Numerical Simulation And Diagnostic Analysis Of A Heavy Snow Process

The influencing system and basic mechanism of storm snow in Henanprovince from January eighteenth to nineteenth in 2006 are elementarydiagnostic analyzed using NCEP globe spectrum model and routine groundand upper air data together with results from MM5 medium numerical modelsimulation. Results are found that cold air and southwest warm moist airtogether lead to this storm snow. Cold vortex from east of Baikal over500hPa, southern beanch trough, warm shear wave over 700hPa, southwestjet current are direct influencing system accompanying with dryintrusion. Occurrence and development of dry intrusion have veryimportant function for storm snow with its down extending along densenssarea of potential equivalent temperature bringing disturbance oftemperature field, causing cyclonic voticity buildup from medium-lowlevel in favor of strong rain befell and development. High and low jetflow emerge during this course. On one hand, low jet flow propitious towarm moist air transportation arouse cold air advection. On the otherhand, coupling of high and low jet flow bring down branch of subcirculationin favor of dry and cold air down transportation, rising branch makingwarm moist air uplift from low level with low convergence and highdivergence making for uplift lead to strong rainfall birth anddevelopment.Model results show that fine grid model simulate better rainfall areatrack and north and south two center position and intensity of rainfallquantity. Basing on good simulation, high space-time differentiate datafrom model are imposed to analyse vapour, temperature, instability,wind, and other factor condition of this course. Results show that theconvergence of middle-low layer vapour is absolutely necessarycondition. Conditions forming snow is more complicated than rainfallmostly because of temperature. Upper boundary of contradictorily temperature layer above Henan provience corresponding with south-westjet flow and down boundary with north-east jet flow is the most favourableflow field for snow. Total and local helicity variety is the goodguideline for snow intensity. Moist potential vorticity (MPV) not onlyshows dynamical, thermodynamical attribute, but also considers vapour' seffect. MPV2 is more important than MPV1 in this course different fromMPV1's dominant effect in storm rain.Finally, numerical simulation sensitivity experiment carried in thiscourse respectively discuss ability of model simulation position andintensity of rainfall, and accuracy under different display, modelresolution, and topographic scheme. Results indicate if only appropriateschemes are selected, results can make for best purpose.Through studying this storm snow weather, characters of occurrence,development and configuraion evolvement of medium scale system primarilyuncovered in the course of winter storm in Henan provience provide stormsnow foecast with reference basis.