Changming Liu

A Gauge-Based Analysis of Daily Precipitation over East Asia

Abstract A new gauge-based analysis of daily precipitation has been constructed on a 0.5° latitude–longitude grid over East Asia (5°–60°N, 65°–155°E) for a 26-yr period from 1978 to 2003 using gauge observations at over 2200 stations collected from several individual sources. First, analyzed fields of daily climatology are computed by interpolating station climatology defined as the summation of the first six harmonics of the 365-calendar-day time series of the mean daily values averaged over a 20-yr period from 1978 to 1997. These fields of daily climatology are then adjusted by the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) monthly precipitation climatology to correct the bias caused by orographic effects. Gridded fields of the ratio of daily precipitation to the daily climatology are created by interpolating the corresponding station values using the optimal interpolation method. Analyses of total daily precipitation are finally calculated by multiplying the daily climatology b...

Determination of daily evaporation and evapotranspiration of winter wheat and maize by large-scale weighing lysimeter and micro-lysimeter

Daily evapotranspiration of irrigated winter wheat (Triticum aestivum L.) and maize (Zea mays L.) were determined for five seasons between 1995 and 2000 using a large-scale weighing lysimeter, and soil evaporation for each crop was measured for one season using two micro-lysimeters at Luancheng Station in the North China Plain. The results showed that total water consumption averaged 453 and 423 mm for winter wheat and maize grown without water deficit. The water consumption of winter wheat during its growth period greatly exceeds the precipitation, which ranges from 50 mm in dry years to 150 mm in wet years. Consequently, supplemental irrigation is very important to winter wheat production in the region. The average crop coefficient during the whole growth period was 0.93 for winter wheat and 1.1 for maize. Evaporation from the soil surface took up 29.7 and 30.3% of the total evapotranspiration for winter wheat and maize, respectively, equaling an annual loss of more than 250 mm water. Thus, reducing soil evaporation could be one of the most important water-saving measures in this serious water deficit region. Leaf area index (LAI) and moisture in the surface soil greatly affect the ratio of soil evaporation to total evapotranspiration. The relationship between this ratio and surface soil moisture and leaf area index was established, and can help to improve field water utilization efficiency.

Multi-decadal trends in global terrestrial evapotranspiration and its components

Evapotranspiration (ET) is the process by which liquid water becomes water vapor and energetically this accounts for much of incoming solar radiation. If this ET did not occur temperatures would be higher, so understanding ET trends is crucial to predict future temperatures. Recent studies have reported prolonged declines in ET in recent decades, although these declines may relate to climate variability. Here, we used a well-validated diagnostic model to estimate daily ET during 1981–2012, and its three components: transpiration from vegetation (Et), direct evaporation from the soil (Es) and vaporization of intercepted rainfall from vegetation (Ei). During this period, ET over land has increased significantly (p < 0.01), caused by increases in Et and Ei, which are partially counteracted by Es decreasing. These contrasting trends are primarily driven by increases in vegetation leaf area index, dominated by greening. The overall increase in Et over land is about twofold of the decrease in Es. These opposing trends are not simulated by most Coupled Model Intercomparison Project phase 5 (CMIP5) models, and highlight the importance of realistically representing vegetation changes in earth system models for predicting future changes in the energy and water cycle.

Recent changes in pan-evaporation dynamics in China

[1] Pan‐evaporation (Epan) as the indicator of atmospheric evaporative demand has decreased worldwide with climate change in the last decades, which is called “Pan Evaporation Paradox”. This study investigates the recent changes in Epan dynamics in China using the observed Epan records for the period 1960–2007. The records show that Epan decreased in China from 1960 to 1991 by �5.4 mm yr �2 . The attribution results show that the significant decreases (P 0.1). The results show that increasing air temperature dominated the change in Epan, which offset the effect of wind speed and led to the increase in Epan. Citation: Liu, X., Y. Luo, D. Zhang, M. Zhang, and C. Liu (2011), Recent changes in pan‐evaporation dynamics in China, Geophys. Res. Lett., 38, L13404, doi:10.1029/2011GL047929.

