and a stronger azimuthal wind maximum at the top of the boundary layer for both schemes differences in the low level asymmetries between the simulated and observed wind fields appear to be related to eyewall asymmetries forced by environmental wind shear the effects of varying horizontal and vertical resolutions are also considered increasing the vertical resolution in the pbl results in minor improvements in the inner core structures increasing the horizontal resolution around the eyewall also leads to improved boundary layers as well as an improvement of the vertical structure of the inner core wind field a summary and discussion of the results of both parts i and ii is provided

a geosat altimeter wind speed algorithm and a method for altimeter wind speed algorithm development a geosat altimeter wind speed algorithm is derived by cross calibrating geosat and seasat altimeter estimates of the normalized radar cross section 0 and modifying an existing seasat altimeter wind speed model function to obtain a model function appropriate for geosat observations it is argued that the 0 distribution measured by an altimeter is relatively stable over a sufficiently large geographical region and a long enough time period systematic differences between 0 estimates from two altimeters can therefore be identified based on comparisons of their 0 histograms any such systematic differences can then be corrected using independent 0 estimates when this method is applied to the geosat and seasat altimeters a systematic difference between the two 0 histograms is shown to be consistent with differences between seasat altimeter and nadir seasat scatterometer estimates of 0 deduced independently by a previous study this supports the conclusions that 1 the 0 distribution is stable and 2 the seasat altimeter estimates of 0 were miscalibrated after modifying the existing seasat altimeter wind speed algorithm to account for this apparent 0 error the resulting geosat estimates of wind speed agree with high quality buoy observations to within an rms difference of less than 2 m s

mixing of event and pre event water in a shallow entisol in sloping farmland based on isotopic and hydrometric measurements sw china

wind induced mesoscale features in a coupled ice ocean system a quasi geostrophic mesoscale eddy resolving model is coupled with free drifting sea ice to examine mesoscale oceanic structures which are induced by wind forcing on a nonuniform ice distribution and redistribution of sea ice initial concentration of sea ice has anomalies on the motionless ocean and the sea ice is suddenly forced by a wind stress differences in ekman transport between the high low concentration area and the surrounding area generate dipole eddylike features in the ocean with anticyclonic and cyclonic eddies on the right left and left right respectively looking in the downwind direction redistribution of ice by the ocean circulation continues after the wind ceases forming arch or hammer head shapes of ice anomalies interactions with the other anomalies can produce various shapes which could lead to misinterpretation of ocean flow field it is suggested that to detect ocean flow field in an ice covered area not near the ice edge trajectories should be used instead of shapes of ice cover

inner core structure of hurricane alicia from airborne doppler radar observations abstract airborne doppler radar measurements are used to determine the horizontal winds vertical air motions radar reflectivity and hydrometer fallspeeds over much of the inner core region within 40 km of the eye of hurricane alicia 1983 the reconstructed flow field is more complete and detailed than any obtained previously the data show both the primary azimuthal and secondary radial height circulations the primary circulation was characterized by an outward sloping maximum of tangential wind the secondary circulation was characterized by a deep layer of radial inflow in the lower troposphere and a layer of intense outflow above 10 km altitude the rising branch of the secondary circulation was located in the eyewall and sloped radially outward discrete convective scale bubbles of more intense upward motion were superimposed on this mean rising current and convective scale downdrafts were located throughout and below the core of maximum precipitation in the eyewall precipitation particle

mesoscale variations in surface stress heat fluxes and drag coefficient in the marginal ice zone during the 1983 marginal ice zone experiment a series of turbulence and mean meteorological measurements were made from an instrumented aircraft during the 1983 marginal ice zone experiment in the greenland sea in july 1983 using the inertial dissipation method estimates of the surface fluxes of momentum sensible heat and latent heat have been obtained for five transects across the marginal ice zone miz the total heat flux was found to be about 30 w m 2 over the ocean and near zero over the ice the 10 m neutral drag coefficient went from an average of 1 3 10 3 over the ocean to 3 3 10 3 over the pack ice a total distance of about 160 km most of the change occurred in a region about 60 km wide in sea breeze conditions the surface stress was reduced about a factor of 2 in the miz center by stability effects

the seasat a satellite scatterometer the geophysical evaluation of remotely sensed wind vectors over the ocean on the seasat a satellite a microwave scatterometer was used to determine the vector wind over the world s oceans the technique is based on the sensitivity of microwave radar backscatter to the centimeter length ocean waves created by the action of the surface wind this paper describes the algorithm used to convert the scatterometer s measurements of ocean normalized radar cross section to the neutral stability vector wind at 19 5 m height and the comparison of these winds with high quality surface observations the wind vector algorithm used an empirical model function to describe the dependence of the ocean 0 on the 19 5 m neutral stability wind vector two model functions developed from a limited base of aircraft and satellite measurements were evaluated by using an independent set of in situ surface wind observations from the joint air sea interaction experiment jasin although these model functions were found to have some weaknesses the results of these comparisons produced better results than the seasat specifications of wind speed accuracy of 2 m s and wind direction accuracy of 20 over the 0 16 m s range of winds observed during jasin an improved model function was later developed by tuning to these jasin data so that the remaining biases between the observed surface winds and the scatterometer derived winds were minimized results are presented for this model function compared against other surface wind observations from the gulf of alaska seasat experiment and the seasat storms hurricane experiment

estimation and mapping of hurricane turbulent energy using airborne doppler measurements abstract hurricane turbulent kinetic energy tke was computed using airborne doppler measurements from the noaa wp 3d tail radars and tke data were retrieved for a variety of storms at different stages of their life cycle the geometry of the radar analysis coupled with the relatively small beam resolution at ranges 8 km allowed for the estimation of subkilometer turbulent processes two dimensional profiles of tke were constructed and revealed that the strongest turbulence was generally located in convective regions such as the eyewall with magnitudes often exceeding 15 m2 s 2 and in the boundary layer with values of 5 10 m2 s 2 in the lowest kilometer a correlation analysis showed that the strong turbulence was generally associated with strong horizontal shear of vertical and radial wind components in the eyewall and strong vertical shear of horizontal wind in the boundary layer mean vertical profiles of tke decrease sharply above the hurricane boundary layer and level off at low magnitude for al

identifying the water source for subsurface flow with deuterium and oxygen 18 isotopes of soil water collected from tension lysimeters and cores the conventional identification of soil water with pre event water limits deep insights into the involvement of stationary and mobile soil water in subsurface hydrological processes in three tilled sloping field plots at a hilly area of southwestern china dominated by entisols soil water collected with a suction lysimeter was distinguished from the total soil water through an analysis of the stable isotopes deuterium and oxygen 18 differences in the depth profile of soil water before and after storm events were observed and used to examine how rainwater mixes with soil water and to identify the source contribution of different fractions of soil water in subsurface flow generation only water in the 0 10 cm soil layer was significantly affected by evaporation and infiltration water in the top 5 cm layer of the soil exhibited the lowest residence time because a storm can replace a substantial proportion of the pre event water soil water at the 10 20 cm depth showed the longest residence time as indicated by its high proportion of pre event water the isotopic signatures demonstrated that piston flow and preferential flow coexisted in this soil high antecedent soil water content and high rain intensity favor the formation of piston flow the water collected with the suction lysimeter represented the mobile fraction of the pre event water in the soil which effectively participates in the generation of subsurface flow newly infiltrated rainwater did not well mix with stationary pre event water in the soil the use of recent rainfall to represent mobile soil water may provide a practical solution for overcoming the negative effect of the spatial heterogeneity of the isotopic composition of soil water on hydrograph separation results bulk soil water and lysimeter water showed significant differences in isotopic composition under low soil water content or in the top soil layer stable isotopes in bulk and lysimeter soil water should be monitored synchronously to reveal the sources and pathways of soil water and their contributions to the generation of subsurface flow in the vadose zone c 2013 elsevier b v all rights reserved

