气象专业英语6.pptx

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1、一、New words1.Apply vt.运用运用;apply to 把把 应用于应用于;apply for 申请；申请；application n.申请；申请；application form 申请表申请表 2.Reversal n.逆转；逆转；reverse vt.3.Adjacent a.邻近的邻近的;surrounding 周围的周围的4.Vigorous a.强盛的强盛的5.Dramatic a.引人注目的引人注目的6.Inhabitant n.居民；居民；resident7.Inland a.内陆内陆8.Prolong vt.延长延长9.Duration n.持续时间；持续时间；

2、period 期间期间10.Substantially ad.实质的，本质的实质的，本质的11.Substructure n.下部结构；下部结构；sub+亚；次级；下级亚；次级；下级 （构词法）（构词法）Subtropical 亚热带Subgrid 次网格Subsystem 分系统Subdivision;subseasonal.第1页/共39页12.Reside vi.驻扎；驻扎；resident 居民居民13.Southern Oscillation 南方涛动；南方涛动；North Atlantic Oscillation(NAO)北大西洋涛动北大西洋涛动 Arctic Oscillatio

3、n(AO)北极涛动；北极涛动；Antarctic Oscillation(AAO)南极涛动；南极涛动；Quasi-Biennial Oscillation(QBO)准两年振荡准两年振荡 Seesaw 翘翘板；翘翘板；Fluctuation n.振荡，振荡，扰动；扰动；Perturbation n.扰动扰动14.Passive a.消极的，被动的；消极的，被动的；active a.主动的主动的15.Quasi-biennial oscillation 准两年振荡准两年振荡 *quasi+准准 （approximate,not exact)For example,quasi-static 准静力；

4、准静力；quasi-geostrophic 准地转的；准地转的；quasi-stationary front 准静止锋，准静止锋，etc.*biennial 两年一次；两年一次；biannual 一年两次一年两次16.Condensation n.浓缩，凝结浓缩，凝结;condense vt.17.Convergence n.汇合，辐合；汇合，辐合；divergence n.辐散；辐散；散度散度18.gradients n.梯度梯度；temperature gradients,pressure gradients,SST gradients,etc.19.Anomaly n.不规则，异常；不规

5、则，异常；anomalies复数复数20.Hypothesize v.假想；假想；hypothesis n.;hypotheses 复数复数 第2页/共39页21.Instability n.不稳定性；不稳定性；stability 稳定性；稳定性；unstable adj.不稳定的不稳定的 in+否定否定 （构词法）（构词法）inaccurate 不精确，不精确，invisible 不可见，不可见，incompressible 不可压缩不可压缩 independent 独立；独立；inhomogeneous 不均匀；不均匀；informal 非正式非正式22.Orographic barrie

6、r 地形分界线；地形分界线；topographic23.Spatial coherence 空间相干性；空间相干性；spatial adj.空间的；空间的；temporal adj.时间的时间的 第3页/共39页二、Meteology Today 有关MONSOON内容第4页/共39页第5页/共39页第6页/共39页第7页/共39页第8页/共39页第9页/共39页第10页/共39页第11页/共39页第12页/共39页第13页/共39页三、气象科技英语900句 有关MONSOON内容第14页/共39页第15页/共39页第16页/共39页第17页/共39页四、课文内容 The term“monso

7、on”appears to have originated from the Arabic word mausim which means season.It is most often applied to the seasonal reversals of wind direction along the shores of the Indian Ocean,especially in the Arabian Sea,that blow from the southwest during one half of the year and from the northeast during

8、the other.As monsoons have come to be better understood,the definition have been broadened to include almost all of the phenomena associated with the annual weather cycle within the tropical and subtropical continents of Asia,Australia,and Africa and the adjacent seas and oceans.It is within these r

9、egions that the most vigorous and dramatic cycles of weather events on the earth take place.Paragraph 1 第18页/共39页 The dominant characteristic of the great monsoon systems,the annual cycle itself,has led the inhabitants of the monsoon regions to divide their lives,customs,and economics into two disti

10、nct phases:the“wet”and the“dry”.The“wet”,of course,refers to the rainy season,during which warm moist and very disturbed winds blow inland from the oceans.The dry refers to the other half of the year,when the wind reverses bringing cool and dry air from the hearts of the winter continents.In some lo

