【推荐2】It had always been assumed that the rarity of lightning in ocean storms was due to cleaner air over the vast seas, but keen observations have shown that even highly polluted air is associated with reduced lightning at sea when sea spray aerosols (气溶胶) are abundant. In their paper published in the journal Nature Communications, an international team of researchers describes their multi-year study of atmospheric conditions over the oceans bordering Africa and what it showed about salt in sea spray aerosols and its impact on lightning.

The researchers obtained atmospheric data on Africa and the oceans around it for the period 2013 to 2017. The data included numbers of lightning flashes, rainfall, temperatures and cloud representations. They looked for differences in atmospheric conditions in storms that occurred over land versus those that occurred over the sea and found one main difference: the amount of salt in the air.

Lightning is produced when upwardly moving air in clouds forms ice crystals (冰晶) — aerosol particles then begin to bump into one another, creating an electrical charge. Lightning happens when the electrical field in one part of the cloud becomes positively charged (usually at the top of the cloud) and another negatively charged (usually at the bottom of the cloud). And clouds form, of course, when vapor evaporates (蒸发) from the surface of the Earth and the water drops bond with aerosols.

The researchers found that things are slightly different over the ocean. When water evaporates from the sea, it bears a load of salt. When the salt water bonds with aerosols to form water droplets, they tend to be bigger and heavier than those that form over land due to the salt — and that results in more of the water in the clouds falling as rain before it can rise up and form ice crystals. The result is far fewer lightning discharges.

The researchers suggest their findings could be useful in improving the accuracy of both climate models and meteorological reports. It could also possibly lead some to attempt to seed storm clouds with salt to reduce their severity.

【推荐1】Ask the new artificial intelligence tool ChatGPT to write an essay about the cause of the American Civil War and you can watch it write a persuasive term paper in a matter of seconds. That’s one reason why New York City school officials this week started blocking the impressive but controversial writing tool that can generate paragraphs of human-like text.

The decision by the largest U.S. school district to restrict the ChatGPT website on school devices and networks could have chain reaction on other schools, and teachers rushing to figure out how to prevent cheating. The creators of ChatGPT say they’re also looking for ways to detect misuse.

ChatGPT launched on Nov. 30 is developed by OpenAI, which has a close relationship with Microsoft. It’s part of a new generation of AI systems that can converse, generate readable text on demand and even produce novel images and video based on what they’ve learned from a vast database of digital books, online writings and other media.

The ChatGPT tool is available for free to anyone with an internet connection and designed to be more user-friendly. It works like a written dialogue between the AI system and the person asking it questions.

Millions of people have played with it over the past month, using it to write silly poems or songs, to try to trick it into making mistakes, or for more practical purposes such as helping compose an email. All of those things are also helping it get smarter.

“To determine if something was written by a human or an AI, you can look for the absence of personal experiences or emotions, check for inconsistency in writing style, and watch for the use of filler words or repetitive phrases. These may be signs that the text was generated by an AI.” That’s what ChatGPT told an AP reporter when asked how to tell the difference.

“We don’t want ChatGPT to be used for misleading purposes in schools or anywhere else, so we’re already developing measures to help anyone identify text generated by that system,” the company said.

【推荐3】Researchers and environmentalists have been pushing for clean energy, as well, contending with the rising threat of climate change. An increasingly researched renewable resource is called Ocean Thermal Energy Conversion (OTEC), in which the sea’s temperature variations are used to produce power. On the surface of the ocean, the temperatures are much warmer compared to the seafloor. It gets considerably colder the deeper you go because the sunlight cannot reach the bottom. These temperature differences are most noticeable in the summer when the sun is present for a majority of the hours of the day. To put it simply, OTEC uses a series of pipes that take the cooler water out in the depths of the ocean. The warm water on the ocean’s surface helps heat the cool water, which then vaporizes (蒸发) a fluid, and as a result, turns a turbine (涡轮机) to produce electricity.

Three types of ocean heat renewable energy systems are being developed and researched. An OTEC closed-cycle is perhaps the most common and well-researched, consisting of a condenser (冷凝器), evaporator, pumps, turbine and generator. There are also open systems and hybrid systems.

Systems work by pumping the warmer surface water through an evaporator containing a working fluid with a low boiling point, such as ammonia. Once the fluid vaporizes, it is used to drive a turbine and generator. From there, the vaporized fluid turns back into a liquid through a condenser, cooled by the cold, deep ocean water that pumps up from the depths. The OTEC systems that use seawater can use condensation to make water without salt.

OTEC systems need to place technology about 1 kilometer below the surface of the water. The cold water intake pipe is in the deepest area, and the piping where warm water enters is above sea level. The pumps are needed to move warm water into the system, and a heat exchanger is required to evaporate the fluid. Condensers condense the steam produced in the system, and a marker keeps the entire system afloat.

Energy is essential for almost all human activities. If the world wants to avoid an energy crisis, people need to begin relying on renewable energy. Fortunately, the three types of OTEC can provide energy for large populations.