observations and modeling of banded orographic convection radar images and numerical simulations of three shallow convective precipitation events over the coastal range in western oregon are presented in one of these events unusually well defined quasi stationary banded formations produced large precipitation enhancements in favored locations while varying degrees of band organization and lighter precipitation accumulations occurred in the other two cases the difference between the more banded and cellular cases appeared to depend on the vertical shear within the orographic cap cloud and the susceptibility of the flow to convection upstream of the mountain numerical simulations showed that the rainbands which appeared to be shear parallel convective roll circulations that formed within the unstable orographic cap cloud developed even over smooth mountains however these banded structures were better organized more stationary and produced greater precipitation enhancement over mountains with small scale topographic obstacles low amplitude random topographic roughness elements were found to be just as effective as more prominent subrange scale peaks at organizing and fixing the location of the orographic rainbands

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

cloud resolving ensemble simulations of the august 2005 alpine flood in this study we explore the potential benefits of applying a cloud resolving ensemble prediction system eps 2 2 km grid spacing over its driving synoptic scale limited area eps cosmo leps 10 km grid spacing driven by the ecmwf eps for a case of heavy precipitation over the alpine region the selected event is the devastating august 2005 flood that affected the northern alpine slopes the cloud resolving eps includes an explicit treatment of deep convection and dynamically downscales the cosmo leps information results are compared against rain gauge and radar data furthermore the sensitivity of the results to initial versus lateral boundary uncertainties are analyzed using a series of additional simulations comparison of the cloud resolving and its driving limited area eps pinpoints the high skill of both ensembles in simulating the major phase of heavy precipitation the high resolution eps yields more realistic rain amounts in particular in areas of active convection but in general the resolution induced differences tend to be smaller than typical member to member variability the differences between the two ensembles can be tied to the synoptic situation stratiform or convective precipitation location of the cyclone to the mesoscale interaction of the flow with the topography flow over the alpine ridge and to the experimental set up lead time and computational domain for the considered event and set up the growth of initial perturbations dominates over lateral boundary uncertainties during the first 12 integration hours afterwards the ensemble spread is controlled by large scale error growth advected from the lateral boundaries into the domain copyright 2008 royal meteorological society

the impact of lee side stratification on the spatial distribution of orographic precipitation numerical simulations are presented in order to investigate the effect of the lee side stratification on the spillover of orographic precipitation the simulations are conducted with idealized topography as well as with idealized large scale flow conditions and consider both moist neutral and convectively unstable situations strong lee side static stability is achieved by creating a basin enclosed by four mountain ridges that is filled with a cold air pool sensitivity tests are also performed with a plateau topography representing the limit of an infinitely stable cold air pool it is found that the presence a cold air pool in the lee of a mountain ridge greatly increases the precipitation spillover because the cold pool suppresses the lee side downslope air motion that otherwise leads to a rapid evaporation of the precipitation the maximum fractional enhancement of the lee side precipitation ranges between one order of magnitude in a convectively unstable environment and two orders of magnitude in a nonconvective one however the largest absolute values are found in the convective cases because convective cells decay more slowly than stratiform precipitation in all simulations with a lee side cold pool the precipitation decay in the lee of the mountain tends to be approximately exponential sensitivity experiments indicate that the lee side precipitation enhancement due to a cold pool depends only weakly on the height and the width of the mountain the precipitation on the upstream side of the mountain also tends to be enhanced by a lee side cold pool due to a change of the gravity wave pattern however this side effect is comparatively small never exceeding a factor of three in the cases tested in this study a notable precipitation enhancement over the mountain crest is found for low mountains only copyright 2005 royal meteorological society

interaction between dynamics and cloud microphysics in orographic precipitation enhancement a high resolution modeling study of two north alpine heavy precipitation events abstract interactions of atmospheric dynamics and cloud microphysics with the alpine orography are investigated for two north alpine heavy precipitation cases 20 22 may 1999 and 22 23 august 2005 both cases were related to a deep cyclone propagating slowly eastward along the alps advecting moist air of mediterranean origin toward the northern side of the alps a validation against high resolution rain gauge data reveals that the average model bias is below 15 in the region of interest but there is a tendency to systematically underestimate very heavy precipitation a scale decomposition of the discrepancies between model and observations reveals that errors on the meso scale contribute at least as much to the total model error as discrepancies on the meso scale on the scale of single mountain ridges and valleys the formation of precipitation maxima at valley locations is investigated with particular emphasis on a region in which a valley receives systematically more precipitation than the adj

