Showing papers in "Meteorological Monthly in 2011"

Research on the Heat Wave Index

Abstract: Heat waves appear usually accompanied by both the abnormal high temperature(or high temperature and muggy weather) and a persistent period of high temperature weather.According to these two characteristics,heat-wave index is designed as an identification index of heat wave weather to show the torridity extent and accumulative effect of high-temperature process,and the classification standard of heat waves is established.Heat-wave index and meteorological grades were tested by daily numbers of heatstroke sufferers in Wuhan during July to August of 1994 and 1995 and daily numbers of death in Shanghai during July to August of 2003.The results show that the heat-wave index is a valid index to predict heat wave weather.The method on grading of heat wave can be applied to the actual operation.

Methods and Uncertainties of Meteorological Forecast

Abstract: The variation and improvement of meteorological forecast method are reviewed in a simple and explicit way,based on historical records on meteorological phenomena and a brief development history and status of atmospheric sciences.The present operational prediction skill and main advancements of the relevant researches are summarized as well.Uncertainties in the result of meteorological forecast are discussed from the perspective of numerical forecasting.Moreover,the way for public to understand and utilize ensemble forecast products is also presented by explaining the principles of ensemble forecast in detail.

A Comparison of TRMM 3B42 Products with Rain Gauge Observations in China

Abstract: The 6-hourly precipitation data from 673 rain gauge records are used to verify the accuracy of Tropical Rainfall Measuring Mission(TRMM) 3B42 products from June to August(JJA) during 2004—2008 in China.The results show that the satellite products are similar to rain gauge data in revealing the spatial patterns of JJA mean precipitation amount and precipitation frequency during 2004—2008.The pattern correlation coefficients of daily rainfall amount and rainfall frequency are 0.79 and 0.84,respectively. The satellite product overestimates rainfall frequency.Based on the spatial distributions of correlation coefficients of daily rainfall amount,the correlation coefficients between TRMM products and rain gauge data range from 0.6 to 0.9 in eastern China.According to the spatial patterns of mean absolute error(MAE) of daily and 6-hourly precipitation amount,the MAE in South China is the largest,followed by the Yangtze River Basin.From diurnal cycle of the 6-hourly total precipitation amount over eight subregions,the TRMM product has a good resemblance with rain gauge observations except the big difference in the after- noon(1400—2000 LST) in South China.Based on the spatial patterns of mean relative error(MRE) of different rainfall amount,the TRMM product behaves as follows;light rains is overestimated nearly in whole country;moderate rain is larger in some regions of eastern China;the MREs of heavy rain and torrential rain are less than 1 in most areas of China.Mean rates of the missing retrieval and the vacancy retrieval are 10%and 14%respectively in China.

Climatic Characters in 2010'China

Abstract: In 2010,the annual mean temperature was 0.7℃higher than normal,which ranked the 10th warmest year since 1961.And it was the warmest summer mean temperature since 1961.Annual precipitation in China was 681 mm,11.1%more than normal,which ranked the second most since 1961.Luring this year,extreme weather and climate events happened frequently.Southwest China experienced the rare severe autumn—winter—spring drought.In winter and spring,unusual persistent low temperature hit Northeast and North China.The most serious snowstorm attacked northern Xinjiang,which broke the historical record.From May to July,heavy rainstorm attacked southern China 14 times.From mid July to early September,severe rainstorm and induced flood attacked northern and western China 10 times.In early and mid October,seldom consecutive heavy rainstorm appeared in Hainan Province.Serious geological hazards such as mountain torrents,mud-rock flow and mudslide happened in Zhugqu of Gansu Province and other sporadic places.In summer,frequent hot waves happened widely and intensely.In early summer, the weather in Northeast China was very hot and the maximum temperature in many areas broke historical records.The number of tropical cyclones was below normal,while the proportion of landing was high.The affected regions concentrated in South China.Typhoons Chanthu and Fanapi brought serious losses.The worst strong wind and hail hazards in recent 20 years occurred in Chongqing and caused heavy casualties.In spring,the strong dust storm affected 21 provinces.In general,in 2010,the losses caused by meteorological hazards were the most since 2000.The direct economic losses and mortalities or the missing caused by meteorological hazards were the most in recent 10 years.

