INTERNATIONAL JOURNAL OF CLIMATOLOGY
Int. J. Climatol. 31: 1665–1678 (2011)
Published online 13 July 2010 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/joc.2193
Statistical behaviours of precipitation regimes in China
and their links with atmospheric circulation 1960–2005
Qiang Zhang,a,b * Chong-Yu Xu,c Xiaohong Chena and Zengxin Zhangd
a
b
Department of Water Resources and Environment, Sun Yat-sen University, Guangzhou 510275, China
Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing
210044, China
c Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway
d Jiangsu Key Laboratory of Forestry Ecological Engineering, Nanjing Forestry University, Nanjing 210037, China
ABSTRACT: In this study, we comprehensively analysed daily precipitation time series of 590 rain stations in China
covering 1960–2005. Ten indices were defined to evaluate changing patterns of precipitation regimes and trend detection
was performed using Mann–Kendall trend test and linear regressive technique. For the sake of better understanding of
underlying causes behind changing properties of precipitation regimes, we also investigated spatial and temporal variations
of atmospheric circulation of water vapour flux. The results revealed different changing properties of precipitation events
across China. Generally, wet tendency was identified in the south China and dry tendency in north China. Besides, slight
wet tendency could be found in northwest China. In addition, increasing precipitation intensity could be observed mainly
in the lower Yangtze River basin and the Pearl River basin. Remarkable seasonal shifts of wet/dry conditions were also
detected in China: wet tendency in winter and dry tendency in summer. Furthermore, this study revealed good agreement
between spatial distribution of precipitation regimes and water vapour flux, showing tremendous influences of water vapour
flux on the precipitation changes across China. Regions east to 100 ° E were dominated by increasing water vapour flux
in winter. Weaker East Asian Summer Monsoon was the main cause responsible for decreasing northward propagation of
water vapour flux, causing different wet (dry) tendency in south (north) China. This study can provide theoretical evidence
for effective water resource management and sound arrangement of agriculture activities on river basin scale under the
changing environment across China. Copyright  2010 Royal Meteorological Society
KEY WORDS
climate changes; precipitation regimes; extreme rainfall; trend test; water vapour flux; atmospheric circulation
Received 7 June 2009; Revised 6 November 2009; Accepted 24 May 2010
1.
Introduction
Tremendous importance has been attached to the study
of climatological variables, such as air temperature, precipitation amount, sea level, atmospheric pressure and so
on (Piervitali et al., 1997). It is particularly the case for
the study of the precipitation variations (Brunetti et al.,
2000; Osborn et al., 2000; Kunkel, 2003; Ramos and
Martı́nez-Casasnovas, 2006; Fatichi and Caporali, 2009)
which can be well justified by the fact that the temporal
and spatial variability of precipitation has always affected
human societies all over the world. Study of changes in
precipitation regimes is believed to be the first step to
understand impacts of climate changes on water resource
availability (Jiang et al., 2007). Rogers (1994) stressed
the necessity to understand changes in means, variances
and persistence of the precipitation regimes with the aim
to improve the accuracy of plans for future water demand.
The tremendous importance of water for human societies
and nature underscores the necessity of understanding
* Correspondence to: Qiang Zhang, Department of Water Resources
and Environment, Sun Yat-sen University, Guangzhou 510275, China.
E-mail: zhangq68@mail.sysu.edu.cn
Copyright  2010 Royal Meteorological Society
how a changing climate could affect regional water supplies (Xu and Singh, 2004; Xu et al., 2006). Thus, a good
understanding of magnitude and frequency of precipitation events, especially extreme precipitation events, is
essential for effective water resource management and
flood control (e.g. Durrans and Kirby, 2004).
Different changing properties of precipitation regimes
have been detected for different regions over the world
implying diverse regional responses of precipitation variations to global climate changes. Karl and Knight (1998)
showed increasing trends in 1-day and multiday heavy
precipitation events with heavy 24-h precipitation totals
in the United States and other countries. Significant
decreasing trends in extreme rainfall events have been
found in Western Australia (Haylock and Nicholls, 2000).
However, some researchers have found an increasing
trend in extreme precipitation events in the United States
(Kunkel, 2003). Other scholars reported no trend in
extreme rainfall events in Canada (Zhang et al., 2001).
As for the studies of precipitation regimes in China,
numerous reports can be found in the literatures. Becker
et al. (2006) found significant changing trends in monthly
precipitation totals in the Yangtze River basin. Wang and
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Q. ZHANG et al.
Zhou (2005) studied trends in annual and seasonal mean
precipitation totals and extreme precipitation events in
China during 1961–2001 using linear regression method
showing increasing annual mean precipitation in southwestern, northwestern and eastern China and decreasing annual mean precipitation in central, northern and
northeastern China. Chen et al. (1991) indicated that the
majority of China was characterized by decreasing precipitation, especially northern and northwest China. Zhai
et al. (1999) reported no significant trend in the annual
precipitation over China between 1951 and 1995. Wang
et al. (2004) showed an increasing precipitation during
the second half of the 20th century in the West China.
Ren et al. (2000) demonstrated an increasing summer
precipitation over the middle and the lower Yangtze River
and a decreasing trend over the Yellow River basin, but
almost no change in the high-latitude areas. Zhai et al.
(2005) investigated the trends in annual and seasonal
total precipitation and in extreme daily precipitation for
the year, summer and winter half years. Zhang et al.
