variations associated with cores and gaps of a pacific narrow cold frontal rainband abstract a noaa p 3 instrumented aircraft observed an intense fast moving narrow cold frontal rainband ncfr as it approached the california coast on 19 february 2001 during the pacific coastal jets experiment airborne doppler radar data obtained while the frontal system was well offshore indicated that a narrow ribbon of very high radar reflectivity convective cores characterized the rainband at low levels with echo tops to 4 5 km and pseudo dual doppler analyses showed the low level convergence of the prefrontal air the ncfr consisted of gaps of weaker reflectivity and cores of stronger reflectivity along its length perhaps as a result of hydrodynamic instability along its advancing leading edge in contrast to some earlier studies of cold frontal rainbands density current theory described well the motion of the overall front the character of the updraft structure along the ncfr varied systematically along the length of the precipitation cores and in the gap regions the vertical shear of the c

numerical study of the orographic forcing of heavy precipitation during map iop 2b abstract this paper investigates the local circulation associated with a heavy orographic rainfall event during 19 21 september 1999 mesoscale alpine programme intensive observing period 2b map iop 2b this event was simulated with a 5 km horizontal grid spacing using the fifth generation pennsylvania state university ncar mesoscale model mm5 the mm5 simulation reproduced the basic features such as the timing and location of the deep trough and the associated precipitation evolution though the total amount of precipitation is slightly higher than that measured by rain gauges 30 in 24 h the near surface flow was dominated by an easterly jet originally from the adriatic sea and a southerly jet from the gulf of genoa a significant westward turning occurred when the southerly flow approached the south side of the alps this deflection was caused by boundary layer friction and rotation as well as mountain blocking effects flow was generally from the south above the surface precipitation was ma

analysis and simulation of local and regional conditions for the rainfall over the lago maggiore target area during map iop 2b the mesoscale alpine programme map operational and research network collected a large variety of measurements during the two days of intensive observing period iop 2b 19 and 20 september 1999 which is one of the most intense rainfall episodes during the special observing period over the lago maggiore area the synoptic situation is a typical one of a southerly flow and associated convection over alpine orography simulations with the non hydrostatic meso nh model are used to describe the rainfall conditions and are successfully validated at the different scales allowed by the map data the two types of pre frontal orographically triggered convective episodes are described 1 sporadic and shallow convection occurs over the coastal mountains and propagates over the po valley the chronology and the intensity of these convective episodes are driven by two main features the low level humidity anomalies and the middle troposphere dry anomaly present over the mediterranean sea 2 the lago maggiore orographic convection has a very long duration and is mainly controlled by both the intensity of the easterly low level wind in the north part of the po valley and the upper level clouds of the cold front the different origins of the air masses transported by this easterly barrier wind and the associated local circulations are detailed copyright 2003 royal meteorological society

interaction of low level flow with the western ghat mountains and offshore convection in the summer monsoon abstract seven year averaged values of percent frequency of occurrence of highly reflective cloud for the months june july and august indicate that offshore convection is a major component of the cloudiness of the southwest monsoon principal areas of convection occur off of the western coats of india burma thailand and the philippines this study concentrates on the area upstream of the western ghats mountains of india analysis of a special boundary layer mission flown during the wmo icsu summer monsoon experiment leads us to believe that partial deceleration of the monsoon flow by upstream blocking effects of the mountains initiates and maintains a vertical and horizontal motion field that could support the observed convection data obtained on this mission allow a large scale momentum budget computation for the subcloud layer which shows pressure deceleration to be significant the budget dominated by advection predicts an increase of average wind speed which is observed the pressure decelera

