cloud to ground lightning throughout the lifetime of a severe storm system in oklahoma cloud to ground cg lightning data are examined relative to digitized radar data for a storm system that occurred in oklahoma on 26 may 1985 this system evolved through three stages 1 two lines of cells one near the dryline and the other 60 km ahead of it 2 a supercell storm and 3 a mesoscale convective system mcs the behavior of lightning in each stage was different initially no ground flashes were observed in either line until reflectivity increased to 46 dbz and vertically integrated liquid vil increased to 10 kg m22 then ground flash rates remained 1 2 min21 for 1 h most ground flashes in the line of storms near the dryline were negative 18 2cg 3 1cg while most in the leading line were positive 11 1cg 3 2cg a pattern of polarity opposite to what usually has been observed approximately 3 h after radar detected the first storm ground flash rates increased to 5 min21 and remained so for 6 h a mesocyclone formed approximately 30 min after flash rates exceeded 5 min 21 and a few positive ground flashes occurred near it ground flash rates increased briefly to 20 min21 as the mesocyclone dissipated and then remained 10 min21 as a squall line formed along the outflow boundary from the dissipating supercell and produced a stratiform region most ground flashes in this mcs occurred in the convective line and had negative polarity the few ground flashes in the stratiform region tended to be positive 42 1cg 32 2cg during 3 h durin g1ho f themcs ground flash rates decreased and then increased again simultaneously in both the convective and stratiform regions a previously undocumented behavior it is possible that this was caused by updrafts in both the convective line and stratiform region changing at roughly the same time it is also possible that most ground flashes in the stratiform region originated near the convective line and so were influenced by the line overall trends in ground flash density flash relative frequency reflectivity vil and severe hail reports appeared similar as the storm system evolved

cloud to ground lightning in hurricane andrew the spatial and temporal distribution of cloud to ground lightning was examined in hurricane andrew of 1992 lightning locations available from the national lightning detection network were superimposed on infrared satellite images to relate lightning activity to hurricane cloud structure a distinct radial variation occurred in time averaged flash density with a weak maximum in the eye wall a region of near zero flash density 40 to 100 km from the center and a steady increase to a large maximum in the outer rainbands 190 km from the center this radial distribution is consistent with the convective structure of mature hurricanes eye wall lightning tended to be episodic occurring almost exclusively prior to and during periods of intensification of the storm during these periods negative flashes occurred several kilometers inward from the highest eye wall cloud tops in the region of the largest radar reflectivity positive eye wall flashes while small in number tended to occur directly under the highest cloud tops the results are suggestive of a normal dipole in sign but outwardly tilted along the sloping eye wall in general hurricane flash characteristics resembled those for a background data set of nonhurricane flashes from the same area the exception occurred for negative flashes in the eye wall which had a much smaller mean peak current than the background 25 3 ka versus 44 9 ka

evidence for ocean acidification in the great barrier reef of australia geochemical records preserved in the long lived carbonate skeleton of corals provide one of the few means to reconstruct changes in seawater ph since the commencement of the industrial era this information is important in not only determining the response of the surface oceans to ocean acidification from enhanced uptake of co2 but also to better understand the effects of ocean acidification on carbonate secreting organisms such as corals whose ability to calcify is highly ph dependent here we report an 200 year d 11 b isotopic record extracted from a long lived porites coral from the central great barrier reef of australia this record covering the period from 1800 to 2004 was sampled at yearly increments from 1940 to the present and 5 year increments prior to 1940 the d 11 b isotopic compositions reflect variations in seawater ph and the d 13 c changes in the carbon composition of surface water due to fossil fuel burning over this period in addition complementary ba ca d 18 o and mg ca data was obtained providing proxies for terrestrial runoff salinity and temperature changes over the past 200 years in this region positive thermal ionization mass spectrometry ptims method was utilized in order to enable the highest precision and most accurate measurements of d 11 b values the internal precision and reproducibility for d 11 b of our measurements are better than 0 2 2r which translates to a precision of better than 0 02 ph units our results indicate that the long term pre industrial variation of seawater ph in this region is partially related to the decadal interdecadal variability of atmospheric and oceanic anomalies in the pacific in the periods around 1940 and 1998 there are also rapid oscillations in d 11 b compositions equivalent changes in ph of almost 0 5 u the 1998 oscillation is co incident with a major coral bleaching event indicating the sensitivity of skeletal d 11 b compositions to loss of zooxanthellate symbionts importantly from the 1940s to the present day there is a general overall trend of ocean acidification with ph decreasing by about 0 2 0 3 u the range being dependent on the value assumed for the fractionation factor a b3 b4 of the boric acid and borate species in seawater correlations of d 11 b with d 13 c during this interval indicate that the increasing trend towards ocean acidification over the past 60 years in this region is the result of enhanced dissolution of co2 in surface waters from the rapidly increasing levels of atmospheric co2 mainly from fossil fuel burning this suggests that the increased levels of anthropogenic co2 in atmosphere has already caused a significant trend towards acidification in the oceans during the past decades observations of surprisingly large decreases in ph across important carbonate producing regions such as the great barrier reef of australia raise serious concerns about the impact of greenhouse gas emissions on coral calcification 2009 elsevier ltd all rights reserved

error analysis for a long range lightning monitoring network of ground based receivers in europe 1 an experimental long range lightning detection system consisting of a network zeus of six ground based radio receivers has been deployed in europe and has been operated since june 2001 the receivers detect and measure the electromagnetic signal emitted by a lightning source in the very low frequency band between 5 and 15 khz sferics which propagates over thousands of kilometers in the earth ionosphere waveguide in this study lightning location retrievals from the zeus network are compared against more definitive sources in order to investigate issues on long range lightning retrieval accuracy and detection efficiency the validation study is carried out over three regions the u s east coast northwestern atlantic the african continent and within the network spain data originate from the u s national lightning detection network the lighting imaging sensor aboard the tropical rainfall measurement mission satellite and the spanish national lightning network we investigate the nature of the errors involved in the lightning location retrieval and propose a new approach for moderating some of these effects location errors are shown to vary between 40 and 400 km mode at 220 km for very long ranges 5000 km within the network the distance error does not exceed 40 km mode at 20 km random simulation results are shown to be in good agreement with validation data error reduction of 12 or 20 km at long range can be achieved by accommodating for the varying propagation velocities in the sferics wave the long range detection efficiency is shown to have a mode at approximately 20 and a relatively small spread with no obvious deviation from day to night

ocean acidification trend in the tropical north pacific since the mid 20th century reconstructed from a coral archive abstract ocean acidification caused by anthropogenically elevated co 2 concentration in the atmosphere can pose a critical threat to calcifying marine organisms and coral reef ecosystems however because of temporally and spatially limited instrumental ph records little is known about the actual long term trend and natural variability of seawater ph during the past century we present an annually resolved time series of a ph proxy record for 1940 1999 using boron isotope composition 11 b in a modern massive porites coral from guam island nw pacific when superimposed onto interannual variability the data show a slightly decreasing trend of 0 39 equivalent to 0 05 0 08 ph units for surface water ph in the northwestern tropical pacific since the mid 20th century this first reported coral based reconstruction of long term open ocean ph is a unique archive for ocean acidification trend in the north pacific ocean for the past which along with 11 b records from south pacific corals can be an important key to ascertaining the extent and rapidity of actual acidification in the pacific ocean in the future

decadal variations in trace metal concentrations on a coral reef evidence from a 159 year record of mn cu and v in a porites coral from the northern south china sea geochemical cycles of trace metals are important influences on the composition and function of the marine ecosystem although spatial distributions of most trace metals have now been determined in at least some parts of the oceans temporal variations have barely been studied on account of data limitations in this paper we report on a 159 year record of trace metal concentrations from a porites coral from the northern south china sea scs and discuss how oceanic and climatic processes control variations in mn cu and v concentrations in this region our results show that trace metal concentrations in the coral skeleton demonstrate decadal to interdecadal fluctuations and that their variations are controlled by different mechanisms the input of mn to reef water is partly controlled by the pacific decadal oscillation pdo which controls precipitation and river runoff surface water concentrations of the nutrient like element cu are controlled by summer upwelling to the east of hainan island the concentrations of v show complex interrelationships and are linked to riverine input prior to the 1990 and to upwelling after the 1990 our results imply that in the northern scs ocean atmosphere climate fluctuations such as the pdo and the east asian summer monsoon easm are important factors that influence long term variability of mn cu and v concentrations in seawater by controlling precipitation related river runoff and the strength of upwelling systems