(2009c) thoroughly analysed annual, winter and summer
precipitation records during 1951–2005 of 160 stations
in China using the rotated empirical orthogonal function, Mann–Kendall (MK) trend test and Continuous
Wavelet Transform method, addressing changing properties of precipitation regimes in different parts of the China
and discussed implications of these changes with respect
to river basin scale water resource management. Zhang
et al. (2008b, 2009a) investigated precipitation extremes
in the Yangtze River basin and Pearl River basin and
linked these changes to atmospheric circulation demonstrating that decreasing northward propagation of water
vapour flux should be the major cause for increasing precipitation maxima in the lower reaches of these river
basins. Besides, study of drought/wetness episodes in the
Pearl River basin (Zhang et al., 2009b) indicated seasonal
shifts of humidity conditions, i.e. summer is being dryer
and winter being wetter. This finding means too much for
scientific management of water resources and agriculture
activities in the Pearl River basin. Table I displays the
major studies for the precipitation changes in China.
Our previous studies (Zhang et al., 2008b, 2009a,
2009b, 2009c) indicated remarkable differences in changing properties of precipitation regimes over China.
Increasing temperature has the potential to alter the
changes of atmospheric circulation of water vapour flux
in both space and time. Furthermore, good relations
between precipitation changes and atmospheric circulation are observed in the Yangtze River basin and the
Pearl River basin (Zhang et al., 2009a, 2009c). Thus,
increasing temperature can cause alterations of spatial and
temporal distribution of precipitation regimes by influencing the atmospheric circulation, and this will exert
tremendous impacts on water resource management at
river basin scale and on agricultural activities over China
(Chavas et al., 2009). In addition, the societal infrastructure is becoming more sensitive to weather and climate
extremes, which would be exacerbated by climate change
(Easterling et al., 2000). Therefore, in this case, we investigate changing properties of the average regime and the
extreme behaviour of the rainfall processes over China
and try to link these changing properties to atmospheric
circulation with the aim to address causes behind precipitation changes. Based on the fact that precipitation
changes are always in close relation with availability and
variability of water resources, we divided the entire territory of China into ten parts based on the range of ten river
basins (Figure 1). The objectives of this study are (1) to
clarify changing properties of precipitation regimes in
China in terms of average and extreme behaviour; (2) to
explore precipitation concentration by analysing fraction
of annual and seasonal total precipitation due to events
exceeding the 75th or falling below the 25th percentile;
(3) to understand causes behind changing properties of
precipitation regimes in China by analysing variations of
water vapour flux in both time and space. This study will
Table I. Summary for the major studies concerning the precipitation changes in China.
Study region
Precipitation indices
Time scales of precipitation changes
References
Yangtze River
Whole China
Yangtze River
Whole China
Whole China
Monthly precipitation
Annual precipitation
Monthly precipitation
Annual precipitation
Annual and seasonal
precipitation
Seasonal 1-day
maximum, annual mean
precipitation intensity
Annual and seasonal
total precipitation
Annual/seasonal
maximum precipitation
Monthly precipitation
Annual precipitation and
summer or winter
precipitation totals
Seasonal scale
Annual scale
Seasonal scale
Decadal scale
Annual and seasonal scale
Becker et al., 2006
Chen et al., 1991
Jiang et al., 2007
Wang et al., 2004
Wang and Zhou, 2005
Annual scale
Zhai et al., 1999
Annual and seasonal scale
Zhai et al., 2005
Annual and seasonal scale
Zhang et al., 2009d
Seasonal scale
Annual and seasonal scale
Zhang et al., 2009a
Zhang et al., 2009b
Whole China
Whole China
Yangtze River
Whole China
Pearl River
Copyright  2010 Royal Meteorological Society
Int. J. Climatol. 31: 1665–1678 (2011)
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STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
Figure 1. Meteorological stations considered in this study and the ten
drainage basins. The solid dots denote the rain stations. Numbers denote
the ten drainage basins: 1, Songhuajiang River; 2, Liaohe River; 3,
Haihe River; 4, Yellow River; 5, Huaihe River; 6, Yangtze River; 7,
SE rivers (rivers in the southeast China); 8, Pearl River; 9, southwest
rivers (rivers in the southwest China); 10, northwest rivers (rivers in
the northwest China).
provide an entire picture of average and extreme
behaviours of precipitation in China and underlying atmospheric circulation background.
2.
Data and methodology
Daily precipitation data of 590 rain stations during
1960–2005 were collected in this study, which were
provided by the National Climate Center of China Meteorological Administration. The spatial distribution of rain
stations over China is shown in Figure 1. The missing
data of 1 or 2 days are replaced by the average precipitation values of the neighbouring days. If consecutive
days have missing data, the missing values are replaced
with long-term averages of the same days. We assumed
that this gap-filling method will have no influence on the
long-term temporal trend. Furthermore, the data consistency was checked by the double-mass method and the
result showed that all the data series used in the study
are consistent (Zhang et al., 2009d).
The precipitation indices are used in other studies (Tebaldi et al., 2006; Fatichi and Caporali, 2009).