in situ calcium carbonate dissolution in the pacific ocean over the past several years researchers have been working to synthesize the woce jgofs global co2 survey data to better understand carbon cycling processes in the oceans the pacific ocean data set has over 35 000 sample locations with at least two carbon parameters oxygen nutrients cfc tracers and hydrographic parameters in this paper we estimate the in situ caco3 dissolution rates in the pacific ocean water column calcium carbonate dissolution rates ranging from 0 01 1 1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon in the north pacific intermediate water between 400 and 800 m caco3 dissolution rates are more than 7 times faster than observed in middle and deep water depths average 0 051 mmol kg1 yr1 the total amount of caco3 that is dissolved within the pacific is determined by integrating excess alkalinity throughout the water column the total inventory of caco3 added by particle dissolution in the pacific ocean north of 40s is 157 pg c this amounts to an average dissolution rate of approximately 0 31 pg c yr1 this estimate is approximately 74 of the export production of caco3 estimated for the pacific ocean these estimates should be considered tomore be upper limits for in situ carbonate dissolution in the pacific ocean since a portion of the alkalinity increase results from inputs from sediments less

factors governing cellular convection in orographic precipitation the development of shallow cellular convection in warm orographic clouds is investigated through idealized numerical simulations of moist flow over topography using a cloud resolving numerical model buoyant instability a necessary element for moist convection is found to be diagnosed most accurately through analysis of

equatorial pacific 13 c water eddies in the eastern subtropical south pacific ocean abstract argo float profile data are used to analyze warm salty weakly stratified subthermocline eddies of tropical origin in the eastern subtropical south pacific ocean these eddies contain anomalous signatures of the equatorial pacific 13 c water that is carried poleward within the peru chile undercurrent pcu as it flows along the west coast of south america from their source along the chilean coast between 29 and 39 s the eddies spread westward and slightly northward likely at least partly advected by the subtropical gyre the eddy water properties contrast strongly with the colder fresher more strongly stratified waters of subantarctic origin being carried northward then westward by the gyre near the eddy source about 6 of argo profiles sample eddies that are above selected thresholds for both salinity and potential vorticity anomalies relative to maps of the mean distributions of these properties on and around the core isopycnal for the eddies the proportion of such profiles dimini

multiple precipitation mechanisms over mountains observed by airborne doppler radar during map iop5 abstract this study uses airborne doppler radar measurements from the special observing period of the mesoscale alpine programme map to document the detailed airflow and precipitation structure over the mountainous regions near the border of northeastern italy and slovenia as a cold frontal system moved eastward and encountered the eastern alps on 4 october 1999 during map iop5 in contrast to previously documented map cases the environmental conditions associated with this case are characterized by a deep layer of strong convective instability in the lower troposphere and by a cold northeasterly continental flow coming down from the mountains the so called bora wind along the southeastern alps over the study region there are two primary mountain barriers the julian alps oriented roughly west east with a peak mountain height of 2500 m and a significant variation in terrain height along its length and the other the dinaric alps a relatively lower mountain range oriented northwest southeast

an observational and modeling study of the interaction of low level southwesterly flow with the olympic mountains during coast iop 4 abstract this paper presents an observational and modeling study of the three dimensional flow and precipitation around the olympic mountains of northwest washington state for a case of relatively steady south southwesterly flow this study utilized data from coast iop 4 the fourth intensive observing period during the coastal observation and simulation with topography field experiment that took place during 9 10 december 1993 one of the most important data sources was the noaa p 3 aircraft which provided flight level data reflectivity and doppler winds as it flew around the olympics features that were mapped successfully with the noaa p 3 included flow splitting around the windward pressure ridge strong southeasterlies to approximately 25 m s 1 northeast of the olympics caused by downgradient acceleration into the lee trough the rapid transition from strong southeasterlies to lighter easterlies 5 10 m s 1 in the strait of juan de fuca strong downslope flow and a hydraulic jump like transiti

moist dynamics and orographic precipitation in northern and central california during the new year s flood of 1997 abstract the dynamics of moist orographic flows during the january 1997 floods in northern and central california are investigated using numerical simulations computed with the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 early in the event 31 december 1996 1 january 1997 the low level winds offshore of california s central coast were blocked by the topography of the santa lucia range and the low level winds in the central valley were blocked by the topography of the central sierra nevada range in contrast moisture laden winds along the northern coast ranges and the northern sierra nevada flowed over topographic barriers as the core of humid air migrated to the south over 24 h the low level barrier jets weakened as the atmospheric stability decreased bringing heavy rainfall to the central and southern sierra nevada at the end of the event the heavy precipitation during this event was largely controlled by the interactio

