title: Recent Reversal of the Upper-Tropospheric Temperature Trend and its Role in Intensifying the East Asian Summer Monsoon.
abstract: At the beginning of the 21st century, the July and August (JA) mean upper-tropospheric temperature over East Asia shows a significant increasing trend, contrary to the decreasing trend in the late 1970 s. The largest warming center is over northern China (between 30°N-45°N and 85°E-120°E) around 300 hPa. Together with the temperature rising, the geo-potential height rises above the warming center and drops below, which connects closely to a correspondingly significant decadal shift of the general circulation over East Asia. In the upper-level of the troposphere, an anomalous anti-cyclone dominates, and the 200-hPa westerly jet strengthens due to the increasing pole-ward geo-potential height gradient. In the lower-troposphere, the anomalous southerly wind increases around Yangtze River Valley and the East Asian summer monsoon intensifies. The integrated circulation changes seriously impact summer precipitation over East Asia. The so-called "southern flood and northern drought" (SFND) pattern since the 1970 s over eastern China has changed. As the cooling center in the 1970 s moves southward, the dry belt moves southward as well. A wet belt dominates the Huaihe River Valley after the temperature trend reversal at 2005 while southern China experiences a dry condition.
authors.affiliation: State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, No. 46 Zhong-Guan-Cun South Street, Beijing, 100081, China.
authors.forename: Siyao
authors.initials: S
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, No. 46 Zhong-Guan-Cun South Street, Beijing, 100081, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, No. 46 Zhong-Guan-Cun South Street, Beijing, 100081, China.
authors.forename: Rucong
authors.initials: R
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, No. 46 Zhong-Guan-Cun South Street, Beijing, 100081, China.
authors.forename: Haoming
authors.initials: H
authors.lastname: Chen