Based on the previous studies, in this article, precipitation indices are defined as (1) total annual precipitation (TAP); (2) total precipitation in summer (JJA)
denoted as TSP; (3) total precipitation in winter (DJF)
denoted as TWP; (4) number of wet days with precipitation >1 mm on annual basis (NWa) and seasonal basis
(NWs for summer and NWw for winter); (5) annual
and seasonal changes in precipitation intensity defined
as mean daily precipitation of wet days in summer (PIs),
winter (PIw) and on annual basis (PIa); (6) number of
days (with respect to wet days with daily precipitation
>1 mm) with daily precipitation exceeding 75th (ND75)
and falling below 25th percentiles (ND25) on seasonal
(NDs75, NDs25 for summer; NDw75, NDw25 for winter) and annual basis (NDa75, NDa25); (7) total precipitation of ND75 and ND25 denoted by T75 and T25,
respectively (Ts75, Ts25 for summer; Tw75, Tw25 for
Copyright  2010 Royal Meteorological Society
winter and Ta75, Ta25 for annual); (8) precipitation intensity defined as T75/ND75 and T25/ND25 denoted by
PI75 and PI25, respectively (PIs75, PIs25 for summer;
PIw75, PIw25 for winter and PIa75, PIa25 for annual);
(9) fraction of annual and seasonal total precipitation due
to events exceeding 75th percentile and falling below
25th percentile. These events are denoted as F75 and F25,
respectively. Fs75 and Fs25 denote fraction of TSP due to
events exceeding 75th percentile and falling below 25th
percentile. Following the same definition rules, Fw75 and
Fw25 for winter and Fa75 and Fa25 for annual. For the
sake of clear presentation, we summarize all the precipitation indices and their meanings in Table II.
For further understanding of the atmospheric circulation patterns behind the spatial and temporal patterns
of precipitation regimes, the moisture and related transport features of the whole ps layer (surface pressure)
−300 hPa will be explored based on the NCAR/NCEP
reanalysis data (Zhang et al., 2008a; 2008b) from 1960 to
2005. In the actual atmosphere, the moisture is very low
over 300 hPa, so p = 300 hPa will be used in the calculation. The zonal moisture transport flux (QU ), meridional
moisture transport flux (QV ) and whole layer moisture
budget (QT ) at regional boundaries were calculated based
on the following equations (Miao et al., 2005; Zhang
et al., 2008b):
Qv (x, y, t) =
QW =
1
g
ϕ2
p
q(x, y, p, t)v(x, y, p, t)dp
ps
Qu (λ1 , y, t) QE =
ϕ1
QS =
λ2
ϕ2
Qu (λ2 , y, t)
ϕ1
Qv (x, ϕ1 , t) QN =
λ1
λ2
Qv (x, ϕ2 , t)
λ1
QT = QW − QE + QS − QN
where u and v are the zonal and meridional components
of the wind field, respectively, q is the specific humidity,
ps is surface pressure, p is atmospheric top pressure,
g is acceleration of the gravity, QW , QE , QS , QN are
the West, East, South and North regional boundaries,
respectively, and ϕ1 , ϕ2 , λ1 , λ2 are the latitude and
longitude according to the regional boundaries (Miao
et al., 2005).
In this study, simple linear regressive technique and the
MK are used to detect the trends and associated significance in the precipitation regimes. The rank-based MK
method (Mann, 1945; Kendall, 1975) is a nonparametric
method and is commonly used to assess the significance
of monotonic trends in hydro-meteorological series (Alan
et al., 2003; Yue and Pilon, 2004; Gao et al., 2007; Zhang
et al., 2008a). MK technique is highly recommended for
general use by the World Meteorological Organization
(Mitchell et al., 1966). The significance level used in this
study is 0.05.
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Table II. Indices of precipitation regimes considered in this study.
Seasons
Abbreviation
Definitions
Annual
TAP
Sum of precipitation of all wet days of a year. Wet day in this study is defined as the rainy
day with precipitation >1 mm
Sum of the days with precipitation of >1 mm
Mean daily precipitation of wet days with precipitation of >1 mm
Number of days with daily precipitation exceeding 75th percentile on the annual basis
This index is defined as the ratio of the total precipitation of days with precipitation exceeding
75th percentile to the TAP amount
This index is defined as the mean daily precipitation of days with precipitation of >75th
percentile
Number of days with daily precipitation falling below 25th percentile on annual basis
This index is defined as the ratio of the total precipitation of days with precipitation falling
below 25th percentile to the TAP amount
This index is defined as the mean daily precipitation of days with precipitation of <25th
percentile
Sum of precipitation of all wet days in summer
Sum of the days with precipitation of >1 mm in summer
Mean daily precipitation of wet days in summer
This index is defined as the ratio of the total precipitation of wet days in summer to the TAP
amount
Number of days with daily precipitation exceeding 75th percentile in summer
This index is defined as the ratio of the total precipitation of days with precipitation exceeding
75th percentile to the total precipitation amount in summer
This index is defined as the mean daily precipitation of days with precipitation of >75th
percentile in summer
Number of days with daily precipitation falling below 25th percentile in summer
This index is defined as the ratio of the total precipitation of days with precipitation falling
below 25th percentile to the total precipitation amount in summer
This index is defined as the mean daily precipitation of days with precipitation of <25th
percentile
Sum of precipitation of all wet days in winter
Sum of the days with precipitation of >1 mm in winter
Mean daily precipitation of wet days in winter
This index is defined as the ratio of the total precipitation of wet days in winter to the TAP
amount
Number of days with daily precipitation exceeding 75th percentile in winter
This index is defined as the ratio of the total precipitation of days with precipitation exceeding
75th percentile to the total precipitation amount in winter
This index is defined as the mean daily precipitation of days with precipitation of >75th
percentile in winter
Number of days with daily precipitation falling below 25th percentile in winter
This index is defined as the ratio of the total precipitation of days with precipitation falling
below 25th percentile to the total precipitation amount in winter
This index is defined as the mean daily precipitation of days with precipitation of <25th
percentile in winter
Nwa
PIa
NDa75
Fa75
PIa75
NDa25
Fa25
PIa25
Summer
TSP
NWs
PIs
Fs
NDs75
Fs75
PIs75
NDs25
Fs25
PIs25
Winter
TWP
NWw
PIw
Fw
NDw75
Fw75
PIw75
NDw25
Fw25
PIw25
3.