application of theory to simulations of observed cases of orographically forced convective rainfall abstractin two recent papers the authors reported on numerical simulations of conditionally unstable flows past an idealized mesoscale mountain ridge these idealized simulations which were performed with a three dimensional explicitly cloud resolving model allowed the investigation of simulated precipitation characteristics as a function of the prescribed environment the numerical solutions were carried out for a uniform wind flowing past a bell shaped ridge and using an idealized unstable sounding with prescribed values of the relevant parameters in the present work the application of these theoretical results to observed cases of orographically forced convective rainfall including the big thompson flood 1976 colorado the oahu flood 1974 hawaii and the gard flood 2002 france is reported specifically numerical simulations have been carried out using observed and idealized soundings relevant to these cases but with idealized topography it is found that using the observed soundings but

turbulence as a mechanism for orographic precipitation enhancement this study examines the dynamical and microphysical mechanisms that enhance precipitation during the passage of winter midlatitude systems over mountain ranges the study uses data obtained over the oregon cascade mountains during the improvement of microphysical parameterization through observational verification experiment 2 improve 2 november december 2001 and over the alps in the mesoscale alpine program map september november 1999 polarimetric scanning and vertically pointing s band doppler radar data suggest that turbulence contributed to the orographic enhancement of the precipitation associated with fronts passing over the mountain barriers cells of strong upward air motion 2ms 1 occurred in a layer just above the melting layer while the frontal precipitation systems passed over the mountain ranges upstream flow appeared to be generally stable except for some weak conditional instability at low levels in the two improve 2 cases the cells occurred in a layer of strong shear at the top of a low level layer of apparently retarded or blocked flow shown by doppler radial velocity data the shear apparently provided a favorable environment for the turbulent cells to develop the updraft cells appeared at the times and locations where the shear was strongest 10 m s 1 km 1 the richardson number was slightly less than 0 25 at the level where the cells were observed suggesting shear generated turbulence could have been the origin of the updraft cells another possibility is that the rough mountainous lower boundary could have triggered buoyancy oscillations within the stable sheared flow the existence of turbulent cells made possible a precipitation growth mechanism that would not have been present in a laminar upslope flow the turbulent cells appeared to facilitate the rapid growth and fallout of condensate generated over the lower windward slopes of the mountains in a laminar flow over terrain upward motions would be unlikely to produce liquid water contents adequate to increase the density and hence the fall speed of precipitating ice particles by riming the turbulent updraft cells apparently create pockets of higher values of liquid water content embedded in the widespread frontal cloud system and snow particles falling from the parent cloud systems can then rapidly rime within the cells and fall out observations by polarimetric radar and direct aircraft sampling indicate the occurrence of rimed aggregate snowflakes and or graupel in the turbulent layer inasmuch as the shear layer is the consequence of retardation or blocking of the low level crossbarrier flow and the turbulence is a response to the shear the shear induced cellularity is an indirect response of the flow to the topography the turbulence embodied in this orographically induced cellularity allows a quick response of the precipitation fallout to the orography since aggregation and riming of ice particles in the turbulent layer produce heavier more rapidly falling precipitation particles without the turbulent cells condensate would more likely be advected farther up and perhaps even over the mountain range small scale cellularity has traditionally been associated with the release of buoyant instability by the upslope flow our results suggest that cellularity may be achieved even if buoyant instability is weak or nonexistent so that even a stable flow has the capacity to form cells that will enhance the precipitation fallout over the windward slopes

radar observations of intense orographic precipitation associated with typhoon xangsane 2000 abstract with measurements from two ground based doppler radars located in northern taiwan this study documents the detailed aspects of intense orographic precipitation associated with typhoon xangsane 2000 as it moved northward immediately off the eastern coast of taiwan bringing strong low level northeasterly to north northeasterly winds impinging on the mountainous northern coast with relatively good persistent coverage of radar echoes on both inland and upstream regions this particular event provides a unique description of the orographic precipitation and its relationship with orographic geometry strong upstream oncoming flow and the precipitation inherently associated with typhoon circulations in this case the heaviest precipitation was observed to occur primarily over two coastal mountain barriers mount da tun dt and the nangang keelung range nkr barrier dt is an approximately 3d mountain barrier and the nkr adjacent to the southeast of dt is a relatively lower narrower 2d moun