observation of tropical cyclones by high resolution scatterometry unprecedented views of surface wind fields in tropical cyclones hereafter tcs are provided by the european remote sensing satellite ers c band scatterometer scatterometer measurements at c band are able to penetrate convective storms clouds observing the surface wind fields with good accuracy however the resolution of the measurements 50x50 km 2 limits the interpretation of the scatterometer signals in such mesoscale events the strong gradients of the surface wind existing at scales of a few kms are smoothed in the measured features such as the intensity and location of the wind maxima and the position of the center beyond the ers systems the scatterometers on board the adeos and metop satellites designed by the jet propulsion laboratory and by the european space agency respectively will be able to produce measurements of the backscattering coefficient at about 25x25 km 2 resolution a few sets of ers 1 orbits sampling tc events were produced with an experimental 25x25 km 2 resolution enhancing the resolution by a factor of 2 allows location of the wind maxima and minima in a tc with a much better accuracy than at 50 km resolution in addition a better resolution reduces the geophysical noise variability of wind speed within the cell and effect of rain that dominates the radiometric noise and hence improves the definition of the backscattering measurements a comprehensive analysis of the backscattering measurements in the case of high winds and high sea states obtained within tcs is proposed in order to refine the interpretation of the wind vector derived from a backscattering model that is currently only calibrated up to moderate winds 20 m s in neutral conditions observations of the topex poseidon dual frequency altimeter are also used for that purpose patterns of the surface winds in tcs are described and characteristic features concerning asymmetries in the maximum winds and in the divergence field are discussed

validating a scatterometer wind algorithm for ers 1 sar the ocean surface wind field is observed from space operationally using scatterometry the european space agency s esas ers 1 satellite scatterometer routinely produces a wind product that is assimilated into forecast models scatterometry cannot give accurate wind estimates close to land however because the field of view of a spaceborne scatterometer is on the order of 50 km side lobe contamination due to the large contrast in backscatter between land and water compounds the problem synthetic aperture radar sar can provide wind speed and direction estimates on a finer scale so that high resolution wind fields can be constructed near shore an algorithm has been developed that uses the spectral expression of wind in sar imagery to estimate wind direction and calibrated backscatter to estimate wind strength three versions based on c band scatterometer algorithms are evaluated for accuracy in potential operational use algorithm estimates are compared with wind measurements from buoys in the gulf of alaska bering strait and off the pacific northwest coast by using a data set of 61 near coincident buoy and ers 1 sar observations representative figures for the accuracy of the algorithm are spl plusmn 2 m s for wind speed and spl plusmn 37 spl deg for wind direction at a 25 km spatial resolution

dual aircraft investigation of the inner core of hurricane norbert part i kinematic structure abstract on 24 25 september 1984 air motions and physical processes in the eyewall region of hurricane norbert were investigated with two national oceanic and atmospheric administration noaa aircraft operations center aoc wp 3d research aircraft one aircraft equipped with the airborne doppler radar flew repeated radial penetrations of the eyewall mapping the three dimensional wind field throughout a 40 km radius of the storm center these data provide the first complete documentation of the three dimensional wind field of the inner core of a hurricane on spatial scales of 10 25 km in the horizontal and 1 km in the vertical and temporal scales of 1 2 h the wind field was asymmetric and the asymmetry varied with altitude as altitude increased the location of the maximum tangential wind sloped upwind from left of the storm track at 1 km altitude to right of the storm track above 3 km the radial wind at 1 km altitude was inward in front of the storm and outward behind this pattern in the radial

the effect of observed ice conditions on the drag coefficient in the summer east greenland sea marginal ice zone the summer east greenland sea marginal ice zone is a region characterized by extreme horizontal variations of surface roughness characteristics the surface drag coefficient is found to be correlated with these roughness characteristics in particular ice concentration and ice floe roughness and size the estimates of wind stress and wind speed yield neutral drag coefficients cdn with standard deviations of 2 3 0 8 10 3 for areas with less than 40 ice concentration and 4 0 1 1 10 3 for ice concentrations greater than 70 much of the variation in cdn for a given ice concentration is explained by differences in ice floe size and roughness very small concentrated rough floes that have been affected by wave action produce twice as much wind stress cdn 4 2 0 7 10 3 as relatively large flat floes cdn 2 1 0 6 10 3 and 4 times as much as typical open ocean for a given wind speed and stability the drag coefficients in this region are higher than other marginal ice zones probably a result of the presence of large amounts of multiyear ice floes that extend higher above the ocean surface and create more drag than first year floes

mesoscale eddies in the fram strait marginal ice zone during the 1983 and 1984 marginal ice zone experiments during the summer marginal ice zone experiment in fram strait in 1983 and 1984 fourteen mesoscale eddies in both deep and shallow water were studied between 78 o and 81on sampling combined satellite and aircraft remote sensing observations conductivity temperature depth observations drift of surface and subsurface floats and current meter measurements typical scales of these eddies were 20 40 km rotation was mainly cyclonic with a maximum speed in several cases subsurface of up to 40 cm s observations further suggest that the eddy lifetime was at least 20 to 30 days five generation sources are suggested for these eddies several of the eddies were topographically trapped while others primarily formed by combined baroclinic and barotropic instability moved as much as 10 15 km d with the mean current the vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear in the most completely observed eddy south of 79on the available potential energy exceeded the kinetic energy by a factor of 2 quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1 2 km d

the use of stream flow routing for direct channel precipitation with isotopically based hydrograph separations the role of new water in stormflow generation abstract understanding the pathways by which event water contributes to stream stormflow provides insight into stormflow generation mechanisms we analyze the impact of storm size on the relative contribution of event water to stormflow by using natural variations in the oxygen isotopic composition of precipitation and stream water to separate multiple stormflow hydrographs from a single fourth order 1212 ha catchment we extend previous isotope based hydrograph separations by independently accounting for the contribution of event water via direct channel precipitation to the stream hydrograph the direct channel precipitation contribution is determined using a numerical model of stream flow routing though the catchment taking precipitation and digital elevation data as input variables for the range of storm sizes sampled having recurrence intervals ranging from less than a week to 4 months essentially all the event water in stream stormflow can be attributed to direct channel precipitation event water not directly falling on the stream channel indirectly contributes to stormflow by increasing the subsurface discharge of pre event water to the stream neither the hydrograph separation data field observations during the precipitation events nor experimental observations of flow in a large scale natural soil column extracted from the watershed are consistent with macropore flow or groundwater ridging as the primary mechanism responsible for increasing subsurface discharge results from a series of artificial rain experiments using the unsaturated natural soil column are consistent with a preferential kinematic flow model and indicate that the discharge of pre event water to the stream during a storm event may be controlled by kinematic flow processes within the watershed soils