3.1.
Results
Changes in annual precipitation regimes
In this study, we comprehensively investigate changes in
precipitation regimes over China and try to relate these
changing properties in both time and space to atmospheric
circulation on seasonal and annual basis. Figure 2(a)
shows increasing TAP in the lower Pearl River and the
Yangtze River basins. Upper Yangtze River and southwest rivers were also characterized by increasing TAP.
Larger magnitude increase of TAP could be observed
mainly in the east parts of the Yangtze River and the Pearl
River basins when compared to other regions of China.
Copyright  2010 Royal Meteorological Society
In addition, Figure 2(a) also illustrates slight increasing
TAP in the river basins of northwest China. Decreasing
TAP can be observed in the middle part of the Yangtze
River basin, a majority of Yellow River basin, northeast
part of Huaihe River, Songhuajiang River, Liaohe River
and Haihe River (Figure 2(a)). In summary, large magnitude of increase in TAP can be found mainly in the east
part of the Pearl River, the Yangtze River and also in the
southwest rivers and the west parts of the Yangtze River
basin. Figure 2(b) shows increasing wet days (with precipitation >1 mm) on annual basis (NWa) in northwest
China. Significant increase in NWa can be found in north
parts of the northwest China. However, regions of China
Int. J. Climatol. 31: 1665–1678 (2011)
STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
(a)
(a)
(b)
(b)
(c)
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(c)
Figure 2. Spatial and temporal distribution of (a) annual total precipitation; (b) wet days with precipitation >1 mm and (c) precipitation
intensity defined as mean daily precipitation of wet days across China.
Dashed contours show decreasing trends and thick dashed contours
show significant decreasing trends. Shaded areas show significant
trends.
Figure 3. Spatial and temporal distribution of changes of precipitation
of >75th percentile. (A) Days with precipitation of >75th percentile;
(b) precipitation intensity defined by daily mean precipitation of days
with precipitation of >75th percentile and (c) ratio of total precipitation
of >75th percentile to the annual total precipitation. Solid contours
denote increasing trend and dashed contours show decreasing trends.
Shaded areas show significant trends.
east to 100 ° E were dominated by decreasing NWa. Precipitation intensity on annual basis is defined as mean
daily precipitation of wet days (PIa). Figure 2(c) illustrates increasing PIa in the east parts of the Yangtze River
basin, majority parts of the Pearl River basin and west
parts of the Huaihe River. North parts of the northwest
China are also characterized by increasing PIa. Stations
characterized by significant increase in PIa distributed
sporadically in the east parts of the Yangtze River basin,
southeast and north parts of the northwest China. Visual
comparison between Figure 2(a)–(c) indicates that the
increasing PIa in the east parts of the Yangtze River and
in the Pearl River was the result of increasing TAP and
decreasing NWa.
We define the precipitation concentration by the number of days with precipitation exceeding 75th and falling
below 25th percentiles and associated total precipitation
and precipitation intensity, i.e. NDa75, NDa25, PIa75,
PIa25, Fa75 and Fa25 as displayed in Table II. It can
be seen from Figure 3(a) that increasing NDa75 was
detected mainly in the northwest China in addition to
parts of the west and east Yangtze River basin. Stations characterized by significant increase in NDa75 distributed sporadically in the west part of the Yangtze
River basin and north parts of the northwest China
(Figure 3(a)). Regions of China east to 100 ° E were dominated by decreasing NDa75. Figure 3(b) shows that most
places of China were characterized by decreasing PIa75.
Stations characterized by increasing PIa75 distributed
mainly in the middle and east parts of the Yangtze River
basin. Similar spatial patterns of Fa75 can be observed
in Figure 3(c) when compared to those of PIa75 in
Copyright  2010 Royal Meteorological Society
Int. J. Climatol. 31: 1665–1678 (2011)
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Q. ZHANG et al.
(a)
in PIa25 were found mainly in the northwest China tending to imply wet-towards tendency in northwest China
(Figure 4(b)). Figure 4(c) shows that the entire China
was characterized by decreasing Fa25, showing decreasing precipitation concentration represented by Fa25.
3.2.
(b)
(c)
Figure 4. Spatial and temporal distribution of changes of precipitation
of <25th percentile. (a) Days with precipitation of <25th percentile;
(b) precipitation intensity defined by daily mean precipitation of days
with precipitation of <25th percentile and (c) ratio of total precipitation
of <25th percentile to the annual total precipitation. Solid contours
denote increasing trend and dashed contours show decreasing trends.
Shaded areas show significant trends.
Figure 3(b). Increasing Fa75 was found mainly in the east
parts of the Yangtze River basin, north part of northwest
China and some regions in the Pearl River basin. Majority
of places of China were dominated by decreasing Fa75.
