idealized simulations of the effect of taiwan and philippines topographies on tropical cyclone tracks the effects of topography on tropical cyclone tc tracks are investigated using the weather research and forecasting model running on a beta plane with actual topography two sets of experiments are performed one focusing on taiwan topography and the other on the philippines in each set different parts of the terrain are set to be either present or absent and the tcs are inserted at a location southeast of the mountain so that landfall occurs at the central part of the mountain in the no terrain control cases relative to the control case a pair of terrain induced gyres is found in all with terrain experiments this pair of gyres rotates cyclonically around the tc and the gyre associated flow near the tc centre causes a northward deflection of the tc track prior to landfall an examination of the potential vorticity tendencies pvts suggests that in addition to the pvt produced by this flow the pvt from diabatic heating cannot be ignored in explaining the tc track during landfall the asymmetric diabatic heating is significant which tends to retard the fast displacement of the tc caused by horizontal advection this diabatic heating distribution results from three different mechanisms an incursion of dry air from the mountain low level convergence induced by the terrain altered wind field in the southwestern part of the tc and the development of convergence cyclonically inward from the eastern side of the mountain to the tc core however the first two mechanisms are apparently missing in the philippine experiments because of the lower height and the moister air over the mountains on luzon island

idealized simulations of the effect of local and remote topographies on tropical cyclone tracks this is the second part of a study on the effect of topography on tropical cyclone tc tracks in part i idealized simulations using the weather research and forecast wrf model were conducted with artificial tcs inserted at a location such that they make landfall on the central part of taiwan and the luzon in this second part the effects of local and remote topographies are studied by examining the tracks of several tcs approaching taiwan at different latitudes tropical cyclones approaching to the south of taiwan remote effect slow down and are first deflected southwestward and then northward moreover a sharp northward deflection occurs for a tc passing further south of taiwan but the deflection is small for a tc passing further north of taiwan in the presence of china s terrain an additional larger but weaker anticyclonic gyre is induced so that the tc is affected even when it is further away from the land the flow associated with this gyre reduces the northward deflection caused by the taiwan terrain but enhances the southwestward shift of the tc however no cyclonic gyre is found over inland china if the tc is far away from china s coast probably because of the irregular elevated topography for tcs making landfall on south china a westward shift is found just prior to landfall which is more significant if the height of china s terrain is doubled this westward shift can be explained by the horizontal advection vertical advection and diabatic heating terms in the potential vorticity tendency equation

influence of mesoscale topography on tropical cyclone tracks further examination of the channeling effect abstractobservations have documented typhoons experiencing pronounced track deflection before making landfall in taiwan in this study idealized full physics model experiments are conducted to assess the orographic influence on tropical cyclone tc track an intense and westward moving tc is simulated to approach the bell shaped terrain imitating the taiwan topography sensitivity numerical experiments are carried out to evaluate the topographic effect under different flow regimes and parameters such as tc intensity terrain height and incident angle of the tc movement toward the topography all the presented simulated storms experience southward track deflection prior to landfall different from the mechanism related to the channeling effect induced low level northerly jet as suggested in previous studies this study indicates the leading role of the northerly asymmetric flow in the midtroposphere in causing the southward deflection of the simulated tc tracks the midtropospheric northerly asymmetric

exploring a multiresolution approach using amip simulations abstractthis study presents a diagnosis of a multiresolution approach using the model for prediction across scales atmosphere mpas a for simulating regional climate four atmospheric model intercomparison project amip experiments were conducted for 1999 2009 in the first two experiments mpas a was configured using global quasi uniform grids at 120 and 30 km grid spacing in the other two experiments mpas a was configured using variable resolution vr mesh with local refinement at 30 km over north america and south america and embedded in a quasi uniform domain at 120 km elsewhere precipitation and related fields in the four simulations are examined to determine how well the vrs reproduce the features simulated by the globally high resolution model in the refined domain in previous analyses of idealized aquaplanet simulations characteristics of the global high resolution simulation in moist processes developed only near the boundary of the refined region in contrast amip simulations with vr g

