单元检测卷（六）Disaster and hope

Dry lightning (雷电) can still be harmful even when conditions aren't so dry, said a study published in Geophysical Research Letters last month. Dry lightning during little to no rainfall was previously thought to cause wildfire danger only with less than 2.5mm of rain in a day. A Washington State University-led study of wildfires in the US West found dry lightning caused wildfires despite up to 7.7 mm of rain.

"The rainfall amounts we recorded should help provide a better understanding of just how much rain can cause a fire risk," said Dmitri Kalashnikov, lead author of the study.

The researchers analyzed (分析) cases on more than 4,600 naturally caused fires from 2015 to 2020. They matched 3,726 of those to the lightning strikes that likely started them with the help of National Lightning Detection Network.

The study found that 15.3% of those were holdover fires which burn without smoke, bringing about over a hundred fires each year. Analyzing the rainfall amounts around the time of the lightning strikes showed greater rainfall than previously thought among the earlier found fires ranging from 1.7 mm to 4.6 mm.

While humans still cause most fires either by accident or on purpose, lightning-caused wildfires burn the most areas. Nearly 70% of the wildfire-burned land in the West was from lightning-caused fires according to the study. For example, the largest wildfire burn area in California history took place in August 2020 after dry lightning caused many wildfires at once.

Dry lightning can also start wildfires in places that are hard for firefighters to reach. This study found the places where holdover fires happened repeatedly were in the forested mountains of the Southwest as well as the middle and southern Rocky Mountains. Holdover fires cause the problem because they are so hard to notice.

Over the last two days, much of Spain has been coated with dust (灰尘), and the skies have turned bright orange. A huge cloud of dust from the Sahara Desert is causing the strange weather. The dust cloud is expected to spread to other parts of Europe.

Across much of Spain on Tuesday morning, a thin layer (层) of red dust coated everything outside. From streets to sidewalks to balconies, everything was covered with a layer of dust. As the sun rose, the dust in the air turned the skies in some cities a strange orange. The cause of the dust and unusual sky colour wasn't a forest fire, but dust from the Sahara Desert.

Every year, a large cloud of dust rises from the Sahara Desert. It's called the Saharan Air Layer. Usually, it crosses the Atlantic Ocean as part of a natural cycle that helps develop farmland and beaches in Central and South America.

But sometimes, depending on the weather, the layer of dust gets forced to the north. Large sandstorms in northern Africa lift sand and dust into the air, where it gets blown towards Spain. Though the particles (微粒) in the air come from sand, they're much more like dust than sand at a beach.

These kinds of storms aren't unknown in Spain. In fact, it has a special name. It's called a "calima". This calima is so large that it can be seen from space. A NASA scientist who studies weather in the atmosphere says it's like a river of dust in the air. That river of dust has met with a river of wet air driven by strong winds.

Spain's weather service described the dust storm as being "very intense (强烈的)". At one point on Tuesday, the air quality in Madrid was the worst in the world. Government health experts warned people not to go outside without a mask, and to keep their windows and doors closed at home.

Very hot temperatures have been breaking records during the summer across the USA. But it's not just in the USA heat wave in June set new record highs. So what is a human to do? 16

· Dress for the Weather

During a heat wave, you have to dress properly. Clothing like loose and light-colored clothes are best if you have to work or be outside. 17 Also be sure to protect your face, hands and any other exposed skin with sunscreen (防晒霜), or you can wear a hat and sunglasses.

· Avoid Outdoor Activities

If possible, participate in outdoor activities during the morning hours. 18 Take frequent breaks in the shade. If you're working outside in the heat, and the activity makes your heart race faster, stop and get inside to cool off and rest, especially if you feel light-headed (头昏眼花的) or confused.

· Keep Cool

19 If that's not possible, try to go to a public place like a library, mall or a movie theater. Many cities will open up shelters during heat waves to provide citizens with relief, especially in areas where air conditioning (空调设备) isn't widely used.

· 20

Heat-related illness can affect anyone, but some people are particularly at risk. If you live with, or know people, like young kids, the sick or elderly, overweight people, outside workers, check on them frequently during a heat wave. We should monitor those at risk at least twice a day for signs of heat exhaustion or heat stroke, and babies and young children, even more frequently.

2005 was a big year for me. After my family moved to New Orleans in June, Hurricane Katrina hit the 21 in August. I sat in my family's car on a highway full of other confused children as we all 22 the city before the storm. A few months later, we returned to New Orleans. But the city was still 23. There were still thousands of people left homeless because of the 24.

Then some 25 people like the coach of New Orleans Saints were taking action. He gave money to schools and charities, helping 26 the city and feeding those who had 27 everything. He helped bring back the 28 that New Orleans once had. The people made it 29 and came back to the stadium to watch the game.

I remember when Louisiana Superdome reopened, the energy of the city 30. I remember when the coach 31 the field, there were loud cheers. I remember how 32 I was when the Saints appeared.

I was too young to understand what the 33 had brought to New Orleans. 34, I'm old enough now to understand that the coach did so much for New Orleans. I'll always be 35 for that. Even though he had retired, he would always be my idol.

On 20 December, a series of huge waves 36 (cause) by an earthquake resulted in many people's deaths. Goldshore beach was the only local beach to survive the disaster. Sabrina, 37 was a girl of ten years old, helped about 100 people escape danger with her knowledge of tsunami.

That day, many people were walking, running or 38 (simple) sitting on the beach, 39 (enjoy) the warm sea air and the soft wind. Sabrina was one of the happy 40 (tourist) until she noticed something odd. It immediately occurred 41 her that these were signs of an approaching tsunami because she had just learnt about it in a Geography lesson.

At first, Sabrina was 42 (frighten), but she soon kept her head. She asked her parents 43 (inform) a safety officer. The officer realized the coming danger, and rapidly cleared the beach of people, just before 44 tsunami arrived. Thus, all the people on the beach 45 (save).

The snowstorm was supposed to hit the evening of Monday. I had to leave my home to go to First Nations University, to sign a financial aid check for a student. As the finance director, I wanted to get it to him quickly, despite the approaching snowstorm. Little did I know that this decision would lead me to an unexpected meeting with André Bouvier aged 75 and his wife.

I figured I had enough time to make the trip safely. When I arrived at the office, my colleague cosigned the check and left. As I packed up, I noticed he had left his laptop bag in my office. I called him and offered to bring it to him, even though it was already late afternoon. To avoid the potentially dangerous road conditions on the highway, I decided to take the country roads to his home. On the way, I stopped to buy a cellphone charger, filled up my SUV with gas, and picked up pizzas. It took me about 15 minutes to drop off the laptop case at my colleague's house.

As I got back on the road, the snow started falling heavily. Within minutes, I was in a whiteout (乳白天空). The snowstorm came down fast, the wind screaming. The windows were fogging up and getting covered with snow, so I opened the driver's side window to better see the road's edge. However, I became disoriented (迷失方向) and unsure of my location. Fearful of driving into a farmer's field, a ditch, or worse, I decided to stop.

I kept the car running to stay warm and called 911. The dispatcher (调度员) advised me to wait until morning for assistance due to the dangerous conditions. Those seconds after the call were extremely painful. Getting out to walk in a whiteout with zero visibility (能见度) and high winds—when I didn't even know where I was—wasn't an option. Breathe, I told myself. Panicking won't help.

It was now about 6 p.m. and dark, and I worried about the visibility of my black SUV in the whiteout. Feeling helpless, I shared my location on Google Maps and posted a screenshot of where I was on Facebook, seeking help from anyone familiar with the area. Soon enough, people started to respond.