barium isotopic fractionation in seawater mediated by barite cycling and oceanic circulation the marine biogeochemical cycle of ba is thought to be controlled by particulate baso4 barite precipitation associated with the microbial oxidation of organic carbon and its subsequent dissolution in the baso4 undersaturated water column despite many of these processes being largely unique to ba cycling concentrations of ba and si in seawater exhibit a strong linear correlation the reasons for this correlation are ambiguous as are the depth ranges corresponding to the most active baso4 cycling and the intermediate sources of ba to particulate baso4 stable isotopic analyses of dissolved ba in seawater should help address these issues as ba isotopic compositions are predicted to be sensitive to the physical and biogeochemical process that cycle ba we report a new methodology for the determination of dissolved ba isotopic compositions in seawater and results from a 4500 m depth profile in the south atlantic at 39 99 s 0 92 e that exhibit oceanographically consistent variation with depth these data reveal that water masses obtain their ba and ba isotopic signatures when at or near the surface which relates to the cycling of marine baso4 the shallow origin of these signatures requires that the substantial ba isotopic variations in the bathypelagic zone were inherited from when those deep waters were last ventilated indeed the water column below 600 m is well explained by conservative mixing of water masses with distinct ba and ba isotopic compositions this leads us to conclude that large scale oceanic circulation is important for sustaining the similar oceanographic distributions of ba and si in the south atlantic and possibly elsewhere these data demonstrate that the processes of organic carbon oxidation baso4 cycling and ba isotopic fractionation in seawater are closely coupled such that ba isotopic analyses harbor great potential as a tracer of the carbon cycle in the modern and paleo oceans

formation mechanisms for convection over the ligurian sea during map iop 8 abstract the dynamical impacts of an unusually strong stable layer that developed over the po valley and northern ligurian sea during mesoscale alpine program map intensive observation period 8 iop 8 on the formation of convection over the ligurian sea are explored based on numerically simulated equivalent potential temperature wind vectors and by a trajectory analysis of parcels both beneath and above the stable layer it is shown that the stable layer behaved as a material surface or effective mountain to the airstreams impinging on it from the south additional analyses show that the leading edge of the stable layer was collocated with maxima in upward motion and a strong positive moisture flux hence it was further argued and demonstrated through inspection of soundings upstream of the cold dome and trajectory analyses that lifting by the stable layer enhanced convective activities over the ligurian sea finally processes contributing to the maintenance of the stable layer during iop 8 were

cross barrier flow during orographic precipitation events results from map and improve abstract ground based and airborne doppler radar data collected during passage of frontal rainstorms over the european alps and cascade mountains of oregon are found to exhibit characteristic cross barrier flow and precipitation patterns a stably stratified layer of blocked or partially blocked low momentum flow below mountain crest level is separated from strong cross barrier flow aloft by a concentrated layer of vertical wind shear this shear layer slopes upward toward the mountain crest and persists for several hours as the storm passes over the mountain range this pattern is remarkably similar from case to case and from one mountain range to the other the orographically enhanced precipitation in these cases exhibits stratiform structure marked by a radar bright band which often drops to a lower height indicating locally cooler conditions immediately adjacent to the windward mountain slopes a terrain induced gravity wave produces strong downslope flow and spillover of precipitation onto the