Temporal-Spatial Characteristics of Cumulative Snow Depth in Northeast China and Its Vicinity

Abstract: Based on the snow cover data and meteorological element data at 123 meteorological stations in Northeast China during the period of 1960—2006,the spatial and temporal characteristics of snow cover are analyzed by the area weighted method,empirical orthogonal function,Morlet wavelet analysis and power spectral method.The results show that the cumulative snow depth in Northeast China is increasing slowly in the recent 40 years.The cumulative snow depth is no obvious changes in autumn,increasing in winter,and decreasing in spring,in which the increasing cumulative snow depth in winter is the key factor to the increasing annual cumulative snow depth.We hold the opinion that there are three main spatial patterns of cumulative snow depth in Northeast China by using EOF method,of which,the first pattern is consistently more(less)than normal,the second pattern is a seesaw between southern(northern)region and northern(southern)region,and the third pattern is a seesaw between central region(other region)and other region(central region).There is a quasi-period of 7 years revealed by Morlet wavelet analysis and power spectral method,its period displays a decreasing trend and has a good response to the global warming.

The Characteristics of Summer Precipitation Diurnal Variations in Three Reanalysis Datasets over China

Abstract: The characteristics of summer precipitation diurnal variations in three reanalysis datasets (NCEP,ERA40 and JRA25) over China were analyzed by comparing with those in station rain gauge observations. Results show that the summer precipitation diurnal variations in the three reanalysis products all present obvious deficiencies.Analyzing the percentages of daytime and nighttime rainfall show that the percentage of the daytime(08-20 BT) rainfall to the whole day rainfall is larger than that of nocturnal(20 -08 BT) rainfall in all reanalysis datasets over the most region of China while comparing with the station gauge data.Further analyses demonstrate that the percentage of the morning(08-14 BT) rainfall is the smallest in the station gauge data,but in NCEP and ERA40 products it is obviously more than that in the station observations.The proportion of the daytime rainfall to nocturnal rainfall in NCEP products over Southwest China is almost reverse to that of station rain gauge data.Generally,the diurnal variations of precipitation amount and frequency in JRA25 products and precipitation intensity in NCEP products are closest to the corresponding components in station data,but the nocturnal rainfall over Southwest China is only partly reproduced by ERA40 products.

Intensifying Mechanism of the Convective Storm Moving from the Mountain to the Plain over Beijing Area

Abstract: A particularly challenging event occurred on 22 July 2009 in Beijing area.The convective storm moving from the mountain to the plain suddenly intensified as it approached the foothills,and then intensified again as it moved onto the plains.Based on the four-dimensional Variational Doppler Radar Analysis System(VDRAS),this paper presented a deep investigation focusing on the intensifying mechanism of the convective storm under weak synoptic-scale forcing over Beijing area using Doppler radar,wind profile,surface observation,4 times daily radiosonde and NCEP data.Results have shown that:The weak cold front triggered the convective storm.The thermodynamic unstable condition including warm,humid,low-level southerly wind and significant accumulation of the convective available potential energy(CAPE) indicated by the sounding over plain,and the significant dynamic instability with strong low-level vertical wind shear indicated by the wind profiler provided the favorable local environment for the intensification of the storm.In the first intensification stage,the terrain forcing played a dominant role,including:(1) acceleration of cold pool outflow whose kinetic energy drived from potential energy,leading to strong down flow and strong convergence;(2) uplift of south warm moist air flow at the south of piedmont,resulting in a strong upward motion;(3) lifting of the thunderstorm cold pool outflow,which formed strong low-level vertical wind shear between north outflow at the low level and south air flow on the surface and led to cold advection over the warm and moist southerly flow,thus enhanced both the dynamic and thermodynamic instability in front of the storm.The second intensification of the thunderstorm in the eastern urban area,was mainly caused by the presence of the strong perturbation temperature gradient zone in the boundary layer in Chaoyang District,resulting from the confrontation of the cold pool outflows of the well-organized thunderstorm and the low-level warm tongue,and the balance between positive and negative vorticities.The intense updrafts pushed by the interactions between the cold outflow and the warm moist southerly flow,coexisted with the downdraft at the rear of the thunderstorm for a long time.The negative vorticity due to the vertical inhomogeneity of the outflow,was balanced with the positive vorticity due to the vertical inhomogeneity of the environmental flow.According to the RKW theory, this equilibrium state was very favorable for the formation of vertical updraft so that maintained the storm and led to the second intensification.