Therefore, increasing precipitation concentration represented by increasing Fa75 mainly occurred in the lower
Yangtze River basin and some areas of the Pearl River
basin. Figure 4 illustrates spatial distribution of precipitation regimes defined by 25th percentile. Remarkable differences could be identified in Figure 4 in terms of spatial
patterns of precipitation regimes by 25th percentile when
compared to those shown in Figure 3. Increasing NDa25
was found mainly in the Yellow River basin, south parts
of the Haihe River and middle parts of the Yangtze
River, showing dry-towards tendency in these regions
(Figure 4(a)). Significant decrease in NDa25 and increase
Copyright  2010 Royal Meteorological Society
Changes in precipitation regimes in summer
China is climatically controlled by East Asian Monsoon
system. Precipitation mainly occurs in summer; therefore, summer is always the flooding season in most parts
of China. In this section, we study the changing properties of precipitation regimes in summer. In this season, increasing TSP prevailed over China (Figure 5(a)).
Similar to TAP, larger magnitude increase of TSP was
observed in the middle and lower reaches of the Yangtze
River basin, in the southwest part of the Yangtze River
basin (Figure 5(a)) and also in the Pearl River basin.
Slight increase of TSP could also be found in northwest China. However, decreasing TSP had the controlling
position in the Yellow River basin, the northeast parts
of the Huaihe River, the Songhuajiang River and the
Liaohe River. Therefore, increase of TSP mainly occurred
in southeast China. The increase in magnitude of TSP
in northwest China and other regions of China were
much smaller when compared to that in southeast China.
NWs was decreasing in a majority of regions in China
(Figure 5(b)). Increasing NWs could be observed mainly
in the east part of the Yangtze River basin and in the west
corner of the northwest China. Significant decrease in
NWs marked by thick dashed lines could be found in east
parts of the Liaohe River and Haihe River. Figure 5(c)
shows that the regions characterized by increasing PIs
distributed in a scattered way across China. Generally,
middle, east and southwest parts of the Yangtze River
basin were featured by increasing and even significant
increase in PIs. Areas characterized by increasing PIs
distributed sporadically in the northwest China. Still, it
can be found from Figure 5(c) that decreasing PIs prevailed over China. Figure 5(d) shows increasing Fs in
middle and lower Yangtze River basin, in the south part
of the Yellow River basin and in the west corner of northwest China. Most places of China were characterized by
decreasing Fs showing decreasing fraction of summer
precipitation in the TAP.
As for changes in NDs75 (Figure 6(a)), increasing
NDs75 was observed mainly in the lower Yangtze River
basin and west parts of the northwest China. Stations
characterized by significant increase in NDs75 distributed
sporadically in the lower Yangtze River basin and in the
northwest China. Decreasing NDs75 still dominated the
entire territory of China. Fewer regions were characterized by increasing PIs75 when compared to those featured by NDs75 (Figure 6(a) and (b)). Figure 6(b) shows
that no fixed spatial patterns could be identified for the
changes in PIs75. Decreasing PIs75 still prevailed across
China. When it comes to the variations of Fs75 shown in
Figure 6(c), increasing Fs75 could be identified mainly
in the middle and east parts of the Yangtze River basin.
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STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
(a)
(a)
(b)
(b)
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(c)
(c)
(d)
Figure 6. Changes of precipitation regimes defined as 75th percentile
in summer in space and time. (a) Wet days with precipitation of >75th
percentile; (b) precipitation intensity of days with precipitation of
>75th percentile and (c) ratio of total precipitation of >75th percentile
to summer total precipitation. Solid contours denote increasing trend
and dashed contours show decreasing trends. Shaded areas show
significant trends.
Figure 5. Changes of summer precipitation regimes in space and
time. (a) Summer total precipitation; (b) wet days with precipitation of
>1 mm; (c) precipitation intensity defined as mean daily precipitation
of wet summer days and (d) ratio of summer total precipitation to
annual total precipitation. Solid contours denote increasing trend and
dashed contours show decreasing trends. Shaded areas show significant
trends.
Besides, north, east and east parts of the northwest China
and some regions in the Pearl River basin were also
featured by increasing Fs75. Even so, decreasing Fs75
occurred in most regions of China (Figure 6(c)).
Copyright  2010 Royal Meteorological Society
Figure 7 shows spatial distribution of changes in
precipitation regimes defined by the 25th percentile.
It can be found in Figure 7(a) that increasing NDs25
mainly occurred in north China, such as east parts of
Songhuajiang River, Liaohe River and Haihe River. In
addition, some regions in the upper Yangtze River and
upper Pearl River were also characterized by increasing
NDs25. Decreasing NDs25 was found in middle and west
China. Significant decrease in NDs25 was observed in
the southwest part of the northwest China (Figure 7(a)).
Figure 7(b) demonstrates that significant decrease in
PIs25 occurred mainly in north China. Only a couple
of stations were characterized by significant increase in
PIs25 and these stations mainly distributed in northwest
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Q. ZHANG et al.
(a)
(a)
(b)
(b)
(c)
(c)
Figure 7. Changes of precipitation regimes defined as 25th percentile
in summer in space and time. (a) Wet days with precipitation of <25th
percentile; (b) precipitation intensity of days with precipitation of
<25th percentile and (c) ratio of total precipitation of <25th percentile
to summer total precipitation. Solid contours denote increasing trend
and dashed contours show decreasing trends. Shaded areas show
significant trends.
(d)
China. Also, China was dominated by decreasing PIs25
though most stations showed no significant decrease in
PIs25. Similarly, China was dominated by decreasing
Fs25. Very few stations showed increasing Fs25.
3.3.