Decadal Climatic Variability, Trends, and Future Scenarios for the North China Plain

Observed decadal climatic variability and trends for the north China plain (NCP) are assessed for significance with Kendall’s test and discussed in light of future climate scenarios from multi-GCM outputs from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The results indicate that the NCP has become warmer and drier over the last four decades. The annual precipitation has declined by about 43.9 mm (6.7%, although not statistically significant), and the annual means of daily mean, maximum, and minimum temperatures have increased by 0.838, 0.188, and 1.468C, respectively, during the past 40 yr. Both trends for annual means of daily mean and minimum temperatures are statistically significant. The future climate of the NCP is projected to be warmer and, with less confidence, wetter. However, streamflow could decline under these projections, based on the results of the two-parameter climate elasticity of streamflow index. This will produce serious challenges for water resources management and likely lead to exacerbated problems for agriculture, industry, urban communities, and the environment.

Decadal Trends in Evaporation from Global Energy and Water Balances

AbstractSatellite and gridded meteorological data can be used to estimate evaporation (E) from land surfaces using simple diagnostic models. Two satellite datasets indicate a positive trend (first time derivative) in global available energy from 1983 to 2006, suggesting that positive trends in evaporation may occur in “wet” regions where energy supply limits evaporation. However, decadal trends in evaporation estimated from water balances of 110 wet catchments do not match trends in evaporation estimated using three alternative methods: 1) , a model-tree ensemble approach that uses statistical relationships between E measured across the global network of flux stations, meteorological drivers, and remotely sensed fraction of absorbed photosynthetically active radiation; 2) , a Budyko-style hydrometeorological model; and 3) , the Penman–Monteith energy-balance equation coupled with a simple biophysical model for surface conductance. Key model inputs for the estimation of and are remotely sensed radiation an...

Dramatic decrease in streamflow from the headwater source in the central route of China's water diversion project: Climatic variation or human influence?

The Danjiangkou Reservoir is the headwater source of the central route of Chinas South to North Water Diversion Project (SNWDP). Average annual streamflow into the Reservoir was 40.97 km(3) from 1951 to 1989, while it was 31.64 km(3) from 1990 to 2006. Between the two periods, the average annual streamflow was reduced by 9.33 km(3), accounting for 71.8% of the proposed amount of water diversion of the central route (13 km3 per year). The sharply decreasing streamflow would inevitably have negative impacts on the implementation of the SNWDP. The reasons for the decrease in streamflow should be investigated before developing any adaption strategies. In this study, the impacts of climatic variation and human activities on streamflow were evaluated by a climate elasticity method. The results show that the impact of climatic variation (indicated by precipitation and potential evapotranspiration) was responsible for 84.1-90.1% of the streamflow reduction, while human activities or other indentified uncertainties contributed 9.9-15.9% of the streamflow reduction. The observed 69.89 mm decrease in average annual precipitation contributed 81.6-87.3% of the decrease in streamflow. According to the observed data during the study period, the planned water diversion could lead to an ecological disaster of the downstream area of the Danjiangkou Reservoir in certain years. We suggest that the water diversion from the Danjiangkou Reservoir should be conducted in an adaptive manner to avoid such an adverse consequence, instead of the current plan of a fixed annual amount of water.

Spatial and temporal change in the potential evapotranspiration sensitivity to meteorological factors in China (1960–2007)