The Role of Sea-Land Breeze Circulation in Local Convective Torrential Rain Happening in Tianjin on 26 September 2009

Abstract: A local torrential rain process occurring in Tianjin on September 26,2009 is diagnosed and a mesoscale analysis of it is performed,based on the conventional and surface densified automatic station observations, data of mesoscale model of TMMB,satellite cloud pictures and Doppler radar data etc.The results show that the heavy rain occurs when the large-scale circulation pattern is adjusted from meridional to zonal.The trough of 500 hPa is the major synoptic scale system in this event,while the main mesoscale systems are surface mesoscale convergence line,humidity frontal zone and sea breeze front visible in Doppler radar imagery,which are driven by sea-land breeze circulation.And a fully developed thermal instability before the occurrence of the torrential rainfall has being established,the synoptic scale environment has considerable energy storage,favorable dynamic condition and moisture convergence from the Bay of Bengal at 700 hPa and the sea to the east of Tianjin at 850 hPa.The collision of synoptic system driven cumulus convection and sea breeze front triggers the release of instable energy,resulting in the heavy precipitation of the first period.The strong easterlies in the boundary layer indicate the essential role of sealand breeze circulation in this torrential rain event.

The Designing and Application of the Atmospheric Observing System Operations and Monitoring in China

Abstract: The integrated meteorological observation system is the foundation of weather forecast service, and guaranteeing the integrated meteorological observation system operation steady and reliable has become the key point of the development of meteorological service in China.This paper expounded the construction structure,the technical route,the key technical methods,the characteristics and the functions of the Atmospheric Observing System Operations and Monitoring(ASOM) in China.Besides,combining with the current situations of China's meteorological equipment monitoring and maintenance,it explored the potential benefits and the future improving direction of the ASOM system.

Numerical Simulation and Analysis on a Heavy Snow of Return-Flow Events in Beijing

Abstract: The typical return-flow events with heavy snow during 2—3 January,2010 by using Beijing local high-resolution rapid update cycle mesoscale model system(BJ-RUC) are simulated.The characteristics of synoptic system in each layer and key snowfall factor are analyzed.The results show that the BJ-RUC model can well simulate the snowfall distribution,position and time change,and the main situations of heavy snowfall which are caused by the cold air return-flow in the low-level,and the 850—700 hPa layer low-vortex system.But the snowfall center has still some deficiency.When the vertical ascending motion is produced in lower atmosphere by the cold return-flow encountering terrain,the snowfall is not high. During the snowfall,the dynamic lifting which is caused by the cold return-flow combining with the ascending motion of the foreside of low vortex,forms a deeply and violent ascending motion,that is the key factor to cause the heavy snow.The durative and cold return-flow with high humidity transports water vapor in the lower atmosphere.The humidity in the lower-mid troposphere is increased by the southwestern air flow.The return-flow increases thickness of wet-layer,reaching above 600 hPa.It plays an important role in producing the heavy snow.The start and intensity of snow fall are related to the moment of the direction change to southern wind and the south wind speed.

Inter-Decadal Change of Hail Events over China and Causation Analysis in Northern China in Recent 50 Years

Abstract: With data of hail days at 755 stations,NCEP/NCAR monthly reanalysis and atmospheric circulation characteristics from 1958 to 2007,we have investigated the inter-decadal change of hail events in China The results indicate that the overall trend of hail events has declined remarkably since the 1980sMost of China has a descending tendency especially in the Northeast China,North China,Northwest China and East-Central Tibetan PlateauAccording to the analysis of relation between hail events and wind fields, height fields,subtropical high,polar vortex and temperature fields,we have found that the hail event has declined significantly in northern China,which is related to the southward shift of the 200 hPa westerly jet stream,the upward elevating of the 850 hPa height field,the weakening of the subtropical high,the strengthening of the polar vortex and the shortening of the distance between 0℃and -20℃

The Preliminary Experiment of GRAPES-MESO Ensemble Prediction Based on TIGGE Data

Abstract: A heavy rainfall is simulated by GRAPES-MESO model,occurring in Huanghuai area on 22 July 2008 to study the forecast uncertainty and the initial perturbation method when establishing GRAPES-MESO ensemble prediction system(called GRAPES-MEPS) based on TIGGE data.The results suggest that the initial perturbation structure can reflect some information of initial uncertainty.The GRAPES-MEPS has the ability to capture the extreme rainfall event and can significantly improve the forecast skill of heavy rainfall.The ensemble mean can capture some characteristics of the mesoscale heavy rainfall validly.The probability forecast gives the high probability area,where the heavy rainfall occurred actually.The ensemble verification results indicate that the relation between the spread and RMSE demonstrates the rationality of the GRAPES-MEPS during the early integral period,but the impact of the initial perturbation decreases in the subsequent integral period owing to the model dynamic adjustment.