Changes in precipitation regimes in winter
Figure 8 illustrates spatial distribution of changes in precipitation regimes in winter. Similar to the changes in
summer precipitation regimes in terms of total seasonal
precipitation amount, larger magnitude of increase of
TWP was found mainly in the lower Yangtze River
basin and in the Pearl River basin. Besides, what is
different from changing patterns of TSP (Figure 5(a))
is increasing TWP prevailed over China. Fewer regions
Copyright  2010 Royal Meteorological Society
Figure 8. Changes of winter precipitation regimes in space and
time. (a) Winter total precipitation; (b) wet days with precipitation of
>1 mm; (c) precipitation intensity defined as mean daily precipitation
of wet winter days and (d) ratio of winter total precipitation to annual
total precipitation. Solid contours denote increasing trend and dashed
contours show decreasing trends. Shaded areas show significant trends.
were characterized by decreasing TWP. Regions dominated by decreasing TSP were characterized by increasing TWP, such as Songhuajiang River, Liaohe River
and Haihe River. Therefore, from the standpoint of
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STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
total seasonal precipitation, China tended to be wetter
in winter; comparatively, China came to be dryer in
summer. Similarly, when compared to changes in NWs
(Figure 5(b)), more areas were characterized by increasing NWw (Figure 8(b)). Specifically, increasing NWw
could be identified in the Songhuajiang River, the upper
Yellow River basin, the upper Yangtze River basin, the
lower Yangtze River basin and the majority of northwest
China. Significant increase in NWw could be observed
mainly in the upper Yangtze River basin, the lower
Yangtze River basin, the north part of northwest China
and the majority of the Songhuajiang River. Comparison
between Figures 5(b) and 8(b) indicates that larger extent
of areas and more stations showed increasing NWw when
compared to NWs. This result also supports the viewpoint that winter in China came to be wetter and summer
tended to be dryer. As for PIw, decreasing PIw could
be identified mainly in the lower Yangtze River basin
and in the Pearl River basin. In addition, increasing PIw
could also be observed in the upper Yangtze River basin
and the upper Yellow River basin. North parts of the
northwest China and the Songhuajiang River were also
dominated by increasing and even significant increase
in PIw. Figure 8(d) shows spatial patterns of Fw over
China. Increasing Fw indicated increasing precipitation
in winter or more seasonal shifts of precipitation in winter when compared to other seasons. It can be seen from
Figure 8(d) that increasing Fw was identified mainly in
the lower and the upper Yangtze River basin, the upper
Pearl River basin, the Yellow River, the Songhuajiang
River and parts of the northwest China. Decreasing Fw
was found in the Liaohe River, the Haihe River and the
middle Yangtze River basin.
Figure 9 shows changes in precipitation regimes
defined by the 75th percentile. Increasing NDw75 was
detected mainly in the lower Yangtze River basin, east
parts of Huaihe River and also in the Pearl River basin
(Figure 9(a)). Besides, increasing NDw75 could also be
found in the north part of the northwest China. The majority of China was characterized by decreasing NDw75,
though the decreasing trends were not significant at
>95% confidence level. Figure 9(b) shows increasing
Fw75 in southeast China, such as the lower Yangtze
River basin, the SE rivers and the Pearl River basin.
The rest of the regions of China were dominated by
decreasing Fw75. This result indicates increasing winter
precipitation fraction relative to the TAP, implying wettowards tendency in these regions in winter. Changes in
precipitation regimes defined by the 25th percentile are
illustrated in Figure 10. Remarkable changing properties
of precipitation regimes were identified in Figure 10 that
NWw25 and Fw25 were decreasing across the entire territory of China. Regions dominated by significant decrease
in NWw25 and Fw25 scattered sporadically over China
without discernable spatial patterns. As for changes in
PIw25 (Figure 10(b)), increasing PIw25 could be identified in northwest China, parts of upper Yellow River basin
and upper Yangtze River basin. Besides, east parts of
the Songhuajiang River were characterized by increasing
Copyright  2010 Royal Meteorological Society
1673
(a)
(b)
Figure 9. Changes of precipitation regimes defined as 75th percentile
in winter in space and time. (a) Wet days with precipitation of >75th
percentile; (b) ratio of total precipitation of >75th percentile to winter
total precipitation. Solid contours denote increasing trend and dashed
contours show decreasing trends. Shaded areas show significant trends.
PIw25. The majority of China was featured by decreasing
PIw25 though the decreasing trends are not significant at
>95% confidence level.
3.4. Large-scale atmospheric circulation
The currently increasing temperature leads to alterations
of atmospheric water budget as a result of the high
sensitivity of the saturation vapour pressure in air to
temperature. Thus, perturbations in the global water cycle
are expected to accompany the climate warming (Allen
et al., 2002). Precipitation efficiency is the fraction of
the average horizontal water vapour flux in a region
that falls as precipitation. Precipitation is overwhelmingly
subject to moisture transportation and propagation and
deep convection (Heideman and Fritsch, 1988). Previous
studies demonstrated good relations between precipitation
changes, hydrological processes and moisture budget or
water vapour propagation (Zhang et al., 2009d, 2008a).