11、cations,the cold and dry winter air flows across the equator toward the hot continents of the summer hemisphere.In this manner,the dry of the winter monsoon is tied to the wet of the summer monsoon,and vice versa.Paragraph 2第19页/共39页第20页/共39页 Surface winds during northern hemisphere a)summer b)winte

12、r第21页/共39页In this article,we shall concentrate mainly on the annual cycle of the monsoon.However,it is incorrect to think of summer and winter phases of the monsoon as just prolonged periods of rain or drought,each of some months duration.There are also significant variations that exist on time scal

13、es ranging from days to weeks.Thus,while the monsoon appears to have a well-defined annual cycle,closer inspection shows that the monsoon varies substantially and that within the cycles a significant substructure exists that becomes evident as the intensity of the monsoon rains wax and wane through

14、the wet season.Paragraph 3第22页/共39页Paragraph 4Short-term variations include the individual weather disturbances（i.e.,a period of disturbed weather or storms lasting some days)that occur in rapid succession during the so-called active-monsoon periods.A prolonged period of one to several weeks marked

15、by an absence of weather disturbances is called a break-monsoon,or more correctly,a break in the active monsoon.During an active phase the weather is unstable with frequent storms that produce the rain deluges traditionally associated with the monsoon.But,during a dormant or break phase of the monso

16、on,the weather is hot,clear,and dry.Monsoon breaks are drought period and,if prolonged,may cause considerable hardship and even famine in the monsoon lands.第23页/共39页In the course of the Southwest monsoon,there are periods when the monsoon trough shifts northwards to the foot of the Himalayas,and rai

17、ns decrease over much of India except along the slopes of the Himalayas and parts of Northeast India,and the Southern peninsula.This synoptic situation is called break in monsoon.The break are most frequent in July and August,and they typically last from a few days to three weeks.Mean pressure depar

18、ture,03GMT,in mb,during break in monsoon.From Rao(1976)第24页/共39页Paragraph 5 A variable of the monsoon system of considerable importance is the timing of the commencement of the set.This,the so-called onset of the monsoon,is usually sudden with the weather changing abruptly from the premonsoon heat(s

19、imilar to the torrid climate of the break-monsoon),to the weather disturbances,storms,and intense rainfall of an active period.For a farmer knowledge of when the onset will occur is critical as with it resides the key to the timing of the planting of his crops.The withdrawal of the monsoon(i.e.,the

20、cessation of rainfall over the continents)during the early autumn is a much more gradual transition than the onset.第25页/共39页Das(1984)describes the following working rules used to define the onset of the monsoon over Kerala:(i)starting with 10 May,if at least 5 out 10 stations in Kerala report 24 hou

21、r rainfall totals of 1 mm for two consecutive（连续的）days,an onset is declared on the second day;(ii)if 3 out of 7 stations in Kerala report no rainfall for the next 3 days,indication are given for a recession（撤回）of the monsoon;(iii)after the monsoon has advanced North of 13N even a temporary recession

22、 is a rare event.Das futher mentions that there are similar working rules for other parts of India.Normal dates of(a)onset,and(b)withdrawal of Southwest monsoon over India.From Rao(1976)(copyright by the Government of India).Onset and withdrawal of monsoon over IndiaOnsetWithdrawal第26页/共39页Paragraph

23、 6Relationships between the Indian monsoon rainfall and the Southern Oscillation were established by Walker in the beginning of this century and versions of them have been used since for operational forecasting of monsoon rainfall.It is,therefore,useful to reexamine the relationship by using the Dar

24、win sea level pressure for the period 1901-1981.Darwin pressure is chosen because its long-term record is considered to be more accurate and more complete than that for any other station in that region.Although Tahiti minus Darwin pressure is considered to be better index of the Southern Oscillation

25、,Tahiti pressure is available only for the period 1935-1981,and for this period the correlation coefficient between the spring Tahiti第27页/共39页Paragraph 6(to be continued)pressure and Indian monsoon rainfall is only 0.01.The summer monsoon rainfall data used in this study is the area weighted average

26、 of the percentage departure for each of the 31 subdivisions of India,and is referred to as the whole Indian monsoon rainfall anomaly.第28页/共39页Paragraph 7 and 8If one is going to predict monsoon rain,it is necessary to examine the Southern Oscillation before the monsoon.However,it should be recalled