Potential evapotranspiration (E0), as an estimate of the evaporative demand of the atmosphere, has been widely studied in the fields of irrigation management, crop water demand and predictions in ungauged basins (PUBs). Analysis of the sensitivity of E0 to meteorological factors is a basic research on the impact of climate change on water resources, and also is important to the optimal allocation of agricultural water resources. This paper dealt with sensitivity of E0 over China, which was divided into ten drainage systems, including Songhua River basin, Liaohe River basin, Haihe River basin, Yellow River basin, Yangtze River basin, Pearl River basin, Huaihe River drainage system, Southeast river drainage system, Northwest river drainage system and Southwest river drainage system. In addition, the calculation method of global radiation in Penman-Monteith formula was improved by optimization, and the sensitivities of Penman-Monteith potential evapotranspiration to the daily maximum temperature (STmax), daily minimum temperature (STmin), wind speed (SU2), global radiation (SRs) and vapor pressure (SVP) were calculated and analyzed based on the long-term meteorological data from 653 meteorological stations in China during the period 1960–2007. Results show that: (1) the correlation coefficient between E0 and pan evaporation increased from 0.61 to 0.75. E0 had the decline trends in eight of ten drainage systems in China, which indicates that “pan evaporation paradox” commonly exists in China from 1960 to 2007. (2) Spatially, Tmax was the most sensitive factor in Haihe River basin, Yellow River basin, Huaihe River drainage system, Yangtze River basin, Pearl River basin and Southeast river drainage system, and VP was the most sensitive factor in Songhua River Basin, Liaohe River basin, Northwest river drainage system while Rs was the most sensitive factor in Southwest river drainage system. For the nation-wide average, the most sensitive factor was VP, followed by Tmax, Rs, U2 and Tmin. In addition, the changes in sensitivity coefficients had a certain correlation with elevation. (3) Temporally, the maximum values of STmax and SRs occurred in July, while the maximum values of STmin, SVP and SU2 occurred in January. Moreover, trend analysis indicates that STmax had decline trends, while STmin, SU2, SRs and SVP had increasing trends.

Estimation of winter wheat evapotranspiration under water stress with two semiempirical approaches