atmospheric factors governing banded orographic convection abstract the three dimensional structure of shallow orographic convection is investigated through simulations performed with a cloud resolving numerical model in moist flows that overcome a given topographic barrier to form statically unstable cap clouds the organization of the convection depends on both the atmospheric structure and the mechanism by which the convection is initiated convection initiated by background thermal fluctuations embedded in the flow over a smooth mountain without any small scale topographic features tends to be cellular and disorganized except that shear parallel bands may form in flows with strong unidirectional vertical shear the development of well organized bands is favored when there is weak static instability inside the cloud and when the dry air surrounding the cloud is strongly stable these bands move with the flow and distribute their cumulative precipitation evenly over the mountain upslope similar shear parallel bands also develop in flows where convection is

toe of slope of a cretaceous carbonate platform in outcrop seismic model and offshore seismic data apulia italy synthetic seismic models of outcrops in the early cretaceous slope of a carbonate platform on the gargano promontory southern italy were compared to an offshore seismic section south of the promontory outcrops of the same age on the promontory have the same sequence stratigraphic characteristics as their offshore equivalent and are the only areas where the transition from platform to basin of early cretaceous is exposed on land two adjacent outcrop areas were combined into one seismic scale lithologic model with the aid of photo mosaics measured sections and biostratigraphic data velocity density and porosity measurements on spot samples were used to construct the impedance model seismic models were generated by vertical incidence and finite difference programs the results indicate that the reflections in the seismic model are controlled by the impedance contrast between low porous intervals rich in debris from the platform and highly porous intervals of pelagic lime mudstone nearly devoid of debris finite difference seismic display showed best resemblance with the real seismic data especially by mapping a drowning unconformity

building the 3 d jigsaw puzzle applications of sequence stratigraphy to 3 d reservoir characterization permian basin reservoir characterization involves the quantification integration reduction and analysis of geological petrophysical seismic and engineering data this is no small task a principal goal of reservoir characterization is to derive a spatial understanding of interwell heterogeneity traditionally geologic attempts to characterize interwell heterogeneity have been done using hand drawn or computer generated two dimensional 2 d maps and cross sections results can be improved dramatically using three dimensional 3 d interpretation and analysis techniques three dimensional reservoir characterization requires the same input data used in 2 d approaches and the cost is equal to and commonly lower than traditional 2 d methods the product of 3 d reservoir characterization is a 3 d reservoir model the language used to communicate the results of a 3 d reservoir model is visualization i e visual images of numerical data all of the available log and core data in a model area are incorporated in a 3 d model but the data are depicted as colored cells rather than as log traces the integrity of the 3 d reservoir model is largely a function of the stratigraphic framework interpreting the correct stratigraphic framework for a subsurface reservoir is the most difficult and creative part of the 3 d modeling process sequence and seismic str tigraphic interpretation provide the best stratigraphic framework for 3 d reservoir modeling the purpose of this paper is to discuss the process of 3 d deterministic reservoir modeling and to illustrate the advantages of using a sequence stratigraphic framework in 3 d modeling mixed carbonate and siliciclastic sediment outcrop and subsurface examples from the permian basin of west texas and new mexico will be used as examples but the concepts and techniques can be applied to reservoirs of any age three dimensional reservoir modeling results in an improved geologic interpretation provides a means of integrating geological petrophysical geophysical and engineering data and allows for immediate model updates as new data are acquired as a result of 3 d reservoir characterization reservoir management decisions data quality control volumetric calculations numerical sim lation input and communication between disciplines are improved

