Irrigation and Storms in the Inner Mongolian Desert

Images from the DECODE project. Clockwise from top left: Microwave radiometer, wind LIDAR, researcher launching rawinsonde, eddy flux observation system, clouds forming at the boundary line, radar image of convective cells initiating along the boundary, photo of supercell storm growing from the boundary line. Photos courtesy of DECODE team.

A Research Spotlight from 32WAF/20Meso/28NWP

An irrigation oasis in Inner Mongolia, China, is providing unusual, real-world evidence about the effects of sharp vegetation contrasts on local and regional weather. Several presentations at the 32nd Conference on Weather Analysis and Forecasting, the 20th Conference on Mesoscale Processes, and the 28th Conference on Numerical Weather Prediction (32WAF/20Meso/28NWP) discussed findings from the 2022 DEsert-oasis COnvergence line and Deep convection Experiment (DECODE).

In Bayannur City, on the north side of a bend in the Yellow River, sits one of China’s largest irrigated areas: the 2,200-year-old, 769,333 hectare Hetao Irrigation District (HID), which was recognized as a World Heritage Irrigation Structure in 2019. All around this irrigation oasis is arid and semi-arid land, including the Kubuqi Desert to the south. We know that borders between land and water influence weather patterns, but there has been less real-world evidence gathered about the effects of differences in vegetation—and you can’t find a sharper divide than this one.

Image showing treeless mountains and sparsely vegetated foothills next to flat land. In the center of the photo is a dark green area of vegetation which contrasts sharply with the otherwise brown/tan landscape. A road runs to one edge of the green area. At the very right of the image, in the middle distance, is a large, wide building with a bright blue roof.
Above: Aerial view showing part of the Hetao Irrigation District and its sharp contrast with the surrounding desert areas. Video still courtesy of Yijing Liu. Below: Diagram of the juxtaposition between the boundary and its associated convective initiation (CI) and downstream propagation relative to surrounding terrain in Hetao Irrigation District. Image courtesy of Zhiyong Meng.

When cooler air from the Irrigation District meets warm wind from the desert, an atmospheric boundary line can sometimes be seen on radar. During the summer, convection often initiates at this boundary—sometimes leading to impressive storms that can travel long distances. DECODE researchers used a comprehensive set of observations—from radar and satellite to balloon sondes to flyovers—to examine this phenomenon. Their mission was to understand how the boundary forms and under what circumstances it might create unusual weather.

Different views of the boundary. Images courtesy of Zhiyong Meng.

On average, in the three months of summer each year from 2012 to 2016, 60 days produced a boundary, and 44 percent of those boundaries resulted in convective initiation (CI), noted Zhiyong Meng, of Peking University, in her July 20 presentation during Session 16 of 32WAF/20Meso/28NWP. The DECODE field experiment itself lasted 36 days in 2022, from 5 July to 9 August. With two field stations located on the oasis side, and four on the desert side, the teams were able to observe 23 boundaries and 11 occurrences of deep convection initiation, and even one case of a tornado.

Video still with green agricultural fiels and dark storm clouds in the background. A tornado funnel cloud is seen in the right side of the image. The DECODE project logo appears at the top left.
A tornado documented by the DECODE research team. It was generated by a thunderstorm formed at the boundary line. Video still courtesy of Yijing Liu.
Video still shows a bright bolt of lightning in the far left of the image. In the bottom right, a laser wind LIDAR device sits on a rooftop, pointing in the direction of the storm.
Lightning strike during the DECODE experiment. Video still courtesy of Yijing Liu.

Yipeng Huang, of Xiamen Key Laboratory of Straits Meteorology, outlined the most common conditions leading to a boundary/CI in a 21 July presentation. The researchers found that a boundary is most likely on warm summer days, when synoptic forcing is relatively weak, with dominant southerly winds opposing the oasis breeze, and a temperature over the desert that is apparently warmer than over the oasis. They found that along the boundary line between the two masses of air, convection initiation may occur when enough moist air advects north at the west edge of the subtropical high, moves out over the dry desert, and converges with a cool oasis breeze in an environment with large enough instability. Hongjun Liu of Peking University presented the mechanism for this process in a case study on 21 July.

Diagram of boundary formation and convection initiation near Hetao Irrigation District. Image courtesy of Zhiyong Meng.

