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Research on climate change: more than hot air

The rate of water vapor pressure increasing with air temperature does not stay constant as scientists believed, but rather decreases with increasing air temperature based on research on climates of northern Eurasia*

Pictured: (l-r) Hengchun Ye and Michael Palacki.
Hengchun Ye receiving the 2010 John Russell Mather Paper of the Year Award from Michael Palacki, president of the Climate Specialty Group, after her special plenary paper presentation session at the Association of American Geographers annual meeting in Washington, DC.

Utilizing both historical weather station records and modern satellite remote sensing data (from Atmospheric Infrared Sounders or AIRS) to examine the climate of northern Eurasia, CSULA Geography Professor Hengchun Ye found that “the rate of atmospheric water vapor content change with temperature varies by season—and generally decreases with increasing air temperature.”

According to Ye, water vapor is a significant greenhouse gas and its role in effecting climate change is very complicated and challenging for scientists to quantify. She explains, “Increasing water vapor will increase the greenhouse effect and thus the air temperature; it also would increase cloud cover, which reflects more sunlight and thus decreases the air temperature.”

Based on this theory, the water vapor will increase exponentially with increasing air temperature on average conditions. “Therefore,” Ye adds, “it is assumed that a warming climate will bring more clouds, more precipitation, and intensified greenhouse effect. However, we cannot find any evidence of increasing precipitation in some subtropical and tropical land areas.”

She says, “During the summer season, we also found decreasing total water vapor with increasing air temperature at the southern and southwestern regions, where climate is dry and the surface lacks vegetation.”

Picture of Atmospheric Infrared Sounder.
Picture of Atmospheric Infrared Sounder. (Source: NASA)

Ye’s research explained this “puzzle” by pointing out that water vapor does not increase, but rather decreases in hot, dry subtropical regions, accompanied by air temperature increases. The implication is that a hot, dry region will experience more severe drought and higher temperatures under a warming climate.

*Definition: Eurasia is a large landmass covering about 10.6 percent of the Earth’s surface (36.2 percent of the land area). Often considered a single continent, Eurasia comprises the traditional continents of Europe and Asia. (source: National Geographic Society)

This research, conducted as part of the Jet Propulsion Laboratory (JPL) summer faculty fellowship program, was recently recognized by the Climate Specialty Group (CSG) of the Association of American Geographers (AAG).

Professor Ye—who coauthored the research article, “Atmospheric moisture content associated with surface air temperatures over northern Eurasia”—received the 2010 John Russell Mather Paper of the Year Award.

The award was presented to Ye and E.J. Fetzer of JPL at the 2010 AAG Annual Meeting held in Washington, DC. She is the only female recipient for this award since its inception a decade ago.

Chart illustrating the rate of vapor change.
(Source: “Atmospheric moisture content associated with surface air temperatures over northern Eurasia,” International Journal of Climatology)

The CSG awards one paper annually that makes significant contributions to climate science, or utilizes innovative research approaches, analyses, and/or techniques. The winner receives a commemorative plaque, cash award, a letter of citation, and recognition at an awards luncheon and meeting.

The research article, to be published soon in the International Journal of Climatology, is available for preview online at

A CSULA faculty member since 2001, Ye often involves CSULA students in her projects. Her research focuses on the characteristics of precipitation, snow, river discharges, and their connections with sea surface temperatures and atmospheric circulation patterns. She also studies atmospheric moisture conditions associated with a warming climate.

Ye has published numerous articles in internationally renowned journals, and her research has garnered several grants from government agencies, such as the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration. She served as an associate faculty of the NSF-funded CEA-CREST (Center for Environmental Analysis-Centers of Research Excellence in Science and Technology) program at Cal State L.A. She received her Ph.D. in climatology from the University of Delaware, and both her master’s degree in atmospheric science and bachelor’s degree in meteorology from Zhejiang University in China.

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Last Update: 01/12/2016