stratified flow over a mountain with a gap linear theory and numerical simulations linear theory and numerical simulations are used to investigate gap flows both gaps embedded in a long mountain ridge and gaps located between two isolated mountain peaks are considered the study mainly focuses on level gaps so as to isolate three dimensional effects from two dimensional gravity wave propagation special attention is given to qualitative differences between the linear and the nonlinear flow regimes the linear regime being defined by the absence of gravity wave breaking in the linear regime wind and pressure perturbations along a level gap axis are found to be qualitatively similar to those over a mountain ridge or peak but of lower amplitude and longer horizontal wavelength they are caused by vertically propagating gravity waves radiating from the mountain ridges peaks towards the gap axis and by low level confluence within the gap in the nonlinear regime however these two processes are of minor importance due to upstream blocking and low level wave breaking instead the pressure difference across the mountain ridge primarily drives the gap flow which tends to be decoupled from the flow over the adjacent ridge in contrast to the linear regime gap winds are as strong as or even stronger than the winds over the mountain ridge surface friction is found to reduce the near surface wind speed more strongly for mountain ridges than for gaps copyright 2002 royal meteorological society

precipitation landsliding and erosion across the olympic mountains washington state usa abstract in the olympic mountains of washington state landsliding is the primary surface process by which bedrock and hillslope regolith are delivered to river networks however the relative importance of large earthquakes versus high magnitude precipitation events to the total volume of landslide material transported to valley bottoms remains unknown in part due to the absence of large historical earthquakes to test the hypothesis that erosion is linked to precipitation approximately 1000 landslides were mapped from google earth imagery between 1990 and 2015 along a 15 km wide 85 km long 1250 km2 swath across the range the volume of hillslope material moved by each slide was calculated using previously published area volume scaling relationships and the spatial distribution of landslide volume was compared to mean annual precipitation data acquired from the prism climate group for the period 1981 2010 statistical analysis reveals a significant correlation r 0 55 p

the orographic impact on patterns of embedded convection during the august 2005 alpine flood convective precipitation structures during an alpine heavy precipitation event in august 2005 are investigated utilising a mesoscale non hydrostatic numerical model and observational data the focus is on the mechanisms of convective initiation during the very beginning of the event when organised cellular updraughts enhanced the precipitation over the southern german alpine foreland a set of sensitivity experiments with systematically modified topography is conducted in order to investigate the role of single topographic obstacles in initiating and arranging convection a reference simulation proves to be capable of qualitatively reproducing the development of two distinct flow parallel aligned non stationary convective precipitation bands which are observed by radar and surface measurements the simulations reveal the presence of two low level convergence lines that provide a primary mechanism for both initiating and aligning convective cells during the analysed period mountains embedded in the alpine foreland are not decisive for triggering and aligning the convective cells in this case since the primary mechanism provides a consistent forcing for the convective precipitation bands however the experiments demonstrate a dependence of the alignment and intensity of one of the precipitation bands upon the position of the pre existing convergence line relative to a flow parallel aligned mountain ridge enhancement weakening of the existing banded structure and convective intensity is achieved if the convergence line is located upstream downstream of the ridge with respect to a cross ridge low level inflow the weakening mode is characterised by a subsiding cross ridge inflow into the convergence line that stabilises the atmosphere and therefore inhibits the formation of a continuous convective precipitation band copyright 2011 royal meteorological society

identifying causes of ground penetrating radar reflections using time domain reflectometry and sedimentological analyses ground penetrating radar gpr is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves however little is known about the exact cause of gpr reflections because few studies have coupled wave theory to petrophysical data in this study a 100 and 200 mhz gpr survey was conducted on aeolian deposits in a quarry time domain reflectometry tdr was used to obtain detailed information on the product of relative permittivity er and relative magnetic permeability lr which mainly controls the gpr contrast parameter in the subsurface combining tdr data and lacquer peels from the quarry wall allowed the identification of various relationships between sediment characteristics and erlr synthetic radar traces constructed using the tdr logs and sedimentological data from the lacquer peels were compared with the actual gpr sections numerous peaks in erlr which are superimposed on a baseline value of 4 for dry sand are caused by potential gpr reflectors these increases in erlr coincide with the presence of either organic material having a higher water content and relative permittivity than the surrounding sediment or iron oxide bands enhancing relative magnetic permeability and causing water to stagnate on top of them sedimentary structures as reflected in textural change only result in possible gpr reflections when the volumetric water content exceeds 0ae055 the synthetic radar traces provide an improved insight into the behaviour of radar waves and show that gpr results may be ambiguous because of multiples and interference