on the characteristic height scales of the hurricane boundary layer in this study data from 794 gps dropsondes deployed by research aircraft in 13 hurricanes are analyzed to studythecharacteristicheightscalesofthehurricaneboundarylayer theheightscalesaredefinedinavariety of ways the height of the maximum total wind speed the inflow layer depth and the mixed layer depth the height of the maximumwind speed and the inflow layerdepth are referred to asthe dynamical boundarylayer heights while the mixed layer depth is referred to as the thermodynamical boundary layer height the data analyses show that there is a clear separation of the thermodynamical and dynamical boundary layer heights consistent with previous studies on the boundary layer structure in individual storms the dynamical boundary layer height is found to decrease with decreasing radius to the storm center the thermodynamic boundary layer height which is much shallower than the dynamical boundary layer height is also found to decrease with decreasing radius to the storm center the results also suggest that using the traditional critical richardson number method to determine the boundary layer height may not accurately reproduce the height scale of the hurricane boundary layer these different height scales reveal the complexity of the hurricane boundary layer structure that should be captured in hurricane model simulations

an estimation of turbulent characteristics in the low level region of intense hurricanes allen 1980 and hugo 1989 this study analyzes the flight level data collected by research aircraft that penetrated the eyewalls of category 5 hurricane hugo 1989 and category 4 hurricane allen 1980 between 1 km and the sea surface estimates of turbulent momentum flux turbulent kinetic energy tke and vertical eddy diffusivity are obtained before and during the eyewall penetrations spatial scales of turbulent eddies are determined through a spectral analysis the turbulence parameters estimated for the eyewall penetration leg are found to be nearly an order of magnitude larger than those for the leg outside the eyewall at similar altitudes in the low level intense eyewall region the horizontal length scale of the dominant turbulent eddies is found to be between 500 and 3000 m and the corresponding vertical length scale is approximately 100 m the results suggest also that it is unwise to include eyewall vorticity maxima evm in the turbulence parameter estimation because the evms are likely to be quasi two dimensional vortex structures that are embedded within the three dimensional turbulence on the inside edge of the eyewall this studyis afirstattempt at estimatingthe characteristics of turbulent flow in the low leveltroposphereof an intense eyewall using in situ aircraft observations the authors believe that the results can offer useful guidance in numerical weather prediction efforts aimed at improving the forecast of hurricane intensity because of the small sample size analyzed in this study further analyses of the turbulent characteristics in the high wind region of hurricanes are imperative

the relationship between wind vector and normalized radar cross section used to derive seasat a satellite scatterometer winds the dependence of ocean normalized radar cross section nrcs or 0 on the 19 5 m neutral stability wind vector for the seasat a satellite scatterometer sass is described for the sass wind vector algorithm this dependence is specified in the form nrcs u where is the radar incidence angle is the angle between wind direction and radar azimuth and u is the neutral stability wind speed in meters per second at a height of 19 5 m the development of models to express this relationship and to provide the basis for inversion of nrcs to sass winds is traced from its initial form based on aircraft scatterometer measurements through the seasat field validation experiments goasex storms and jasin to its final form comparison of the model nrcs versus surface wind speed with sass data from these experiments are made

a simple model of the hurricane boundary layer revisited a simple slab model for the boundary layer of a hurricane is re examined and a small error in the original calculation is corrected with this correction the development of supergradient winds is a ubiquitous feature of the solutions the boundary layer shows two types of behaviour in the inner core of the vortex depending on the depth of the layer and the maximum tangential wind speed above the layer for small depths and or large tangential wind speeds large supergradient winds develop and lead to a rapid deceleration of the inflow such that the inflow becomes zero at some radius inside the radius of maximum tangential wind speed above the boundary layer for large depths and or small tangential wind speeds the solutions do not become singular until within a few kilometres of the rotation axis the transition between the two regimes is very abrupt interpretations are given for the foregoing behaviour other aspects of the boundary layer dynamics and thermodynamics are investigated including the dependence on mixing by shallow convection the effects of a radially varying boundary layer depth the effects of downward momentum transport the dependence of thermodynamical quantities on the boundary layer depth and the radial variation of equivalent potential temperature predicted values of the last quantity are in acceptable agreement with observations made in category five hurricane isabel 2003 the version with radially varying depth gives more realistic vertical velocities in the inner core region of the vortex the limitations and strengths of the slab model are discussed copyright 2008 royal meteorological society

coastal wind jets flowing into the tsushima strait and their effect on wind wave development abstract coastal wind jets that flow into the tsushima strait japan and their effects on wind waves are investigated using synthetic aperture radar sar images and altimeter derived wind and waves the coastal wind jets appear in 7 of 28 sar derived wind fields under the conditions of ambient southeasterly winds atmospheric conditions corresponding to the appearance of the coastal wind jets are examined by a high resolution atmospheric community model which indicates that stratified flows are influenced by the land topography and then pass through the strait forming low level jet flows sensitivity experiments reveal that easterly to southerly stratified flows are a necessary condition for a jet s formation and the degree of its enhancement is mostly controlled by the froude number of the upstream flows atmospheric conditions in which the sar observed the coastal jets meet the model derived necessary conditions which corroborate the validity of the model simulation and the jet s formation mechanism

hydrograph separation using isotopic chemical and hydrological approaches strengbach catchment france the streamflow components were determined in a small catchment located in eastern france for a 40 mm rain event using isotopic and chemical tracing with particular focus on the spatial and temporal variations of catchment sources precipitation soil solution springwater and streamwaters were sampled and analysed for stable water isotopes 18o and 2h major chemical parameters so42 no3 cl na k ca2 mg2 nh4 h h4sio4 alkalinity and conductivity dissolved organic carbon doc and trace elements al rb sr ba pb and u 18o si doc ba and u were finally selected to assess the different contributing sources using mass balance equations and end member mixing diagrams isotopic hydrograph separation shows that the pre event water only contributes to 2 at the beginning of the stormflow to 13 at the main peak flow doc associated to si and u to ba allow to identify the different contributing areas upper layers of the saturated areas deep layers of the hillslope and rainwater the streamflow 70 originates from the deep layers of the hillslope the remaining being supplied by the small saturated areas the combination of chemical both trace and major elements and isotopic tracers allows to identify the origin of water pathways during the first stage of the storm event a significant part of the runoff 30 39 comes from the small extended saturated areas located down part of the basin overland runoff then groundwater ridging during the second stage the contribution of waters from the deep layers of the hillslope in the upper subcatchment becomes more significant the final state is characterised by a balanced contribution between aquifers located in moraine and downslopes indeed this study demonstrates the interest of combining a variety of hydrometric data geochemical and isotopic tracers to identify the components of the streamwater in such conditions

observations of bora events over the adriatic sea and black sea by spaceborne synthetic aperture radar abstract bora events over the adriatic sea and black sea are investigated by using synthetic aperture radar sar images acquired by the advanced sar asar on board the european satellite envisat it is shown that the sea surface roughness patterns associated with bora events which are captured by sar yield information on the finescale structure of the bora wind field that cannot be obtained by other spaceborne instruments in particular sar is capable of resolving 1 bora induced wind jets and wakes that are organized in bands normal to the coastline 2 atmospheric gravity waves and 3 boundaries between the bora wind fields and ambient wind fields quantitative information on the sea surface wind field is extracted from the envisat asar images by inferring the wind direction from wind induced streaks visible on sar images and by using the c band wind scatterometer model cmod ifr2 to convert normalized cross sections into wind speeds it is argued that spaceborne sar images acquired over the east c

