氣象科技英語翻譯

1、 Like a fish in the ocean, man is confined to a very shallow layer of atmosphere.The gaseous envelope of the Earth is physically inhomogeneous in both the vertical and horizontal directions, although the horizontal inhomogeneity is much less marked than the vertical inhomogeneity. Various criteria h

2、ave been devised for dividing the atmosphere into layers. This division can be based on the nature of the vertical temperature profile, on the gaseous composition of the air at different altitudes, and the effect of the atmosphere on aircraft at different altitudes, etc. The division based on the va

3、riation of the air temperature with altitude is used most commonly in the meteorological literature. According to a publication of the agrological commission of the World Meteorological Organization (WMO) in 1961, the Earths atmosphere, is divided into five main layers: the troposphere, the stratosp

4、here, the mesosphere, the thermosphere and the exosphere. These layers are bounded by four thin transition regions: the tropospause, the stratospause, the mesospause, the thermospause . The troposphere is the lower layer of the atmosphere between the Earths surface and the tropopause. The temperatur

5、e drops with increasing height in the troposphere, at a mean rate of 6.5 per kilometer (lapse rate). The upper boundary of the troposphere lies at a height of approximately 8 to 12 km in the polar and troposphere contains about 75% of the total mass of atmospheric air, while in the tropics it contai

6、ns about 90%. The tropoause is an intermediate layer in which either a temperature in version or an isothermal temperature distribution is observed. The stratosphere is the atmospheric layer above the troposphere. In the stratosphere the temperature either increases with height or remains nearly con

7、stant. In the lower part of the stratosphere (up to approximately 20 km above the Earths surface) the temperature is practically constant (about 56 ). While further up the temperature increases with altitude at a rate of about 1 /km at heights of 20 to 30 km and about 2.8 /km at altitudes from 32 to

8、 47 km. Under the standard conditions the temperature at the 47 km level is normally -2.5 . This increase in temperature with height is due to the absorption of UV solar radiation by ozone molecules. It should be noted that about 99% of the total mass of atmospheric air is concentrated in the tropos

9、phere and stratosphere, which extend up to an latitude of 30 or 35 km. The stratopause is an intermediate layer between the stratosphere and the mesosphere (in the altitude region from 47 to 52 km ), in which the temperature remains constant at about 0.The thermosphere is the atmospheric layer above

10、 the mesopause. The temperature in this layer increases with increasing altitude, reaching about 2000 at about 450km, the mean height of the upper boundary of the thermosphere. The temperature increase in this layer is mainly caused by the absorption of UV solar radiation by oxygen molecules, which

11、dissociate as a result of this.The exosphere is the furthest out and the least studied part of the upper atmosphere. It is located above 450km altitude. The air density in the exosphere is so low that atoms and molecules can escape from it into interplanetary space.Finally, along with the above divi

12、sion of the atmosphere, we will also make use of a division based on the extent of atmospheric interaction with the Earths surface. According to this principe,the atmosphere is usually divided into a so called boundary layer (sometimes also called the friction layer) and the free atmosphere. The atm

13、ospheric boundary layer(up to 1 or 1.5 km) is influenced considerably by the Earths surface and by eddy-viscosity forces. At the same time, we can neglect, as a first approximation, the influence of eddy-viscosity forces in the free atmosphere.Of all the above atmospheric layers, only the tropospher

14、e(especially its boundary layer) is characterized by a marked instability of the vertical distribution of the meteorological parameters. It is in this layer that both temperature inversions and superadiabatic temperature variations with height are observed.The Earths atmosphere is a mixture of gases

15、 and aerosols, the latter being the name given to a system comprised of small liquid and solid particles distributed in the air. Air is not a specific gas :rather, it is a mixture of many gases. Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric

16、components that remain in fixed proportions to the total gas volume. Other constituents such as water vapor, carbon dioxide, and ozone vary in quantity from place to place and form time to time. The principal sources of nitrogen, the most abundant constituent of air, are decaying from agricultural d

17、ebris, animal matter, and volcanic eruption. On the other side of the ledger, nitrogen is removed from the atmosphere by biological processes involving plants and sea life. To a lesser extent, lightning and high temperature combustion processes convert nitrogen gas to nitrogen compounds that are was