decoupling of coral skeletal δ13c and solar irradiance over the past millennium caused by the oceanic suess effect many factors influence the seasonal changes in c levels in coral skeletons consequently the climatic and environmental significance of such changes is complicated and controversial however it is widely accepted that the secular declining trend of coral c over the past 200 years reflects the changes in the additional flux of anthropogenic co from the atmosphere into the surface oceans even so the centennial scale variations and their significance of coral c before the industrial revolution remain unclear based on an annually resolved coral c record from the northern south china sea the centennial scale variations of coral c over the past millennium were studied the coral c and total solar irradiance tsi have a significant positive pearson correlation and coupled variation during the medieval warm period and little ice age when natural forcing controlled the climate and environment this covariation suggests that tsi controls coral c by affecting the photosynthetic activity of the endosymbiotic zooxanthellae over centennial timescales however there was a decoupling of the coral skeletal c and tsi during the current warm period the period in which the climate and environment became linked to anthropogenic factors instead coral c levels have a significant pearson correlation with both the atmospheric co concentration and c levels in atmospheric co the correlation between coral c and atmospheric co suggests that the oceanic c suess effect caused by the addition of increasing amounts of anthropogenic co to the surface ocean has led to the decoupling of coral c and tsi at the centennial scale

comparing e field changes aloft to lightning mapping data 1 a newly developed balloon borne instrument contains electric and magnetic sensors for determining how lightning alters electric field vectors relative to a coordinate system fixed with the earth by combining data from this instrument with results from the compact lightning mapping array lma at langmuir laboratory in central new mexico and the national lightning detection network nldn charge transported to ground by several strokes in a cloud to ground cg lightning flash can be quantified as the flash progresses the locations of the charge centers drained by successive strokes are seen to move further from the ground strike point using this new instrument and two different models to map lma source points onto charge centers the charge transported in an intracloud ic flash is also estimated details of the instrument design and data analysis are also presented

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

case studies of developing east pacific easterly waves this paper contains a study of developing east pacific easterly waves observed during the summer of 1991 with aircraft in situ and radar data and geosynchronous infrared satellite imagery the circulation and divergence profiles surface momentum and entropy fluxes as well as 700 mb and 975 mb saturated and actual equivalent potential temperatures were measured repeatedly for three disturbances that evolved into east pacific hurricanes as the disturbances develop the level of maximum updraught mass flux decreases which leads to increased convergence at low levels this process appears to be coupled to an increase in the mid level relative humidity which in turn suppresses the development of convective downdraughts comparison of the respective tendencies of convergence and surface friction to spin up and spin down a developing disturbance suggests that friction is unimportant in the early stages of development however as the surface circulation develops the two effects become comparable in magnitude if surface friction is deposited through a fairly deep layer of the troposphere the observations appear to rule out boundary layer ekman balance in these developing systems though more accurate observations of the eddy fluxes of absolute vorticity into such systems are needed to answer this question with certainty

deconvolving the long term impacts of ocean acidification and warming on coral biomineralisation abstract identifying the long term effects of ocean acidification oa and global warming on coral calcification has proven elusive yet has major implications for the continuing viability of coral reefs in the face of climate change here we address this question using seasonally and annually resolved boron proxies 11b 10b and b ca of calcifying fluid cf phcf and carbonate ion concentrations co 3 2 cf preserved in a long lived porites coral from the great barrier reef gbr from 1939 to 2013 we find that the coral phcf closely followed the decline in seawater ph of 0 1 units but at a reduced rate of 60 indicative of biological buffering of the decline in phcf 82 is attributed to oa and 17 to the 0 5 c long term warming observed over this period this long term warming induced change in phcf is consistent with the much larger seasonally modulated changes in phcf where 4 to 6 c seasonal changes in temperatures are accompanied by relatively large antithetic 0 1 changes in phcf furthermore we find that although the supply of dissolved inorganic carbon dic of the coral cf has remained at constant elevated levels of 1 5 seawater there has been a significant long term decline 4 to 11 in the co 3 2 cf due primarily to the oa induced change in phcf this decline in co 3 2 cf a critical parameter controlling calcification is thus likely responsible for the 15 decline in coral calcification observed since 1939 and across the gbr generally

effects of vertical wind shear on the intensity and structure of numerically simulated hurricanes a series of numerical simulations of tropical cyclones in idealized large scale environments is performed to examine the effects of vertical wind shear on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic pennsylvania state university national center for atmospheric research fifth generation mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when large scale vertical shears are applied to mature tropical cyclones the storms quickly develop wavenumber one asymmetries with upward motion and rainfall concentrated on the left side of the shear vector looking downshear in agreement with earlier studies the asymmetries develop due to the storm s response to imbalances caused by the shear the storms in shear weaken with time and eventually reach an approximate steady state intensity that is well below their theoretical maximum potential intensity as expected the magnitude of the weakening increases with increasing shear all of the storms experience time lags between the imposition of the large scale shear and the resulting rise in the minimum central pressure while the lag is at most a few hours when the storm is placed in very strong 15 m s21 shear storms in weaker shears experience much longer lag times with th e5ms 21 shear case showing no signs of weakening until more than 36 h after the shear is applied these lags suggest that the storm intensity is to some degree predictable from observations of largescale shear changes in all cases both the development of the asymmetries in core structure and the subsequent weakening of the storm occur before any resolvable tilt of the storm s vertical axis occurs it is hypothesized that the weakening of the storm occurs via the following sequence of events first the shear causes the structure of the eyewall region to become highly asymmetric throughout the depth of the storm second the asymmetries in the upper troposphere where the storm circulation is weaker become sufficiently strong that air with high values of potential vorticity and equivalent potential temperature are mixed outward rather than into the eye this allows the shear to ventilate the eye resulting in a loss of the warm core at upper levels which causes the central pressure to rise weakening the entire storm the maximum potential vorticity becomes concentrated in saturated portions of the eyewall cloud aloft rather than in the eye third the asymmetric features at upper levels are advected by the shear causing the upper portions of the vortex to tilt approximately downshear the storm weakens from the top down reaching an approximate steady state intensity when the ventilated layer can descend no farther due to the increasing strength and stability of the vortex at lower levels

variations in the pacific decadal oscillation since 1853 in a coral record from the northern south china sea 1 the pacific decadal oscillation pdo has been shown to have significant climatic and environmental impacts across the pan pacific basin however there are no records of pdo activity from the south china sea scs the largest marginal sea in the northwest pacific ocean this study suggests that a series of geochemical profiles obtained from a modern coral in the northern scs records annual pdo activity dating back to 1853 these geochemical data are significantly correlated with the pdo index and their patterns of variation closely match those of the pdo index over the last century the relationship between the pdo and coral geochemistry may be related to the influence of the pdo on rainfall on hainan island rainfall patterns influence the volume of terrestrial runoff which in turn is a primary determinant of 18o and 18o values in coral however coral 13c values are also influenced by the 13c suess effect the results indicate that sr ca ratios in coral are affected by a combination of sea surface temperature and terrestrial runoff

mesoscale interactions in tropical cyclone genesis with the multitude of cloud clusters over tropical oceans it has been perplexing that so few develop into tropical cyclones the authors postulate that a major obstacle has been the complexity of scale interactions particularly those on the mesoscale which have only recently been observable while there are well known climatological requirements these are by no means sufficient a major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development observations exist for only a few forming cases in these the moist convection in the preformation environment is organized into mesoscale convective systems each of which have associated mesoscale potential vortices in the midlevels interactions between these systems may lead to merger growth to the surface and development of both the nascent eye and inner rainbands of a tropical cyclone the process is essentially stochastic but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences for example a monsoon trough provides a region of reduced deformation radius which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices further a strong monsoon trough provides a vertical wind shear that enables long lived midlevel mesoscale vortices that are able to maintain or even redevelop the associated convective system the authors develop this hypothesis by use of a detailed case study of the formation of tropical cyclone oliver observed during toga coare 1993 in this case two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband the eye developed on the edge of the major convective system and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere the importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western north pacific