atmospheric boundary layer rolls observed by the synthetic aperture radar aboard the ers 1 satellite two synthetic aperture radar sar images acquired by the european remote sensing satellite ers 1 over the jade weser estuary in the german bight of the north sea on january 2 and 20 1992 are analyzed the images show sea surface manifestations of atmospheric boundary layer rolls this is inferred from the orientation of the quasi periodic sea surface patterns which are aligned approximately with the wind direction from the ratio of the wavelength of the patterns to the height of the boundary layer and from the conditions encountered in the atmospheric boundary layer as measured quasi simultaneously by radiosondes the atmospheric boundary layer rolls were generated by a dynamic instability on january 2 and by a thermal instability on january 20 for the first time quantitative estimates of variations of the wind velocity at the sea surface associated with the atmospheric rolls are extracted from a spaceborne radar sar image it is shown that wind velocities derived from sar image intensity variations are in agreement with theoretical estimates

gap winds and wakes sar observations and numerical simulations the nature of terrain induced gap winds and wakes in the atmosphere is examined using surface wind data from synthetic aperture radar sar and the shallow water equations the shallow water model is used to predict the types of wake jet wind patterns that might occur behind an idealized pair of bell shaped hills with a gap between them a regime diagram is constructed based on the width of the gap and the upstream froude number specific predictions of the model are found to compare moderately well with sar data from four examples of airflow near unimak island in the aleutian chain the model predicts the observed wakes and jets including jets that exceed the upstream speed theoretical analysis considers the relative importance of rising terrain and narrowing valley walls in the acceleration of gap winds wind speeds in the wake region are controlled by the bernoulli function and regional pressure gap winds therefore are streams of air that have avoided bernoulli loss over the terrain by passing through gaps the speed of gap winds can exceed the upstream speed only in ridgelike situations when the regional leeside pressure is lower than the upstream pressure

ocean wind fields retrieved from radar image sequences 1 the dependency of radar backscatter on the surface wind field is investigated using a nautical x band radar operating at grazing incidence and horizontal polarization in transmit and receive this resulted in development of an algorithm for wind retrieval from nautical radar image sequences the algorithm consists of two parts in the first part wind directions are extracted from wind induced streaks that are in line with the mean surface wind direction these streaks are visible in the temporal integrated radar images at scales between 100 and 500 m the orientation of the streaks is determined from the local gradients which are derived from the radar images smoothed and reduced to the appropriate scales in the second part wind speeds are derived from the backscatter of the temporal integrated radar image sequence and the radar retrieved wind direction the dependency of the radar backscatter on the local surface wind and geometry of the radar is parameterized by training a neural network the algorithm is applied to radar image sequences acquired by a nautical x band radar mounted aboard an offshore platform in the north sea the radar derived winds are validated by comparison to in situ wind data measured at the platform the comparison of wind directions resulted in a correlation of 0 99 with a standard deviation of 14 2 for wind speeds the correlation is 0 97 with a standard deviation of 0 85 m s 1 in contrast to traditional offshore wind sensors the retrieval of the wind field from the backscatter of the ocean surface makes the system independent of the sensors motion and installation height and reduces the effects due to platform induced blockage and turbulence effects

the dynamics of boundary layer jets within the tropical cyclone core part i linear theory abstract observations of wind profiles within the tropical cyclone boundary layer have until recently been quite rare the recent massive increase in observations due to the operational implementation of the global positioning system dropwindsonde has emphasised that a low level wind speed maximum is a common feature of the tropical cyclone boundary layer here is proposed a mechanism for producing such a maximum whereby strong inward advection of angular momentum generates the supergradient flow the processes that maintain the necessary inflow against the outward acceleration resulting from gradient wind imbalance are identified as being i vertical diffusion ii vertical advection and iii horizontal advection two complementary tools are used to diagnose the properties and dynamics of the jet the first presented here is a linear analytical model of the boundary layer flow in a translating tropical cyclone it is an extension of the classical ekman boundary layer model as well as of earlier w

the aerodynamic roughness of different types of sea ice the aerodynamic roughness for all major types of sea ice is specified on the basis of surface layer measurements from ship and ice floe platforms median neutral surface drag coefficients cdn 1000 for grease and nilas ice are 0 7 and 1 6 small medium large and fused pancake ice have cdn equal to 0 9 1 6 2 4 and 1 9 young ice cdn ranges from 2 3 to 3 1 very smooth first year or multiyear ice with no pressure ridges has cdn equal to 1 5 pack ice has median values of 2 0 and 2 2 for first year and multiyear ice marginal ice zone ice averages 3 1 and 3 4 first year multiyear if unaffected by wave action wave affected ice has cdn values of 4 2 and 4 6 first year multiyear extremely rough multiyear ice in intense shear or compaction regions has cdn equal to 8 0 open ocean areas within 100 km of an ice edge averaged 1 8 while ice free water downwind of ice with small or no waves is 1 4 these values can be adjusted if heat fluxes are present the accuracy of the cdn averages is estimated to be 20 or better

an expanded dataset of hurricane eyewall sizes and slopes abstractusing airborne doppler radar data from 39 flights into hurricanes from 2004 to 2010 the authors examine the outward slope of the eyewall revisiting the recent studies of stern and nolan the slope of the radius of maximum winds rmw is found to increase nearly linearly with size and is uncorrelated with intensity the slope of the eyewall absolute angular momentum surface m increases with increasing size strong correlation and decreases with increasing intensity weak to moderate correlation two other measures of eyewall slope are also investigated the 20 dbz reflectivity isosurface dbz20 and the radius of maximum azimuthal mean updraft rwmax the slopes of both dbz20 and rwmax increase with their size the slope of dbz20 decreases with intensity though the correlation is weak while the slope of rwmax is uncorrelated with intensity the absolute angular momentum decreases on average along the rmw by 9 from 2 to 8 km heights with this larger dataset the previous results are genera

simultaneous observations of ocean surface winds and waves by geosat radar altimeter and airborne synthetic aperture radar during the 1988 norwegian continental shelf experiment quasi simultaneous measurements of the ocean surface by the canada centre for remote sensing ccrs convair 580 cv 580 synthetic aperture radar sar were acquired on march 20 1988 along an ascending pass of the geosat radar altimeter as part of the prelaunch ers 1 norwegian continental shelf experiment norcsex 88 over a region where the sar look direction is parallel to the wind vector a relationship between the ocean scattering cross sections measured by the geosat altimeter and the sar is obtained in the regions where the wind direction is changing an estimate of the wind direction is derived from the differences measured between the altimeter and the sar scattering cross sections wavelength and wave directions derived from the sar wave spectra are in good agreement with the sea truth data obtained with the wave directional buoys and with the altimeter derived swell estimates significant wave height measured by the geosat altimeter is compared with the buoy measurements and is used to assess the validity of the significant wave height deduced from the sar