18、hed out of the atmosphere by rain or snow. The destruction of nitrogen is in the atmospheres in balance with production. Oxygen, a gas crucial to life on Earth, has an average residence time in the atmosphere of about 3000 years. It is produced by vegetation that, in the photosynthetic growth proces

19、s, takes up carbon dioxide and releases oxygen. It is removed from the atmosphere by humans and animals, whose respiratory systems are just the reverse of those of the plant communities. We inhale oxygen and exhale carbon dioxide. Oxygen dissolves in the lakes, rivers and oceans, where it serves to

20、maintain marine organisms. It is also consumed in the process of decay of organic matter and in chemical reactions with many other substances. For example, the rusting of steel involves its oxidation. From the human point of view, the scarce, highly variable gases are of great importance. The mass o

21、f water vapor, that is,H2O in a gaseous state, in the atmosphere is relatively small and is added to and removed from the atmosphere relatively fast. As a result ,the average residence time of water vapor is only 11 days. Water vapor is the source of rain and snow, without which we could not survive

22、. From common experiences it is well known that the water vapor content of air varies a great deal. In a desert region the concentration of water vapor can be so low as to represent only a tiny fraction of the air volume. At the other extreme, in hot, moist air near sea level, say over an equatorial

23、 ocean, water vapor may account for as much as perhaps 5 percent of the air volume.There are large variations of atmospheric water vapor from place to place and from time to time, but the total quantity over the entire Earth is virtually constant. The same can not be said about carbon dioxide (co2).

24、The concentration of this sparse but important gas has been increasing for the last hundred years or so. Carbon dioxide is added to the atmosphere by the decay of plant material and humus in the soil ,and by the burning of fossil fuels: coal, oil, and gas. The principal sinks of co2 are the oceans a

25、nd plant life that uses co2 in photosynthesis. In the middle 1980s,atmospheric chemists were still debating about the effects on atmospheric co2 of burning, harvesting and clearing of forests. The oceans take up large amounts of co2,about half the amount released by fossil fuel combustion. It is exp

26、ected that this fraction will diminish with the passing decades whereas the total mass of co2 released will increase ,at least through the early part of the next century. During the 1980s atmospheric co2 was accumulating at a rate of about 1 part per million (ppm)of air per year, but it is expected

27、to increase more rapidly in decades to come .In1983 it averaged about 340 ppm of air. Ozone(o3),another important, highly variable gas, occurs mostly at upper altitudes ,but it is also found in urban localities having a great deal of industry and automotive traffic and a generous supply of sunshine.

28、 In cities such as Los Angeles, ozone concentration may be more than 0.1ppm in extreme cases. Most atmospheric ozone concentrations often exceed 1.0ppm and may be large as 10 ppm. They vary greatly with latitude, season ,time of day, and weather patterns. The high-altitude ozone layer is maintained

29、by photochemical reactions. The ozone layer is important because, by absorbing UV radiation in the upper atmosphere, it reduces the amount reaching the surface of the Earth, exposure to increased doses of ultraviolet rays would cause more severe sunburns and increase the risk of skin cancers. Biolog

30、ists indicate that a substantial increase in UV radiation could also affect other components of the biosphere.Certain gages, if they exist in sufficiently high concentrations, can be toxic to people, animal and plant life. For example, when ozone occurs in high concentrations, it is toxic to biologi

31、cal organisms. This does not happen often, but in heavily polluted localities such as Los Angeles, ozone near the ground sometimes is sufficiently abundant to cause leaf damage to certain plant species. Very large quantities of potentially hazardous gases are introduced into the atmosphere as a resu

32、lt of human activities. Air pollutants are emitted from furnaces, factories, refineries, and engines, particularly automobile engines. All these things and others like them burn fossil fuels: coal, oil, gasoline, and kerosene. In the process they emit gases and smoke particles that may spend a great

33、 deal of time in the atmosphere reacting with other substances and causing the formation of toxic compounds.The most widespread and potentially hazardous gaseous pollutants are carbon monoxide ,sulfur dioxide, nitrogen oxide, and hydrocarbons. The last of these compounds comes from vaporized gasolin