a new look at the binary interaction potential vorticity diagnosis of the unusual southward movement of tropical storm bopha 2000 and its interaction with supertyphoon saomai 2000 tropical storm bopha 2000 showed a very unusual southward course parallel to the east coast of taiwan mainly steered by the circulation associated with supertyphoon saomai 2000 to bopha s east the binary interaction between the two typhoons is well demonstrated by the potential vorticity pv diagnosis with the use of the piecewise pv inversion this paper quantitatively evaluates how bopha moved southward due to the binary interaction with saomai a newly proposed centroid relative track with the position weighting based on the steering flow induced by the pv anomaly associated with the other storm is plotted to highlight such binary interaction processes note that the above analysis can be well used to understand the more complicated vortex merging and interacting processes between tropical cyclones either from observational data or numerical experiments the results also shed some light on the prediction of nearby tropical cyclones

euxinia caused the late ordovician extinction evidence from pyrite morphology and pyritic sulfur isotopic composition in the yangtze area south china abstract the late ordovician mass extinction lome was a severe biocrisis during the phanerozoic and in this extinction trilobites brachiopods mollusks graptolites conodonts and other types suffered severe mortality and 85 of marine invertebrate species were eliminated the potential cause of this mass extinction remains unclear although glaciation and marine anoxia have received the greatest attention herein we present findings on pyrite morphology pyritic sulfur isotopic composition and total organic carbon content toc to analyze the evolution of redox conditions across the ordovician silurian boundary in the yangtze area of south china our results show that long term euxinic conditions interrupted by episodic dysoxic oxic events occurred from the upper katian stage to the lower rhuddanian stage the two extinction pulses of lome were coincident with euxinic conditions suggesting that marine euxinia may have been the main cause of this mass extinction event

sensitivity of typhoon track to asymmetric latent heating rainfall induced by taiwan topography a numerical study of typhoon fanapi 2010 1 typhoon fanapi 2010 traveled westward across the central mountain range of taiwan on 19 september and its rainfall shifted from a symmetric to an asymmetric pattern with convection mostly to the south and southeast meanwhile the storm slowed down from 22 to 14 km h 1 for 12 h upon leaving taiwan and led to heavy rainfall 800 mm and serious flooding over the low lying southwestern plains through simulation and sensitivity tests using the cloud resolving storm simulator at 3 km grid size this study shows that the sudden and temporary speed reduction was caused by the asymmetric latent heating lh not the environmental flow specifically over a 9 h period the model storm moved westward at 16 km h 1 in the control run but increasingly faster and more toward the northwest when the moisture and thus the lh effect and its asymmetry is gradually reduced steering flow analysis and estimation using model results suggest an eastward motion vector of about 8 km h 1 consistent with the observation is produced by the asymmetric lh effect when the effects from the vertical wind shear and beta drift are both taken into account this result is further supported by the diagnosis on storm motion based on potential vorticity tendency although important such feedback to typhoon track from rainfall asymmetry that is induced by the blocking effect of topography have not been reported or studied

a numerical study of the effect of island terrain on tropical cyclones abstract a triply nested movable mesh model was used to study the behavior of tropical cyclones encountering island mountain ranges the integration domain consisted of a 37 wide and 45 long channel with an innermost mesh resolution of 1 6 the storms used for this study were embedded in easterly flows of 5 and 10 m s 1 initially realistic distributions of island topography at 1 6 resolution were inserted into the model domain for the region of the caribbean including the islands of cuba hispaniola and puerto rico the island of taiwan and the region of luzon in the northern philippines it was found that the islands affected the basic flow as well as the wind field directly associated with the storm system the combination of these effects caused changes in the track and translational speed of the storm in particular in the case of the 5 m s 1 easterly flow the storm accelerated and veered to the north well before reaching taiwan for the other island distributions the northward deflecti