seismic models of a shelf margin depositional sequence upper san andres formation last chance canyon new mexico abstract the seismic resolution of stratal geometries and facies distributions observed in san andres formation permian outcrops in last chance canyon guadalupe mountains new mexico is studied by seismic modeling of a published detailed stratigraphic cross section the outcrops in last chance canyon are composed of two fourth order depositional sequences an aggrading carbonate bank upper san andres 3 usa3 followed by a strongly progradational offlapping mixed carbonate siliciclastic succession upper san andres 4 usa4 each sequence comprises a number of subsidiary high frequency sequences fifth order two alternative impedance models were used model a in which all facies transitions are reflecting boundaries and model b in which only time significant surfaces act as reflectors and lateral facies transitions are represented by horizontal velocity gradients the vertical incidence modeling technique was used to compute perfectly migrated time and depth sections with different frequencies using a low frequency wavelet 25 hz the sequence boundary separating the two fourth order cycles usa3 and usa4 is poorly imaged instead one is tempted to incorrectly interpret an onlap pattern generated by a high frequency cycle within usa4 as this major sequence boundary in addition the 25 hz runs show toplap and downlap lap out patterns in an overly oblique fashion obscuring true asymptotic stratal relationships both at 35 hz and 50 hz profiles based on model b image the genetic structure of both usa3 and usa4 relatively well at 50 hz model a incorrectly shows a transition from a ramp to a rimmed margin within usa4 the 35 hz models are qualitatively compared with a published exxon production research co seismic line located approximately 50 km along depositional str ke to the northeast model a shows an unexpected good match with the exxon seismic line whereas model b comes much closer to the depositional anatomy observed in outcrop our results show that the resolution of stratal geometries and facies distributions in last chance canyon is strongly related to carbonate sandstone alternations and the way impedance contrasts at carbonate sandstone transitions are represented

the effects of composition laminar structure and burial depth on connected pore characteristics in a shale oil reservoir the raoyang sag of the bohai bay basin china abstract to evaluate the effects of the composition laminar structure and burial depth on pore volumes connected by pore throats of different sizes in a shale oil reservoir the es1x formation in the raoyang sag of the bohai bay basin was selected as an example the effects of component contents laminar structure and burial depth on pore volumes connected by pore throats with widths of

numerical simulations of the 12 13 august 2002 flooding event in eastern germany in this paper high resolution numerical simulations of the 12 13 august 2002 flooding event in eastern germany are presented the simulations are performed with the penn state national center for atmospheric research mesoscale model mm5 in a four domain configuration with a finest horizontal resolution of 1 km sensitivity experiments are performed with coarser resolutions 3 and 9 km with different cloud microphysical parametrizations and with a different date of initialization moreover tests with i km resolution but the smoothed topography of the 9 km runs are conducted in order to isolate the contribution of the model topography to the differences between the 1 km runs and the 9 km runs the results show that the high resolution runs reproduce the observed structure of the precipitation field very well in particular the location of the rainfall maximum is correct to within 15 km the quantitative agreement between model results and observations is fairly good in regions with light to moderate rain but large amounts of precipitation tend to be underpredicted for observed 36 hour rainfall accumulations exceeding 200 mm the negative bias typically ranges between 15 and 30 with fairly little dependence on the microphysical parametrization in the coarser resolved runs the bias at high precipitation amounts becomes even more pronounced and it is found that this behaviour is not only due to the fact that a coarser resolution is associated with a smoother topography this indicates a systematic deficiency in the microphysical parametrizations limiting their ability to simulate heavy precipitation