Vertical Distributions of Aerosols Under Different Weather Conditions in Beijing

Abstract: In this study,aerosol(0.1-3.0μm) vertical distributions of 17 in-situ aircraft measurements during 2005 and 2006 springs are analyzed.The 17 flights are carefully selected to exclude dust events,and the analyses are focused on the vertical distributions of aerosol particles associated with anthropogenic activities. The results show that the vertical distributions of aerosol particles are strongly affected by weather and meteorological conditions,and 3 different types of aerosol vertical distributions corresponding to different weather systems are defined in this study.The measurement with a flat vertical gradient and low surface aerosol concentrations is defined as type-1;a gradually decrease of aerosols with altitudes and modest surface aerosol concentrations is defined as type-2;a sharp vertical gradient(aerosols being strongly depressed in the PBL) with high surface aerosol concentrations is defined as type-3.The weather conditions corresponding to the 3 different aerosol types are high pressure,between two high pressures,and low pressure systems(frontal inversions),respectively.The vertical mixing and horizontal transport for the 3 different vertical distributions are analyzed.Under the type-1 condition,the vertical mixing and horizontal transport were rapid,leading to a strong dilution of aerosols in both vertical and horizontal direc- tions.As a result,the aerosol concentrations in PBL(planetary boundary layer) were very low,and the vertical distribution was flat.Under the type-2 condition,the vertical mixing was strong and there was no strong barrier at the PBL height.The horizontal transport(wind flux) was modest.As a result,the aerosol concentrations were gradually reduced with altitude,with modest surface aerosol concentrations.Under the type-3 condition,there was a cold front near the region.As a result,a frontal inversion associated with weak vertical mixing appeared at the top of the inversion layer,forming a very strong barrier to prevent aerosol particles being exchanged from the PBL height to the free troposphere.Therefore,the aerosol particles were strongly depressed in the PBL height,producing high surface aerosol concentrations.

Climate Characteristics and Variation of Rainstorm in South China

Abstract: Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China,the climatic characteristics and variation of torrential rain days,rainstorm intensity and contribution which is in annual,the first and second flood seasons in South China were studied by using statistical and diagnostic methods,such as linear regression analysis,Mann-Kendall test,wavelet analysis and the computation of trend coefficients.The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years,the highest center is in Dongxing of Guangxi(14.9 d),and the lowest center is in Longlin of Guangxi(3.2 d).About 72%of the total torrential rain days occurred in the flood seasons with about 45%in the first season and 27%in the second season.The mean torrential rain days have increased faintly in annual,the first and second flood seasons in South China,but it is not obvious.There are the characteristics of interannual and interdecadal changes.The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China.However,since 2005 it has become obviously.The mean rainstorm intensity has declined in the second flood season,but it is not obvious.The annual mean rainstorm contribution to the total rainfall has increased obviously,but the mean contribution is not obvious in the first and second flood seasons.The wavelet analysis has shown that the changes of torrential rain days,intensity and contribution which is in annual,the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.

Distinguishing the Category of the Summer Convective Weather by Sounding Data in Beijing

Abstract: This paper calculated 18 physical parameters and their 6-h,12-h,and 24-h variations by the sounding data from Beijing Nanjiao Observatory,and then analyzed the physical parameter differences of hailstone,thunderstorm gale,and storm rainfall from May to September in 2007 and 2008.The results show that,as the physical parameters,the 0℃height,the—20℃height,the difference of temperature between 500 hPa and 850 hPa,the inversion height and the low-level wind shear could distinguish the category of the rainstorm and hailstorm.Besides,the depression of dew point of 850 hPa and the difference ofθ_(se) between 500 hPa and 850 hPa are also the important conditions.On the other hand,for the 6-h variations of the CAPE,DCAPE,K index,the difference ofθ_(se) between 500 hPa and 850 hPa,PW,and the vertical wind shear of the lower troposphere could also be better to distinguish the hailstorm and the storm rainfall.The results indicate that it is possible to distinguish the summer convective weather by better using of sounding data.