In this study, to better understand the changes in the
precipitation regimes in space and time, we analyse the
spatial and temporal variations of water vapour flux over
China with the aim to explore the underlying causes of
precipitation changes. This will help to shed light on
the mechanisms behind the precipitation changes and
benefit effective water resource management on river
basin scale under the changing climate, particularly under
the well-evidenced global warming. Figure 11 shows
trends of water vapour flux in latitudinal direction. The
upper panel shows trends of water vapour flux in space
Int. J. Climatol. 31: 1665–1678 (2011)
1674
Q. ZHANG et al.
(a)
(b)
(c)
Figure 10. Changes of precipitation regimes defined as 25th percentile
in winter in space and time. (a) Wet days with precipitation of <25th
percentile; (b) precipitation intensity of days with precipitation of
<25th percentile and (c) ratio of total precipitation of <25th percentile
to winter total precipitation. Solid contours denote increasing trend and
dashed contours show decreasing trends. Shaded areas show significant
trends.
and time for summer. It can be seen from Figure 11
that regions north to the Yangtze River basin were
characterized by decreasing water vapour flux. Parts of
the northwest China were also featured by decreasing
water vapour flux. North corner and southeast parts
of the northwest China were dominated by increasing
water vapour flux. In addition, it can be clearly observed
from the upper panel of Figure 11 that there was a
belt dominated by increasing water vapour flux which
extended westwards from the lower Yangtze River basin
to the upper Yangtze River basin and till the south part
of northwest China. Parts of the Pearl River basin were
dominated by decreasing water vapour flux. In winter
(middle panel of Figure 11), however, the majority of
regions in China was characterized by increasing water
vapour flux. Larger magnitude of increase of water
Copyright  2010 Royal Meteorological Society
vapour flux could be found in the Pearl River basin and
the lower Yangtze River basin and also in the northeast
China. Besides, increasing water vapour flux could also
be identified in the north part of the northwest China.
Decreasing water vapour flux could be found only in
the middle and south part of the northwest China. As
for the annual trends of water vapour flux (the lower
panel of Figure 11), regions north to the Yangtze River
basin were controlled by decreasing water vapour flux.
Increasing water vapour flux was observed mainly in the
regions south to the Yangtze River basin, including the
Yangtze River basin itself. North corner of the northwest
China was characterized by increasing water vapour and
decreasing water vapour flux was found in the middle
and the west part of the northwest China.
Figure 12 demonstrates spatial patterns of trends of
water vapour flux propagating in longitudinal direction.
Upper panel shows changes of water vapour flux in
summer. The remarkable features of trends of water
vapour flux in summer were decreasing water vapour
flux in the east China. Middle parts of the northwest
China were characterized by decreasing water vapour
flux. Increasing water vapour flux could be found in
the southwest China (upper panel of Figure 12). Middle
panel of Figure 12 shows distinctly different properties
of water vapour flux trends. Generally, regions east
to 100 ° E were largely controlled by increasing water
vapour flux. Furthermore, larger magnitude of increase in
water vapour flux could be found in the lower Yangtze
River basin and in the Pearl River basin. In addition,
northwest China was also characterized by increasing
water vapour flux, except middle parts of the northwest
China. Lower panel of Figure 12 shows similar spatial
patterns of trends of annual water vapour flux changes
when compared to those in summer (upper panel of
Figure 12). Decreasing water vapour flux dominated the
east China. Increasing water vapour flux occurred in
northwest China except middle parts of the northwest
China (lower panel of Figure 12). Generally, propagation
of the water vapour flux along the east China was
decreasing and this should be attributed to weakening
strength of East Asian Summer Monsoon. This point will
be discussed in more detail in the next section.
4.
Discussions
Spatial and temporal distribution of precipitation changes
exerts considerable impacts on water resource management on river basin scale and also on the agricultural activities. Particularly, the currently well-evidenced
global warming characterized by increasing temperature
has the potential to alter the distribution of water vapour
flux and moisture budget at regional and global scale.
And just because of this reason, the regional patterns of
the surface hydro-climatological changes tend to be more
complicated when compared to changes in temperature
series. Even so, under the influences of altered spatial distribution of atmospheric circulation, distribution of precipitation regimes in time and space will also be driven to
Int. J. Climatol. 31: 1665–1678 (2011)
STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
1675
Figure 11. Linear trends of water vapour flux (unit: kg/m·s) in latitudinal direction for summer (upper panel), winter (middle panel) and annual
(lower panel).
shift annually and seasonally and the direct consequences
of altered precipitation changes are the decreasing and/or
increasing runoff at regional or global scale (Milly et al.,
2005), which posed new challenges for the water resource
management. China is climatically characterized by various climate zones, from arid, semi-arid, semi-humid, to
Copyright  2010 Royal Meteorological Society
humid climates. Different intensity of human activities
and various underlying surface properties can be identified within the entire territory of China. Therefore, different regional or local responses of precipitation regimes to
global climate changes could be expected. Our previous
studies indicated weaker East Asian Summer Monsoon
Int. J. Climatol. 31: 1665–1678 (2011)
1676
Q. ZHANG et al.
Figure 12. Linear trends of water vapour flux (unit: kg/m·s) in longitudinal direction for summer (upper panel), winter (middle panel) and annual
(lower panel).