34、e and other petroleum products. 就像海洋中的魚一樣,人類被局限在大氣中一個非常狹窄的層次之。雖然地球的大氣層在水平方向上的不均勻性比在垂直高度上的不均勻性要小得多。但它確確實實在水平和垂直兩個方向上都是不均勻的。 人們設(shè)計了各種各樣的標(biāo)準(zhǔn)來劃分大氣的層次。有的基于垂直溫度廓線的性質(zhì)，有的根據(jù)空氣在不同高度上的大氣成分，有的根據(jù)大氣在不同高度上對飛機(jī)的影響來劃分等等。根據(jù)空氣溫度隨高度的變化來劃分（大氣的層次）是氣象文獻(xiàn)中用得最普遍的一種劃分方法。根據(jù)1961年世界氣象組織大氣學(xué)委會公布的標(biāo)準(zhǔn)，地球大氣被劃分為5個主要層次：對流層，平流層，中層，熱成層以

35、與外逸層。這些層次之間鄰接著4個淺薄的過渡區(qū)域：對流層頂，平流層頂，中層頂以與熱成層頂。 對流層是介于地球表面和對流層頂之間的大氣低層在對流層中，溫度以平均6.5/km的遞減率隨高度的增加而降低，其上邊界在極地和中緯度地區(qū)大約位于812Km的高度，在熱帶地區(qū)大約位于16-18Km的高度。在極地和中緯度，對流層包含了大氣層中空氣質(zhì)量的75%左右，然而在熱帶地區(qū)，包含了大約90%。對流層頂是一個中間層次，據(jù)觀測，其溫度是逆溫或是等溫分布。平流層是位于對流層之上的大氣層，在平流層中，溫度或是隨高度增加，或是幾乎保持定常。在平流層的低層（直到地球表面之上大約20Km）溫度實際是一個常數(shù)（大約

36、-56 ）。然而再向上，大約20Km30Km的高度，溫度隨高度以1 /km的速度增加，從30Km47Km高度上，以2.8 /km的速率增加。在標(biāo)準(zhǔn)情況下，47Km高度上正常的溫度是-2.5攝氏度。溫度隨高度的增加是由于太陽輻射的紫外線被臭氧分子吸收的緣故。值得一提的是大氣層中空氣總質(zhì)量的99%都集中在對流層和平流層中，一直伸展到30-35Km的高度上。平流層頂 位于平流層和中間層的中間層（大約從47-52Km的高度上），平流層頂溫度保持定常，約為0攝氏度。 熱成層是位于中層頂上的大氣層，其溫度隨高度的增加而增加，到熱成層上邊界的平均高度，即大約在450Km高度上，達(dá)到大約2000攝氏度。該層中

37、溫度的增加主要是因為太陽輻射的紫外線被氧分子吸收，分解所致。 外逸層是最遠(yuǎn)的，也是研究最少的大氣的上層部分。它位于大約450Km的高度上。外逸層中空氣的密度非常小，以致原子和分子都能逃逸到星際空間。最后，除了以上對大氣的劃分以外，我們也可以根據(jù)大氣和地面的相互作用得到另一種分法。根據(jù)此原則，大氣通常被劃分為所謂的邊界層（有時也稱摩擦層）和自由大氣。地球表面和渦度粘滯力對大氣邊界層（知道1-1.5Km）有相當(dāng)大的影響；同時，作為一級近似，在自由大氣中我們可以忽略渦度粘滯力的影響。 以上這些大氣層中，只有對流層（尤其是邊界層）中氣象參數(shù)的垂直分布具有顯著的不穩(wěn)定性的特征。人們觀測到該層中存在逆穩(wěn)和

38、溫度隨高度超絕熱變化。地球大氣是氣體和氣溶膠的混合物，所謂的氣溶膠指的是由分布在空氣中的微小的液體和固體顆粒組成的系統(tǒng)。空氣不是一種特殊的氣體，而是由許多氣體混合成的。其中一些氣體，如，氮，氧，氬，氖等，作為空氣的永久組成成分，總是以固定的比例存在于大氣中。其中一些成分，如，水汽，二氧化碳和臭氧的含量是隨時間和地點的不同而改變。氮在空氣中的含量最多，其中主要來源是腐爛的作物殘渣，動物尸體與火山爆發(fā)。另一方面，大氣中的氮又為包括植物和海洋生物在的生物過程的所消耗。閃電與高溫燃燒過程將少量氮氣轉(zhuǎn)化為氮化物，再由雨雪帶出大氣。大氣中氮的損耗和產(chǎn)生是平衡的。地球生命必不可少的氣體氧氣，在大氣中已有三千