Analysis of the 4 March 2007 Heavy Snowstorm in Northeast China

Abstract: In this paper,the synoptic background,the non-geostropic Q-vector contribution and the phase change of the conditions are analyzed in the process of heavy snowstorm and heavy rain in Northeast China during March 3-6,2007.The results have shown that:a wide range and strong southerly jet is not only a strong water vapor belt,but also the necessary conditions for the lower front and low-level system to strengthen and move;the forcing of secondary circulation in the torrential rain plays an important role in the occurrence and development of process,its strength is directly related with the rainfall intensity.The level of cloud systems and whereabouts in the process of stratification state of the lower front to a certain extent determine the phase state of precipitation on the ground.Deep strong front zone,Jiang-Huai cyclones, low-level jet,and the intensity of nongeostrophic Q vector are closely related with the location of precipitation band and its intensity.

Anomalies of Ocean and Atmospheric Circulation in 2010 and Their Impacts on Climate in China

Abstract: In order to conclude the reasons of climatic anomaly and improve the skill of climatic prediction, the observation data and physical mechanism diagnostic method were used to analyze the climatic anomaly reasons in 2010.Results showed that the climatic anomaly in 2010 ranked the first within recent 10 years and the abnormity of ocean and atmospheric circulation features may lead to that.A moderate El Nino event occurred from June of 2009 to April of 2010 and followed by La Nina event from July of 2010.The tropical Indian Ocean sea surface temperature anomaly(SSTA) experienced two important periods:from basin-wide warming to negative Indian Ocean Dipole(IOD) mode,and North Atlantic SSTA was characterized as triple mode in the same period.Due to the influences forced by SSTA and interaction between ocean and atmosphere,the atmospheric circulation over the Northern Hemisphere showed the dominant anomalies which have been featured as response as follows:subtropical high over the West Pacific (SHWP) was stronger than normal and further west to its normal position because of El Nino event before October of 2010,and afterwards it was weaker than normal and further east to its normal position due to La Nina event,and the location of its ridge line also showed significant stage characteristics.The strength of the South China Sea summer monsoon was the weakest since 1951 and East Asian monsoon was weaker than normal;Blocking highs were located over middle-high latitudes in Boreal summer.Furthermore,the Arctic Oscillation ranked the extreme negative phase in 2009/2010 winter within 60 years.SSTA forcing and internal atmospheric dynamic processes may lead to the climatic anomaly in China in 2010.

A Study of Temporal-Spatial Distribution and Synoptic Characteristics of Severe Convective Weather in Beijing, Tianjin and Hebei

Abstract: Based on the hazardous weather report,disaster telegraph data and NCEP 1°×1°reanalysis data from 175 stations in Beijing,Tianjin and Hebei from May to September during 2001—2008,the statistical analyses are used to explore the temporal-spatial distribution and synoptic characteristics of severe convective weather there.The analysis results indicate that:(1) In this period,the wind force always reaches 7- 8 scales with prevailing northerly and westerly winds,the south-central and northwest of Hebei area,and Beijing and Tianjin have strong winds;Larger hails often occur in Beijing,Tianjin and the northwest and north of Hebei;Within 10—60 minutes,the precipitation easily reaches 20—25 mm,while during 130- 180 minutes,the precipitation can reach 50—100 mm.(2) During 2001—2008,the winds often occur in May and June,the hails occur in June,but the short-time rainstorms occur in July and August;(3) Except for short-time rainstorms,winds and hails approach to the Taihang and Yinshan Mountains and reduce gradually from northwest to southeast.The severe convective weather has the obvious characteristics of daily variation,a majority of severe convective weathers(62%) occur in the afternoon and early evening (14:00—20:00 BT).(4) There are three main weather circulations:the cold vortex pattern in which mainly appear hails accompanied by gales or short-time rainstorms,the cold trough pattern in which mainly appear strong winds with short-time rainstorm,and the trough and subtropical anticyclone pattern which always brings short-time rainstorms.A weather conceptual model which is established through the typical case has a good significance for weather forecasting.