aerial observations of the yugoslavian bora abstract the first aircraft observations of the bora in yugoslavia were accomplished during the alpex project in 1982 data from all five alpex bora flights have been analyzed in a comparative study of bora structure although the bora varies considerably in depth in the strength of the incoming low level flow and in the direction of the winds aloft several common features are evident these include upstream descent and acceleration beginning where the mountains rise an approximate coincidence between the depth of the uppermost descending streamline and the wind reversal level upstream when a reversal exists a decoupling of the flow aloft associated with a splitting of the inversion and the formation of a thick mixed layer downstream a narrow region of intense turbulence and an ascending jet just downstream of the plunging bora the bora structure is similar in many respects to the boulder windstorm internal hydraulic theory taking into account the decoupling effect of the intermediate layer a

triple doppler radar analysis of the heavy rain event observed in the lago maggiore region during map iop 2b this paper presents analyses of data collected with three ground based doppler radars during the mesoscale alpine programme map intensive observation period iop 2b from 1900 utc 19 september until 1100 utc 20 september 1999 during this period the synoptic situation was characterized by the propagation of a deep upper tropospheric trough towards the alps as often observed when heavy precipitation occurs on the southern slopes of the alpine massif a frontal cloud system with embedded convective cells passed over northern italy in association with the trough moving rapidly eastwards ahead of the advancing cold front a strong south to south easterly low level flow impinged on the mountains near lago maggiore and produced copious amounts of rain 200mm at several locations an analysis of three dimensional radar derived wind and precipitation fields shows that the most intense precipitation occurred where and when the easterly component of the low to mid level flow was the strongest with however a preferential location on the southern slopes of the alps this phenomenon can be explained by enhanced confluence between the main southerly flow and an intensifying easterly flow and or more favourable orientation of the moist inflow perpendicular to the mountain slopes in addition the propagation of convective cells from the po valley toward the alps led to enhanced precipitation over the mountainous area taking advantage of the approximately two dimensional character of the event the different terms of the water budget are calculated for a series of 25 successive vertical cross sections to analyse the transformation of atmospheric moisture into surface rainfall copyright 2003 royal meteorological society

barium in deep sea bamboo corals phase associations barium stable isotopes prospects for paleoceanography abstract reconstruction of past seawater 138 134 banist barium isotopic compositions can augment existing proxies of water mass provenance and deep ocean circulation deep sea bamboo corals are uniquely poised to record ba isotopic variations given their widespread oceanographic distribution and incorporation of ambient ba in approximate proportion to that in surrounding seawater however the utility of such records requires knowing the phases hosting ba in deep sea coral skeletons that specimens faithfully capture modern ba isotopic chemistry and that internal skeletal variability relates principally to historical variations in the composition of ambient seawater we investigated each of these requirements using a stepped cleaning experiment a core top comparison of eight live collected specimens from the california margin 870 2 055 m against ambient seawater and through examination of historical variability in skeletal ba chemistry respectively first we report that non carbonate phases minimally contribute to bamboo coral ba ca obviating the need for chemical cleaning of live collected specimens second using newly obtained profiles of northeast pacific ba isotopic chemistry we observe that bamboo corals faithfully reflect ambient seawater with a taxonomically and environmentally invariant ba isotopic offset 138 134 bacoral sw of 0 37 0 03 2 sd n 8 the partition coefficient for ba k d ba is similarly insensitive to taxonomy but linearly decreases with depth the driving mechanism is unresolved third we find minimal ba ca and ba isotopic variability in historical growth representing the past century we interpret this invariance as evidencing the overall fidelity of deep sea bamboo corals for ambient ba chemistry over their long lifespans the insensitivity of 138 134 bacoral sw to environmental gradients indicates that the ba isotopic composition of bamboo corals can be solely interpreted in terms of seawater composition which should find myriad applications to the study of past ocean circulation over a range of timescales

investigation of orographic precipitation over an isolated three dimensional complex topography with a dense gauge network radar observations and upslope model abstractthis study uses a dense rain gauge network radar observations and an upslope model to document the detailed aspects of precipitation over da tun mountain dt of northern taiwan under pre