during 1975–2005 when compared to 1961–1974 (Zhang
et al., 2008a). The spatial distribution patterns of the
geopotential height in the Eurasia and west Pacific Ocean
do not benefit the northward propagation of the water
vapour flux. Decreasing transportation of water vapour
flux in the longitudinal direction in the east China further
Copyright  2010 Royal Meteorological Society
corroborates this viewpoint. Increasing water vapour flux
could be identified in northwest China except in the middle parts of the northwest China. Propagation of water
vapour flux in latitudinal direction was decreasing in
regions north to the Yangtze River basin. Increasing water
vapour flux in latitudinal direction could be observed
Int. J. Climatol. 31: 1665–1678 (2011)
STATISTICAL BEHAVIOURS OF PRECIPITATION IN CHINA
mainly in south China. This kind of spatial pattern of
water vapour flux decided the spatial changes in precipitation regimes. Precipitation in north China was decreasing
and was increasing in south China, showing tremendous
influences of propagation of water vapour flux on changes
in precipitation regimes in time and space. In addition,
visual comparison of the aforementioned figures showed
good agreement in the spatial distribution of precipitation
regimes and that of trends in water vapour flux. What
deserves attention is the generally increasing precipitation regimes defined by thresholds or total annual and
seasonal precipitation across the entire territory of China
in winter. However, the precipitation changes in summer
present adverse changing properties. This phenomenon
manifested wetting tendency of winter and drying trend of
summer. We also found that the Pearl River basin tended
to be wetter in winter and dryer in summer. Wet tendency
of the Pearl River basin was reflected by increasing number of wet winters across the Pearl River basin and this
could be attributed to increasing moisture content and
moisture budget in winter (Zhang et al., 2009b). Now,
based on the results of this study, we can say that the wet
tendency dominated the majority of the territory of China.
In addition, study on the precipitation regimes defined by
the 75th and 25th percentiles indicated increasing precipitation concentration in the lower and the upper Yangtze
River and also in the Pearl River basin, the northwest
China. Based on the aforementioned, we can say that,
under the influences of global warming, the winter came
to be wetter and the summer dryer. In addition, north
China (regions north to the Yangtze River basin) came
to be controlled by dry tendency; wet tendency dominates the south China, i.e. regions south to the Yangtze
River basin, including the Yangtze River basin itself. The
northwest China was also in wet tendency which is due
to increasing propagation of water vapour flux in longitudinal direction.
5.
Conclusions
In this study, we systematically analyse changing properties of average regime and the extreme behaviour of
the precipitation process over China. Precipitation concentration defined as the ratio of total precipitation of
the 75th and 25th percentiles to the annual and seasonal total precipitation is also studied in terms of its
changes in space and time. To better understand causes
and mechanisms behind these changing characteristics of
precipitation regimes, atmospheric circulation of water
vapour flux based on NCAR/NCEP reanalysis dataset is
also analysed. We obtain some interesting and important
conclusions based on the aforementioned analyses.
1. Increasing precipitation mainly occurred in the middle
and lower Yangtze River basin and in the Pearl River
basin. Slight increase of precipitation could also be
observed in the northwest China. On the contrary,
north China (regions north to the Yangtze River
Copyright  2010 Royal Meteorological Society
1677
basin) was dominated by decreasing precipitation
regimes. Precipitation concentration and precipitation
intensity was increasing in the lower Yangtze River
basin and also in the north and south parts of the
northwest China. No fixed spatial patterns could be
found for changes in precipitation regimes. Stations
characterized by significant trends usually distributed
sporadically across China showing inhomogeneous
distribution of precipitation changes.
2. Remarkable seasonal shift of precipitation changes
could be detected in China. Generally, winter came
to be wetter and summer tended to be dryer. It was
particularly the case for the northeast China, the upper
and the lower Yangtze River, the Pearl River basin
and the northwest China. Slight wet tendency could
also be found in the Yellow River which was reflected
by increasing ratio of winter total precipitation to the
annual total precipitation. These altered precipitation
changes pose new challenges for the water resource
management and sound arrangement of agricultural
activities on river basin scale under the changing
environment. Timely and effective policy making
should be carried out accordingly based on changing
precipitation scenarios and altered humid conditions
in different parts of China.
3. Spatial patterns of changes in precipitation regimes
matched well with the trends of water vapour flux over
China. With respect to the water vapour flux in latitudinal direction, in summer, the Yangtze River basin
was controlled by a belt characterized by increasing
water vapour flux. On annual basis, the Yangtze River
basin and the Pearl River basin were both characterized by increasing water vapour flux. Decreasing
water vapour flux in north China led to decreasing precipitation. In the northwest China, the regions
dominated by increasing precipitation regimes were
controlled by increasing water vapour flux showing
tremendous influences of water vapour flux propagation on changes of precipitation in time and space.
Decreasing water vapour flux in longitudinal direction dominated in the east China could be attributed
to weakening East Asian Summer Monsoon (Zhang
et al., 2009c). Weaker East Asian Summer Monsoon
in recent decades did benefit northward propagation of
water vapour flux and had potential to cause increasing
moisture content and moisture budget in the regions
south to the Yangtze River basin. Furthermore, altered
atmospheric moisture, temperature fields and shifts in
strength of Asian monsoon could have driven across
the board shifts in the precipitation intensity and precipitation regimes in the south and northwest China.
Acknowledgements
This work was financially supported by the ‘985 Project’
(Grant No. 37000-3171315), the Program for Outstanding
Young Teachers of the Sun Yat-sen University (Grant
No.: 2009-37000-1132381), the Key National Natural
Science Foundation of China (Grant No.: 50839005), the
Int. J. Climatol. 31: 1665–1678 (2011)
1678
Q. ZHANG et al.
Scientific Project of Xinjiang (Grant No.: 200931105),
the Program of Introducing Talents of Discipline to
Universities – the 111 Project of Hohai University, and
by the KLME (Grant No. KLME0801). Thanks should
be owed to the National Climate Centre of China for
providing meteorological data. Cordial gratitude should
be extended to the professional comments and advices
from the two anonymous reviewers and the editor, Prof.
Dr Glenn McGregor, which greatly improved the quality
of this article.
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