Effect Simulation of Chengdu Fine Underlying Surface Information on Urban Meteorology

Abstract: In order to improve the level of Chengdu fine weather forecast,using Chengdu fine underlying surface data,the urban meteorological characteristics of Chengdu are simulated by the WRF coupled with single-layer urban canopy model for a clear day,on July 6,2008,and those are compared to simulations with old land-use data and slab model.The result shows that because of urban impervious underlying surface area increasing,the surface evaporation and upward moisture flux are significantly reduced,latent heat flux decreases and sensible heat flux increases.Urban buildings can intercept long-wave radiation energy, so urban turbulence enhances and boundary layer height becomes higher;With the fine land-use data and single-layer urban canopy model,both negative bias and root-meansquare error of 2-m temperature decrease;Urban area expansion and more buildings have led to the result that the urban heat island effect strengthens,urban 10-m wind speed decreases,heat circulation between urban and suburban areas enhances, and local vertical circulation boosts.

Risk Division and Assessment of Typhoon Rainstorm Flooding Disasters in Hangzhou City

Abstract: Based on the typhoon precipitation data from seven stations in Hangzhou City during the period from 1960 to 2009 and combined with the society economic and natural geographic factors,this study builds a set of typhoon rainstorm flooding disaster assessment model including hazard factors,hazard inducing environment,hazard-affected body and disaster prevention ability.And a map of Hangzhou's typhoon rainstorm flooding disaster risk division was drawn using 100 m X 100 m raster as basic assessment unit, by means of GIS spatial analysis technique for rasterizing evaluation indices and fuzzy comprehensive assessment methods.Finally,the five risk zones of Hangzhou,i.e.higher risk,sub-high risk,medium risk,inferior risk and lower risk,were mapped.Results show that the typhoon rainstorm flooding disaster risk in Hangzhou has an increasing tendency from southwest to northeast.The coastal plain,involved with Xiaoshan District,Yuhang City,main urban area of Hangzhou,and so on,has relative high risk,while the mid-west mountain and hilly area,involved with Jiande City,Chun'an County,and so on,has slightly lower risk.

Climatic Characteristics of Fog in Hebei Province and Trend Research

Abstract: For studying climatic characteristics and change trend of fog in Hebei Province,based on the observational data from 49 meteorological stations in Hebei Province during 1965—2006,the temporal and spatial features of fog,diurnal variational law and the long-term variation trend are analyzed by using the correlation analysis,trend analysis and Mann-Kendall test methods.Results show that annual fog days are 15 d in Hebei Province,those in plain are more than 20 d,and in plateau,mountains and hills are less than 10 d.The fog-prone season is in autumn and winter,the 15.7%of fog frequency in November is the highest. Except summer,foggy days in plain are more than other topographic regions in general.The turning point of fog in Hebei Province is in the early 1970s.First,it is less from 1965 to 1971 then,after 1972 it experiences a more—less—more variational process.Frequency that fog occurs is the highest at 05:00 BT accounting for 22.2%,and frequency that fog dissipates is the highest at 08:00 BT accounting for 18.8%. The short-time fog within 3 hours occurs easily.Foggy days in Hebei Province hava a change trend,stations in piedmont plain show an upward trend mostly,but stations in other topographic regions show a downward trend commonly.

Study of Bias-Correction in T213 Global Ensemble Forecast

Abstract: In view of existence of model systematic error,a study of bias-correction has been done to estimate and reduce systematic error.One-moment bias-correction has been introduced in this paper.The merit of this method is that quantity of samples needed is smaller,thus estimation and bias-correction could be carried out quickly and economically.One-moment bias-correction towards T213 global ensemble forecast of 500 hPa height,850 hPa temperature and 2-m temperature has been done.Verification towards raw forecast and bias-corrected forecast shows that ensemble member homogeneity and cold bias have been improved,and ensemble mean RMSE and ACC also have been improved,especially bigger systematic error of 2-m temperature forecast has been improved obviously.

Distribution and Spatiotemporal Variations of Deep Convective Clouds over China During the Warm Season