27、 that one of Walkers most important findings was that monsoon rainfall has very significant correlations with the subsequent global circulation.第29页/共39页Paragraph 8The most remarkable of Walkers results was his discovery of the control that the Southern Oscillation seemingly exerted upon subsequent

28、events and in particular of the fact that the index for the Southern Oscillation as a whole for the summer quarter June-August,had a correlation coefficient of 0.8 with the same index for the following winter-quarter,though only of 0.2 with the previous winter quarter.第30页/共39页Paragraph 8(to be cont

29、inued)It is quite in keeping with this that the Indian monsoon rainfall has its connections with later rather than earlier events.The Indian monsoon therefore stands out as an active,not a passive feature in world weather more efficient as a broadcasting tool than as an event to be forecast.第31页/共39

30、页Paragraph 9 During the recent years we have gained a better understanding of large-scale atmospheric phenomena such as El Nino and the Southern Oscillation,the quasi-biennial oscillation and atmospheric blocking.This new knowledge provides a better synoptic and dynamical framework to examine the in

31、terannual and long-term variability of monsoon.The El Nino Southern Oscillation seems to be the single most important feature of the ocean-atmosphere systems.Its period is quite large(2-5 years)and therefore it can be of practical value for predicting fluctuations of a seasonal phenomenon like the m

32、onsoon.第32页/共39页 It is therefore necessary to document the main features of the global circulation,including the monsoon,during different phases of the Southern Oscillation.It should,however,be recognized that the fluctuations of the monsoon can also be one of the important factors affecting the Sou

33、thern Oscillation.Paragraph 9(to be continued)第33页/共39页Paragraph 10 The prospects for long-range forecasting of large-scale,seasonal mean monsoon rainfall appear to be good.There are significant correlations between large-scale seasonal mean Indian(rainfall)anomalies and low-frequency changes in the

34、 Southern Oscillation.There are also significant correlations between seasonal Indian rainfall anomalies and slowly varying boundary conditions of sea surface temperature and snow cover.第34页/共39页Paragraph 11Tropical and monsoon flows are dominated by the thermally forced planetary scale Hadley and W

35、alker type circulations for which the primary energy source is the latent heat of condensation.The large-scale moisture convergence required for the release of the latent energy is organized by gradients of temperature at the earths surface.Solar heating can produce thermal low-pressure areas over t

36、he land which can further deepen due to latent-heating if the dynamical circulation is favorable for moisture convergence.Therefore fluctuations of soil moisture can influence the intensity of the tropical heat sources over the land.第35页/共39页Paragraph 11(to be continued)Similarly,the tropical heat s

37、ource over the oceans can be influenced by the anomalies of sea surface temperature.It is therefore reasonable to expect that the changes in the large-scale tropical flows would be related to the changes in the slowly varying boundary conditions at the earths surface.Since dynamical instabilities ar

38、e not too strong in the tropics,it is also reasonable to hypothesize that the changes in the large-scale flows are dominated by the changes in the boundary conditions.Therefore arguments collectively suggest that there is a physical basis for predictability of the large-scale,seasonally averaged mon

39、soon flow and rainfall.第36页/共39页Paragraph 12If the daily rainfall patterns related to the monsoons high frequency,synoptic scale disturbances were the consequence of dynamical instabilities of the large-scale flow,and if the changes of the large-scale flow itself were caused mainly by its interactio

40、n with such unstable?Forecasting beyond the limits of deterministic prediction would not be very good.Fortunately this does not appear to be the case.While it is indeed true that the rain producing disturbances form only when the structure of the large-scale flow(i.e.,horizontal and vertical gradien

41、ts of wind,temperature,and moisture)is favorable,the changes in the large-scale flow itself 第37页/共39页Paragraph 12(to be continued)appear to be primarily related to planetary-scale boundary forcing manifested as tropical heat sources and to orographic barriers.This provides a physical basis as well a

42、s hope for long-range forecasting of monsoon rainfall.It is also of interest that during the monsoon season,even the biweekly and monthly anomalies have significant spatial coherence,which further suggests that the prospects for predicting biweekly and monthly anomalies are also quite good.第38页/共39页感谢您的观看。第39页/共39页