Extreme Temperature Diary- Thursday July 22nd, 2021/ Main Topic: First The Heat Then The Flood…Case In Point China

The main purpose of this ongoing blog will be to track planetary extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: First The Heat Then The Flood…Case In Point China

Dear Diary. One day before we concentrate non-stop on a burgeoning historic U.S. heatwave, let’s look at a big climate crisis event that has recently happened in China. As I keep repeating, many times when heatwaves break we see flooding. A warmer than average atmosphere or hot parcel of air over a given area garners moisture over time. When a front of cooler air or a tropical system butts up against this warm parcel copious amounts of water may precipitate down on unfortunate residents.

Such was the case in a section of China recently. Here are more details from the Washington Post:


Capital Weather Gang

Eight inches in one hour: How a deadly downpour flooded Zhengzhou, China

At least 25 are dead after disastrous flooding that submerged trains and turned roads into rivers

The aftermath Wednesday of the heavy rain in Zhengzhou, a city in China’s eastern Henan province. (AFP/Getty )

By Matthew Cappucci Wednesday at 4:42 p.m. EDT

At least 25 people were killed in subway cars amid devastating flooding in eastern China on Tuesday. Zhengzhou, the capital of Henan province and home to more than 10 million people, suffered an extreme downpour that proved the heaviest ever observed in China and among the most significant on record globally.

A staggering 7.95 inches (201.9 millimeters) of rain came down between 4 and 5 p.m. Tuesday, one of many reports of significant to prolific rainfall that resulted in deaths and damage across eastern China. It contributed to a daily rain total that exceeded 24 inches in Zhengzhou.

That is almost a year’s worth of precipitation; the city averages 25.4 inches annually.

A man pushes his bicycle through a flooded intersection in Zhengzhou on Tuesday. (Chinatopix/AP)

Passengers died when their train cars filled with water, the subway system suddenly overwhelmed by rapid torrents of rainfall gushing in. Dramatic footage posted to social media captured a woman being rescued from a whirlpool, presumably leading to a drain or cistern. Abandoned vehicles littered flooded roadways; others were simply submerged or swept away.

Rescue efforts underway after Chinese floods displace 1.2 million

The calamitous rainfall resulted from a trifecta of meteorological conditions that, intensified by human-caused climate change, resulted in catastrophe.

Tropical moisture had been in place across much of southern China. Typhoon Cempaka made landfall in Yangjian, west of Hong Kong, on Tuesday morning at Category 1-equivalent strength. A second typhoon, In-fa, remains a high-end Category 2 that’s churning north of Taiwan. The former helped pump in moisture from the South China Sea, while the latter has been inducing a moist onshore flow from the East China Sea.

A pair of typhoons swirl near China on Tuesday, trucking tropical moisture ashore. (RAMMB/CIRA)

Meteorologists refer to precipitable water indexes (PWATs), or the total amount of moisture present in a column of air, as an indicator for heavy rain potential. PWATs over 1.5 inches can support heavy downpours; 2-inch PWATs are tropical. On Tuesday, PWATs in eastern China reached a whopping 2.5 to 3 inches.

That had two effects. The first was, obviously, providing the moisture necessary for heavy downpours. Much of that moisture pooled along a diffuse, semi-stationary boundary known as the Meiyu front. It passes through eastern China and north of Taiwan during the summertime, helping to focus heavy downpours.

The other effect of the high PWATs was increased precipitation efficiency. When rain, hail or snow, collectively known as “hydrometeors,” fall to the ground, the air below is seldom at 100 percent relative humidity. As a result, dry air induces some evaporation on the hydrometeor’s way down, eroding its mass from the outside. It’s not unusual for a raindrop to lose 30 or 40 percent of its water on the way down.

A traffic officer guides residents across a flooded road with a rope in Zhengzhou on Tuesday. (China Daily/Reuters)

But with the entire column saturated, meaning the air was considerably moist, there wasn’t much dry air to eat away at the raindrops. That meant most of the water in the clouds was falling all the way to the surface, stacking up more quickly.

Those elements helped the downpour to kick into overdrive. By the time the worst began mid- to late afternoon, morning rains — also tallying about 8 inches — had left the ground saturated. Many drainage systems were already close to maximum capacity before the worst rolled around.

Altogether, the dice were loaded for a top-tier event. Doppler radar data showed that the thunderstorm cell that produced the downpour sat and hovered over Zhengzhou. Weak upper-level winds, typical of a summertime weather pattern in mainland China, meant the storm was in no hurry to move.

Inside the flooded China subway, which trapped commuters up to their necks in water

Even after the heaviest bouts concluded, another 6 to 8 inches of rain fell across the city.

In addition to setting a record for China, the remarkable rainfall is in elite company when compared against similar records around the world. According to the World Meteorological Organization, the greatest one-hour rainfall reliably observed globally was 305 millimeters, or 1 foot, in Holt, Mo., on June 22, 1947.

The Chinese national record in Zhengzhou may be the most prolific short-term rain event to ever affect a major international city.

Precipitation extremes like this may become more common in the future as the world continues to warm thanks to climate change. Warm air can hold more moisture, which translates to more “moisture loading” of thunderstorms and a greater propensity for extreme downpours. It’s a phenomenon that’s already been observed in many major U.S. cities, including Houston, where high-end rainfall events are twice as common as in the 1970s.

Perspective: Fire, flood and heat disasters are an indictment of decades of poor planning

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By Matthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy.  Twitter

Here are more major “ET’s” reported on Thursday:

Here is more climate and weather news from Thursday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

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Guy Walton “The Climate Guy”

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