Abstract: Based on the nearly-twelve-year hourly geostationary satellite multi-channel(IR1,IR2 and water vapor channels) digital infrared image dataset,the distribution and spatiotemporal variations of deep convective clouds over China and its vicinity during the warm season(March -October) from 1996 to 2008 (lacking 2004 data,part data missing) are analyzed,and comparative analysis is conducted on the distribution of thunderstorm days and the density distribution of lightning obtained from low-orbit satellites.In this paper,TB_(ir1)≤-52℃(Infrared 1-channel brightness temperature),TB_(ir1)-TB_(ir2)3 K(Infrared 2- channel brightness temperature),and TB_(ir1)-TB_(wv)≤8 K(water vapor channel brightness temperature) are used to identify the deep convetive clouds.The results show that:There are four active regions of deep convective clouds during the warm season,i.e.,the middle-east of Qinghai-Tibetan Plateau,South China and Northeast of Yunnan-Guizhou Plateau,Xinjiang Ili River Valley and its surrounding area,and the most parts of Zhejiang-Fujian-Jiangxi regions;Overall,deep convective clouds over summer(June-August) are the most active;in spring(March-May) followed by;the autumn(September-October) are the least;The geographical distribution of deep convective clouds in different seasons is significantly different;The feature of diurnal variations of deep convective clouds has a significantly difference in different seasons and regions;Autumn diurnal variation is the least significant;As spring sunset time is earlier than the summer,in general,the diurnal variation of deep convective clouds in the spring is earlier than the summer peak hours;Deep convective clouds in the middle-east of Qinghai-Tibetan Plateau,Guangdong and Guangxi hills and the Zhejiang and Fujian hilly regions are of the single peak diurnal variation;At Sichuan Basin,the deep convective clouds often have nocturnal occurrence;In spring and summer,the diurnal variations of deep convective clouds are of bimodal type in Jianghuai region,which may be related to the region more closely related to MαCS;Thermal convections in the eastern part of Qinghai-Tibetan Plateau are active;In Guangdong and Guangxi hills,Sichuan Basin,and Jianghuai region it is not only very active heat convection,but other weather systems(such as typhoons,Meiyu front,etc.) to trigger and maintain the convection are also very active in summer.

The Role of Sea Breeze Front in Local Storm of Bohai Coast

Abstract: Using the data obtained by conventional observations,ground densified automatic weather stations, Doppler radar observations and mesoscale TJ-WRF model,we analyze the heavy rain occurring on 6 July 2009 at Ninghe District of Tianjin and highlight the trigger mechanism of coastal local storm caused by sea breeze front of the Bohai Gulf.The results show that the heavy rain occurred in the favorable weather conditions,and there were local instability and adequate vapor conditions.Sea breeze front itself has a convergent uplift area where weak convection exists;when sea breeze front moves to the unstable and adequate vapor areas,it will strengthen the convergence positive movement of convergent uplift area and lead to the new storm development.The meeting of the sea breeze front and thunderstorm will play a strengthened role in its development.By analyzing the data obtained by mesoscale WRF model,we can see that at the warm and dry ground in front area near the north end of the wet air interchange,the intersection of the two convergence lines is easy to stimulate strong thunderstorms,and thunderstorm accrues at the intersection of the north of the subaerial warm and dry front zone and humid air.Sea breeze front plays an important role in the development of the thunderstorm.

The Analysis and Discussion on Operational Forecast Errors of Super Typhoon Muifa(1109)

Abstract: During operational forecasting and service for Super Typhoon Muifa(1109) in Central Meteorological Observatory,there are some errors in its track,intensity and precipitation forecasting.The forecast errors partly caused a passive situation in its operational forecasting and service.In this paper,conventional and unconventional meteorological data,operational numerical prediction models,NCEP reanalysis data (1°×1°) and coupled ocean-atmosphere model of National Meteorological Centre(NMC) are used to make a preliminary analysis on these forecast errors.The results show that;(1) The track forecast error for Muifa is mainly attributed to the optimistic estimation of the westward movement toward the Yellow Sea of the subtropical high near Japan,while westerly trough and binary typhoons have an important influence on the northward movement of Muifa.And the northeastward movement of Typhoon Merbok(1110) at the east of Muifa has a certain sense of direction for the southward withdraw of the subtropical high.(2) When there are big differences between operational numerical prediction models,it is the key how to better use ensemble and consensus forecast products for further improving the accuracy of typhoon track prediction. (3) The intensity prediction error of Muifa is mainly due to the one sided consideration about the impact of sea surface temperature on typhoon intensity change,while ignoring the influences of dry air and environmental vertical wind shear.(1) In addition to be concerned with the forecast errors of the track and intensity,the precipitation forecast error for Muifa is also related to the underestimation on the characteristics of dry typhoon about Muifa and the weak interaction between the low and middle latitude systems.