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones ix some effects of orography on rainbands abstract the effects of orography on the mesoscale structures and precipitation processes in warm frontal warm sector wide cold frontal narrow cold frontal and post frontal rainbands in four pacific cyclones are described the rainbands were tracked with a doppler radar as they approached the washington coast and then for 150 km inland as they passed over topographic features ranging from modest hills to mountain ranges the rainbands were affected in a variety of ways by orography ranging from dissipation to formation and precipitation from the bands was enhanced and reduced in different situations these effects are discussed with respect to the large scale flow mesoscale air motions and precipitation growth mechanisms

radar observations and numerical modeling of a precipitating line during map iop 5 abstract during the special observing period of the mesoscale alpine programme a narrow north south oriented frontal precipitation band was observed by two airborne and one operational doppler radar on 4 october 1999 over the friuli target area in northeast italy convective precipitation was mostly concentrated to the south of the eastern alps in regions of smooth orography and warm southerly flow ahead of the cold front while stratiform rain formed above the mountainous chain where a marked cold northerly flow wrapping around the eastern alps progressed southwestward doppler data collected in both convective and stratiform regions of the precipitation line as well as high resolution numerical simulations performed with the nonhydrostatic meso nh model are used to investigate the associated flow structure in connection with the underlying topography the mutually consistent observed and simulated precipitation and wind fields clearly identify low level flow convergence relative to the cold front

the kinematic structure of a wasatch mountain winter storm during ipex iop3 the influence of orographic circulations on the precipitation structure of a wasatch mountain winter storm is examined using observations collected during the third intensive observing period iop3 of the intermountain precipitation experiment ipex the event featured the passage of a midlevel 700 550 hpa trough followed 3 h later by a surface trough prior to and during the midlevel trough passage large scale southwesterly flow impinged on the wasatch mountains low level confluence was observed between this southwesterly flow and along barrier southerly flow within 20 40 km of the wasatch mountains this confluence zone which moved toward the wasatch mountains during and following the passage of the midlevel trough was accompanied by low level convergence and precipitation enhancement over the upstream lowlands dual doppler analysis revealed the presence of a shallow along barrier jet near the base of the wasatch mountains that was surmounted by southwesterly cross barrier flow at mid and uppermountain levels this cross barrier flow produced strong 1 2 m s 1 ascent as it interacted with the steep windward slopes of the wasatch mountains where precipitation was roughly double that observed in the lowlands upstream flow deflection and splitting were also observed near the highest terrain features a narrow region of strong subsidence which at times exceede d2ms 1 was found to the lee of the wasatch and based on radar imagery appeared to modulate hydrometeor spillover aloft processes contributing to the evolution of the near barrier flow field including topographic blocking diabatic effects and surface friction contrasts are discussed

airborne doppler observations of a landfalling cold front upstream of steep coastal orography abstract this study uses airborne doppler radar observations to describe the mesoscale structure and evolution of a cold frontal system as it made landfall on the mountainous coast of oregon and northern california on 1 december 1995 during the coastal observations and simulations with topography experiment this section of coastline constitutes a steep approximately two dimensional north south oriented orographic barrier the front exhibited a northeast southwest orientation and thus intersected the axis of high terrain at an acute angle the along barrier pressure gradient and low level winds increased with time along the coastal zone and reached a maximum as the front made landfall stably stratified prefrontal flow was strongly blocked by the orography resulting in a confluent transition from pervasive southwesterly winds offshore to a narrow zone of accelerated south southwesterly flow near the coast where wind speeds approached 30 m s 1 at a height of 750 m above mean sea level postfrontal flow

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones part v the substructure of narrow cold frontal rainbands abstract the organization and structure of a narrow cold frontal rainband ncfr on the small mesoscale and the microscale have been investigated through quantitative radar reflectivity doppler radar observations airborne observations and surface measurements the ncfr was composed of small mesoscale regions of heavy precipitation called precipitation cores pcs oriented at an angle to the synoptic scale cold front in horizontal cross section the pcs were roughly elliptical in shape areas of lighter precipitation called gap regions grs separated the pcs the pcs were so oriented that their loading edges were regions of strong low level convergence the weather associated with the passage of a pc resembled that of a squall line gust front with concurrent windshifts and pressure checks occurring 5 min before heavy precipitation and a fall in temperature the changes in surface weather that accompanied the passage of a gr were more variable but tended to be less marked than for pcs thus the se