numerical simulation of orographic rainbands 1 this study based on a statistical analysis of simulated warm rain event and radar data aims at highlighting the main physical mechanisms that lead to organize shallow convection on the relief the region of investigation the cevennes vivarais is located in the southeast part of france radar images from the cevennes experiment fall 1986 1988 reveal a characteristic and repetitive structure of the rain distribution organized in narrow bands or plumes oriented south north in the case of stationary southerly mediterranean flow the event of 14 november 1986 has been selected and constitutes the data set of this numerical study this work is closely associated with the previous work by miniscloux et al 2001 which presents in detail the results of a geostatistical analysis of the radar data set extracted from the cevennes experiment data base the main results highlight the physical characteristics and the dynamics of the rain patterns following the recent work of cosma et al 2002 high resolution i km simulations have been continued with the nonhydrostatic three dimensional 3d atmospheric model mesonh in order to reproduce the observed rainbands over the ceveunes region the numerical model correctly reproduces the structure and the dynamics of the rainbands the geostatistical analysis has been applied for the simulated rain fields the model slightly overestimates the northward advection velocity of the rain cells within the bands 75 km h 1 against 60 km h 1 for the observation and the simulated rainbands are narrower and more organized around the n 180 direction than the observed rain field the comparison allows the qualification and validation of the choice of the numerical methodology and realism of the physical parameterizations the analysis of the 3d simulated fields confirms the physical mechanisms responsible for the rain organization demonstrated by cosma et al 2002 through idealized simulations the statistical analysis highlights the presence of mean topographic features under low level convergence zones composed of a succession of ridges and penetrating valleys orientated east west the rainbands are generated upstream of these topographic features and enhanced on the leeside due to the convergence created by the flow deflection around the obstacle and its penetration into the valleys the simulated triggering takes place further to the south than the observed one and the triggering is active as soon as the relief is suitably described in the model

an improved method for computing horizontal diffusion in a sigma coordinate model and its application to simulations over mountainous topography abstract a set of modifications is presented to reduce the unphysical impact of horizontal diffusion in numerical models with a terrain following sigma coordinate system at model levels sufficiently far away from the ground vertical interpolation is used to compute diffusion truly horizontally when the coordinate surfaces are sloping close to the ground where truly horizontal computation of diffusion is not everywhere possible without intersecting the topography a combination of one sided truly horizontal diffusion and orography adjusted diffusion along the sigma surfaces is used for most of the variables the latter means that the diffusion coefficient is reduced strongly when the grid points involved in the computation of horizontal diffusion are located at greatly different heights for temperature one sided horizontal diffusion is not used because it damps the slope wind circulation in an unphysical way however a temperature gradient correction is applied to the terrain following part of the t

dynamics of a local alpine flooding event in october 2011 moisture source and large scale circulation alpine heavy precipitation events often affect small catchments although the circulation pattern leading to the event extends over the entire north atlantic the various scale interactions involved are particularly challenging for the numerical weather prediction of such events unlike previous studies focusing on the southern alps here a comprehensive study of a heavy precipitation event in the northern alps in october 2011 is presented with particular focus on the role of the large scale circulation in the north atlantic european region during the event exceptionally high amounts of total precipitable water occurred in and north of the alps this moisture was initially transported along the flanks of a blocking ridge over the north atlantic subsequently strong and persistent northerly flow established at the upstream flank of a trough over europe and steered the moisture towards the northern alps lagrangian diagnostics reveal that a large fraction of the moisture emerged from the west african coast where a subtropical upper level cut off low served as an important moisture collector wave activity flux diagnostics show that the ridge was initiated as part of a low frequency large scale rossby wave train while convergence of fast transients helped to amplify it locally in the north atlantic a novel diagnostic for advective potential vorticity tendencies sheds more light on this amplification and further emphasizes the role of the ridge in amplifying the trough over europe operational forecasts misrepresented the amplitude and orientation of this trough for the first time this study documents an important pathway for northern alpine flooding in which the interaction of synoptic scale to large scale weather systems and of long range moisture transport from the tropics are dominant moreover the trapping of moisture in a subtropical cut off near the west african coast is found to be a crucial precursor to the observed european high impact weather

seismic models of a mixed carbonate siliciclastic shelf margin permian upper san andres formation last chance canyon new mexico seismic models based on randomly distributed samples from the permian upper san andres formation last chance canyon new mexico verify that the most prominent seismic reflections are related to stratal geometry however at least some reflections arise from lateral facies transitions that are commonly associated with highly prograding mixed carbonate siliciclastic sediments understanding seismic reflections and reflection terminations in sedimentary rocks requires simulation of at least 2 d cross sections of the impedance distribution to investigate the cause of reflections in strongly prograding mixed carbonate siliciclastic shelf margins acoustic velocity and bulk density were measured on more than 60 plugs that spatially cover one higher order genetic sequence the resulting impedance values were gridded and contoured and the genetic sequence was repeated to create a cross section averaging impedance values for each lithofacies zone generated a second impedance cross section seismic models of both impedance cross sections revealed the following observations 1 reflections associated with the sequence boundaries are subject to amplitude and polarity phase changes and 2 at least one reflection within the high order sequences is related to subhorizontal facies changes and is associated with two pseudounconformities the contoured impedance model is suggested to closer resemble the true impedance function in outcrop and shows subtle vertical shifts and significantly higher impedance contrasts