the influence of island topography on typhoon track deflection abstracthigh resolution simulations for typhoon krosa 2007 and a set of idealized experiments are conducted using a full physics model to investigate the eminent deflection of typhoon track prior to its landfall over mountainous island topography the terrain height of taiwan plays the most important role in typhoon krosa s looping motion at its landfall while the surface properties details in the topographic shape of taiwan and the cloud microphysics are shown to be secondary to the track deflection a simulation with 3 km resolution and realistic model settings reproduces the observed krosa s track while that with 9 km resolution fails suggesting that high resolution to better resolve the typhoon terrain interactions is important for the prediction and simulation of typhoon track deflection prior to landfall results from idealized experiments with model configurations mimicking those of supertyphoon krosa show that vortices approaching the northern and central topography are significantly deflec

effects of landfall location and the approach angle of a cyclone vortex encountering a mesoscale mountain range abstractthe orographic effects of landfall location approach angle and their combination on track deflection during the passage of a cyclone vortex over a mesoscale mountain range are investigated using idealized model simulations for an elongated mesoscale mountain range the local vorticity generation driving the cyclone vortex track deflection is more dominated by vorticity advection upstream of the mountain range by vorticity stretching over the lee side and its immediate downstream area and by vorticity advection again far downstream of the mountain as it steers the vortex back to its original direction of movement the vorticity advection upstream of the mountain range is caused by the flow splitting associated with orographic blocking it is found that the ideally simulated cyclone vortex tracks compare reasonably well with observed tracks of typhoons over taiwan s central mountain range cmr in analyzing the relative vorticity budget the authors found that jumps in the vortex path are lar

a numerical study of the track deflection of supertyphoon haitang 2005 prior to its landfall in taiwan abstract a series of numerical simulations are conducted using the advanced research version of the weather research and forecasting model with a 4 km fine mesh to examine the physical processes responsible for the significant track deflection and looping motion before the landfall of supertyphoon haitang 2005 in taiwan which poses a unique scientific and forecasting issue in the control experiment a low level northerly jet induced by the channeling effect forms in the western quadrant of the approaching storm where the inner core circulation is constrained by the presence of taiwan s terrain because of the channeling effect the strongest winds of the storm are shifted to the western portion of the eyewall the northerly advection flow averaged asymmetric winds within 100 km radius results in a sharp southward turn of the westward moving storm the time series of the advection flow shows that the advection wind vectors rotate cyclonically in time and well match the motion of the simulated vortex

on the geographic asymmetry of typhoon translation speed across the mountainous island of taiwan abstractthis paper examines the effect of topographically phase locked convection on the motion of typhoons across the island of taiwan data for 84 typhoons that reached taiwan s eastern coast from 1960 to 2010 are analyzed with motions compared to the long term average overland translation speed for 61 continuous track typhoons among all cases 77 of the slow moving tropical cyclones tcs made landfall on the northern end of taiwan s eastern coast while 60 of the fast storms had southeastern coastal landfalls this geographic asymmetry with respect to typhoon translation speeds widened after landfall as the slow movers typically decelerated during the overland period whereas the faster tcs sped up in particular the average overland duration was 16 h for the slow class compared to only 3 h for the fast moving typhoons the combination of slower translation with longer duration for the northern class of tcs led to large rainfall on the southwestern slope of the island s central mountain range we

interaction of typhoons with the taiwan orography part ii continuous and discontinuous tracks across the island abstract numerical model simulations of west moving tropical cyclones approaching and crossing the taiwan orography are shown to contain many of the observed surface features vortices tend to track continuously around the northern end of the island due to the deflection of the deep layer mean flow and the vortex circulation is modified less because the higher winds to the right of the center do not have a strong interaction with the barrier discontinuous tracks predominate for vortices approaching the central southern portions of the taiwan orography severe distortions of the inner core circulation occur and the surface pressure and surface wind centers become decoupled and may be dissipated at different rates numerical sensitivity studies demonstrate that more intense and rapidly moving vortices are more like to cross directly over the barrier and thus maintain a continuous track in one special case of a weak but fast moving vortex approaching the southern end the model simulates the existence of