relative influences of the interdecadal pacific oscillation and enso on the south pacific convergence zone 1 the south pacific convergence zone spcz one of the most extensive features of the global atmospheric circulation is shown to vary its location according to both the polarity of the el nino southern oscillation enso and of the interdecadal pacific oscillation ipo we first demonstrate that the ipo can be regarded as the quasi symmetric pacific wide manifestation of the pacific decadal oscillation that has been described for the north pacific shifts in the position of the spcz related to enso on interannual time scales and to the ipo on decadal time scales appear to be of similar magnitude and are largely linearly independent a station pressure based index of variations in spcz latitude is shown to be significantly related to the polarity of the ipo when enso influences are accounted for movements of this sensitive section of the spcz have occurred in phase with those of the ipo since the 1890s

external influences on hurricane intensity part iii potential vorticity structure abstract the interaction of hurricane elena 1985 with a baroclinic wave was reexamined using both potential vorticity pv and a formulation for eliassen palm fluxes in cylindrical coordinates the hurricane began to deepen rapidly as a narrow upper level positive pv anomaly became nearly superposed over the low level center the intensification appeared to represent an evaporation wind feedback activated by constructive interference of the pv anomalies enhanced convection associated with this process eroded the upper pv anomaly and prevented it from crossing the hurricane and reversing the intensification the eliassen palm flux divergence showed that maximum eddy activity remained in the upper troposphere prior to the reintensification this activity was produced in part because the action of the outflow anticyclone of the hurricane contributed to synoptic scale wave breaking the upper level pv anomaly that approached the center was much narrower in extent than the original synoptic scale trough th

some aspects of hurricane inner core dynamics and energetics abstract the energy cycle of the mature hurricane resides in the secondary circulation that passes through the storm s eyewall by equating the generation of energy in this cycle to boundary layer dissipation an upper bound on wind speed is derived this bound depends on the degree of thermodynamic disequilibrium between the tropical ocean and atmosphere on the difference between sea surface and outflow absolute temperatures and also on the ratio between the enthalpy exchange and surface drag coefficients such a bound proves to be an excellent predictor of maximum wind speeds in two different axisymmetric numerical models and does not appear to depend on the existence of the hurricane eye but further consideration of the detailed dynamics of the eye and eyewall show that the intensification of hurricanes is accelerated by feedbacks associated with a component of eye subsidence forced by radial turbulent diffusion of momentum this radial momentum diffusion is an inevitable by product of the strong fr

the effect of vertical shear on tropical cyclone intensity change abstract the effect of vertical shear on tropical cyclone intensity change is usually explained in terms of ventilation where heat and moisture at upper levels are advected away from the low level circulation which inhibits development a simple two layer diagnostic balance model is used to provide an alternate explanation of the effect of shear when the upper layer wind in the vortex environment differs from that in the lower layer the potential vorticity pv pattern associated with the vortex circulation becomes tilted in the vertical the balanced mass field associated with the tilted pv pattern requires an increased midlevel temperature perturbation near the vortex center it is hypothesized that this midlevel warming reduces the convective activity and inhibits the storm development previous studies have shown that diabatic heating near the storm center acts to reduce the vertical tilt of the vortex circulation these studies have also shown that there is an adiabatic process that acts to redu

performance evaluation of the u s national lightning detection network in eastern new york 2 location accuracy we have evaluated the location accuracy of the u s national lightning detection network nldn via comparison of individual nldn stroke locations with their corresponding stroke terminations as determined from multiple site video recordings of local cloud to ground lightning flashes the video records used in this analysis were acquired in the vicinity of albany new york during the summers of 1994 and 1995 seasons corresponding to the initial and final phases of the upgrade of the nldn to the improved accuracy from combined technology impact configuration for 1994 a total of 751 strokes were located in common between the video and nldn data sets yielding median and mean values of the nldn video location separation of 2 21 km and 3 74 km respectively constraint of the 1994 data to the best video locations those with a semimajor axis value of the 50 error ellipse less than 500 m yielded a subset of 53 strokes with median and mean values of the nldn video location separation of 2 61 km and 4 74 km respectively for 1995 a total of 219 strokes were located in common yielding median and mean values of the nldn video location separation of 442 m and 865 m respectively constraint of the 1995 data to that year s best video locations those with a semimajor axis value of the 50 error ellipse less than 200 m yielded a subset of 79 common strokes with median and mean values of the nldn video location separation of 435 m and 625 m respectively the impact upgrade of the nldn apparently has resulted in about a fivefold increase in location accuracy a special subset of 11 strokes occurred in 1995 these were located by the nldn and observed to terminate on local structures of accurately known location for these 11 strokes the median and mean values of the nldn location error are 518 m and 484 m respectively a result quite consistent with the overall nldn video location comparison and the claimed 500 m median location accuracy for the upgraded network indeed we argue that removal of an apparent residual bias in the nldn locations ultimately could yield a median location accuracy in this region approaching 250 m finally we find that the nldn location error is a function of the estimated stroke peak current with the weakest peak currents having the poorest locations for both years for the 1995 data strokes with peak currents of intermediate magnitude 20 30 ka were the most accurately located

convective structure of hurricanes as revealed by lightning locations cloud to ground lightning flash locations were examined for nine atlantic basin hurricanes using data from the national lightning detection network a common radial distribution in ground flash density was evident a weak maximum in the eyewall region a clear minimum 80 100 km outside the eyewall and a strong maximum in the vicinity of outer rainbands 210 290 km radius these results are consistent with the authors previous study of hurricane andrew none of the storms showed this characteristic radial structure during prehurricane stages the results support the division of precipitation in the hurricane into three distinct regimes the eyewall is a unique phenomenon but shares some attributes with deep weakly electrified oceanic monsoonal convection the region outside the eyewall and under the central dense overcast has characteristics of the trailing stratiform region of mesoscale convective systems including a relatively high fraction of positive polarity flashes the outer bands with mean maximum flash density at the 250 km radius contain the vast majority of ground flashes in the storms eyewall lightning defined as that within 40 km of the center was examined for four moderate to strong hurricanes such lightning occurred episodically during hurricane stage with 93 of hourly intervals containing no detected flashes eyewall lightning outbreaks over water always occurred at the beginning of or during times of intensification but often were indicative of the imminent end of deepening it is proposed that the existence of such inner core lightning might reveal the presence of an eyewall cycle for the one storm with available aircraft reconnaissance data eyewall cycles were reliably identified by the occurrence of inner core lightning and inner core lightning appeared only during such cycles suggestions are made as to how eyewall flashes in existing hurricanes might be used to help predict hurricane intensity change

the relationship between storm motion vertical wind shear and convective asymmetries in tropical cyclones abstract the influence of the direction of storm motion on the azimuthal distribution of electrified convection in 35 atlantic basin tropical cyclones from 1985 to 1999 was examined using data from the national lightning detection network in the inner 100 km flashes most often occurred in the front half of storms with a preference for the right front quadrant in the outer rainbands r 100 300 km flashes occurred predominantly to the right of motion although the maximum remained in the right front quadrant the results are shown to be consistent with previous studies of asymmetries in rainfall radar reflectivity and vertical motion with respect to tropical cyclone motion the motion effect has been attributed to the influence of asymmetric friction in the tropical cyclone boundary layer the authors previously found a strong signature in the azimuthal distribution of lightning with respect to vertical wind shear because both effects show clearly vertical wind shear and storm motion must themse

wet and cold climate conditions recorded by coral geochemical proxies during the beginning of the first millennium ce in the northern south china sea abstract the past two millennia include some distinct climate intervals such as the medieval warm period mwp and the little ice age lia which were caused by natural forcing factors as well as the current warm period cwp that has been linked to anthropogenic factors therefore this period has been of great interest to climate change researchers however most studies are based on terrestrial proxy records historical documentary data and simulation results and the ocean and the tropical record are very limited the eastern han three kingdoms and western jin periods 25 316 ce cover the beginning first millennium ce in china and were characterized by a cold climate and frequent wars and regime changes this study used paired sr ca and 18o series recovered from a fossil coral to reconstruct the sea surface water conditions during the late eastern han to western jin periods 167 309 ce at wenchang eastern hainan island in the northern south china sea scs to investigate climate change at this time the long term sea surface temperature sst during the study interval was 25 1 c which is about 1 5 c lower than that of the cwp 26 6 c compared with the average value of 0 40 during the cwp the long term average seawater 18o 0 06 was more negative these results indicate that the climate conditions during the study period were cold and wet and comparable with those of the lia this colder climate may have been associated with the weaker summer solar irradiance the wet conditions were caused by the reduced northward shift of the intertropical convergence zone monsoon rainbelt associated with the retreat of the east asian summer monsoon interannual and interdecadal climate variability may also have contributed to the variations in sst and seawater 18o recorded over the study period

