Trees Reveal Modern Storms Are the Rainiest of Centuries

Tropical cyclones such as Hurricane Ida can cause severe flooding, cause disturbances, damage, and loss of life. As with other types of weather, tropical storms and hurricanes on the U.S. East Coast have become more severe in recent decades. Although there are a few controversy in the magnitude of the increase in intensity, there is evidence that such storms are moving slower than before. This slow movement causes storms to last and longer and result more rain. However, because the usual weather records date back to 1948, it is unclear how unusual these slow storms were compared to earlier weather patterns.

A recent study This question is answered by using wood rings to reconstruct hundreds of years of rainfall levels during storms. The studied trees, about 300 years old, showed that heavy rainfall increased by 2 to 4 millimeters per decade, resulting in a cumulative increase in rainfall of up to 128 mm ( 5 inches) compared to the early 1700s. The greatest improvement has occurred in the last 60 years, and recent exacerbations are unmatched by any previous events.

In addition to establishing these re-established historical records, researchers are working with these data sets to develop predictions of what this region might do in the future.

Good For Growth — Low For the Tree

In the first job, Justin Maxwell and his colleagues found that longleaf pine trees on the East Coast of the US may serve as indicators of tropical storm precipitation, as measured in the late season in trees (June to October) growth bands. These smaller, more numerous local studies show that the new rainfall levels are greater than anything experienced by trees earlier in their lives.

That’s an unexpected finding, because wood ring records often show evidence of severe weather scattered throughout their history, even if the frequency may vary. The findings prompt a new study, which examines whether this pattern exists in a broader area.

“Typically, tree ring alterations show us that the severe climate we have recorded using instruments (weather stations) over the past 120 years has exceeded the past,” Maxwell told Ars Technica. “Our past research has shown that the new severe ones are unmatched in the past-all of the highest values ​​have been common since the 1990s, which is a big surprise, and that inspires us to sample a wider area to determine if this increase is local or now in a larger region. ”

Combining existing data sets with two new locations, the researchers included trees from a total of seven sites across North and South Carolina. Within North America, this region receives the most rainfall from tropical storms, and it also has the most complete world record of this type of rainfall.

The new data sets include a selection of samples from 13 to 36 old growing trees per site (taken in a way that causes minimal damage to the trees), as well as stumps. . The next step for the researchers was to calibrate their model by comparing wood ring patterns with known rainfall measurements from 1948 to the present.

Rebuilding the past to predict the future

As expected, tree rings represent more seasonal rainfall than the frequency or peak of individual storms. But growth patterns clearly suggest a reduction in rainfall during storms over the past centuries.

A year with a lot of rain doesn’t mean a giant storm has passed. “[It] may represent rain from a hurricane, or it may be multiple hurricanes, ”Maxwell wrote. “What we found in this paper is that this area receives more tropical storm rainfall throughout the season.” While researchers in the field are still debating the cause, many suggest it has to do with the flow of storms moving in the area more slowly.

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