using variable resolution meshes to model tropical cyclones in the community atmosphere model abstracta statically nested variable mesh option has recently been introduced into the community atmosphere model s cam s spectral element se dynamical core that has become the default in cam version 5 3 this paper presents a series of tests of increasing complexity that highlight the use of variable resolution grids in cam se to improve tropical cyclone representation by dynamically resolving storms without requiring the computational demand of a global high resolution grid as a simplified initial test a dry vortex is advected through grid transition regions in variable resolution meshes on an irrotational planet with the cam subgrid parameterization package turned off vortex structure and intensity is only affected by grid resolution and no spurious artifacts are observed cam se model simulations using an idealized tropical cyclone test case on an aquaplanet show no numerical distortion or wave reflection when the cyclone interacts with an abrupt transition region using the same test case th

temperature variations at diffuse and focused flow hydrothermal vent sites along the northern east pacific rise in the decade following documented volcanic activity on the east pacific rise near 9 50 n we monitored hydrothermal vent fluid temperature variations in conjunction with approximately yearly vent fluid sampling to better understand the processes and physical conditions that govern the evolution of seafloor hydrothermal systems the temperature of both diffuse flow low temperature and focused flow high temperature vent fluids decreased significantly within several years of eruptions in 1991 and 1992 after mid 1994 focused flow vents generally exhibited periods of relatively stable slowly varying temperatures with occasional high and low temperature excursions lasting days to weeks one such positive temperature excursion was associated with a crustal cracking event another with both positive and negative excursions demonstrated a subsurface connection between adjacent focused flow and diffuse flow vents diffuse flow vents exhibit much greater temperature variability than adjacent higher temperature vents on timescales of a week or less temperatures at a given position within a diffuse flow field often varied by 5 10 c synchronous with near bottom currents dominated by tidal and inertial forcing on timescales of a week and longer diffuse flow temperatures varied slowly and incoherently among different vent fields at diffuse flow vent sites the conceptual model of a thermal boundary layer immediately above the seafloor explains many of the temporal and spatial temperature variations observed within a single vent field the thermal boundary layer is a lens of warm water injected from beneath the seafloor that is mixed and distended by lateral near bottom currents the volume of the boundary layer is delineated by the position of mature communities of sessile e g tubeworms and relatively slow moving organisms e g mussels vertical flow rates of hydrothermal fluids exiting the seafloor at diffuse vents are less than lateral flow rates of near bottom currents 5 10 cm s the presence of a subsurface shallow reservoir of warm hydrothermal fluids can explain differing temperature behaviors of adjacent diffuse flow and focused flow vents at 9 50 n different average temperatures and daily temperature ranges are explained by variable amounts of mixing of hydrothermal fluids with ambient seawater through subsurface conduits that have varying lateral permeability

interaction of typhoons with the taiwan orography part i upstream track deflections abstract a combined observational and numerical modeling approach is used to study the upstream track deflections of westward moving tropical cyclones approaching the mountainous terrain of taiwan although the standard deviations are large the mean track deflections are larger and have a different orientation for storms approaching the southern end of the island from those approaching the northern end the deflections tend to be larger for weaker and slower moving storms two distinct regions of upstream track deflections that are detected in the observations are explored in a sensitivity study with a 45 km horizontal resolution and 16 layer numerical model as the outer circulation of the tropical cyclone begins to interact with the mountain barrier the zonal decelerations and southward track deflections are explained by an enhanced blocking and deflection of the environmental flow advecting the cyclone the larger effect for southern approaching storms compared to northern storms is because the stron

idealized simulations of the effect of taiwan topography on the tracks of tropical cyclones with different steering flow strengths this is the fourth part of a study on the effect of topography on tropical cyclone tc tracks in previous parts idealized simulations were conducted using the weather research and forecasting model to investigate the underlying mechanisms for the upstream deflection and the local and remote topography effect on tcs with different sizes none of these simulations included any background flow in this part uniform easterly steering flows of 5 and 10 m s 1 are introduced to study the track changes under such conditions lee vortices are generated downstream of the taiwan topography by the steering flow the tc terrain induced gyres found in the previous parts also develop when the tc circulation begins to interact with the topography and subsequently dominate over taiwan the cyclonic gyre merges with the cyclonic lee vortex induced by the steering flow and the anticyclonic gyre is advected cyclonically around the tc centre which later deflects the tc because the circulation at the outer radii of a tc competes with the steering flow a smaller tc under a stronger steering flow has to move closer to taiwan in order to generate such gyres this delayed generation of the gyres then leads to the delayed onset of the northward deflection for such a tc for a large tc the circulation at its southern part is weakened by the steering flow so that the track of the anticyclonic terrain induced gyre is changed which results in a larger track deflection of the tc