yin yang grid an overset grid in spherical geometry 1 a new kind of overset grid named yin yang grid for spherical geometry is proposed the yin yang grid is composed of two identical component grids that are combined in a complemental way to cover a spherical surface with partial overlap on their boundaries each component grid is a low latitude part of the latitude longitude grid therefore the grid spacing is quasi uniform and the metric tensors are simple and analytically known one can directly apply mathematical and numerical resources that have been written in the spherical polar coordinates or latitude longitude grid the complemental combination of the two identical component grids enables us to make efficient and concise programs simulation codes for geodynamo and mantle convection simulations using finite difference scheme based on the yin yang grid are developed and tested the yin yang grid is suitable for massively parallel computers

diurnal and seasonal variations of carbonate system parameters on luhuitou fringing reef sanya bay hainan island south china sea the 3 day diurnal dynamics of carbonate system and related parameters on luhuitou fringing reef of sanya bay adjacent to the south china sea scs were observed in december of 2009 early winter april spring july summer and november late autumn of 2010 the luhuitou fringing reef ecosystem was generally dominated by macro and planktonic algae throughout the year except by coralline algae in winter the system parameters showed distinct diurnal trends in the four seasons averaged ranges of diurnal variation for dissolved oxygen and partial pressure of co2 pco 2 were higher in the autumn 4 67 mg l 1 and 218 2 mu atm respectively than other seasons averaged ranges of diurnal variation for normalized total alkalinity nta was higher in the winter 61 3 mu mol kg 1 and lower in the spring 16 0 mu nol kg 1 the diurnal variations are mainly controlled by biological activities especially by the processes of photosynthesis and respiration in the reef ecosystem in winter however calcification and dissolution contributed more to the diurnal variations compared with the other three seasons total alkalinity was largely related to seasonal changes in river inflow rates dissolved oxygen ph total co2 and aragonite saturation also showed seasonal variations these variations were mainly controlled by the seasonal changes of photosynthesis and respiration which were mainly affected by changes in benthic community structure temperature and river inflow rates the oversaturated pco 2 in the reef ecosystem with respect to the atmosphere in the winter and summer resulted in co2 discharge from the reef ecosystem to the scs the whole system served as net source of co2 to the atmosphere and the adjacent south china sea on an annual time scale c 2013 elsevier ltd all rights reserved

a composite study of the interactions between tropical cyclones and upper tropospheric troughs abstract the objective of this study is to understand how interactions with upper tropospheric troughs affect the intensity of tropical cyclones the study includes all named atlantic tropical cyclones between 1985 and 1996 to minimize other factors affecting intensity change times when storms are over subcritical sea surface temperatures 26 c or near landfall are removed from the sample a trough interaction is defined to occur when the eddy momentum flux convergence calculated over a 300 600 km radial range is greater than 10 m s 1 day 1 the trough interaction cases are separated into four composites i favorable superposition tropical cyclone intensifies with an upper tropospheric potential vorticity pv maximum within 400 km of the tropical cyclone center ii unfavorable superposition iii favorable distant interaction upper pv maximum between 400 and 1000 km from the tropical cyclone center and iv unfavorable distant interaction for comparison two additional composites are cre

tropical storm formation in a baroclinic environment abstract an analysis is presented of the large scale conditions associated with the initial development of tropical storm diana september 1984 in a baroclinic environment ordinary extratropical wave cyclogenesis began along an old frontal boundary east of florida after 0000 utc 7 september and culminated in tropical cyclogenesis 48 h later water vapor satellite imagery showed that the initial cyclogenesis and incipient tropical storm formation was nearly indistinguishable from a classical midlatitude development cyclogenesis occurred in three stages a large scale cold trough and associated frontal system crossed the atlantic coast while a small potential vorticity maximum aloft fractured off the main trough and stalled over central florida in the first stage as the main trough sheared off eastward cyclogenesis began along the southwestern end of the stalled frontal zone east of florida anticyclogenesis to the north in the wake of the shearing trough allowed a surge of cooler and drier air to flo

forte radio frequency observations of lightning strokes detected by the national lightning detection network this work compares simultaneous observations of lightning from two complementary systems forte is a low earth orbit satellite carrying radiowave and optical instruments for the study of lightning the radio receivers aboard forte observe very high frequency vhf emissions from the air breakdown process preceding and sometimes accompanying a lightning current the national lightning detection network nldn is a ground based array of sensors in the contiguous united states observing the low frequency lf and very low frequency vlf radiation from vertical currents prior to the launch of forte in 1997 essentially no work had been done on the statistical correlations between 1 ground based lf vlf and 2 spaced based vhf remote sensing of lightning during a 6 month campaign in april september 1998 forte took most of its triggered vhf data over and near the contiguous united states and nldn data were specially postprocessed in a loosened criterion mode providing enhanced detection range beyond the coastline and borders of the array itself the time history of reported events from the two systems was compared and event pairs each pair containing one event from forte the other from nldn which were candidate correlations closer than 200 ms from each other were scrutinized to determine whether the members of a pair actually came from the same discharge process we have found that there is a statistically significant correlation for a subset of forte events this correlation is most likely to occur for intracloud and less likely to occur for cloud to ground discharges the correlated vhf and nldn events tend to occur within 30 s of each other after correction for the propagation of the vhf signal to forte from the nldn geolocated stroke location most correlations outside of 30 s turn out to be merely a statistical accident the nldn furnished geolocation allows the correlated forte detected vhf pulses to be better interpreted in particular we can deduce from the lag of the vhf ground reflection echo the height of the vhf emission region in the storm

the role of synoptic scale flow during tropical cyclogenesis over the north atlantic ocean abstract the synoptic scale flow during tropical cyclogenesis and cyclolysis over the north atlantic ocean is investigated using compositing methods genesis and lysis are defined using the national hurricane center nhc now known as the tropical prediction center best track data genesis lysis occurs when nhc first last identifies and tracks a tropical depression in the final best track dataset storm centered composites are created with the analysis of the tropical oceanic lower level atoll 900 hpa and 200 hpa winds for june november produced by nhc for the years 1975 93 results show that significant regional differences exist in 200 hpa flow during genesis across the atlantic basin composites of genesis in the western part of the basin show a 200 hpa trough ridge located to the west east of the atoll disturbance in the eastern half of the basin composites of genesis show a sprawling 200 hpa ridge centered northeast of the atoll disturbance the major axis of this elliptically shaped 20

ground based detection of sprites and their parent lightning flashes over africa during the 2006 amma campaign sprites have been detected in video camera observations from niger over mesoscale convective systems in nigeria during the 2006 amma african monsoon multidisciplinary analysis campaign the parent lightning flashes have been detected by multiple extremely low frequency elf receiving stations worldwide the recorded charge moments of the parent lightning flashes are often in excellent agreement between different receiving sites and are furthermore consistent with conventional dielectric breakdown in the mesosphere as the origin of the sprites analysis of the polarization of the horizontal magnetic field at the distant receivers provides evidence that the departure from linear magnetic polarization at elf is caused primarily by the day night asymmetry of the earth ionosphere cavity copyright c 2009 royal meteorological society

global transport on a spherical multiple cell grid abstractsecond and third order upstream nonoscillatory uno advection schemes are applied on a spherical multiple cell smc grid for global transport similar to the reduced grid the smc grid relaxes the courant friedrichs lewy cfl restriction of the eulerian advection time step on the conventional latitude longitude grid by zonally merging cells toward the poles round polar cells are introduced to remove the polar singularity of the spherical coordinate system the unstructured feature of the smc grid allows unused cells to be removed out of memory and transport calculations solid body rotation and deformation flow tests are used for comparison with other transport schemes application on the global ocean surface is used to demonstrate the flexibility of the smc grid by removing all land points and making possible the extension of global ocean surface wave models to cover the arctic in response to the retreating sea ice in recent summers numerical results suggest that uno schemes on the smc grid

