Microwave brightness temperature on prime of seen reflectance for Hurricane Harvey earlier than its landfall in Texas. Credit score: Penn State
In 2017, Hurricane Harvey stalled after making landfall over coastal Texas, pouring down file rainfall, flooding communities, and changing into one of many wettest and most damaging storms in United States historical past. A brand new method utilizing available information reduces forecast errors and will enhance observe, depth, and rainfall forecasts for future storms like Hurricane Harvey, in accordance with Penn State scientists.
“Our examine signifies that avenues exist for producing extra correct forecasts for tropical cyclones utilizing accessible but underutilized information,” mentioned Yunji Zhang, assistant analysis professor within the Division of Meteorology and Atmospheric Science at Penn State. “This might result in higher warnings and preparedness for tropical cyclone-associated hazards sooner or later.”
Including microwave information collected by low-Earth-orbiting satellites to present pc climate forecast fashions confirmed enhancements in forecasting storm observe, depth, and rainfall when utilizing Hurricane Harvey as a case-study, the scientists mentioned.
“Over the ocean, we don’t have different kinds of observations beneath the cloud tops to inform us the place eyewalls are, the place the strongest convections are, and what number of rain or snow particles there are in these areas, besides for infrequent reconnaissance plane that fly into a few of hurricanes,” Zhang mentioned. “This is essential for later predictions of how intense storms shall be or how a lot rainfall hurricanes will deliver.”
The analysis builds on the staff’s prior work that improved hurricane forecasts utilizing information assimilation, a statistical technique that goals to color essentially the most correct image of present climate circumstances, necessary as a result of even small modifications within the ambiance can result in giant discrepancies in forecasts over time.
Within the prior work, scientists with Penn State’s Heart for Superior Knowledge Assimilation and Predictability Methods assimilated infrared brightness temperature information from the U.S. Geostationary Operational Environmental Satellite tv for pc, GOES-16. Brightness temperatures present how a lot radiation is emitted by objects on Earth and within the ambiance, and the scientists used infrared brightness temperatures at totally different frequencies to color a greater image of atmospheric water vapor and cloud formation.
However infrared sensors solely seize what is occurring on the cloud tops. Microwave sensors view a complete vertical column, providing new perception into what is occurring beneath clouds after storms have fashioned, the scientists mentioned.
“That is particularly necessary when a hurricane matures in later levels of improvement, when pronounced and coherent cloud constructions exist and you may’t see what’s happening beneath them,” Zhang mentioned. “That’s the time when hurricanes are most harmful as a result of they’re very sturdy and generally already approaching landfall and threatening folks. That’s when the microwave information are going to offer essentially the most beneficial data.”
Combining assimilated infrared and microwave information lowered forecast errors in observe, speedy intensification, and peak depth in comparison with infrared radiation alone for Hurricane Harvey, the researchers reported within the journal Geophysical Analysis Letters. They mentioned assimilating each units of information resulted in a 24-hour enhance in forecast lead-time for the speedy intensification of the storm, a essential time when some storms rapidly achieve power.
Assimilating the microwave information additionally led to a greater understanding of the quantity of water particles within the storm and extra correct rainfall totals for Harvey, the scientists mentioned.
“Rainfall predictions are extraordinarily essential for making ready the general public for hazards and evacuations,” Zhang mentioned. “If we now have a greater understanding of what number of rainfall particles there are within the storm, we now have the next chance of extra correct forecasts of how a lot rainfall there shall be. Primarily based on that, we could have extra superior steerage on how folks ought to react.”
The scientists mentioned extra work is required to enhance the mannequin’s microphysics to simulate water and ice particles extra realistically.
This examine is predicated on work by former Penn State Distinguished Professor Fuqing Zhang, who led the venture on the time of his surprising demise in July 2019.
“When our expensive pal and colleague Fuqing Zhang died, the thread of concepts that wove collectively our ongoing mixed infrared and microwave radiance information assimilation experiments unraveled,” mentioned Eugene Clothiaux, professor of meteorology and atmospheric science and a co-author of the paper. “We got here collectively over an prolonged time period to reassemble the thread as finest as doable.”
Reference: “Ensemble-Primarily based Assimilation of Satellite tv for pc All-Sky Microwave Radiances Improves Depth and Rainfall Predictions for Hurricane Harvey (2017)” by Yunji Zhang, Scott B. Sieron, Yinghui Lu, Xingchao Chen, Robert G. Nystrom, Masashi Minamide, Man-Yau Chan, Christopher M. Hartman, Zhu Yao, James H. Ruppert Jr., Atsushi Okazaki, Steven J. Greybush, Eugene E. Clothiaux and Fuqing Zhang, 13 December 2021, Geophysical Analysis Letters.
DOI: 10.1029/2021GL096410
Additionally contributing from Penn State have been Steven Greybush, affiliate professor; Xingchao Chen, assistant professor; and Man-Yau Chan, Christopher Hartman and Zhu Yao, graduate college students.
A number of former Penn State doctoral college students, postdocs and school additionally contributed: Scott Sieron, assist scientist at I.M. Methods Group; Yinghui Lu, affiliate professor at Nanjing College in China; Robert Nystrom, postdoc on the Nationwide Heart for Atmospheric Analysis; Masashi Minamide, assistant professor on the College of Tokyo; James Ruppert, assistant professor on the College of Oklahoma; and Atsushi Okazaki, assistant professor at Hirosaki College in Japan.
The Nationwide Science Basis, NASA, the Nationwide Oceanic and Atmospheric Administration and the Division of Vitality Organic and Environmental Analysis program supported this work.
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