S5.4 secondary circulation and spin down 次级环流和旋转减弱 presentation演讲稿

第一篇：S5.4 secondary circulation and spin down 次级环流和旋转减弱 presentation演讲稿

Good evening everyone.My topic is section five point four, secondary circulation and spin down.[click] There are five parts in my presentation, key words, secondary circulation, spin down, Physical meaning,and summary.[click]Firstly, let us see the key words.The secondary circulation is a circulation superposed on the primary circulation by the physical constraints of the system.And the spin down is a mechanism for destroying vorticity in a rotating atmosphere by losing angular momentum.The Angular momentum measures an object's tendency to continue to spin.And angular momentum is equal to the vector product among mass, velocity and distance(from point object is spinning or orbiting around)[click] Both the mixed-layer solution and the Ekman spiral solution indicate that in the planetary boundary layer the horizontal wind has a component directed toward lower pressure.As the rad arrows shown in Fig.5.6, [click]this implies mass convergence in a cyclonic circulation and mass divergence in an anticyclonic circulation, which by mass continuity requires vertical motion out of and into the boundary layer, respectively.[click] In order to estimate the magnitude of this induced vertical motion, we note that if vg = 0 so that ug is independent of x, the cross isobaric mass transport per unit area at any level in the boundary layer is given by ρ0v.For the Ekman spiral, it is given by the equation five point thirty five, where De is equal to πdivide byγ, and is the Ekman layer depth defined in Section 5.3.4.[click]Integrating the mean continuity equation(5.13)through the depth of the boundary layer gives equation five point thirty six.Assuming that w(0)= 0, and vg = 0 , and comparing with(5.35)that the mass transport at the top of the Ekman layer is given by equation five point thirty seven.[click]Noting that minus partial ug divide by partial y is just the geostrophic vorticity in this case.we find equation five point thirty eight after substituting into(5.36), where we have neglected the variation of density with height in the boundary layer and have assumed that one plus e to minus π is approximately equal to 1.Hence, we obtain the important result that the vertical velocity at the top of the boundary layer is proportional to the geostrophic vorticity.In this way the effect of boundary layer fluxes is communicated directly to the free atmosphere through a forced secondary circulation.This process is often referred to as boundary layer pumping.It only occurs in rotating fluids and is one of the fundamental distinctions between rotating and nonrotating flow.For a typical synoptic-scale system , the vertical velocity given by(5.38)is of the order of a few millimeters per second.[click] An analogous boundary layer pumping is responsible for the decay of the circulation created when a cup of tea is stirre.Radial inflow takes place near the bottom of the cup.By continuity of mass, the radial inflow in the bottom boundary layer requires upward motion and a slow compensating outward radial flow throughout the remaining depth of the tea.This slow outward radial flow approximately conserves angular momentum, and by replacing high angular momentum fluid by low angular momentum fluid serves to spin down the vorticity in the cup far more rapidly than could mere diffusion.[click] For synoptic-scale motions the barotropic vorticity equation(4.24)can be written approximately as equation four point twenty four.where we have neglected ζg compared to f in the divergence term and have also neglected the latitudinal variation of f.Recalling that the geostrophic vorticity is independent of height in a barotropic atmosphere,(5.39)can be integrated easily from the top of the Ekman layer(z = De)to the tropopause(z = H)to give equation five point forty.Substituting for w(De)from(5.38), assuming that w(H)= 0 and that H is much lager than De, the equation(5.40)may be written as equation five point forty one.This equation may be integrated in time to give equation five point forty two.where ζg(0)is the value of the geostrophic vorticity at time t = 0, and τe is the time that it takes the vorticity to decrease to e −1 of its original value.[click] This e-folding time scale is referred to as the barotropic spin-down time.Taking typical values of the parameters as follows, we find that τe approximates 4 days.Thus, for nidlatitude synoptic-scale disturbances in a barotropic atmosphere, the spin-down time is a few days.This decay time scale should be compared to the time scale for ordinary viscous diffusion.For viscous diffusion the time scale can be estimated from scale analysis of the diffusion equation five point forty three.So that for the above value of H and Km, the diffusion time scale is thus about 100 days.Hence, in the absence of convective clouds the spin-down process is a far more effective mechanism for destroying vorticity in a rotating atmosphere than eddy diffusion.[click] Physically the spindown process in the atmospheric case is primarily the Coriolis force that balances the pressure gradient force away from the boundary.The Coriolis force for the outward-flowing fluid is directed clockwise, and this force thus exerts a torque opposite to the direction of the circulation of the vortex.In the case of boundary layer, viscosity is responsible for the presence of the secondary circulation.In a stably stratified baroclinic atmosphere, the buoyancy force will act to suppress vertical motion.So the interior secondary circulation will decrease with altitude, shown in Fig.five point eight.This flow will rather quickly spin down the vorticity at the top of Ekman layer that is enough to bring ζg to zero.The result is a baroclinic vortex with a vertical shear of the azimuthal velocity that is very strong.[click]This vertical shear of the geostrophic wind requires a radial temperature gradient that is in fact produced during the spin-down phase by adiabatic cooling of the air forced out of the Ekman layer.[click] Finally, let us see my summary.By the physical constraints of the system, a secondary circulation will occur.It only occurs in rotating fluids.And in boundary layer, viscosity is responsible for the presence of it.The secondary circulation can spin down an atmosphere vortex.The e-folding time is referred to as the barotropic spin-down time.The secondary circulation in the baroclinic atmosphere serves two purposes: it changes the azimuthal velocity field of the vortex through the action of the Coriolis force and it changes the temperature distribution so that a thermal wind balance is always maintained between the vertical shear of the azimuthal velocity and the radial temperature gradient.That’s all.Thanks four your attention, thank you!