a linear theory of orographic precipitation a linear theory of orographic precipitation is developed including airflow dynamics condensed water advection and downslope evaporation the formulation extends the widely used upslope model vertically integrated steady state governing equations for condensed water are solved using fourier transform techniques closed form expressions are derived for special cases for more general cases the precipitation field is computed quickly by multiplying the terrain transform by a wavenumber dependent transfer function five length scales are included in the model mountain width a buoyancy wave scale the moist layer depth and two condensed water advection distances the efficiency of precipitation in the model is sensitive to the decay of the forced ascent through the moist layer and to the advection of condensed water downwind into the region of descent the strong influence of horizontal scale on precipitation pattern and amount predicted by the model is discussed the model is illustrated by applying it to the olympic mountains in washington state

orographic effects on rainfall in map cases iop 2b and iop 8 although the large scale flow was similar important differences in mesoscale atmospheric structure made the difference between moderately intense rain in intensive observing period iop 2b and relatively light rain in iop 8 in the lago maggiore target area lmta this conclusion is supported here through analysis of data from and numerical simulations of these two cases analysis of the large scale data shows that there was in both cases a moist tongue of southerly flow moving from the west to the east of the alpine south side mesoscale data analysis and numerical simulations suggest that the most important difference between the two cases was the presence of a cold stable air mass in the po valley in iop 8 which persisted through the period in which the large scale moist tongue was progressing eastward and prevented the most humid air from reaching the lmta another difference contributing to the greater rainfall in the lmta in iop 2b was the development of conditional instability with associated convective rain due to the effect of the alps on the eastward passage of the moist tongue in iop 8 the atmosphere remained locally stable throughout the period copyright 2003 royal meteorological society

the climatology of small scale orographic precipitation over the olympic mountains patterns and processes the climatology of small scale patterns of mountain precipitation is poorly constrained yet important for applications ranging from natural hazard assessment to understanding the geologic evolution of mountain ranges synthesizing four rainy seasons of high resolution precipitation observations and mesoscale model output from the penn state ncar mm5 reveals a persistent small scale pattern of precipitation over the 10 km wide 800 m high ridges and valleys of the western olympic mountains washington state usa this pattern is characterized by a 50 70 excess accumulation over the ridge crests relative to the adjacent valleys in the annual mean while the model shows excellent skill in simulating these patterns at seasonal time scales major errors exist for individual storms investigation of a range of storm events has revealed the following mechanism for the climatological pattern regions of enhanced condensation of cloud water are produced by ascent in stable flow over the windward slopes of major ridges synoptically generated precipitation grows by collection within these clouds leading to enhanced precipitation which is advected by the prevailing winds instances of atypical patterns of precipitation suggest that under certain conditions during periods with a low freezing level or convective cells fundamental changes in small scale patterns may occur however case studies and composite analysis suggest that departures from the pattern of ridge top enhancement are rare the basic patterns and processes appear robust to changes in temperature winds and background rainfall rates copyright 2008 royal meteorological society

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

the role of small scale orographic features in the spatial distribution of precipitation radar images from the cevennes experiment which took place during the autumns of 1986 88 on the southeastern flank of the massif central in france reveal a characteristic and repetitive structure of the precipitation distribution in southerly mediterranean flows which are frequent there in autumn precipitation is often organized into narrow bands or plumes oriented south north the period 14 and 15 november 1986 has been selected as an example on which to perform numerical simulations and analyse the mechanism yielding this specific precipitation organization the numerical model correctly reproduces the bands especially at high horizontal resolution 1 km these rainfall bands are focused on the small scale topography oriented east west composed of a succession of ridges and penetrating valleys the bands are generated upstream of these ridges and enhanced on the lee side by convergence created by deflection around the obstacle and penetration of the flow into the valleys idealized simulations and sensitivity experiments have been carried out to verify these hypotheses these simulations suggest that small scale orography plays a decisive role in forcing the precipitation into bands while upstream moisture conditions mainly affect the precipitation intensity and its south north extent copyright 2002 royal meteorological society