Observed Changes in the Distributions of Daily Precipitation Frequency and Amount over China from 1960 to 2013

Abstract

26In this study, daily precipitation (P) records for 1960-2013 from 632 stations in China were 27 homogenized and then applied to study the changes in the frequency of dry (P=0) and trace 28 (0<P<0.1mm/day) days and all precipitation events (P≥0.1mm/day), and the frequency and 29 accumulated amount of precipitation at different intensities. Over China as a whole, very heavy 30 precipitation (P≥50mm/day) events have increased significantly from 1960-2013, while light 31 (0.1≤P<10mm/day) and moderate (10≤P<25 mm/day) events have decreased significantly, 32 accompanying the significant increases of dry days and decreases of trace days. This indicates a 33 shift from light to intense precipitation, implying increased risks of drought and floods over 34 China since 1960. Although the consistent increases of dry days and decreases of trace days and 35 light and total precipitation days are seen over most of China, changes in other precipitation 36 categories exhibit clear regional differences. Over the Yangtze River valley (YZ) and Southeast 37 China (SE), very heavy precipitation events have increased while light precipitation events have 38 decreased. However, positive trends are seen for all precipitation categories over Northwest 39 (NW) China, while trends are generally negative over Southwest (SW), Northeast (NE) and 40 North China (NC). To examine the association with global warming, the dependence of the 41 precipitation change for each intensity category over China on global-mean temperature was 42 analyzed using interannual to decadal variations. Results show that dry and trace days, very 43 light and very heavy precipitation events exhibit larger changes per unit global warming than 44 medium-intensity precipitation events.45 3

Detectable Anthropogenic Shift toward Heavy Precipitation over Eastern China

“…Trenberth et al (2003) argued that precipitation intensity from storms is likely to increase with the increasing rate of water vapor (;7% K 21 ), which implies that precipitation frequency should decrease. This thermodynamic argument has roughly held true in many subsequent analyses of climate model projections (e.g., Sun et al 2007;Chou et al 2012;Lau et al 2013) and historical data (e.g., Goswami et al 2006;Qian et al 2007;Allan and Soden 2008;Liu et al 2009;Shiu et al 2012;Lau and Wu 2007;Westra et al 2013;Ma et al 2015).…”

“…As in Ma et al (2015), for a given station (grid) and year (season), precipitation frequency in each intensity interval is the ratio (in percent) of the number of days whose daily precipitation rate is within the corresponding intensity interval to the number of all days with data; the precipitation amount in each intensity bin is the accumulated precipitation amount over the precipitation days within the corresponding intensity interval. To estimate the regionally averaged precipitation amount and frequency at each intensity interval, at each station and model grid, the annual (seasonal) precipitation amount and frequency at each intensity bin were calculated.…”

Regional moisture budget associated with drought/flood events over China

“…Using both the climatological mean precipitation and the temperature increase from northwest China to southeast China ( Fig. 1), as in the 2013 China Climate Bulletin (CMA 2014) and also in Ma et al (2015), we divided China into six subregions. In this way, different subregions show different climate characteristics-for example, northwest China is cold and dry, and southeast China is relatively warm and wet.…”

Impacts of internal climate variability on meteorological drought changes in China

“…To focus on drought variations over large areas (rather than small spatial scale drought variations), a common approach is to divide mainland China into several regions (Wang, Lettenmaier, and Sheffield 2011;Ma et al 2015;Li, Zhou, and Chen 2015). Following the climate division defined in Ma et al (2015), mainland China is divided into seven regions (Figure 1(a)): northwest (NW), northeast (NE), North Center (NC), Yangtze River valley (YZ), southeast (SE), southwest (SW), and Western Tibet (WT).…”

“…Following the climate division defined in Ma et al (2015), mainland China is divided into seven regions (Figure 1(a)): northwest (NW), northeast (NE), North Center (NC), Yangtze River valley (YZ), southeast (SE), southwest (SW), and Western Tibet (WT). Monthly precipitation from both CESM_LE simulations and OBS are regionally averaged before they are further analyzed.…”