coprecipitation and isotopic fractionation of boron in modern biogenic carbonates abstract the abundances and isotopic composition of boron in modern biogenic calcareous skeletons from the gulf of elat israel the great barrier reef australia and in deep sea sediments have been examined by negative thermal ionization mass spectrometry the selected species foraminifera pteropoda corals gastropoda and pelecypoda yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals the boron content of the biogenic skeletons is independent of mineralogical composition and is probably related to biological vital effects the 11 b values of the carbonates range from 14 2 to 32 2 relative to nbs srm 951 and overlap with the 11 b values of modern deep sea carbonate sediments 11 b 8 9 to 26 2 the variations of 11 b may be controlled by isotopic exchange of boron species in which 10 b is preferentially partitioned into the tetrahedral species and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates carbonates with low 11 b values 15 may indicate preferential incorporation of tetrahedral species whereas the higher 11 b values 30 may indicate 1 1 uptake of both boron species assuming equilibrium with seawater 2 2 preferential incorporation of b oh 4 from in situ high ph internal fluids of organisms that are isolated from seawater the b content and 11 b values of deep sea sediments foraminifera tests and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition as a result of enrichment of b in corals a substantially higher biogenic sink of 6 4 0 9 10 10 g yr is calculated for carbonates this is only slightly lower than the sink for desorbable b in marine sediments 10 10 10 g yr and approximately half that of altered oceanic crust 14 10 10 g yr thus carbonates are an important sink for b in the oceans being 20 of the total sinks the preferential incorporation of 10 b into calcium carbonate results in oceanic 11 b enrichment estimated as 1 2 0 3 10 12 per mil g yr the boron isotope composition of authigenic well preserved carbonate skeletons may provide a useful tool to record secular boron isotope variations in seawater at various times in the geological record the potential use of boron isotope geochemistry in skeletons as a tracer for palaeoenvironments is demonstrated in ostracoda and foraminifera from the gulf of carpentaria australia the 11 b values of glacial age buried skeletons 4 0 and 4 9 respectively are lower than that of their modern equivalents 17 6 and 13 3 respectively this may reflect a terrestrial boron isotope signature of the water in the gulf during the late quaternary when it was isolated from the ocean

quantifying the ph vital effect in the temperate zooxanthellate coral cladocora caespitosa validation of the boron seawater ph proxy boron isotopic and elemental systematics are used to define the vital effects for the temperate shallow water mediterranean coral cladocora caespitosa the corals are from a range of seawater ph conditions pht 7 6 to 8 1 and environmental settings 1 naturally living colonies harvested from normal ph waters offshore levanto 2 colonies transplanted nearby a subsea volcanic vent system and 3 corals cultured in aquaria exposed to high 700 atm and near present day 400 atm pco2 levels b ca compositions measured using laser ablation inductively coupled mass spectrometry la icpms show that boron uptake by c caespitosa cultured at different pco2 levels is independent of ambient seawater ph being mainly controlled by temperature dependent calcification in contrast the boron isotope compositions 11bcarb of the full suite of corals determined by positive thermal ionisation mass spectrometry ptims shows a clear trend of decreasing 11bcarb from 26 7 to 22 2 with decreasing seawater ph reflecting the strong ph dependence of the boron isotope system the 11bcarb compositions together with measurements of ambient seawater parameters enable calibration of the boron ph proxy for c caespitosa by using a new approach that defines the relationship between ambient seawater ph phsw and the internally controlled ph at the site of calcification phbiol c caespitosa exhibits a linear relationship between phsw and the shift in ph due to physiological processes ph phbiol phsw giving the regression phclad 4 80 0 52 phsw for this species we further apply this method ph phsw to calibrate tropical species of porites acropora and stylophora reported in the literature the temperate and tropical species calibrations are all linearly correlated r2 0 9 and the biological fractionation component ph between species varies within 0 2 ph units our ph phsw approach provides a robust and accurate tool to reconstruct palaeoseawater phsw for both temperate and tropical corals further validating the boron fractionation factor b3 b4 1 0272 determined experimentally by klochko et al 2006 and the boron isotope ph proxy both of which have been the foci of considerable debate

evaluation of a long range lightning detection network with receivers in europe and africa this study focuses on the performance evaluation of the experimental long range lightning detection network zeus with receivers located in europe and africa the evaluation is carried out in terms of locating error and detection performance zeus receivers record the radio noise sferics emitted by cloud to ground lightning discharges in the very low frequency bandwidth between 5 and 15 khz the lightning location is retrieved by means of the arrival time difference atd triangulation technique the presented study includes evaluation of the system s locating error and detection performance over the african continent equatorial mid atlantic the caribbean and northern south america this dataset is validated over a period extending from july through october 2004 the lightning imaging sensor onboard nasa s tropical rainfall measuring mission satellite is used as the validation source the analysis shows that the number of receivers as well as their relative location relative position of the flash event to the network s receivers plays a key role in the retrieval error magnitude median error values within the network s periphery are found to be approximately 20 km while outside the periphery significantly larger spl sim 130 km simulation of chi square values implemented from the atd algorithm shows an adequate agreement between theoretical error related computations and the network s retrievals in terms of detection performance the zeus system is also validated over the same area period the chief observation is that the detection performance is likewise dependent on the number of receivers used by the system rather than their relative location

external influences on hurricane intensity part i outflow layer eddy angular momentum fluxes abstract outflow layer winds were objectively analyzed every 12 h for 6 days during the life cycle of hurricane elena 1985 a high correlation was found between angular momentum fluxes by azimuthal eddies at large radii and central pressure changes in the storm 27 33 h later momentum flux by eddies exceeded that by the azimuthal mean outside the 800 km radius while vortex spinup by the eddies reached instantaneous magnitudes as large as 25 m s 1 day outflow maxima and minima repeatedly appeared more than 1000 km from the hurricane center and tracked inward with time the results provide evidence of significant environmental control on the behavior of the storm after reaching hurricane strength elena experienced a major secondary intensification associated with a large inward cyclonic eddy momentum flux produced by the passage of a middle latitude trough north of the hurricane an outflow maximum appeared radially inside of the eddy momentum source consistent with balanced vortex theory and tracke

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

carbon and oxygen isotopic composition of a guam coral and their relationships to environmental variables in the western pacific we examine the high resolution 32 samples year carbon and oxygen isotopic composition 13ccoral and 18ocoral in a coral core porites lobata from double reef guam over the years 1980 2000 the 13ccoral shows clear seasonal variations with mean seasonal amplitude of 1 89 which roughly corresponds with seasonal variations in solar radiation the seasonal amplitude of 18ocoral variations are small 0 23 0 57 but they are significantly correlated with sea surface temperature sst and salinity sss the 18ocoral and sst are more strongly correlated during el nino southern oscillation enso warm phases r 0 81 p 28 c and lower values of 18osw at guam these differences in oceanic parameters result from movements of the western pacific warm pool wpwp during the different phases of enso anomalies in 18osw inferred from the 18ocoral and instrumental sst are consistent with sss anomalies for the years 1980 2000 these 18osw anomalies may reflect changes in sss and evaporation precipitation due to movements of the wpwp this detailed analysis of a coral from guam suggests that it may contain an excellent archive of past enso events

the evolution of hurricane danny 1997 at landfall doppler observed eyewall replacement vortex contraction intensification and low level wind maxima danny made landfall as a minimal hurricane on the alabama coast on 19 july 1997 after drifting over mobile bay for over 10 h danny s unusually close proximity to the doppler radar wsr 88d in mobile provided an unprecedented view of the storm s complex and dramatic evolution during a prolonged landfall event over a 1 day period base reflectivity and velocity products were combined with aircraft reconnaissance information to detail the formation of concentric eyewalls and complete evolution of an eyewall replacement cycle this highly symmetric hurricane then underwent a rapid asymmetric transition in mobile bay during which a small eyewall mesovortex developed adjacent to intense convection in the western eyewall radar estimated rainfall increased dramatically during the asymmetric phase rates exceeded 100 mm h21 for nine consecutive hours west of the center while precipitation nearly vanished to the east changes in the distribution of precipitation corresponded with changes in the low level wind velocity structure a 25 h temporal composite of wsr 88d base velocities displayed axisymmetric intensification and contraction of danny s core during the eyewall replacement cycle later the asymmetric phase was dominated by further contraction and intensification on the west side only in the western eyewall a persistent boundary layer wind maximum evolved and contracted to a radius of only 10 13 km from the center concurrently eastside boundary layer winds diminished as the maximum winds rose to 1 1 5 km altitude and the radius expanded danny reached maximum intensity during this asymmetric phase in mobile bay with base velocities 44 m s21 85 kt at 600 m elevation eyewall contraction in the meandering storm combined with climatologically elevated ssts in shallow mobile bay probably played significant roles in danny s continued intensification there discrepancies arose in determining danny s structural patterns intensity and evolution during landfall interpretation varied depending on the type of platform used to observe the storm the continual sampling of the storm by the nearby wsr 88d provided detail not available from aircraft data alone doppler base velocities in the intense westside convection were much stronger than measured at flight level yet the opposite was true in the storm s drier east side doppler radar showed that the westside base velocity maxima were confined to the boundary layer 600 700 m and represented a slightly conservative estimate of maximum surface gusts recorded at dauphin island during the passage of danny s convective eyewall thus winds probably were even stronger at boundary layer levels below the wsr 88d s lowest scan elevation the shallowness and persistence of danny s boundary layer velocity maxima stressed the need for accurate wind information in the lowest few hundred meters of a tropical cyclone s eyewall for a better indication of the storm s true intensity and near surface wind velocities