第二篇：Presentation演讲稿

Good morning，everyone.It’s my pleasure to introduce my hometown，especially as the first to eat crab [kræb].Have you ever heard of the tower [ˈtauə]? Yes, it’s Yellow Crane [krein] Tower.(Chinese: 黄鹤楼).It is a famous and historic [hisˈtɔrik] tower, and built in the year 223 AD.The tower is the landmark in Hubei province [ˈprɔvins].Yes, I come from Hubei.At first, I will give an overview [ˈəʊvəˌvju:] of Hubei.Hubei province, with a population of 60 million, is located [ləʊˈkeɪtɪd] in the middle reaches of the Yangtze river, and to the north of dongting lake, with Wuhan as the provincial [prəˈvɪnʃəl] capital[ ˈkæpitl], and Qichun as my birthplace.Hubei covers an area of over 180,000 square kilometers with over 12 prefecture [ˈpri:fektʃuə]-level city, and 102 counties.It is well known as “a thoroughfare [ˈθɜ:rəʊˌfeə] of 9 provinces(Chinese:九省通衢)”for its networks of transportation by air, water, highway and railway.Hubei is the birthplace for Chu culture.Chu culture is a highly developed and unique [ju:ˈni:k] style regional culture in south china from the eastern Zhou period to the end of the Qin dynasty [ˈdainəsti].it reaches a fairly high level in many aspects [ˈæspekt] like bronze [brɔnz] casting, handicraft [ˈhændi:ˌkræft] industry, porcelain [ˈpɔ:slin], music, literature [ˈlitəritʃə] and painting, and so on.Hubei, known as”the province with a thousand lakes”and “the land of fish and rice”, is one of the major areas in China to produce rice, cotton, oil and fish.With its solid [ˈsɔlid] industrial foundations, Hubei has a system of modern industry.Its main industries includes electricity, metallurgy [ˈmetlˌɜ:dʒi:], machinery, electronic [ɪlɛkˈtrɑnɪk] information, and so on.The economy of Hubei province is in rapid development in recent years, and will obtain new opportunities [ˌɔpəˈtju:niti] in future..Higher education level of Hubei province is in the front of whole country, the number of college students is 1.3 million, of which more than 1.05 million in wuhan.When you come to a new city, maybe you are most concerned about the local [ˈləukəl] diet, so I focused on catering [ˈkeɪtərɪŋ] culture.Hubei cuisine [kwɪˈzi:n] composed[kəmˈpəuz] of three kinds of local dishes from Wuhan, Jingzhou and Huangzhou.Hot-and-dry noodles is the best choice for breakfast in Wuhan.Wuchang fish, that is produced in the vicinity [viˈsiniti] of Wuchang, as early as 1,700 years ago in the Three Kingdoms period, has been well known in north-south river.Chairman Mao Zedong said, “Having had water in Changsha, now I am having fish in Wuchang”.The famous poem was published, so Wuchang fish is even more famous in world.At last, I will give an introduction about my birthplace.Qichun County(Chinese: 蕲春县)is a county of Huanggang, Hubei.Qichun County is the birthplace of famous herbalist [ˈhɜ:bəlɪst] Li Shizhen, who was born and lived in Qizhou town, on the southern edge of the County, alongside the Yangtze River.In turn, Qichun is a major center of the herbal industry in China.Four local specialties [ˈspeʃəlti:] of Qichun are Ay Tsao, bamboo, turtle [ˈtə:tl] and snake, and they are called The four treasures in Qichun.They have good medicinal [mɪˈdɪsənəl] value in traditional Chinese medicine.All of the above is my hometown.Thank you for your attention.

