Forecasting Methods

There are several different methods that can be used to create a forecast. The method a forecaster chooses depends upon the experience of the forecaster, the amount of information available to the forecaster, the level of difficulty that the forecast situation presents, and the degree of accuracy or confidence¹ needed in the forecast.

The first of these methods is the persistence method; the simplest way of producing a forecast. The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 87 degrees today, the persistence method predicts that it will be sunny and 87 degrees tomorrow. If two inches of rain fell today, the persistence method would predict two inches of rain for tomorrow. However, if weather conditions change significantly² from day to day, the persistence method usually breaks down³ and is not the best forecasting method to use.

The trends method involves determining⁴ the speed and direction of movement for fronts⁵, high and low pressure centers, and areas of clouds and precipitation. Using this information, the forecaster can predict where he or she expects those features⁶ to be at some future time. For example, if a storm system is 1,000 miles west of your location and moving to the east at 250 miles per day, using the trends method you would predict it to arrive in your area in 4 days. The trends method works well when systems⁷ continue to move at the same speed in the same direction for a long period of time. If they slow down, speed up, change intensity, or change direction⁸, the trends forecast will probably not work as well.

The climatology method is another simple way of producing a forecast. This method involves averaging weather statistics accumulated over many years to make the forecast. For example, if you were using the climatology method to predict the weather for New York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average. The climatology method only works well when the weather pattern is similar to that expected for the chosen time of year. If the pattern is quite unusual for the given time of year, the climatology method will often fail.

The analog method is a slightly more complicated method of producing a forecast. It involves examining today’s forecast scenario and remembering a day in the past when the weather scenario looked very similar (an analog⁹). The forecaster would predict that the weather in this forecast will behave the same as it did in the past. The analog method is difficult to use because it is virtually¹⁰ impossible to find a predict analog. Various weather features rarely align themselves in the same locations as they were in the previous time¹¹. Even small differences between the current time and the analog can lead to very different results.

词汇:

forecaster /5fC:kB:stE/n.(天气)预报员    下:降水量 ;降雨量

climatology /klaimE5tClEdVi/n.气候学    

scenario /si5nB:riEu/n.某事物（件）的模式，状况

precipitation /pri7sipi5teiFEn/n.(雨、雪、冰雹等的 )降      

注释：  

1. the degree of accuracy or confidence: cnedifnoc指的是“置信度”，所以该词之前用 or说明与 the degree of accuracy有意义上的联系，不能解释为“信心”。

2. significantly:意为“ greatly, considerably”(显著地 )。

3. break down:意为“ fail”(出问题，出故障 )。

4. determining: determine (确定)的动名词形式，其后跟三个宾语 : the speed and direction of movement for front high and low pressure centers, and areas of clouds and precipitation.

5. front:铮(锋面:不同温度和密度的两大气团交界处 )，如: cold front冷锋 warm front热锋

6. features:指上句中 determining的三个宾语所涉及的内容。见注释 4。

7. system:意为“a group of naturally occurring phenomena”(一组自然现象 )。这里指风暴等自然现象。见前句 : … if a storm system is 1,000 miles west of …

8. If they slow down, speed up, change intensity, or change direction,…：如果他们减速，或加速，或强度发生变化，或方向改变……

9. analog:相似物

10. virtually:事实上

The limitation of the trends method is the same as the persistence method in that

A:it makes predications about weather B:it makes predications about precipitation C:the weather features need to be well defined D:the weather features need to be constant for a long period of time

Since rail network is not as extensive as highway network in most countries and its limitation to fixed track facilities, as a result, railroads provide （） service.

A:Door to door B:Door to cy C:Door to cfs D:Terminal to terminal

The classic difficulty felt with democracy arises from the fact that democracy can never express the will of the whole people because there never exists any such unchanging will (at least in any society that call itself democratic). The concept of government of the whole people by the whole people must be looked on as being in the poetry rather than in the prose of democracy; the fact of prose is that real democracy means government by some kind of dominant majority. 　　And the ever-present danger, repeatedly realized in fact, is that this dominant majority may behave toward those who are not of the majority in such a manner as to undermine the moral basis of the right of people, because they are people, to have some important say in the setting of their own course and in the use of their own faculties. Other forms of government may similarly fail to respect human independence. But there is at least no contradiction in that; the underlying assumption of every kind of government by wisers and betters is that people on the whole are not fit to manage their own affairs, but must have someone else do it for them, and there is no paradox when such a government treats its subjects without respect, or deals with them on the basis of their having no rights that the government must take into account. 　　But democracy affirms that people are fit to control themselves, and it cannot live in the same air with the theory that there is no limit to the extent to which public power--even the power of a majority--can interfere with the lives of people. 　　Rational limitation on power is therefore not a contradiction to democracy, but is of the very essence of democracy as such. Other sorts of government may impose such limitations on themselves as an act of grace. Democracy is under the moral duty of limiting itself because such limitation is essential to the survival of that respect for humankind which is in the foundations of democracy. Respect for the freedom of all people cannot, of course, be the only guide, for there would then be no government. Delicate ongoing compromise is what must be looked for. But democracy, unless it is to deny its own moral basis, must accept the necessity for making this compromise and for giving real weight to the claims of those without the presently effective political power to make their claims prevail in elections By "the prose of democracy" ( Par. 1 ) the author most probably means its