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

recent 121 year variability of western boundary upwelling in the northern south china sea 1 coastal upwelling is typically related to the eastern boundary upwelling system whereas the powerful southwest asian summer monsoon can also generate significant cold nutrient rich deep water in western coastal zones here we present a sea surface temperature record a d 1876 1996 derived from coral porites sr ca for an upwelling zone in the northern south china sea the upwelling induced sea surface temperature anomaly record reveals prominent multidecadal variability driven by asian summer monsoon dynamics with an abrupt transition from warmer to colder conditions in 1930 and a return to warmer conditions after 1960 previous studies suggest the expected increase in atmospheric co2 for the coming decades may result in intensification in the eastern boundary upwelling system which could enhance upwelling of co2 rich deep water thus exacerbating the impact of acidification in these productive zones in contrast the weakening trend since 1961 in the upwelling time series from the northern south china sea suggests moderate regional ocean acidification from upwelling thus a stress relief for marine life in this region

experimental measurement of boron isotope fractionation in seawater abstract the boron isotopic composition of marine carbonates is considered to be a tracer of seawater ph use of this proxy benefits from an intimate understanding of chemical kinetics and thermodynamic isotope exchange reactions between the two dominant boron bearing species in seawater boric acid b oh 3 and borate ion b oh 4 however because of our inability to quantitatively separate these species in solution the degree of boron isotope exchange has only been known through theoretical estimates in this study we present results of a spectrophotometric procedure wherein the boron isotope equilibrium constant 11 10 k b is determined empirically from the difference in the dissociation constants of 11 b oh 3 and 10 b oh 3 in pure water 0 6 mol kg 1 h 2 o kcl and artificial seawater within experimental uncertainty our results show no dependence of 11 10 k b on temperature but 11 10 k b at 25 c in pure water was statistically different than results obtained in solutions at high ionic strength 11 10 k b of the seawater s 35 b t 0 01 mol kg 1 h 2 o at 25 c is 1 0272 0 0006 this result is significantly larger than the theoretical value used in numerous paleo ph studies 11 10 k b 1 0194

an experimental study of the remote location of lightning flashes using a vlf arrival time difference technique the operational cathode ray direction finding crdf network for the location of lightning flashes at ranges up to thousands of kilometres can be replaced by a system using the arrival time difference atd technique the atd technique has theoretical advantages over crdf which could lead to substantially improved flash location but the extent to which it suffers from certain propagation effects in practice must be quantified in an experiment using the atd technique equipments were deployed in the u k and gibraltar these captured the vertical electric field of vlf electromagnetic radiation from individual lightning flashes synchronized to crdf selected flashes and recorded against an accurate timebase by analysing the data using techniques analogous to those of hyperbolic navigation the flash location was inferred together with a measure of the data consistency atd location of independent flashes observed in time proximity frequently gave the tight grouping expected from an isolated active thunderstorm cell groups of diameter 2 10 km were observed at megametre ranges atd flash locations were compared with crdf and other meteorological data positioning agreed within the limited accuracy of current techniques but the crdf system s potential for poor accuracy was highlighted an analysis method was developed relating the internal consistency of the atd flash data to geographical location accuracy and atd accuracy of less than 5 s was measured experimentally on this basis an atd system can locate flashes over a synoptic scale area with errors comparable with a storm cell diameter

cloud to ground lightning in tropical cyclones a study of hurricanes hugo 1989 and jerry 1989 abstract cloud to ground lightning characteristics of two atlantic cyclones of 1989 hurricanes hugo and jerry are presented statistics on the number of flashes location polarity peak currents and multiplicity number of strokes per flash are examined in an 18 h period divided into prelandfall and postlandfall categories land based and aircraft lower fuselage radar data are also analyzed to determine the nature of the precipitation in which lightning is detected jerry is found to be more electrically active than hugo with 691 flashes detected compared with 33 flashes for hugo the majority of these flashes regardless of the polarity are located in the right front and right rear quadrants of the hurricanes almost exclusively in outer convective rainbands one reason for the large difference in the number of flashes between the two storms is the presence of many convective rainbands in jerry compared to only a few in hugo more than 20 of the flashes in each storm have a positive polarity me

reflectivity ice scattering and lightning characteristics of hurricane eyewalls and rainbands part ii intercomparison of observations abstract part i of this two part paper treats tropical rainfall measuring mission trmm radar passive microwave and lightning observations in hurricanes individually this paper part ii examines relationships between these parameters and implications of the relationships quantitative relationships between lightning occurrence and 85 ghz brightness temperature 37 ghz brightness temperature and radar reflectivity in the mixed phase region are established separately for hurricane eyewall regions inner rainband regions and outer rainband regions other tropical oceanic regions and tropical continental regions when any of the brightness temperature or radar parameters are held constant as controls lightning is more frequent in hurricane outer rainbands than elsewhere over tropical oceans and more frequent over continents than even in the outer rainbands reflectivity profiles associated with specific brightness temperatures are presented demonstrating a link between high altitude ice phase pre

global boron cycle in the anthropocene this paper presents a revised and updated synthesis of the biogeochemical cycle of boron at the earth s surface where the largest fluxes are associated with the injection of sea salt aerosols to the atmosphere 1 44 tg b yr production and combustion of fossil fuels 1 2 tg b yr atmospheric deposition 3 48 tg b yr the mining of b ores 1 1 tg b yr and the transport of dissolved and suspended matter in rivers 0 80 tg b yr the new estimates show that anthropogenic mobilization of b from the continental crust exceeds the naturally occurring processes resulting in substantial fluxes to the ocean and the hydrosphere the anthropogenic component contributes 81 of the flux in rivers the mean residence time for b in seawater supports the use of 11b in marine carbonates as an index of changes in the ph of seawater over time periods of 1 ma

mesoscale observations of the genesis of hurricane dolly 1996 abstract recent numerical studies of tropical cyclone genesis suggest a new paradigm for how the surface vortex is established based on a highly nonaxisymmetric mechanism involving the interaction of low level cyclonic circulations generated by deep cumulonimbus convection a reexamination of mesoscale observations during the genesis of hurricane guillermo 1991 confirms the presence of multiple cyclonic circulations more recently airborne doppler radar wind observations during the genesis of atlantic hurricane dolly 1996 also reveal multiple lower to middle tropospheric mesoscale cyclonic circulations during sequential 15 20 min compositing periods a particularly well organized but initially weak mean tangential wind of 7 m s 1 low level cyclonic vortex embedded within the pre dolly tropical disturbance is observed coincident with deep vertically penetrating cumulonimbus convection the earliest observations of this vortex show the peak circulation near 2 km height with a mean diameter of 30 4

the effects of vertical wind shear on the distribution of convection in tropical cyclones abstract the influence of vertical wind shear on the azimuthal distribution of cloud to ground lightning in tropical cyclones was examined using flash locations from the national lightning detection network the study covers 35 atlantic basin tropical cyclones from 1985 99 while they were over land and within 400 km of the coast over water a strong correlation was found between the azimuthal distribution of flashes and the direction of the vertical wind shear in the environment when the magnitude of the vertical shear exceeded 5 m s 1 more than 90 of flashes occurred downshear in both the storm core defined as the inner 100 km and the outer band region r 100 300 km a slight preference for downshear left occurred in the storm core and a strong preference for downshear right in the outer rainbands the results were valid both over land and water and for depression storm and hurricane stages it is argued that in convectively active tropical cyclones deep divergent circulations oppose the ver

