The Role of Changes in the Annual Cycle in Earlier Onset of Climatic Spring in Northern China |
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| Authors: | QIAN Cheng FU Congbin Zhaohua WU and YAN Zhongwei |
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| Institution: | The Role of Changes in the Annual Cycle in Earlier Onset of Climatic Spring in Northern China,Key Laboratory of Regional Climate--Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, Institute for Climate and Global Change Research, School of Atmospheric Sciences, Nanjing University, Nanjing 210093,Department of Earth, Ocean and Atmospheric Science & Center for Ocean--Atmospheric Prediction Studies, Florida State University, Tallahassee, Florida, USA,Key Laboratory of Regional Climate--Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | Climatic changes in the onset of spring in northern China associated
with changes in the annual cycle and with a recent warming trend were
quantified using a recently developed adaptive data analysis tool, the Ensemble
Empirical Mode Decomposition. The study was based on a homogenized daily
surface air temperature (SAT) dataset for the period 1955--2003. The annual
cycle here is referred to as a refined modulated annual cycle (MAC). The
results show that spring at Beijing has arrived significantly earlier by about
2.98 d (10 yr)-1, of which about 1.85 d (10 yr)-1 is due to changes
in the annual cycle and 1.13 d (10 yr)-1 due to the long-term warming
trend. Variations in the MAC component explain about 92.5% of the total
variance in the Beijing daily SAT series and could cause as much as a 20-day
shift in the onset of spring from one year to another. The onset of spring has
been advancing all over northern China, but more significant in the east than
in the west part of the region. These differences are somehow unexplainable by
the zonal pattern of the warming trend over the whole region, but can be
explained by opposite changes in the spring phase of the MAC, i.e. advancing in
the east while delaying in the west. In the east of northern China, the change
in the spring phase of MAC explains 40%--60% of the spring onset trend
and is attributable to a weakening Asian winter monsoon. The average sea level
pressure in Siberia (55o--80oN, 50o--110oE), an index of the strength of the winter monsoon, could serve as a potential short-term predictor for the onset of spring in the east of northern China. |
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| Keywords: | spring onset Ensemble Empirical Mode Decomposition modulated annual cycle Asian winter monsoon global warming |
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