based on ET estimations would allow limited groundwater supplies to be used more efficiently for wheat proWinter wheat (Triticum aestivum L.) is one of most important duction. crops in the North China Plain. However, soil water deficit (SWD) often occurs due to lack of precipitation in its growing season. In this To calculate crop ET over seasonal time, it is essential study, we introduce two semiempirical approaches, a recharge model to simplify ET-estimated methods in the NCP due to and the crop coefficient (Kc)–reference evapotranspiration (ET0) aplack of enough weather, soil, and crop physiological proach, to estimate wheat actual evapotranspiration (ETa) under no data. Thus, it is convenient and suitable to use empirical SWD and slight and severe SWD conditions. The recharge model approaches to estimate crop ETa. These methods are allocated ET0 to reference evaporation and reference transpiration mainly based on the Kc–ET0 approach and on soil water as a function of leaf area index. In the model, ETa is limited by soil balance (SWB) calculation (Rana and Katerji, 2000). water content, and crop water extraction for ETa is distributed through When limited by soil water content, water uptake for the soil profile as exponential functions of soil and root depth. The crop transpiration from a point in a soil profile is an exKc–ET0 approach regarded ETa under the SWD condition as a logarithponential function of soil and root depth (Novak, 1987). mic function of soil water availability. Under no SWD condition, the recharge model simulated 10-d ETa with a root mean square error The Kc–ET0 approach estimates crop ETa as a fraction (RMSE) of 5.58 mm and a bias of 0.95 mm compared with measureof the ET0 (Allen et al., 1998). The Kc–ET0 approach ments from a large-scale weighing lysimeter. The two approaches is simple because the method calculates ETa only by both estimated seasonal evapotranspiration (ET) well compared with estimating ET0 and Kc as well as Ks (Doorenbos and the adjusted ET (from the soil water balance and the recharge model– Pruitt, 1977, p. 144; Kerr et al., 1993; Kang et al., 2000). simulated deep drainage). The recharge model, which simulated the Reference evapotranspiration can be estimated from seasonal ET with the RMSE of 27.8 mm and the bias of 8.0 mm, pan evaporation data (Doorenbos and Pruitt, 1977, was better than the Kc–ET0 approach (RMSE 31.7 mm and bias p. 144). It is also estimated with more data-intensive 33.1 mm). The seasonal pattern of soil water stress coefficient (Ks) methods, e.g., the modified Penman equation and the showed that there were faster water losses at grain-filling stage than modified Penman–Monteith formula (Doorenbos and at other stages. Pruitt, 1977, p. 144; Allen et al., 1989; Allen, 2000). The crop coefficient, Kc, can be determined by the ratio of crop ETa under no SWD condition to ET0. The soil T North China Plain (NCP), one of the most water stress coefficient, Ks, is mainly estimated by a important centers of agricultural production in relationship to the average soil moisture contents or China, contains about 22% of the cultivated land in the matric potential in a soil layer. And, it can usually be country but less than 4% of the water resources (Jin et estimated by an empirical formula based on soil water al., 1999). Winter wheat is one of the most important contents or relative soil available water contents (Jensen crops in the NCP. Serious water shortage problems exist et al., 1970). Poulovassilis et al. (2001) assumed that Ks in the winter wheat season, and the situation has been is an exponential function of the soil water content. aggravated by an increase in agricultural and industrial Kang et al. (2000) found that Ks is highly related to soil demand for groundwater over the last 20 yr (Zhang water availability (Aw) in a logarithmic function. The et al., 2001). Another reason the groundwater table is Kc–ET0 approach has been successfully applied at many persistently declining is that NCP farmers irrigate exceslocations (Kang et al., 2000; Abdelhadi et al., 2000; Alsively by pumping groundwater, which unnecessarily len, 2000; Poulovassilis et al., 2001; Sepaskhah and Anmaximizes crop transpiration and soil evaporation and dam, 2001; De Medeiros et al., 2001; Liu et al., 2002). increases the proportion of nonbeneficial soil water conActual evapotranspiration can also be estimated from sumption (Zhang et al., 2002). Irrigation management ET0, soil water content, and leaf area index (LAI) (Campbell and Norman, 1998; Kendy et al., 2003). ReferYongqiang Zhang, Qiang Yu, and Changming Liu, Luancheng Agroecosyst. Stn., Inst. of Geogr. Sci. and Nat. Resour. Res., Chinese Acad. ence evapotranspiration is partitioned into reference of Sci., Bldg. 917, Datun Rd., Beijing 100101, China; Yongqiang Zhang evaporation from soil and reference transpiration from and Xiying Zhang, Shijiazhuang Inst. of Agric. Modernization, Chiplants, and the ratio of reference evaporation to refernese Acad. of Sci., 286 Huaizhong Rd., Shijiazhuang 050021, P.R. China; and Jie Jiang, Inst. of Environ. Sci., Beijing Normal Univ., Beijing 100875, P.R. China. Received 31 Oct. 2002. *Corresponding Abbreviations: Aw, soil water availability; ET, evapotranspiration; author (zhangyq@igsnrr.ac.cn). ETa, actual evapotranspiration; ET0, reference evapotranspiration; Kc, crop coefficient; Ks, soil water stress coefficient; LAI, leaf area index; Published in Agron. J. 96:159–168 (2004).  American Society of Agronomy NCP, North China Plain; RMSE, root mean square error; SWB, soil water balance; SWD, soil water deficit; SWS, soil water storage. 677 S. Segoe Rd., Madison, WI 53711 USA

Dependence of trends in and sensitivity of drought over China (1961–2013) on potential evaporation model

The Palmer Drought Severity Index (PDSI) can lead to controversial results in assessing droughts responding to global warming. Here we assess recent changes in the droughts over China (1961–2013) using the PDSI with two different estimates, i.e., the Thornthwaite (PDSI_th) and Penman-Monteith (PDSI_pm) approaches. We found that droughts have become more severe in the PDSI_th but slightly lessened in the PDSI_pm estimate. To quantify and interpret the different responses in the PDSI_th and PDSI_pm, we designed numerical experiments and found that drying trend of the PDSI_th responding to the warming alone is 3.4 times higher than that of the PDSI_pm, and the latter was further compensated by decreases in wind speed and solar radiation causing the slightly wetting in the PDSI_pm. Interestingly, we found that interbasin difference in the PDSI_th and PDSI_pm responses to the warming alone tends to be larger in warmer basins, exponentially depending on mean temperature.