第三篇：英语PRESENTATION演讲稿

good afternoon,everyone.he is my favorite singer---vae.do you know the chinese meaning of ‘vae’?he does not look handsome at all.sometime,just like your neighborhood,but he is very talented.his was born on 14th march,in 1986.he graduated from anhui medical university.attention,he is a doctor.isn’t it amazing that xusong turns to be a famous musian finally? roses funeral,the burial of your memorise.(玫瑰花的葬礼，埋葬关于你的回忆。)star light,and water thrawn up by the fold.（星光点亮了，海水泛起褶皱）sad lyrics,sad melody,vae’s interpretation（艺术表现）of the plain with a little bit sad.vae is a man who can tell us what is independence.he is my idol.his perserverance,his effort,his great idea,always inspire me.篇二：英语presentation演讲稿

before i start my presentation, let’s see some pictures;.yes, thesepictures lead us into my topic today: to be good netizens.nowadays we have stepped in a totally new age, in which we mainly receive the information from the internet.and we can see,the netizen population is growing fast the last decade.by 2000 it was just several millions of netizens in china but now, ten years later, we have more than 50 million.this number increased so fast that we have no time for preparing, so this lead to the situation that i show you before.and why that situation is so bad, let’s look at this picture.we can see, besides the large number, we have another problem: most of the netizens are young people;in other words, the next generation.such a bad internet environment can really influence their future, which means: influence our nation’s future.and although there is many benefits, we should first know whether our movement helps(even if just help a tiny little.)these are four big events which we netizens make many contributions: the event of south china tiger, the 2008 olympic, the train event, and the event of extracting bile from live bears.with our effort, a lot more people know these four events and that really helped to force the government to deal with it more properly.so we now know a good harmonious environment is important and we do can take actions to help create it.so why do we move right now.and these examples are far form enough, to create a good environment, there is a long way to go.篇三：presentation演讲稿 at first, i will give an overview [???v??vju:] of hubei.hubei province, with a population of 60 million, is located [l???ke?t?d] in the middle reaches of the yangtze river, and to the north of dongting lake, with wuhan as the provincial [pr??v?n??l] capital[ ?k?pitl], and qichun as my birthplace.hubei covers an area of over 180,000 square kilometers with over 12 prefecture [?pri:fekt?u?]-level city, and 102 counties.it is well known as “a thoroughfare [?θ?:r???fe?] of 9 provinces(chinese:九省通衢)”for its networks of transportation by air, water, highway and railway.hubei is the birthplace for chu culture.chu culture is a highly developed and unique [ju:?ni:k] style regional culture in south china from the eastern zhou period to the end of the qin dynasty [?dain?sti].it reaches a fairly high level in many aspects [??spekt] like bronze [br?nz] casting, handicraft [?h?ndi:?kr?ft] industry, porcelain [?p?:slin], music, literature [?lit?rit??] and painting, and so on.hubei, known as”the province with a thousand lakes”and “the land of fish and rice”, is one of the major areas in china to produce rice, cotton, oil and fish.with its solid [?s?lid] industrial foundations, hubei has a system of modern industry.its main industries includes electricity, metallurgy [?metl??:d?i:], machinery, electronic [?l?k?trɑn?k] information, and so on.the economy of hubei province is in rapid development in recent years, and will obtain new opportunities [??p??tju:niti] in future..higher education level of hubei province is in the front of whole country, the number of college students is 1.3 million, of which more than 1.05 million in wuhan.wuchang fish, that is produced in the vicinity [vi?siniti] of wuchang, as early as 1,700 years ago in the three kingdoms period, has been well known in north-south river.chairman mao zedong said, having had water in changsha, now i am having fish in wuchang.the famous poem was published, so wuchang fish is even more famous in world.at last, i will give an introduction about my birthplace.qichun county(chinese: 蕲春县)is a county of huanggang, hubei.qichun county is the birthplace of famous herbalist [?h?:b?l?st] li shizhen, who was born and lived in qizhou town, on the southern edge of the county, alongside the yangtze river.in turn, qichun is a major center of the herbal industry in china.four local specialties [?spe??lti:] of qichun are ay tsao, bamboo, turtle [?t?:tl] and snake, and they are called the four treasures in qichun.they have good medicinal [m??d?s?n?l] value in traditional chinese medicine.all of the above is my hometown.thank you for your attention.篇四：presentation.smile演讲ppt 篇五：英文presentation ppt 演示讲稿引导句

开场白祝贺语：

“good afternoon, ladies and gentlemen.“

介绍开场白：

“let me introduce myself.i’m ulrike huber, manager’s assistant...”