ecohydrological separation in wet low energy northern environments a preliminary assessment using different soil water extraction techniques ecohydrological studies in seasonally dry climatic regions have revealed isotopic separation of the sources of water used by trees and those that generate stream flow also referred to as the two water worlds hypothesis here we investigated whether similar separation occurs in a wet low energy northern latitude 57 environment in scotland for two common soil types histosols and podzols at three soil depths and at both forested with scots pine pinus sylvestris and non forested sites we compared the stable isotope composition of soil water held at increasing soil water tensions these were assessed by different soil water extraction techniques rhizon samplers mobile water centrifugation at different speeds representing different tensions and cryogenic extraction bulk water sampling occurred during a relatively dry summer water that was held at increasing tensions appeared more depleted than more mobile water consistent with older winter precipitation this pattern was independent of soil type vegetation cover and time during the growing season although there was a slight tendency towards less separation with soil depth nevertheless soil waters in this generally wet low energy environment exhibited only minor evaporative enrichment limited to the upper soil profile only furthermore stream water showed no deviation from the local meteoric water line preliminary sampling for tree xylem water suggested uptake of evaporated soil water from the near surface soil horizons upper 10 cm where fine root densities are concentrated for histosols in particular tree water appeared lagged in its isotopic composition compared to the soil water time series although more work is needed to fully test the two water worlds hypothesis our initial analyses did not provide clear evidence to support this in wet low energy northern environments copyright 2015 john wiley sons ltd

mesoscale wind measurements using recalibrated ers sar images the precision images pri of the synthetic aperture radars sar on board the european remote sensing satellites ers 1 and ers 2 are used to derive mesoscale wind fields over the ocean for calculation of the wind speed the c band model cmod4 is used which was originally developed by stoffelen and anderson 1993 for the european space agency esa to derive wind fields from measurements of the wind scatterometer scat in the case of the ers 1 2 sar the cmod4 is used to compute the wind speed from the normalized radar backscatter cross section nrcs and the incidence angle of the radar beam both computed from the sar pri data the third input variable is the wind direction which is estimated from the wind streaks in the images or from ground truth measurements the sar data are affected by a power loss caused by saturation of the analog to digital converter adc of the sar therefore the images have to be recalibrated errors in the derived wind speed are mainly due to adc saturation and uncertainties of the input wind direction these errors are estimated for various wind conditions mesoscale wind fields computed from ers 1 2 sar pri images taken between the shetland islands and the west coast of norway are compared to ground truth measurements and modeled wind fields from the german weather service dwd wind fields of the nonhydrostatic mesoscale model geesthacht simulation model of the atmosphere gesima are compared to the derived wind field of the ers 1 sar pri image at the island rugen in the baltic sea

reexamining the vertical structure of tangential winds in tropical cyclones observations and theory a few commonly held beliefs regarding the vertical structure of tropical cyclones drawn from prior studies bothobservationalandtheoretical areexaminedinthisstudy oneofthesebeliefsisthattheoutwardslopeof the radius of maximumwinds rmw is a function of the size of the rmw another belief is that the outward slope of the rmw is also a function of the intensity of the storm specifically shea and gray found that the rmw becomes increasingly vertical with increasing intensity and decreasing radius the third belief evaluated here is that the rmw is a surface of constant absolute angular momentum m these three conventional wisdoms of vertical structure are revisited with a dataset of three dimensional doppler wind analyses comprising seven hurricanes on 17 different days azimuthal mean tangential winds are calculated for each storm andtheslopesofthermwandmsurfacesareobjectivelydetermined theoutwardslopeofthermw is shown to increase with radius which supports prior studies in contrast to prior results no relationship is found between the slope of the rmw and intensity it is shown that the rmw is indeed closely approximated by an m surface for the majority of storms however there is a small but systematic tendency for m to decrease upward along the rmw utilizing emanuel s analytical hurricane model a new equation is derived for the slope of the rmw in radius pressure space this predicts a linear increase of slope with radius and essentiallyno dependence of slope on intensity an exactly analogous equationcan be derivedin log pressure height coordinates and a numerical solution yields the same conclusions in geometric height coordinates these conclusions are further supported by the results of simulations utilizing emanuel s simple timedependent axisymmetric hurricane model as both the model and the analytical theory are governed by the dual constraints of thermal wind balance and slantwise moist neutrality it is demonstrated that it is these two assumptionsthat requirethe slope of the rmw to be a functionof its size but not of the intensityof the storm finally it is shown that within the context of emanuel s theory the rmw must very closely approximate an m surface through most of the depth of the vortex

on a satellite scatterometer as an anemometer the seasat a satellite scatterometer sass wind algorithm was tested against surface wind fields three classes of surface wind fields were used point measurements an isotach field over an intensively measured triangle with 200 km sides and synoptic scale winds determined from pressure and temperature fields and a planetary boundary layer model these comparisons can verify optimal capabilities of sass at accuracies of 2 m s 1 and 20 sass ability to locate fronts accurately is also established complications in nonsteady highly variable fields indicate problems exist in unqualified application of the sass algorithm to all conditions

oceanographic conditions in the marginal ice zone north of svalbard in early fall 1979 with an emphasis on mesoscale processes during september october 1979 the norwegian remote sensing experiment was carried out in the marginal ice zone north of svalbard convergence of the ice cover is correlated with along ice edge winds with the ice to the right while divergence occurs during office winds or calm conditions a wind driven ice edge jet is observed wind driven upwelling of the pycnocline of up to 7 m was present along the ice edge during a 10 to 15 m s easterly wind event the upwelling is due to ekman divergence at the ice edge caused by higher wind stress over ice than over open water the ice edge meanders with a scale of 20 40 km and sheds eddies with a scale of 5 to 15 km into the open water this scale is of the same order as the rossby radius of deformation eddies with the same scale are also seen in the conductivity temperature and depth observations conditions during the experiment were such that barotropic instabilities could have generated these eddies

hydrograph separation using stable isotopes silica and electrical conductivity an alpine example abstract hydrograph separation of runoff events in two nested alpine subalpine basins in the coast mountains of british columbia was carried out using electrical conductivity specific concentration of silica and the stable isotopes oxygen 18 and deuterium as hydrological tracers the methods predicted consistent high pre storm water contribution for the subalpine site 60 90 but more variable contribution at the alpine basin outlet 25 90 the pre storm water contribution is much larger than had previously been expected precipitation is believed to run off as overland flow due to the steep slopes in combination with the hydrophobic soils until it can enter the subsurface environment the rapid influx of stored water is possibly caused by pressure propagation in the macropore system which could be enhanced by the heavily fractured bedrock and permeable landslide debris acting as efficient hydrological conduits the study suggests that alternative hydrological tracers such as electrical conductivity and silica concentration can be used under certain hydrological and lithological conditions these alternative tracers should however be verified against more conventional tracers before use as the behaviour depends on specific characteristics of each basin at the upper basin outlet both electrical conductivity ec and silica underestimated the pre storm contribution at the lower station silica and ec showed a similar pattern to deuterium and oxygen 18 tracers the calculated pre storm component using ec was however 10 20 lower than the calculated values from the other three tracers the advantage of using these alternative tracers is that hydrograph separation results can a priori be anticipated

