没听出来
听错了
First of all, let's look at why temperatures tend to be higher in city than in the rural areas. This happens because almost 50% of the urban areas are comprised of hard surfaces like paved street, parking lot, buildings and roof tops. As a result, any amount of rainfall is quickly repelled by this service and carried away by storm drains and gutters. Especially water just does not have the chance to stand around until evaporate, during the process of the evaporation that heat is removed from the air. So in cities where there is less evaporation temperatures will be higher and of course there are also be issue of added heat coming from building heating system, from industry, cars and even human body. Even we being in the city itself, temperatures can vary significantly. For example, in winter streets that get a lot of use will be 2 or 3 degrees warmer than less travel streets. In place where cars sits for a while like a stoplight can be in another 3 degrees warmer. On the other hand, low spots in the city where cold air collect will be much colder than higher places. Rain and snowfall are also affected by urbanization. Cities tend to get quiet less snowfall than the surrounding countryside because of warmer temperature in the city. But rainfall in the city can be 5 to 10 percent higher. That happens because of two factors. First, the warmer city temperature, second the larger number of dust particles in the urban air. It seems dust particles are important requirement for condensation. The water vapor in the atmosphere is able to change to liquid by planning to dust particles suspended in the air. So where there is the higher number of dust particles, condansation take place more easily. That is why fogs and clouds are usually more frequent around the city. Once condensation take place the rainfall is not far behind, in the London area, for example, thunderstorms can produce 30% more rainfall than the surrounding countryside. Some urban climatologists go so far as they argue that they can see a pattern increasing the rainfall during the workweek. They believe rainfall amounts are small around the weekend because the dust particle by cars and factories are reduced.
To continue our study of jazz, today we will focus on the blues, and listen to some recordings by BS, who is considered by many to be the greatest of all jazz singers. The blues developed in the Southern United States from music of black people who were brought from Africa and forced to work as slaves on Southern plantations. The earliest form of the blues were work songs and field howlers that was the musical form of a communication among the slaves. The name blues comes from the loneliness and sorrow typically expressed in the song lyrics. The blues started out as strictly vocal but over time musicians begin to accompany blue singers. Jazz greats like LA and FA accompanied BS in her recordings. The example of blues we will hear today is the reissue of some of BS’s classic recordings. These songs are from the late 1920’s when she was at the peak of her career. It is no wonder she was known as the emperor
of the blues. She made 160 recordings and was also a sort after live performer in New York, Boston and Chicago as well as the larger cities in the south. Know her rich powerful contract
her voice, in fact, in life performances she refused to use microphone. BS’s songs typified the earthiness and realism of the blues.
Most of you are probably familiar with the flow of lava they can result from a volcanic eruption. Lava actually being mixture of magma and convince to be produce underground. And many people think this eruption refers only to an explosion, but in geology, an eruption is any release of magma. This can and often does common the form of the explosion. But sometimes the magma just blows out over the mouth of volcano. In any event, let's take a look now at some of the other hazards caused by volcanic events. Pyroclastics is the word used to describe the fragmentary rocks that were rejected during the volcanic eruption. A Pyroclastics fall is combination of rock fragments and fluid fire lava that built in the air. This project tiles can be just tiny piece of ash or they can be rock fragments that are typically the size of baseball or volleyball. Although some can be so enormous they weigh many tons, the most dangerous of all volcanic events what we call a pyroclastic flow, in this explosion, there are tremendous released pressure and these result in avalanche of super heated mixture of gas and rock. This glowing avalanche as it called can reach the temperature of 1000 degree centigrade and can travel as far as 600km in an hour. It can literally destroy everything as it passed. And that’s what happen when Mount Pelee erupt on Martinique island in 1902. Within minutes after the volcano erupted, the town of Saint Pierre
was completely wiped out.