39、年左右的時間了。氧氣由植物釋放出來，即通過植物的光合作用吸收二氧化碳，釋放氧氣，被人類和動物所吸收，人和動物的呼吸系統(tǒng)同植物的呼吸系統(tǒng)恰恰相反。我們吸進(jìn)氧氣呼出二氧化碳，氧氣溶進(jìn)湖，河和海洋中，來維持海洋生物的生存。在同其他物質(zhì)發(fā)生化學(xué)反應(yīng)或是有機(jī)物的腐爛過程也要消耗氧氣，比如說鋼鐵生銹就涉與到氧化過程。對人類來說，稀少的，多變的氣體是非常重要的。水汽，即水的氣態(tài)，在大氣 的含量是比較稀少的，而且它的生成和消耗是比較快的。因此，水汽在大氣中存在的平均時間只有11天，水汽是雨雪得源泉，沒有水汽我們就不能生存。眾所周知，水汽在大氣中的含量是多變的，在沙漠地帶，水汽含量非常低，只占空氣總量的很少的一

40、部分，相反，在其他地區(qū)，特別是潮濕的熱的海面上，或者赤道洋面上，水汽可以占到大氣總量的5%左右。盡管大氣中的水汽的含量隨時間和地點的不同有很大的變化，但它在整個地球上的總量實際上是不變的。而二氧化碳卻不是這樣的。在過去的一百年里，這種稀少的但卻很重要的氣體的含量一直在上升腐爛的植物，土壤中的腐殖物以與燃燒煤，石油，天然氣，等化石燃料都能向大氣釋放二氧化碳。二氧化碳主要的匯是海洋和植物，植物需要二氧化碳進(jìn)行光合作用，二十世紀(jì)八十年代中期，大氣化學(xué)家就森林的燃燒，砍伐對大氣中二氧化碳產(chǎn)生的影響進(jìn)行了爭論。海洋吸收了大量的二氧化碳，大約占化石燃料燃燒釋放的二氧化碳總量的一半。人們預(yù)測，往后的幾十年，

41、這部分吸收量將會逐步減少，而釋放的二氧化碳的總量則會增加，這種情況至少會延續(xù)到下個世紀(jì)初。二十世紀(jì)八十年代，大氣中的二氧化碳，每年以空氣的百萬分之一的速度增加。但是，據(jù)預(yù)測，這種增加速度在未來的幾十年中還要更快一些。1983年，其含量平均為空氣的百萬分之340。另一種重要多變的氣體 -臭氧（O3），多存在于高層大氣中，但在交通擁擠，有許多工廠或是充足照射的地區(qū)也有臭氧存在。像洛杉磯這樣的城市，O3最多時可超過0.1ppm。大氣中臭氧的含量大多在1.010ppm之間。它們隨高度，季節(jié)，時間，天氣狀況的不同而不同。高層大氣中的O3 層是由光化學(xué)反應(yīng)造成的。臭氧層之所以重要，是因為它通過吸收上層大氣

42、紫外線輻射，從而減少紫外線到達(dá)地面的總量，接受紫外線照射的時間越長，就越容易造成嚴(yán)重的灼傷，從而增加皮膚癌的危險。生物學(xué)家指出，紫外線過度的增加還會影響生物圈中的其它組成成分。 有些氣體，如果濃度過高，對人，動物與植物生命可能有害，比如，O3濃度過高會對生物有機(jī)體造成危害。雖然這種情況不常發(fā)生。但洛杉磯這樣污染嚴(yán)重的城市，有時接近地面的O3含量變得足以毀壞某些植物表面的葉片。人類活動將大量具有潛在危險的氣體帶入大氣。大型鍋爐，工廠，煉油廠和發(fā)動機(jī)，特別是汽油發(fā)動機(jī)排放出空氣污染物。所有這些場所以與其它特別類似場所：燃燒煤，石油，汽油，煤油等化石燃料，在燃燒過程中，它們向空氣中排放氣體或煙塵顆粒