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

comparison of sar derived wind speed with model predictions and ocean buoy measurements as part of the alaska synthetic aperture radar sar demonstration project in 1999 and 2000 wide swath radarsat sar imagery has been acquired on a regular basis in the gulf of alaska and the bering sea during 1998 and 1999 similar data were acquired off the east coast of the united states as part of the stormwatch project the radar cross section measurements from these images were combined with wind direction estimates from the navy operational global atmospheric prediction system model to produce high resolution maps of the surface wind speed for this study 2862 sar image frames were collected and examined averaged wind estimates from this data base have been systematically compared with corresponding wind speed estimates from buoy measurements and model predictions and very good agreement has been found the standard deviation between the buoy wind speed and the sar estimates is 1 76 m s details of the sar wind extraction procedure are discussed along with implications of the comparisons on the c band polarization ratio

slab and height resolving models of the tropical cyclone boundary layer part i comparing the simulations diagnostic models of the tropical cyclone boundary layer have important practical uses including engineering design and climatological risk assessment studies and as components of tropical cyclone potential intensity models a widely used class of such models has been slab models in which the governing equations are depth averaged here a slab model is compared with one that fully resolves height and it is shown that the vertical averaging leads to substantial differences in the simulations the slab model produces excessively strong inflow and too great a departure of the boundary layer mean winds from gradient balance in moving storms the slab models produce much too strong a motion induced asymmetry and can support an asymmetric analogue of the quasi inertial oscillation previously noted in axisymmetric slab models given the considerable impact of the vertical averaging in slab models on the simulated flow in the tropical cyclone boundary layer it is difficult to recommend their further use for applications where quantitative accuracy is important other applications will require care to ensure that the results are not unduly affected by the depth averaging part ii of this article presents a detailed analysis of the reasons for the differences between depth averaged and height resolving simulations of the tropical cyclone boundary layer 2010 published by john wiley sons ltd

tower based measurements of the ocean c band radar backscattering cross section continuous measurements of the c band normalized radar cross section nrcs at vertical vertical polarization as a function of wind speed and direction were carried out from a research platform in the north sea during a period of 11 months in 1984 the nrcss have been correlated with other environmental data routinely collected at the platform like air water temperature difference water temperature and ocean wave slope the wind speed exponent of the c band nrcs at 45 incidence angle was determined as 1 50 valid in the wind speed range 2 19 m s our data set shows that the c band nrcs depends strongly on the air sea temperature difference for example when the air sea temperature difference decreases from 5 c to 5 c the nrcs increases by 6 db at a wind speed of 8 9 m s and an incidence angle of 45 for stable air sea interfaces and low wind speeds the nrcs increases with increasing root mean square wave slope however no systematic dependence on water temperature was observed

analysis of water movement through an unsaturated soil zone in jeju island korea using stable oxygen and hydrogen isotopes summary in order to analyze water movement through an unsaturated soil zone in jeju island korea temporal variations in the oxygen 18 and deuterium isotopes of precipitation and soil waters at three different depths were monitored for about one year the stable oxygen and hydrogen isotopic compositions of the soil waters are plotted between or near the two local meteoric water lines for summer and winter precipitation indicating that the soil waters were recharged from the year around precipitation and evaporation was negligible even during hot summer season in the study area mean residence times of the soil waters were then estimated from the 18o d and deuterium excess or d values of the precipitation and soil waters using two well mixed or exponential models em and one exponential piston flow model epm the regression results show that the combination of the exponential piston flow model and the d values of the precipitation and soil waters gives the most reasonable estimation of the mean residence times of the soil waters in the study area it suggests that the deuterium excess or d values can be used as a better parameter than the 18o or d values alone for estimating mean residence times of subsurface waters not only in korea but also in other northeast asian countries the estimated low moisture contents and hydraulic diffusivities of the soils at the three different depths also indicate that the boundary between the upper fine grained soil and the lower coarse grained soil may act as a capillary barrier and the soil waters probably flow slowly through micropores rather than rapidly through macropores in the unsaturated soil zone

a model of the atmospheric boundary layer over the marginal ice zone a one layer primitive equation model is presented for the atmospheric boundary layer over the marginal ice zone miz the model simulates the slow rate of inversion growth and rate of warming of the boundary layer seaward of an ice edge for off ice winds observed on two cruises in the bering sea by the noaa r v surveyor the horizontal temperature gradient in the boundary layer caused by the oceanic heat flux seaward of an ice edge induced an increase in wind speed with a maximum increase of 8 at 50 km seaward of the edge at 100 km off ice a momentum balance is established between accelerative terms boundary layer baroclinity momentum entrainment synoptic scale scale pressure gradient and decelerative terms surface drag and the local pressure force resulting from inversion rise wind velocity in the boundary later over the miz during off ice winds is sensitive to changes in surface roughness when an miz is modeled as a smooth interior cd 2 10 3 and a 30 km wide rough marginal ice zone cd 3 8 10 3 with an unstable surface layer over the ocean the model shows a decrease in wind speed of 9 at the windward side of the miz and an 18 increase in wind speed from 5 km interior to the ice edge to 40 km seaward of the edge these results suggest an atmospheric mechanism for rafting at the windward side of the marginal ice zone divergence of the ice at the edge and ice band formation seaward of the edge

hurricane boundary layer theory in the light of the plethora of definitions for the hurricane boundary layer we advocate a dynamical definition based on the distribution of agradient flow we seek also to clarify the fundamental role of the boundary layer in the hurricane intensification process in particular we contrast the differences between unsteady boundary layers that are able to facilitate the spin up of the vortex above and steady boundary layers that cannot if slaved to the time dependent vortex aloft the latter can spin up the interior vortex only indirectly by changing its thermodynamic properties through vertical advection of these from below and adjustment to thermal wind balance these differences are highlighted by an analytical demonstration that the application of a zero vertical gradient condition on velocity above a steady boundary layer does not provide a direct means of allowing the boundary layer to determine the flow in the interior vortex this result assumes that frictional forces are negligible at this boundary finally echoing a few previous insights we question the applicability of conventional boundary layer theory at radii of strong ascent into the eyewall where the flow is akin to that of separation in aerodynamic boundary layers copyright c 2010 royal meteorological society

sar retrieved wind in polar regions comparison with in situ data and atmospheric model output european remote sensing ers satellites synthetic aperture radar sar wind retrievals using cmod ifr2 are for the first time retrieved in the marginal ice zone miz and in arctic coastal areas and compared with in situ observations from reseach vessels rvs and output from a high resolution atmospheric model the root mean squares rms of the comparisons were 1 6 m s sup 1 and 2 m s sup 1 respectively the spatial variation of the sar wind fields established a decrease in wind speed close to the ice edge for the late summer situations where the wind was along the ice edge with the ice to the left this decrease is believed to be due to changes in atmospheric stability possibly through development of an internal boundary layer caused by the cold ice cover and melt water lower wind speed near the ice edge is confirmed by the atmospheric model and the in situ observations furthermore good results are obtained from sar wind retrieval in leads when compared with model output during a cold air outbreak routine measurements in the miz are useful for estimating the wind stress and therefore sar may play an important role in this region finally the identification of a jet out from hinlopen strait in the svalbard region and low wind wakes along the coast in the sar retrieved wind field is confirmed by in situ observations as the rv moves through the region the jet is also confirmed by the atmospheric model which is able to reproduce the situation

katabatic wind fields in coastal areas studied by ers 1 synthetic aperture radar imagery and numerical modeling synthetic aperture radar sar images acquired over mediterranean coastal waters from the first european remote sensing satellite ers 1 showing sea surface manifestations of katabatic wind fields are presented in particular sea surface roughness patterns generated by katabatic winds blowing from 1800 in high mountains through a broad valley at the western coast of calabria southern italy into the gulf of gioia is investigated the ers 1 sar images show that their areal extent and shape vary strongly depending on the meteorological conditions the roughness pattern sometimes has the form of a mushroom an elongated tongue a broad blob or a narrow truncated band for one event september 8 1992 we have simulated the wind field at the sea surface by using a nonhydrostatic mesoscale atmospheric model and then compared it with the wind field derived from the ers 1 sar image by using the c band wind scatterometer model cmod4 the comparison shows that the atmospheric model reproduces quite well the mushroom like form of the wind field pattern while the wind speed is obtained somewhat lower than the one inferred from the sar image this study demonstrates that sar images acquired over coastal waters are well suited to study local wind fields in coastal areas and to test numerical models that describe local wind fields which extend from the coast onto the sea