Study on the Inversion of Clear Sky Atmospheric Humidity Profiles with Artificial Neural Network

Abstract: AIRS(Atmospheric Infrared Sounder),the first high spectral atmospheric infrared detector, started a new era of satellite sounding atmosphere.The samples,composed of the radiosonde observations and the AIRS brightness temperature value simulated by the SARTA(Stand-Alone Radiative Transfer Algorithm) v1.05 forward mode,were inversed to the atmospheric humidity profiles using neural network. The results show that,compared with the result of eigenvector statistics,the neural network inversion is of higher precision,and the humidity profiles obtained are closer to the true profiles.AIRS displays the fine structure of the atmosphere because of its high spectral resolution(high vertical resolution).Neural network has a strong nonliner processing capability in the issue that the inversion of the atmospheric humidity profiles is based on high spectral data.

Assessment on the Rainfall Monitoring of Typhoon Morakot by Ground-Gauged and Satellite Precipitation Products

Abstract: Based on the automatic weather stations(AWS)precipitation data,an assessment of multi precipitation products is conducted on the rainfall monitoring of typhoon Morakot in the August of 2009.The results show that,the CPAP(China Precipitation Analysis Product)daily grid precipitation data display an accurate spacial distribution and rain intensity on the land,but not in ocean because of the limitation of station distribution.Compared to the ground-gauged rainfall measurements,the method CMORPH can well present an exact spiral rain-belt around typhoon eye,and also its evolvement,but the location of maximal rainfall center rooted in the rain-belt deviates greatly from the actuality.And the intensity of rainfall in the CMORPH is much weaker than that in gauged.In oceans,FY2C does not perform as good as the CMORPH owing to its discontinued rainfall distribution along the coastal areas.Taking the advantages of the gauged rainfall(accuracy)and the CMORPH(pattern),we may get a high-quality precipitation product.

Discussion on Genesis of Wire Icing in Guizhou During the Freezing Rain and Snow Storm in January 2008

Abstract: Using the meteorological wire icing observations,radio sonde and surface observations,and NCEP reanalysis data,the distribution and intensity of wire icing in Guizhou Province during the hazardous sleet in 2008 are analyzedThe meteorological conditions for wire ice accretion and its melting in Guizhou are discussedThe results show that the serious wire ice accretion in Guizhou in the sleet is characterized by wide range,long lasting time and thicker wire ice in the east than the westWire icing events in Guizhou are mainly in forms of glaze,rime and mixed freezing consisting of glaze and rimeQuasi-stationary frontal precipitation and frontal temperature inversion play an important role in the formation of glaze iceThe condition that temperature maintains within—5—0℃for a relatively long period and sufficient water vapor exists in the lower level determines the wire ice accretion and its growthWire ice stops growing when relative humidity is below 85%,and the melting rate of wire ice is relevant to the local temperature rising rate

The Relationship Between the Strength Variability of Freezing Rain and the Character of Inversion in the Beginning of 2008

Abstract: Using the NCEP/NCAR reanalysis data and observation data(8 times daily) from the Central Meteorological Observatory from January 10 to February 2,2008,we analyzed the characters of spatialtemporal structure about temperature inversion layers,the variability of intensity of the four freezing rain processes happening in southern China and the relationship between them.The results show that the third out of the four main freezing rain processes is the strongest,then is followed by the second,and the first is the weakest process.Meanwhile,there is a close relationship between the strength variability of freezing rain and reversion layers,which could be revealed either from the regional average value or from the horizontal distribution.Furthermore,the thicknesses and altitudes of the cold layer,the warm layer and the whole inversion layer are able to affect the formation of the freezing rain,but the influence on the strength of the freezing rain is not significant.The results provide a good idea for forecasting the variability of the freezing rain,which is of reference value.

Introduction and Examination of Potential Forecast for Strong Convective Weather at National Level

Abstract: To promote the process of weather forecasting to be more professional and accurate,the potential forecast for predicting severe weather area has been conducted by Severe Weather Prediction Center in NMC since 2009.Real-time products for monitoring strong convective weather based on severe weather report from automatic weather stations,observations from national lightning monitoring network,FY-series satellite and radar networking etc.have been put in use.Criterion for mesoscale weather analysis has been established in MICAPS V3.0 system.The diagnostic products of mesoscale convective system outputted by the application of T639 global model,GRAPES-RUC model and WRF-EPS model have been developed. Guiding products for predicting classified severe weather(thunderstorm,hail and gale) area have also been issued.Prediction qualities were examined and assessed from April to September in 2009.The results show that the 6-hour-interval TS scores of thunderstorm,local torrential rain,and hail and gale are 18%, 2.6%,and 2.1%separately,while 12-hour-interval TS scores for each are 18.4%,4.1%and 1.3%,respectively.