track deflection of typhoon nesat 2017 as realized by multiresolution simulations of a global model abstracttyphoon nesat 2017 headed west northwestward toward taiwan but took a relatively larger northward deflection about 300 km away and then a leftward deflection after landfall at northern ta

orographic influence on a drifting cyclone abstract in this study a primitive equation numerical model is adopted to investigate the orographic influence on a drifting cyclone over an idealized topography similar to that of taiwan for a cyclone propagating from the east and impinging on the central portion of the mountain a northerly surface jet tends to form upstream of the mountain between the primary cyclone and the mountain due to blocking and channeling effects two pressure ridges and one trough are also produced when the cyclone approaches the mountain the low level vorticity and low pressure centers decelerate and turn southward upstream of the mountain due to orographic blocking at the same time the upstream low level vorticity is blocked by the mountain the abrupt increase of surface vorticity and the contraction of cyclone scale on the lee side are explained by the generation of new potential vorticity pv due to wave breaking associated with the severe downslope wind and hydraulic jump the generation of this new pv is evidenc

on the upstream track deflection of tropical cyclones past a mountain range idealized experiments abstractupstream track deflection of a propagating cyclonic vortex past an isolated mountain range is investigated by using idealized simulations with both boundary layer turbulent mixing and cloud effects the westbound vortex past a shorter mountain range may experience an earlier northward deflection prior to landfall the vortex then takes a sudden southward turn as it gets closer to the mountain range in response to the effects of the stronger northerly wind over the mountain due to the effects of channeling flow the vortex may deflect southward when approaching a longer mountain range and then rebound northward upstream of the mountain ridge the southward deflection is primarily induced by the convergence stretching effect due to the combination of the speedy core at the southwestern flank of the vortex and a northerly jet between the vortex and the mountain the vortex then rebounds northward to pass over the mountain as the speedy core rotates counterclockwise to the eastern flank of the vort

control parameters for the influence of a mesoscale mountain range on cyclone track continuity and deflection abstract in this study prospective control parameters are identified for diagnosing the continuity and deflection of cyclone tracks across a mesoscale mountain range based on idealized simulations of a westward moving cyclone it was found that the cyclone track becomes a discontinuous continuous track and the cyclone experiences more less deflection with a combination of small large values of vmax nh u nh r ly u flx and vmax fr and large small value of h lx the symbols are defined as follows vmax the maximum tangential wind n the brunt vaisala frequency h the mountain height u the basic wind speed r the radius of vmax f the coriolis parameter and lx and ly the horizontal scales of the mountain in x and y directions respectively a conceptual model is proposed to explain track deflection and continuity for a westward moving cyclone encountering idealized topography representative of the central mountain range of taiwan with weak orographic blocking a cyclone crosses over the mount

a comparison of mesh refinement in the global mpas a and wrf models using an idealized normal mode baroclinic wave simulation abstractidealized normal mode baroclinic wave simulations are conducted to examine the impact of continuous mesh refinement compared with stepwise changes in resolution using nested grids the nested grid results are produced using the advanced research weather research and forecasting wrf arw model hereafter arw and the continuous refinement results are produced using the atmospheric component of the model for prediction across scales atmosphere mpas a for the nested domain simulations with the arw variants of both one way and two way nesting techniques are examined significant reflection and distortion of waves are evident in results using one way nesting with the error increasing with decreasing boundary update frequency with continuous updating of the boundary conditions in one way and two way nesting wave distortion is still evident near the lateral boundaries but the distortion is much less than with infrequent boundary updates the conformal voronoi meshes in mpas provide a much smoothe