baroclinically induced tropical cyclogenesis abstract the authors investigate the transition of numerous subtropical cyclones into late season tropical storms and hurricanes during the 2000 and 2001 atlantic tropical cyclone seasons in all transitioning cases 10 the 900 200 hpa wind shear was initially near or in excess of the upper limit of vertical shear deemed suitable for tropical cyclogenesis in many of these cases the vertical shear decreased markedly near or prior to the time of tropical cyclone formation in cases that did not become named tropical cyclones either the tropospheric vertical shear remained in excess of 15 20 m s 1 or the underlying sea surface temperature sst dropped below about 26 c prior to or during the weakening of the shear cases in which the shear remained large featured multiple short wave upper tropospheric troughs interacting with the developing lower tropospheric disturbance such that classical occlusion did not occur through detailed analysis and simulation of the development of hurricane michael in 2000

tropical cyclogenesis via convectively forced vortex rossby waves in a shallow water primitive equation model abstract this work examines further the problem of tropical cyclogenesis by convective generation of vertical vorticity within a preexisting cyclonic circulation whose initial maximum tangential wind is approximately 5 m s 1 this paper validates and extends recent work examining the suggested upscale cascade mechanism in a three dimensional quasigeostrophic framework using a simple shallow water primitive equation swpe numerical model and helps clarify certain aspects of the rossby adjustment problem on a nonresting basic state for finite amplitude nonaxisymmetric disturbances the swpe approach serves as a meaningful intermediate step between the quasigeostrophic and full physics frameworks and allows a simple investigation of the effects of unbalanced dynamics contributions of gravity waves and rossby numbers of order unity the authors compare quantitative results of the two models on the storm spinup time and magnitude for asymmetric initial conditions whose mass and wind field are out of balanc

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

elf sferic energy as a proxy indicator for sprite occurrence broadband elf vlf measurements of sferics near ft collins colorado demonstrate that elf sferic en ergy is a proxy for sprite occurrence which can be used to estimate the number of sprites produced by a thunderstorm ultra long range 12 000 km measurements at palmer station antarctica conrm the application of this proxy to storms where no video observations of sprites are avail able comparison with high resolution photometer measure ments demonstrate the simultaneity of sprite luminosity and an elf second pulse believed to be radiated by electri cal currents within the sprite body cummer et al 1998 measurements of the second elf pulse are used to identify a quantitative relationship between the current in sprites and total sprite luminosity

vertical motion characteristics of tropical cyclones determined with airborne doppler radial velocities abstract vertical motions in seven atlantic hurricanes are determined from data recorded by doppler radars on research aircraft the database consists of doppler velocities and reflectivities from vertically pointing radar rays collected along radial flight legs through the hurricane centers the vertical motions are estimated throughout the depth of the troposphere from the doppler velocities and bulk estimates of particle fallspeeds portions of the flight tracks are subjectively divided into eyewall rainband stratiform and other regions characteristics of the vertical velocity and radar structure are described as a function of altitude for the entire dataset and each of the four regions in all of the regions more than 70 of the vertical velocities range from 2 to 2 m s 1 the broadest distribution of vertical motion is in the eyewall region where 5 of the vertical motions are 5 m s 1 averaged over the entire dataset the mean vertical velocity is upward at all altitudes mean downward mot

tropical cyclone formation in a sheared environment a case study abstract the development of hurricane danny 1997 from depression to hurricane was examined using cloud to ground lightning data reconnaissance aircraft data and satellite imagery vertical wind shear between 850 and 200 hpa of 5 11 m s 1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development early in the period the storm intensified steadily in the presence of this downshear convection during the last and most intense outbreak a second vortex appeared to develop within the convection evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original based on these events it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process equivalent potential temperature fields within 500 m of the surface were examined only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of eq

interannual and decadal variability of the western pacific sea surface condition for the years 1787 2000 reconstruction based on stable isotope record from a guam coral 1 we present a monthly resolved 213 year stable isotope time series from a coral from guam 13 n 145 e which is located on the northern edge of the western pacific warm pool oxygen isotopic composition of the coral skeleton 18ocoral shows seasonal interannual and decadal variability which documents significant oceanographic changes related to thermal and hydrologic variations in this region the 18ocoral anomaly reflects sea surface temperature sst anomaly and sea surface salinity sss anomaly with significant r values of 0 69 and 0 49 respectively which are strongly linked to oceanographic changes that occur during el nino southern oscillation enso warm and cool phases we identified 46 enso warm el nino and 53 cool phases la nina in the coral record which are consistent with those phases reconstructed by nino 3 4 sst anomaly spectral analyses of the 18ocoral anomaly record for the years 1790 1999 identified significant peaks around 3 to 7 years these results indicate that the guam coral has recorded enso periodicity the 18ocoral anomaly shows decadal variability of 15 to 45 year periodicity with significant shifts 0 2 from warmer to cooler condition and vice versa an accumulative decrease in 18ocoral time series may imply 0 75 c warming of sst and 0 23 freshening of seawater 18o corresponding to a decrease of sss by 0 85 in the northwestern tropical pacific over the last 2 centuries

numerical simulations of the genesis of hurricane diana 1984 part i control simulation abstract the complete transformation of a weak baroclinic disturbance into hurricane diana is reproduced by numerical simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model three distinct phases of the evolution are evident first baroclinic and barotropic development strongly modified by the effects of latent heating occurs during the latter part of this phase the low level circulation is strengthened through the axisymmetrization of remote potential vorticity anomalies that are generated by condensational heating and then advected toward the incipient storm the axisymmetrization process evinces properties of both nonlinear discrete vortex merger and vortex rossby wave dynamics the transformation from cold core to warm core vortex occurs in this development stage in the second phase lasting 10 12 h little deepening occurs spiral bands of convection begin to form and the core of the storm moistens eventually reaching 95

a wave prediction system for real time sea state forecasting the considerable increase in requirements for sea state forecasts in recent years has led to development of a numerical wave forecasting system in the meteorological office this is based on a wave prediction model which combines the advantages of the parametric technique in predicting a growing wind sea with those of a discrete spectral model in the swell regime this is done using a discrete model by parametrizing the nonlinear interactions term in the energy balance equation in a way that reproduces the behaviour of the parametric model the main difficulty with the method is in the separation of wind sea and swell required to do this propagation of wave energy is performed using an accurate form of the lax wendroff integration scheme a two term representation of wave growth is used whilst dissipation is modelled by an explicit whitecapping mechanism shallow water effects are included by representations of shoaling refraction and bottom friction the operational numerical atmospheric model at the meteorological office provides the wind input an extensive program of evaluation has shown that the results provide high quality guidance with 24 hour forecasts of wave height having a r m s error ranging from 0 6 m in the southern north sea to 1 0 m east of the shetlands

linking benthic community structure to terrestrial runoff and upwelling in the coral reefs of northeastern hainan island abstract near shore coral reefs in northeastern hainan island are close to river mouths and aquaculture ponds and also located at the center of the qiongdong upwelling qdu however it is still unclear how terrestrial runoff and upwelling influence the community composition and spatial distribution of the benthos during three cruises in 2010 and 2011 in wenchang northeastern hainan island we determined a subset of environmental parameters in seawater e g temperature salinity do dissolved inorganic nutrient din turbidity and transparency and macroalgal 15 n and investigated the benthic communities e g live coral cover coral species richness juvenile coral density macroalgal cover and coverage of calcified algae by video transect and visual census techniques at 10 stations i e 1s 6d the results showed that the qdu has influenced the reef waters in wenchang in 2011 the upwelling started in early may peaked in july and disappeared in september and most upwelling events lasted for 1 2 weeks between may and july the results also demonstrated that the reef water was nutrient enriched stations close to the river mouth and aquaculture ponds had higher levels of din and a higher percentage of ammonia in din and there was consistently lower live coral cover juvenile coral density and higher macroalgal cover at some stations in this study live coral cover was negatively correlated with macroalgal cover i e 2s 6d live coral cover species richness and juvenile coral density all increased with the distance away from the river outlet and decreased with the rise of din these results suggest that terrestrial runoff and upwelling stimulate nutrient enrichment and that overgrowing macroalgae has an important influence on the coral communities in northeastern hainan island