the accuracy of vertical air velocities from doppler radar data abstract eight methods of calculating vertical air velocity in a column are compared each method requires some or all of the following data horizontal divergence vertical precipitation velocity hydrometeor terminal fall speed and vertical air velocity boundary conditions some or all of these quantities are commonly deduced or specified by a researcher during the analysis of doppler radar data the responses of the methods to different magnitudes and behaviors of errors in the input data are examined with a monte carlo method the experiments are conducted with both random and systematic errors two idealized kinds of systematic errors are considered bias error a constant error through the column and trend error an error of constant magnitude that changes sign at the midpoint of the mass of the column the performances of the methods are mapped over error space a researcher knowing approximately the characteristics of the errors of a particular set of doppler radar data can use the results of

distribution and mechanisms of orographic precipitation associated with typhoon morakot 2009 abstractusing a combination of doppler radar observations and rain gauge data this study documents detailed aspects of the orographic precipitation associated with typhoon morakot 2009 rainfall distribution over underlying topographical features and possible physical mechanisms responsible for the observed orographic enhancement are explored the study region constitutes an approximately two dimensional south north oriented orographic barrier with higher wider lower narrower terrain features in its northern southern portions i e the northern and southern barriers upstream conditions were characterized by abundant typhoon background precipitation embedded within strong nearly saturated westerly to west southwesterly oncoming flow the observations show that a wide area of topographically enhanced precipitation and the rainfall maxima were confined to the windward slopes of the northern barrier whereas the strongest rainfall tended to occur near and or slightly downstream of the mountain c

orographic precipitation forcing along the coast of northern california during a landfalling winter storm abstractthis study documents orographic precipitation forcing along the coastal mountains of northern california during the landfall of a significant winter storm over the period 16 18 february 2004 the primary observing asset is a scanning x band doppler radar deployed on the coast at fort ross california which provides low level e g below 1 km msl horizontal and vertical scans of radial velocity and reflectivity to characterize airflow and precipitation structures further context is provided by a wind profiling radar a radio acoustic sounding system rass balloon soundings buoys a gps receiver and surface meteorological sensors the winter storm is divided into two episodes each having pre cold frontal low level jet llj structures and atmospheric river characteristics episode 1 has a corridor of terrain trapped airflow tta that forms an interface with the llj the interface extends 25 km offshore in a 0 5 km vertical layer and the western edge of this interface near the ocean surf

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

formation and maintenance of a long lived taiwan rainband during 1 3 march 2003 abstracttaiwan rainbands trs defined here as convective lines which form off the mountainous eastern coast of taiwan under weakly synoptically forced weather conditions are a well known mesoscale phenomenon but their formative processes remain the subject of debate this study uses surface and radar observations within the coastal zone of eastern taiwan and ncep reanalysis data to document a long lived tr with a lifetime of 36 h during 1 3 march 2003 to advance the current general understanding of mechanisms responsible for the tr s formation and maintenance detailed analyses indicate that the rainband was initiated by convergence that was produced as low level environmental northeasterly easterly onshore flow encountered topographically blocked northerlies that developed nearshore the northerly blocked flow was observed to weaken and subsequently dissipate because of changing synoptic pressure patterns that caused prevailing southeasterlies southerlies at low levels however colder nearshore ai

high resolution numerical simulations of the convective system observed in the lago maggiore area on 17 september 1999 map iop 2a during intensive observing period iop 2a of the mesoscale alpine programme map a significant convective system developed in the lago maggiore area its evolution is simulated using the meso nh model run over three nested domains with a 2 km horizontal resolution for the finest grid model results are assessed by comparing computed precipitation and model radar reflectivities with observed parameters a control simulation initialized with european centre for medium range weather forecasts analyses and run with the standard microphysical scheme of the model yields fairly realistic results neglecting the ice processes in the microphysical scheme degrades the numerical results whereas significant improvement is obtained when heavy rimed particles are considered to be hail instead of graupel copyright 2003 royal meteorological society