Meng described “The most beautiful case, on July 29 [2022, when] the boundary produced a CI and the storm became very strong; it actually produced five-millimeter hail in the eastern part of the oasis.” They were also able to observe another storm as it split into two separate supercells. On July 25, a preexisting storm that passed over the area dissipated somewhat, likely due to sinking air over the oasis, then re-initiated strongly once it reached the boundary/convergence line over the desert. On occasion, the boundary would extend over the oasis and strongly increase the precipitation there.

Radar and photograph images of a large thunderstorm forming along the boundary line in the Kubuqi Desert on 29 July, 2022.

In the presentation immediately following Meng’s, Murong Zhang of Xiamen University noted that the team’s real-time forecasts were able to predict the formation of the boundary line in 21 out of 23 cases, although predicting convection initiation was more difficult. They were only able to predict 6 out of 11 CIs, as the numerical model tended to over-predict surface temperature, but under-predict moisture. The observations obtained from DECODE have been used to effectively improve the surface heat flux over the irrigated area, as shown in a presentation by Xuelei Wang of Peking University on the first day of the conference. You can see more from the DECODE team in this video created as part of the project:

With researchers from many institutions* participating, DECODE is an epic undertaking to study a unique natural phenomenon. As field research pioneer Prof. Edward Zipser of Utah University noted after Zhang’s talk, it’s “a program that we want to hear more about.”     

Group photo of the DECODE onsite team at one of the desert stations. Photo courtesy of Yijing Liu.

*DECODE participating organizations include Peking University, Inner Mongolia Meteorological Bureau, Nanjing University of Information Science and Technology, Xiamen Key Laboratory of Straits Meteorology, Xiamen University, Nanjing University, National Satellite Meteorological Center, Foshan Meteorological Bureau, and Jiangxi Storm Hunting Videos Culture Co., Ltd.

Featured image collage: Images from the DECODE project. Clockwise from top left: Microwave radiometer, wind LIDAR, researcher launching rawinsonde, eddy flux observation system, clouds forming at the boundary line, radar image of convective cells initiating along the boundary, photo of supercell storm growing from the boundary line. Photos courtesy of DECODE team.

About 32WAF/20Meso/28NWP

Predicting and understanding storms and other weather events is a complex business with real-world impacts. The American Meteorological Society’s 32nd Conference on Weather Analysis and Forecasting/28th Conference on Numerical Weather Prediction/20th Conference on Mesoscale Processes brought researchers, forecasters, emergency managers, and more together to learn about and discuss the latest scientific developments. The conferences took place in Madison, WI, and online 17–21 July, 2023. Recordings of the sessions are available here.

“Once in a Generation”: The 2022 Buffalo Blizzard

Truck in snowdrift

A Research Spotlight from 32WAF/28NWP/20Meso

On 23 December, 2022, David Zaff of the National Weather Service’s Buffalo office walked out into a blank white world of howling wind. He headed to his car to get supplies, knowing there was no way to get home. He and his coworkers were trapped at the office, in the middle of one of the most deadly and disastrous blizzards Buffalo has ever seen.

Video by David Zaff, showing whiteout conditions outside NWS Buffalo office, December 23, 2022.

At the height of the 2022 holiday travel season, the four-day blizzard and lake-effect snow event knocked out power for more than 100,000 people, paralyzed emergency services and holiday travel, and left at least 47 dead. New York Governor Kathy Hochul described it as “the most devastating storm in Buffalo’s long, storied history.” Yet days earlier, Zaff and colleagues encountered skepticism from the public as they worked to warn the region.

Presenting at the J3 Joint Session at the 32nd Conference on Weather Analysis and Forecasting, the 20th Conference on Mesoscale Processes, and the 28th Conference on Numerical Weather Prediction, Zaff talked about the disaster and how the NWS countered accusations of hyperbole to get the word out.

Sounding the Alarm

The December 2022 snow was shocking, but not surprising. The pattern was easy enough to recognize, even 7–10 days earlier: a large high-pressure ridge forming over the western U.S., with a major trough in the east. “We knew something big was coming,” said Zaff. Five days before the storm, even low-resolution models suggested a major event. Four days ahead, the NWS started ringing the alarm bell. “We started saying, ‘A powerful storm will impact the region heading into the holiday weekend.’”