decadal variability in seawater ph in the west pacific evidence from coral δ11b records long term seawater ph records are essential for evaluating the rates of ocean acidification oa driven by anthropogenic emissions widespread natural decadal variability in seawater ph superimposes on the long term anthropogenic variations likely influencing the oa rates estimated from the ph records here we report a record of annual seawater ph estimated using the b proxy over the past 159 years reconstructed from a porites coral collected to the east of hainan island in the northern south china sea scs by coupling this time series with previously reported long term seawater ph records in the west pacific the decadal variability in seawater ph records and its possible driving mechanisms were investigated the results indicate that large decadal variability in seawater ph has occurred off eastern hainan island over the past 159 years in agreement with previous records the qiongdong upwelling system which controls nutrient supplies regulates surface water productivity and is driven by the east asian summer monsoon is the primary control of this decadal variability while terrestrial inputs appear not influence significantly meanwhile the impacts of the pacific decadal oscillation pdo and the el nino and southern oscillation enso systems on seawater ph off eastern hainan island is likely limited in contrast the pdo is the main factor to influence the decadal seawater ph variability offshore the east australia while the mechanism controlling the decadal seawater ph variability in guam is not clear yet meanwhile the rate of decrease in seawater ph estimated from coral records are significantly different in different regions and over different time spans which may reflect a combination of natural decadal variability in seawater ph and long term variations therefore understanding the mechanisms driving natural variability in seawater ph is important for improving estimates of ocean acidification rates driven by anthropogenic emissions

the effect of skeletal mass accumulation in porites on coral sr ca and δ18o paleothermometry 1 paleotemperature estimates based on coral sr ca have not been widely accepted because the reconstructed glacial holocene shift in tropical sea surface temperature 4 6 c is larger than that indicated by foraminiferal mg ca 2 4 c we show that corals over estimate changes in sea surface temperature sst because their records are attenuated during skeletogenesis within the living tissue layer to quantify this process we microprofiled skeletal mass accumulation within the tissue layer of porites from australasian coral reefs and laboratory culturing experiments the results show that the sensitivity of the sr ca and 18o thermometers in porites will be suppressed variable and dependent on the relationship between skeletal growth rate and mass accumulation within the tissue layer our findings help explain why 18o sst sensitivities for porites range from 0 08 c to 0 22 c and are always less than the value of 0 23 c established for biogenic aragonite based on this observation we recalibrated the coral sr ca thermometer to determine a revised sensitivity of 0 084 mmol mol c after rescaling most of the published sr ca sst estimates for the indo pacific region for the last 14 000 years 7 c to 2 c relative to modern fall within the 95 confidence envelope of the foraminiferal mg ca sst records we conclude that two types of calibration scales are required for coral paleothermometry an attenuated porites specific thermometer sensitivity for studies of seasonal to interannual change in sst and importantly the rescaled 0 084 mmol mol c sr ca sensitivity for studies of 20th century trends and millennial scale changes in mean sst the calibration scaling concept will apply to the development of transfer functions for all geochemical tracers in corals

mesoscale aspects of the downshear reformation of a tropical cyclone the downshear reformation of tropical storm gabrielle 2001 was investigated using radar reflectivity and lightning data that were nearly continuous in time as well as frequent aircraft reconnaissance flights initially the storm was a marginal tropical storm in an environment with strong 850 200 hpa vertical wind shear of 12 13 m s 1 and an approaching upper tropospheric trough both the observed outflow and an adiabatic balance model calculation showed that the radial vertical circulation increased with time as the trough approached convection was highly asymmetric with almost all radar return located in one quadrant left of downshear in the storm reconnaissance data show that an intense mesovortex formed downshear of the original center this vortex was located just south of rather than within a strong downshear left lightning outbreak consistent with tilting of the horizontal vorticity associated with the vertical wind shear the downshear mesovortex contained a 972 hpa minimum central pressure 20 hpa lower than minimum pressure in the original vortex just 3 h earlier the mesovortex became the new center of the storm but weakened somewhat prior to landfall it is argued that dry air carried around the storm from the region of upshear subsidence as well as the direct effects of the shear prevented the reformed vortex from continuing to intensify despite the subsequent weakening of the reformed center it reached land with greater intensity than the original center it is argued that this intensification process was set into motion by the vertical wind shear in the presence of an environment with upward motion forced by the upper tropospheric trough in addition the new center formed much closer to the coast and made landfall much earlier than predicted such vertical shear induced intensity and track fluctuations are important to understand especially in storms approaching the coast

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

long range lightning geolocation using a vlf radio atmospheric waveform bank 1 lightning discharges generate broadband electromagnetic pulses with a peak component in the very low frequency vlf 3 30 khz range vlf waves propagate through the earth ionosphere waveguide with relatively low attenuation enabling the detection of these radio atmospherics at great distances from the lightning discharge a new technique of long range 6000 km global lightning geolocation via sferic detection is presented this new technique catalogs the dominant variation in expected received waveforms in a set of waveform banks which are then used to estimate the propagation distance and accurately determine the arrival time using three sensors in a trial network this new technique is used to demonstrate a median accuracy of 1 4 km depending on the time of day an overall cloud to ground cg stroke detection efficiency between 40 and 60 is estimated by correlating individual lightning stroke events to data from the national lightning detection network nldn additional events reported by the trial network are shown to have a tight spatial clustering to storm clusters identified by nldn suggesting that many of the unmatched events correspond to weak cloud to ground strokes m components or cloud pulses exploiting an empirical correlation between peak vlf field strength and peak current values reported by nldn we also provide unvalidated estimates of the peak current and lightning channel polarity the trial network does not distinguish between cloud and ground discharges so these peak current estimates only relate to an earth referenced channel current for the subset of reported events that are return strokes

the vertical profile of radar reflectivity of convective cells a strong indicator of storm intensity and lightning probability abstract reflectivity data from doppler radars are used to construct vertical profiles of radar reflectivity vprr of convective cells in mesoscale convective systems mcss in three different environmental regimes the national center for atmospheric research cp 3 and cp 4 radars are used to calculate median vprr for mcss in the oklahoma kansas preliminary regional experiment for storm central in 1985 the national oceanic and atmospheric administration tropical ocean global atmosphere radar in darwin australia is used to calculate vprr for mcss observed both in oceanic monsoon regimes and in continental break period regimes during the wet seasons of 1987 88 and 1988 89 the midlatitude and tropical continental vprrs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level in sharp contrast the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with he

wind and topography influence on an upwelling system at the eastern hainan coast 1 during the summer monsoon an upwelling dominates east of hainan island which can be observed by means of field studies and satellite sea surface temperature images the centers of cold water at the surface always show a strong patchiness a 3 d high resolution model is applied to study the impact of the topography on the wind driven upwelling system the experiments show that the upwelling favoring wind is the main driving force and we concluded that the formation of the centers of cold water at the surface significantly depends on the strength of southwesterly and southerly winds moreover the internal waves are generated at the shelf break representing the most prominent interaction between inner shelf and open ocean the alongshore topographic variations play an important role in the distribution of the upwelling centers this combined effect of wind and topography leads to the following processes 1 when the southwesterly or southerly wind is strong enough topographic variations cause upwelling centers at the downstream side of topographic high and a downwelling center at the upstream side which in turn lead to density variations 2 these density variations cause additional pressure gradients which advect the upwelling centers toward the northeast 3 a longer period of upwelling favorable winds support the advection processes which cause an enlargement of the cold water centers all these processes together can explain the observed uneven distribution of upwelling centers

the convective evolution and rapid intensification of hurricane earl 2010 abstractthe relationship between an inner core r 100 km lightning outbreak and the subsequent rapid intensification ri of hurricane earl 2010 is examined using lightning strikes recorded by the world wide lightning location network wwlln and in situ observations from various aircraft missions moderate 8 4 m s 1 northeasterly deep layer 850 200 hpa vertical wind shear caused by outflow from hurricane danielle existed over earl at the beginning of a prolonged period of ri over 70 of the lightning strikes within a 500 km radius occurred downshear with a preference toward downshear right in the outer rainbands in agreement with previous studies the location of inner core strikes in earl differed markedly from previous studies the inner core lightning activity precessed from left of shear to upshear an extremely rare event beginning just prior to the onset of ri diagnosis of the vortex tilt midway through the lightning precession showed this convection was occurring downtilt in the ups

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