A:popular interpretation. B:actual operation. C:ongoing compromise. D:rational limitation.

The classic difficulty felt with democracy arises from the fact that democracy can never express the will of the whole people because there never exists any such unchanging will (at least in any society that call itself democratic). The concept of government of the whole people by the whole people must be looked on as being in the poetry rather than in the prose of democracy; the fact of prose is that real democracy means government by some kind of dominant majority. 　　And the ever-present danger, repeatedly realized in fact, is that this dominant majority may behave toward those who are not of the majority in such a manner as to undermine the moral basis of the right of people, because they are people, to have some important say in the setting of their own course and in the use of their own faculties. Other forms of government may similarly fail to respect human independence. But there is at least no contradiction in that; the underlying assumption of every kind of government by wisers and betters is that people on the whole are not fit to manage their own affairs, but must have someone else do it for them, and there is no paradox when such a government treats its subjects without respect, or deals with them on the basis of their having no rights that the government must take into account. 　　But democracy affirms that people are fit to control themselves, and it cannot live in the same air with the theory that there is no limit to the extent to which public power--even the power of a majority--can interfere with the lives of people. 　　Rational limitation on power is therefore not a contradiction to democracy, but is of the very essence of democracy as such. Other sorts of government may impose such limitations on themselves as an act of grace. Democracy is under the moral duty of limiting itself because such limitation is essential to the survival of that respect for humankind which is in the foundations of democracy. Respect for the freedom of all people cannot, of course, be the only guide, for there would then be no government. Delicate ongoing compromise is what must be looked for. But democracy, unless it is to deny its own moral basis, must accept the necessity for making this compromise and for giving real weight to the claims of those without the presently effective political power to make their claims prevail in elections By "the prose of democracy" ( Par. 1 ) the author most probably means its

A:popular interpretation. B:actual operation. C:ongoing compromise. D:rational limitation.

The classic difficulty felt with democracy arises from the fact that democracy can never express the will of the whole people because there never exists any such unchanging will (at least in any society that call itself democratic). The concept of government of the whole people by the whole people must be looked on as being in the poetry rather than in the prose of democracy; the fact of prose is that real democracy means government by some kind of dominant majority. 　　And the ever-present danger, repeatedly realized in fact, is that this dominant majority may behave toward those who are not of the majority in such a manner as to undermine the moral basis of the right of people, because they are people, to have some important say in the setting of their own course and in the use of their own faculties. Other forms of government may similarly fail to respect human independence. But there is at least no contradiction in that; the underlying assumption of every kind of government by wisers and betters is that people on the whole are not fit to manage their own affairs, but must have someone else do it for them, and there is no paradox when such a government treats its subjects without respect, or deals with them on the basis of their having no rights that the government must take into account. 　　But democracy affirms that people are fit to control themselves, and it cannot live in the same air with the theory that there is no limit to the extent to which public power--even the power of a majority--can interfere with the lives of people. 　　Rational limitation on power is therefore not a contradiction to democracy, but is of the very essence of democracy as such. Other sorts of government may impose such limitations on themselves as an act of grace. Democracy is under the moral duty of limiting itself because such limitation is essential to the survival of that respect for humankind which is in the foundations of democracy. Respect for the freedom of all people cannot, of course, be the only guide, for there would then be no government. Delicate ongoing compromise is what must be looked for. But democracy, unless it is to deny its own moral basis, must accept the necessity for making this compromise and for giving real weight to the claims of those without the presently effective political power to make their claims prevail in elections By "the prose of democracy" ( Par. 1 ) the author most probably means its

A:popular interpretation. B:actual operation. C:ongoing compromise. D:rational limitation.

The load limitation of governor should be reduced when ship navigating at sea, the main reason is to .

A:prevent the diesel engine surging B:prevent governor from being damaged because of swing C:reduce the probability of the crank shaft being torsional vibrated and resonated D:prevent the main engine being overload or overspeed