【推荐1】Why the East Coast has had such a weak winter

Overall, winter across the East Coast this year has been pretty weak. “I was in shorts and a T-shirt,” said Jeff Weber, a research meteorologist (气象学家) at the University Corporation for Atmospheric Research. Meteorologists descended upon Boston in mid-January for the annual meeting of the American Meteorological Society. January is Boston's coldest month, but during the weather conference, meteorologists experienced 75 degrees Fahrenheit temperatures.

A major reason is that the polar vortex (极地涡旋) — which is a circulating stream of air that forms over the Arctic during winter — has stayed rigid and in place, keeping its cold air mostly locked up north. Consequently, little of this exceptionally chilly air has got into the U.S. this winter.

Arctic blasts (北极寒流), like those in January 2019, happen when the polar vortex becomes unstable, allowing frigid air to spill south. “But this winter, instead of a weak polar vortex, we’ve had strong polar vortex conditions,” said Andrea Lang, an atmospheric scientist at the University of Albany who researches changes in seasonal winter weather.

The polar vortex has stayed strong because other weather systems, sometimes originating from the Pacific. Ocean, haven’t come along and knocked the spinning vortex out of place.

A frequent culprit (问题的起因) in disturbing the polar vortex is a powerful stream of air traveling some 30,000 to 35,000 miles up in the atmosphere (where jets fly) which we commonly call the jet stream. The jet stream shoots from west to east around Earth at speeds of 120 to 250 miles per hour, but can become dramatically wavier when it’s disturbed by strong storm activity or encounters masses of hot or cold air.

But this winter season, the meandering (蜿蜒前进的) jet stream has not knocked the polar vortex off its pole, explained Lang. Instead, the jet stream has bent dramatically south, right through the heart of the central U. S.

Atmospheric scientists are deeply interested in why a perturbed polar vortex has become more frequent. There’s evidence that the incessantly warming Arctic — the fastest-warming place on Earth — has led to a weaker and less stable polar vortex, which means more outbreaks of freezing Arctic air. Just not this winter — so far, anyway.

【推荐2】No matter where you live in the world, natural disasters are always a threat. Of course, we humans take steps, both at an individual and social level, to prepare ourselves for the possibility of natural disasters. But preparing for these events requires understanding the types of natural disasters, what causes them, and the dangers they cause.

A technical term for a period of very cold weather, a cold wave is a type of natural disaster where the temperature drops rapidly over the course of 24 hours. While cold weather in itself isn’t necessarily enough to cause a natural disaster, a rapid dropping of the temperature could lead to lots of problems for communities in a region.

Interestingly, there isn’t an precise temperature threshold (起点) that must reach to be. Rather, cold waves are classified (分类) by how fast the temperature falls. Since what’s considered to be “cold” varies widely from region to region, local weather services will use local weather averages to determine if a weather event is actually a cold wave.

There are many reasons why a cold wave might occur. One of the most common causes of a cold wave is the arrival of a very strong high pressure system from the polar regions. Alternatively, movement in the jet streams can also drive very cold weather southward in just a matter of hours.

The primary danger of a cold wave is, indeed, the cold weather itself. This can lead to a higher risk of hypothermia (低温症) and other cold-related injuries. Additionally, cold weather can cause ice and frost to build up quickly, damaging basic facilities. Cold waves are also particularly dangerous for aircraft and other machinery. Extreme cold can use up vehicle batteries or cause petrol to come together. So, whenever in extreme cold weather, people need to be careful.

【推荐2】Although billions of locusts(蝗虫) appearing on East African countries greatly panicked farmers in 2020, they managed to see through this unexpected crisis. “Their success primarily results from a technology-driven anti-locust operation,” said Mr. Cressman, an officer in the UN Food and Agriculture Organization.

Normally, these locusts live alone across the deserts of North Africa, Southwest Asia and the Middle East. But when rains arrive, they change from a slightly brown into a deep yellow and form groups of more than 15 million insects per square mile. Such quantities of locusts can consume the equivalent amount of food in a single day as more than 13 000 people.

Locust trackers in Sudan and Eritrea find the insects by using a tablet-based program to transmit data to authorities so experts can design appropriate control strategies. But people who want to use this system might encounter a technological problem: The version of the tablets that the locust-tracking program was written for is not manufactured and newer tablets are unsuitable for the software.

Rather than rewriting the locust-tracking software for newer tablets, Mr. Cressman thought creating a simple smartphone app would make anyone collect data like an expert. He sought help from Dr. Hughes, who had already created PlantVillage to track a crop pest. Borrowing from this blueprint Dr. Hughes and his colleagues completed eLocust3m, which anyone with a smartphone can use. The app presents photos of locusts at different stages of their life cycles, which helps users diagnose what they see in the field. The locations are then automatically recorded by GPS and algorithms(算法) double check submitted photos. If necessary, pesticide-spraying aircraft will take position.

The F.A.O. estimates that this effort in East Africa has prevented the loss of agricultural products with a commercial value of $ 1.5 billion, saving the livelihood of 34 million people.

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【推荐1】Many international students studying abroad in America have several supposed ideas about American culture. After visiting the country, many international students showed the culture shock they received in America. Here are some culture shocks in America that most of the international students came across.

It's surprising to note that kids, the youth and adults refer to each other with their first names, This is a very uncommon sight. Many international students might find it surprising and take time to adjust to this tradition.

Another culture shock is that, in America, there could be only one or two classes a day. Usually, they’re conducted in the afternoon or in the evening. This means the students get enough time to sleep late, wake up around noon and have time for different chores (琐事). Besides, having convenience in the schedule of classes, students also enjoy long hours of breaks.

Among the many culture shocks in America, multiple languages are quite common there. Many international students would move to America, believing that the only language is English. However, that's not the case. The citizens commonly speak languages such as Spanish, French, German, Chinese and others, So if you're comfortable with any of the above-mentioned languages, you might get surprises.

Many international students are used to using kilograms, metres, litres, degrees centigrade as the units of weight, length, volume, temperature. But they might be perplexed to see a different metric system in America. There, pounds, feet and Fahrenheit are usually used as units for measurements. This system is quite puzzling to comprehend at the beginning for many international students.

Many international students might find various culture shocks in America depending on the background they come from. Thus, they may need a long time to adjust themselves to the unfamiliar environment.