Three days out, the NWS issued an unusually emphatic Area Forecast Discussion (AFD):

“Some of the parameters of this intense storm are forecast to be climatologically ‘off the charts’ … One could certainly describe this storm system as a once in a generation type of event.”

NWS Lead Forecaster Robert Hamilton, Tuesday, December 20, 2022

That caused a stir, but many on social media dismissed it as hype. “People started saying, ‘There goes the weather service again,’” says Zaff.

He tried to find a way to show the science graphically, highlighting the forecast as “‘outside’ the climatology” for the time of year.

The graphic and its accompanying description got attention. By then, NWS Buffalo was communicating in earnest, including on social media. A tweet with a text-filled screengrab of the Winter Weather Message received 485,000 views. “A picture is worth a thousand words,” Zaff said, “except when people actually read the words, and see how impressive this event might be.”

Left: Graphic showing forecast surface pressure for Friday, December 23, 2022, with shading showing the relative frequency of the forecast MSLP values in the Buffalo region at that time of year. Source: David Zaff.

Surviving the Storm

Before noon on 23 December, visibility dropped to near zero, and it remained that way until around midnight on 25 December. 500 Millibar heights were “extraordinary” as the pressure trough moved into the Ohio Valley, and surface-level pressure was similarly unbelievable. A top wind speed of 79 mph was measured in downtown Buffalo at 10:10 a.m. on the 23rd, and winds in the 60–70 mph range lasted for 12 hours. “[It was] just an incredible bomb cyclone,” Zaff said. “An incredible storm.”

Zaff and some colleagues slept at the office; others attempted to drive in whiteout conditions using GPS alone, while some got stuck in drifts near the office and had to leave their cars to hike the rest of the way. Meanwhile, firefighters and airport employees worked to rescue motorists trapped nearby.

On December 24, the City of Buffalo issued “the scariest tweet I’ve ever seen,” said Zaff. The tweet stated that there were “no emergency services available” for Buffalo and numerous other towns.

“We knew by this time that there were fatalities occurring,” Zaff said. “And it just got worse and worse.”

Blizzard conditions lasted a full 37 hours–and lake effect snow wouldn’t stop for another two days. Three power substations shut down, frozen solid. Hundreds of power poles fell, and a significant percentage of locals were without power during the storm’s peak (some for days afterwards).

The 47 fatalities included people stranded outside, others who died from hypothermia in their homes, and some deaths due to delayed EMS response, according to Erie County. Hundreds of motorists were stranded on roadways during the storm. The Buffalo Niagara International Airport, with a proud legacy of operating under even the most horrific conditions, was closed for six days.

Zaff didn’t return home until late afternoon on the 25th, 18 hours after official blizzard conditions were over and having clocked 50+ hours at the office. On the drive, he saw iced-over buildings and trucks buried in snowdrifts. “It reminded me of [the movie] The Day After Tomorrow. … The impacts were tremendous.”

In his AMS presentation, Zaff compared the 2022 event to disastrous storms in 1977 (20+ fatalities, 69 mph winds, only 12” of snow yet drifts swallowed homes) and 1985 (5 fatalities, 53 mph winds, 33” snow), as well as the “Great Christmas Storm” of 1878, one of the first well-documented lake effect snow events, though lake-effect processes weren’t understood at the time. “This will likely be the storm of comparison now,” he says. “Once-in-a-generation” turned out to be right.

Future Lessons

Moving forward, said Zaff later, “Our intention is to further our relations with our Core Partners, including elected officials, emergency management, and the media [and] provide more probabilistic information that supports our ongoing Impact Decision Support Services. We hope to improve our outreach as well, instilling more confidence with the public.”

NWS will continue to provide improved decision support for partners, which may lead to more proactive road and school closures that could save lives in the future.

Photo at top: Buffalo roadways at 4 p.m. on December 25, 2022, 18 hours after blizzard conditions had passed. Photo credit: David Zaff.

About 32WAF/20Meso/28NWP

Predicting and understanding storms and other weather events is a complex business with real-world impacts. The American Meteorological Society’s 32nd Conference on Weather Analysis and Forecasting/28th Conference on Numerical Weather Prediction/20th Conference on Mesoscale Processes brought researchers, forecasters, emergency managers, and more together to learn about and discuss the latest scientific developments. The conferences took place in Madison, WI, and online 17–21 July, 2023. Recordings of the sessions are available here.