“i am a consultant to...”

引出主题：

“the subject of today’s presentation is...”

“i’ll give you an overview of...”

“today i want to update you on...”

内容概述：

“let me first give you a brief overview.” “i’ll start off by explaining..., then focus on...” “i’ll be talking about...first, then move on to...”

英文邀请信范本(salutation), i would like to invite you to visit ____ for a period of ___(days, weeks or months), beginning on or about ___(date).this visit will provide an opportunity for you to contribute your expertise to the ___ division’s work on(subject of meetings, workshop, discussions, or research).we will provide you with workspace and other work-related support as needed.we understand that you will arrange funding for the remainder of your expenses.if you have any questions about the visit, please contact ___ at(tel.)___ or by email ___.if you have questions about these requirements, please do not hesitate to contact the individual mentioned above.any questions regarding your immigration status should be addressed to mr.____ from ____.示用例句： i’d like to begin by telling you about...so that was the background...let’s move on to...if you look at this diagram, you can see...that brings me to...to sum up then,...i’d like to conclude by saying...thank you very much for your attention.if you have any questions, i’ll be happy to answer them now.despite our pressing need for delivery and a lot of troubles caused to your loading work, at the last minute the ____(product’s name)has been dispatched successfully.we appreciate so much your intense devotion to work and the firm stance of bearing clients’ interest in mind and will understand if you 催货款的邮件 dear mr.smith, with eyes open widely, we regret not have seen your payment yet.we presume you must have once again overlooked your outstanding account with us.we for the last time request your immediate payment for ____(amount)before ____(date).please think it over if it is worthwhile for you to spend additional money and extra time if missing the time again!洽谈单价 the price for 33 euro has increased to 33.5 euro, packing charge and freight remaining unchanged.we thank you for your understanding and look forward to having a good cooperation with you.开发信 we are marching with big steps towards the best time of the year: christmas with surprises and the new year’s eve with candle lights and sweet cookies.wish you enjoy the preparation time and gifts of the celebration!在商务信函中常用的提醒付款句式举例： we wish to call your attention to the enclosed account which is now past due.we shall appreciate your prompt remittance.兹随函附上逾期账单，提醒注意。如蒙迅速支付甚为感激。please consider this letter as a friendly reminder.谨以此函向贵方做出友好的支付提醒。although we have sent you many reminders before, you have not reimbursed our bill of __(date)until today.尽管多次提醒您付款，您至今对我们__（日期）的账单仍未履行付款义务。please recall the payment dated __(date).我们提醒您__（日期）付款。we would like to call your special attention to our bill.我们想提请贵方特别注意我公司的帐单。

客户满意度是我们衡量服务的标准.customers’ satisfactions are the standard of our service.我们老板重视质过于量，还看重顾客满意度。our boss emphasizes quality over quantity and customer satisfaction.国际业务部从各方面完善自我，以提高客户满意度。international business department seeks for improvement wherever we can in order to serve our customers to their entire satisfaction.将客户满意率从80%提升至85%.increased the rate of customer satisfaction from 80% to 85%.销售业绩和客户满意度是工作衡量的重要指标。this job will be measured by sales performance and customer satisfaction level.我们提供100%顾客满意服务。we offer 100% customer satisfaction services.我们的成功取决于客户是否满意。our success depends on customer satisfaction.因资金紧张我们不得不放弃原方案。we have to give up our project for shortage of funds.the point is that we are short of funds.问题是我们短缺资金。our funds are running low.我们的资金越来越少。

现在我们公司的资金相当紧张。disease in the running of the economy in china, which intensified the financial strain of enterprises and made many enterprises hard to continue their production and operation.企业相互拖欠货款，应收帐款居高不下，已成为我国经济运行中的一大顽症，加剧了企业资金紧张的局面，也使不少企业生产经营难以为继。

第四篇：英语Presentation演讲稿

Good afternoon,everyone.Turn on the QQ music chart,the first is always JAY,and the followed is VAE,a spotless（一尘不染的）clean boy and have the name of his photo,light smile.People can’t imagine that this is a boy who has high popularity in the Internet.He is my favorite singer---Vae.Do you know the Chinese meaning of ‘Vae’?He does not look handsome at all.Sometime,just like your neighborhood,but he is very talented.His was born on 14th March,in 1986.He graduated from AnHui Medical University.Attention,he is a doctor.Isn’t it amazing that XuSong turns to be a famous musianfinally?