a small scale oceanic eddy off the coast of west africa studied by multi sensor satellite and surface drifter data a small scale oceanic eddy which was generated in autumn 2011 at the headland of cap vert off the coast of senegal west africa and then propagated westward into the open north atlantic ocean is studied by multi sensor satellite and surface drifter data the eddy was generated after a sudden increase of the trade winds causing an enhanced southward flow and upwelling at the coast of senegal after this wind burst event an extremely nonlinear cyclonic eddy with a radius of about 10 to 20 km evolved downstream of cap vert with rossby number larger than one our analysis suggests that the eddy was generated by flow separation at the headland of cap vert the eddy was tracked on its way into the open north atlantic ocean from satellites over 31 days via its sea surface temperature and chlorophyll a chl signature and by a satellite tracked surface drifter the satellite images show that this small scale eddy transported nutrients from the upwelling region westward into the oligotrophic north atlantic thus giving rise to enhanced chl concentration there maximum chl concentration was encountered few days after vortex generation which is consistent with a delayed plankton growth following nutrient supply into the euphotic zone within the eddy furthermore the eddy was imaged by the synthetic aperture radar sar onboard the envisat satellite it is shown that the radar signatures of cold eddies result from damping of short surface waves by biogenic surface films which arise from surface active material secreted by the biota in the cold eddy as well as by the change of the stability of the air sea interface highlights processes during the onset of coastal upwelling off west africa multi sensor remote sensing and in situ observations highly nonlinear small scale eddy generation at cap vert nrcs reduction in parts of the eddy due to biogenic surface films

photogrammetric analysis of the 2013 el reno tornado combined with mobile x band polarimetric radar data abstractthis study presents rapid scanning x band polarimetric radar data combined with photogrammetry of the el reno tornado of 31 may 2013 the relationship between the hook echo weak echo hole weh weak echo column wec and the rotational couplet with the visual characteristics of the tornado are shown for the first time cross correlation coefficient hv and differential reflectivity zdr data are included in the photogrammetric analyses the tornado was accompanied by a large tornadic debris signature tds with a diameter 2 km wide during the analysis time the center of the tds was not collocated with the weh and the rotational couplet instead the tds was displaced 1 km to the north and within the weak echo notch of the hook echo a debris overhang was identified in vertical cross sections of the hv fields the overhang was located in a weak echo trench and a notch of high hv consistent with the position of the tornado updraft the updraft was hypothesized to be carrying small deb

the dynamics of boundary layer jets within the tropical cyclone core part ii nonlinear enhancement abstract observations of wind profiles within the tropical cyclone boundary layer until recently have been quite rare however the recent spate of observations from the gps dropsonde have confirmed that a low level wind speed maximum is a common feature of the tropical cyclone boundary layer in part i a mechanism for producing such a maximum was proposed whereby strong inward advection of angular momentum generates the supergradient flow the processes that maintain the necessary inflow against the outward acceleration due to gradient wind imbalance were identified as being i vertical diffusion ii vertical advection and iii horizontal advection and a linear analytical model of the boundary layer flow in a translating tropical cyclone was presented and used to diagnose the properties of the jet and the near surface flow a significant shortcoming was that the jet was too weak which was argued to be due to the neglect of vertical advection here a high resolution dry hydrostatic numerical

a coupled ice ocean model of upwelling in the marginal ice zone a dynamical coupled ice ocean numerical model for the marginal ice zone miz is suggested and used to study upwelling dynamics in the miz the nonlinear sea ice model has a variable ice concentration and includes internal ice stress the model is forced by stresses on the air ocean and air ice surfaces the main coupling between the ice and the ocean is in the form of an interfacial stress on the ice ocean interface the ocean model is a linear reduced gravity model the wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water while the interfacial stress ice ocean is proportional to the concentration of ice a new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium the upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport on the basis of numerical model an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

observed boundary layer wind structure and balance in the hurricane core part i hurricane georges abstract the gps dropsonde allows observations at unprecedentedly high horizontal and vertical resolution and of very high accuracy within the tropical cyclone boundary layer these data are used to document the boundary layer wind field of the core of hurricane georges 1998 when it was close to its maximum intensity the spatial variability of the boundary layer wind structure is found to agree very well with the theoretical predictions in the works of kepert and wang in particular the ratio of the near surface wind speed to that above the boundary layer is found to increase inward toward the radius of maximum winds and to be larger to the left of the track than to the right while the low level wind maximum is both more marked and at lower altitude on the left of the storm track than on the right however the expected supergradient flow in the upper boundary layer is not found with the winds being diagnosed as close to gradient balance the tropical cyclone boundary layer model of kepert and wan

coastal wind field retrievals from ers synthetic aperture radar images a unique series of european remote sensing satellite ers 1 and 2 c band synthetic aperture radar sar images was obtained off the southern coast of norway during the coast watch 95 experiment in september 1995 in this paper we carry out a systematic analysis of the mesoscale coastal wind field conditions expressed in the sar images four different categories of phenomena including windrows fetch limited seas wind fronts and oceanographic fronts are examined and discussed the quantitative retrievals of the wind field are based on examination of both the sar image backscatter characteristics and the spectral properties results are compared and validated against coincident ship and buoy data providing complementary and independent observations of the oceanographic and meteorological conditions

finescale structure of the lagrange wyoming tornado during vortex2 gbvtd and photogrammetric analyses abstracta ground based velocity track display gbvtd analysis of the lagrange wyoming tornado on 5 june 2009 during the second verification of the origins of rotation in tornadoes experiment vortex2 is photogrammetrically combined with a series of pictures of the funnel cloud this analysis reveals the relationship between the vertical velocity radial and tangential velocities perturbation pressure vertical vorticity and angular momentum with the visual features of the tornado an intense axial downdraft was evident and was supported by a downward directed perturbation pressure gradient the radial inflow at low levels was weak and difficult to retrieve owing to a combination of centrifuging of hydrometeors debris in the intense circulation and the inability of the radar beam to fully resolve the flow the tornado was weakening during the analysis period which was supported by angular momentum being advected out of the tornado the availability of a dual doppler wind synthesis for this tornadic e