43、，這些顆粒經(jīng)過相當(dāng)長的時間又和空氣中其他成分發(fā)生反應(yīng)，形成有毒的化合物。 分布最廣泛的，而且潛在危險最大的氣體污染物是一氧化碳，二氧化硫，氧化氮和碳?xì)浠衔?。這些化合物最終來源于蒸發(fā)的汽油和其他石油產(chǎn)物。 第一課 大氣的結(jié)構(gòu)和組成 Unit Two: Frontogenesis and frontal characteristics第二課 鋒生和鋒的特征The first real advance in our detailed understanding of mid-latitude weather variations was made with the discover that ma

44、ny of the day-to-day changes are associated with the formation and movement of boundaries, or fronts, between different air masses.Observations of the temperature, wind directions, humidity and other physical phenomena during unsettled periods showed that discontinuities often persist between imping

45、ing air masses of differing characteristics. The term “front”, for these surfaces of air mass conflict, was a logical one proposed during the First World War by a group of meteorologists working in Norway, and their ideas are still an integral part of most weather analysis and forecasting particular

46、ly in middle and high latitudes. 1.     Frontal wavesIt was observed that the typical geometry of the air mass interface, or front, resembles a wave from. Similar wave patterns are, in fact, found to occur on the interface between many different media, for example, waves on sea s

47、urface, ripples on beach sand, aeolian sand dunes, etc. Unlike these wave forms, however, the frontal waves in the atmosphere are commonly unstable: that is, they suddenly originate, increase in size, and then gradually dissipate. Numerical model calculations show that, in middle latitudes waves in

48、a baroclinic atmosphere are unstable if their wavelength exceeds a few thousand kilometers. Frontal wave cyclones are typically 1500-3000 km in wavelength. The initially attractive analogy between atmospheric wave systems and waves formed on interface of other media is, therefore, an insufficient-ba

49、sis on which to develop explanations of frontal waves. In particular, the circulation of the upper troposphere plays a key role in providing appropriate conditions for their development and growth, as will be shown below.2.The frontal wave depressionA depression (also termed a low or cyclone) is an

50、area of relatively low pressure, with a more or less circular isobaric pattern. It covers an area 100-3000 km in diameter and usually has a life-span of 4-7 days. Systems with these characteristics, which are prominent on daily weather maps are referred to as synoptic scale features. The depression,

51、 in mid-latitudes at least, is usually associated with a convergence of contrasting air masses. The interface between these air mass develops into a wave form with its apex located at the centre of the low-pressure area. The wave encloses a mass of warm air between modified cold air in front and fre

52、sh cold air in the rear. The formation of the wave also creates a distinction between the two sections of the original air mass discontinuity for, although each section still marks the boundary between cold and warm air, the weather characteristics found in the neighborhood of each section are very

53、different. The two sections of the frontal surface are distinguished by the names warm front for the leading edge of the wave and cold front for that of the cold air to the rear.The depression usually achieves its maximum intensity 12-24 hours after the beginning of occlusion.Frontal characteristics

54、The activity of a front in terms of weather depends upon the vertical motion in the air masses. If the air in the warm sector is rising relative to the frontal zone the fronts are usually very active and are termed ana-fronts. Whereas sinking of the warm air relative to the cold air masses gives ris

55、e to less inactive kata-fronts.1. The warm front The warm front represents the leading edge of the warm sector in the wave. The frontal zone here has a very gentle slope, of the order 1/2°-1°, so that the cloud systems associated with the upper portion of the front herald its approach some

56、 12 hours or more before the arrival of the surface front. The ana-warm front, with rising warm air, has multi-layered cloud which steadily thickens and lowers towards the surface position of the front. The first clouds are thin, wispy cirrus, followed by sheets of cirrus and cirrostratus and altost

57、ratus . The sun is obscured as the altostratus layer thickens, and drizzle or rain begins to fall. The cloud often extends through most of the troposphere and with continuous precipitation occurring is generally designated as nimbostratus. Patches of stratus may also form in the cold air as rain fal

58、ling through this air undergoes evaporation and quickly saturates it.The descending warm air of the kata-warm front greatly restricts the development of medium-and high-level clouds. The frontal cloud is mainly stratocumulus, with a limited depth as a result of the subsidence inversions in both air masses. Precipitation is usually light rain or drizzle formed by coalescence since the freezing level tends to be above the inversion layer , particularly in summer. In the passage of the warm front the wi