So far he realeased four albums.And I would like to point out that the albums are his own independence,including the lyricsist,composer,arranger,singing,production and cover designing.Roses funeral,the burial of your memorise.(玫瑰花的葬礼，埋葬关于你的回忆。)Star light,and water thrawn up by the fold.（星光点亮了，海水泛起褶皱）Sad lyrics,sad melody,Vae’s interpretation（艺术表现）of the plain with a little bit sad.Except for the intelligence of music,Vae also is good at writing.During his student’s ages,more than 20 articles were published by《萌芽》、《少年文艺》.He once wrote a composition《把伤痕当酒窝》which was used in JiangSu province as a College Entrance Examination question.Also,he play computer very well.He won the first of ‘xunfei’ in 2001 cup national webpage designing match in Anhui.Vae is a man who can tell us what is independence.He is my idol.His perserverance,his effort,his great idea,always inspire me.

第五篇：英语Presentation演讲稿[推荐]

[开课件，直到名字和学号出现]

-Hello, everyone.So, just let’s start our topic now.Thank you for giving me the opportunity to tell you something about ‘smile’ here.Over the next ten minutes, you are going to hear about something that will change the way your live your life.-If you have any questions, I will be pleased to answer them at the end of the presentation.-In fact, I am going to examine these topics in the following order.Let’s look at the screen please.[点课件，直到四个小标题全部出现]

This is the whole structure of my presentation.======== Ok, let’s start from the chapter1.[点小标题一的超链接,直到大小黑色标题出现。]

As you see, here I’ll show you some pictures and everyone here please think of the feelings of them.========

Ababy with her father on the beach, smiling.Alittle girl with her lovely toy bear, smiling.Afarmer in the harvest season, smiling.An old grandmother with her little grandson in the Spring Festival, smiling.Ok, Let’s look at this question.If we ourselves fill in the blank, what should be included?

【……】or what?

-As far as I am concerned, smiling just means a kind of warmth.It sends us light in the darkness and brings us warm sunlight on a cold winter day.Smiles can break the ice.Smiles are like rainbows.Rainy days end and the sky is beautiful again.-Of course , everyone may have your own answer.I believe you can find it in our everyday life.========-Ok, let’s come into the next part.Part 2,Do u know.Here I would like to tell

you something about ‘smile’ that you may feel so surprised.======== ·Laughing reduces stress and strengthens the immune system.In other words, “laughter is the best medicine.”

·Laughing for 10 to 15 minutes increases heart rate, and can burn up to 240 calories.·Humour improves communication, creativity and overall performance in the workplace.The ability to appreciate humour, the ability to laugh and make other people laugh, actually has physiological effects on the body that cause people to become more bonded.·Smiling reduces the fat and cholesterol build-up in the coronary arteries.·Not only Cartoons but also smile can help children cope with painful

procedures, such as needles or visits to the dentist.======== OK,so much for this part.let’s continue.Part 3.celebrity well-known saying.Here are some famous sentences about smile.let’s have a look and try to remember some.If you are interested in it, just make a note.========

And this one, yes, it’s my favorite.by Shaw, one of the most famous dramatist in the England.I hope you can get some power of smile and courage.======== SO, it’s time for the final part, part 4.Whenever.·During our journey if people sit at a distance freely talk with smile, suddenly our loneness cut down.·Every time we open the door and see the neighbor’s smiling face, we will devote ourselves to working more positively.·We make telephone to our relatives with a smile even though they cannot see our smile, there is no doubt that our voice has already sent love signal.·What makes us deliver speeches without nervousness in public and gain success is the audience’ big smile.·When we confronted with tough tasks, co-workers’ smile means support and encouragement, from which we can easily get confidence and energy to overcome difficulties.· The smile between lovers are quite sweet, everyone pass them by, can feel the happiness and is deeply affected.·When we get knowledge from book, work or other experience, we grow up gradually,showing a mature smile.·with no doubt ,families who are always by our side can bring us the biggest smile！!

========

So, what are you thinking of after seeing these pictures..?

In fact,Smiles show love and friendship.Teachers' smiles encourage us.Mothers' smiles warm us.Friends' smiles make us feel closer.We welcome smiles from others.And we should give others our smiles too.No one is

richer than a man who often smiles at others.If a man doesn't smile at you, just smile at him.Smiles help you forget your sadness.Life is a long road.Why not cover it with smiles?

================================= In conclusion, I hope all of you here have found this useful and would like to see you live with smile every day.That’s all, thank u.If you have any questions, please feel free to ask.