a coupled field study of subsurface fracture flow and colloid transport field studies of subsurface transport of colloids which may act as carriers of contaminants are still rare this is particularly true for heterogeneous and fractured matrices to address this knowledge gap a 30 m long monitoring trench was constructed at the lower end of sloping farmland in central sichuan southwest china during the summer of 2013 high resolution dynamic and temporal fracture flow discharging from the interface between fractured mudrock and impermeable sandstone was obtained at intervals of 5 min for fast rising stages 30 60 min for slow falling stages or 15 min at all other times this discharge was analyzed to elucidate fracture flow and colloid transport in response to rainfall events colloid concentrations were observed to increase quickly once rainfall started 15 90 min and reached peak values of up to 188 mg l interestingly maximum colloid concentration occurred prior to the arrival of flow discharge peak i e maximum colloid concentration was observed before saturation of the soil layer rainfall intensity rather than its duration was noted to be the main factor controlling colloid response and transport dissolved organic carbon concentration and 6180 dynamics in combination with soil water potential were used to apportion water sources of fracture flow at different stages these approaches suggested the main source of the colloids discharged to be associated with the flushing of colloids from the soil mesopores and macropores beyond the scientific interest of colloid mobilization and transport at the field scale these results have important implications for a region of about 160 000 km 2 in southwest china that featured similar hydrogeologic settings as the experimental site in this agriculture dominated area application of pesticides and fertilizers to farmland is prevalent these results highlight the need to avoid such applications immediately before rainfall events in order to reduce rapid migration to groundwater via fracture flow in either dissolved form or in association with colloids c 2015 elsevier b v all rights reserved

testing the groundwater ridging hypothesis of streamflow generation during snowmelt in a forested catchment hydrometric and isotopic techniques were used to test the groundwater ridging hypothesis of stream flow generation during snowmelt in a forested catchment on the canadian shield the catchment contains a central wetland that drains to an ephemeral channel hydrograph separation using 2h as a tracer indicated that approximately 60 of total stream flow during snowmelt was supplied by pre event water this was supported by hydrometric results however contrary to the groundwater ridging hypothesis the response of water table levels in near stream areas to initial melt inputs failed to promote a rapid flux of ground water to the wetland and stream all stream flow originated as saturation overland flow from the wetland and groundwater flow during much of the melt was directed down the catchment s main axis and back under hillslopes surrounding the wetland and channel although the hydrograph separation indicated pronounced short term variations in pre event discharge from the catchment groundwater fluxes to the wetland remained relatively invariant following initiation of surface saturation streamflow fluctuations appear to have been generated by displacement of water held in surface storage induced by melt and rainwater inputs to the wetland this stored water had an isotopic signature intermediate between that of event and pre event water suggested oscillations in pre event runoff were an artifact of the mixing model approach to hydrograph separation rather than the result of rapid changes in groundwater fluxes to the wetland

case study of a coastal jet at spitsbergen comparison of sar and model estimated wind a combination of in situ ship measurements synthetic aperture radar sar imagery and high resolution numerical modeling was used to investigate a mesoscale coastal jet radiating out from hinlopenstretet norway on 14 august 1996 in the meteorological analysis a light breeze and high static stability were found upstream of svalbard by studying results of numerical simulations in relation to the topography upstream stagnation flow splitting and downstream jets and wakes were identified in the hinlopenstretet area this flow pattern was confirmed by in situ ship measurements and the sar estimated wind through investigations of sensitivity simulations it was found that the low level jet mainly was a result of stratified flow around dynamically steep isolated topography while the channeling effect of hinlopenstretet had a minor influence in the core of the jet the velocity was increased by a factor of about 3 compared to the upstream velocity

revisiting the relationship between eyewall contraction and intensification abstractin the widely accepted convective ring model of tropical cyclone intensification the intensification of the maximum winds and the contraction of the radius of maximum winds rmw occur simultaneously this study shows that in idealized numerical simulations contraction and intensification commence at the same time but that contraction ceases long before peak intensity is achieved the rate of contraction decreases with increasing initial size while the rate of intensification does not vary systematically with initial size utilizing a diagnostic expression for the rate of contraction it is shown that contraction is halted in association with a rapid increase in the sharpness of the tangential wind profile near the rmw and is not due to changes in the radial gradient of the tangential wind tendency it is shown that a number of real storms exhibit a relationship between contraction and intensification that is similar to what is seen in the idealized simulations in particular the statistical

wind vector retrieval using ers 1 synthetic aperture radar imagery an automated algorithm intended for operational use is developed and tested for estimating wind speed and direction using ers 1 sar imagery the wind direction comes from the orientation of low frequency linear signatures in the sar imagery that the authors believe are manifestations of roll vortices within the planetary boundary layer the wind direction thus has inherently a 180 spl deg ambiguity since only a single sar image is used wind speed is estimated by using a new algorithm that utilizes both the estimated wind direction and spl sigma sub 0 values to invert radar cross section models the authors show that 1 on average the direction of the roll vortices signatures is approximately 11 spl deg to the right of the surface wind direction and can be used to estimate the surface wind direction to within spl plusmn 19 spl deg and 2 utilizing these estimated wind directions from the sar imagery subsequently improves wind speed estimation generating errors of approximately spl plusmn 1 2 m s for ers 1 sar data collected during the norwegian continental shelf experiment in 1991

dissecting the variable source area concept subsurface flow pathways and water mixing processes in a hillslope summary this study uses an instrumented trenched 0 5 ha hillslope in the southern tier of new york state usa to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope measurements of water fluxes in the trench upslope water table dynamics surface and bedrock topography and isotopic and geochemical tracers have been combined for a four dimensional space time characterization of subsurface storm flow responses during events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers with much 33 71 of the total discharge of the hillslope originating from deeper water flow below the fragipan during storm events with wet antecedent conditions and large rainfall amounts shallow lateral flow of event and pre event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events in addition mobilization of total dissolved phosphorus tdp with subsurface flow played a greater role than with overland or near surface flow during all events tdp loads were highest in the total discharge during peak flows 8 11 5 kg ha 1 d 1 except during the largest storm event when tdp concentrations were highly diluted these results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading

a stable isotope study of recharge processes in the english chalk the 2h and 18o values of water contained in unsaturated chalk have been measured in drillcore profiles taken over a period of 28 months on arable land in cambridgeshire eastern england the isotopic composition of rainfall and lysimeter drainage on the same site has also been monitored over a period of four years the distribution of isotope values in the upper few metres of soil and unsaturated chalk shows that the mechanism of infiltration is not simple piston like downward displacement since the scale of vertical fluctuations is incompatible with estimated annual infiltration and the apparent rates of movement of matrix water derived from thermonuclear tritium studies lysimeter drainage is not isotopically identical to matrix water at the same depth suggesting that different routes to water table are associated with consistently different isotopic content although there is an apparent difference between matrix water beneath arable and permanent grassland these differences appear to cancel out in the composition of bulk recharge beneath these land types the regional aquifer has a uniform isotopic composition similar in value to weighted average rainfall and lysimeter drainage suggesting that the recharge abstraction system has been in isotopic equilibrium for many years despite changes in pumping rates and land use two other chalk sites in southern england have been investigated in less detail but indicate clear difference in infiltration behaviour from that seen in cambridgeshire this seems to be related to a higher matrix conductivity and annual rainfall amount

multiscale analysis of tropical cyclone kinematic structure from airborne doppler radar composites abstractthe multiscale inner core structure of mature tropical cyclones is presented via the use of composites of airborne doppler radar analyses the structure of the axisymmetric vortex and the convective and turbulent scale properties within this axisymmetric framework are shown to be consistent with many previous studies focusing on individual cases or using different airborne data sources on the vortex scale these structures include the primary and secondary circulations eyewall slope decay of the tangential wind with height low level inflow layer and region of enhanced outflow radial variation of convective and stratiform reflectivity eyewall vorticity and divergence fields and rainband signatures in the radial wind vertical velocity vorticity and divergence composite mean and variance fields statistics of convective scale fields and how they vary as a function of proximity to the radius of maximum wind show that the inner eyewall edge is associated with stronger updrafts and higher refl

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t