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Liu L.,Nanjing University | Liu L.,Guizhou Key Laboratory of Mountainous Climate and Resources | Wang T.,Nanjing University | Sun Z.,Academy of Military Medical Science | And 4 more authors.
Advances in Atmospheric Sciences | Year: 2012

Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames. Performances of three methods of coordinate rotation: double rotation (DR), triple rotation (TR), and classic planar-fit rotation (PF) were examined in terms of correction of eddy covariance flux. Using the commonly used DR and TR methods, unreasonable rotation angles are encountered at low wind speeds and cause significant run-to-run errors of some turbulence characteristics. The PF method rotates the coordinate system to an ensemble-averaged plane, and shows large tilt error due to an inaccurate fit plane over variable terrain slopes. In this paper, we propose another coordinate rotation scheme. The observational data were separated into two groups according to wind direction. The PF method was adapted to find an ensemble-averaged streamline plane for each group of hourly runs with wind speed exceeding 1. 0 m s -1. Then, the coordinate systems were rotated to their respective best-fit planes for all available hourly observations. We call this the PF10 method. The implications of tilt corrections for the turbulence characteristics are discussed with a focus on integral turbulence characteristics, the spectra of wind-velocity components, and sensible heat and momentum fluxes under various atmospheric stabilities. Our results show that the adapted application of PF provides greatly improved estimates of integral turbulence characteristics in complex terrain and maintains data quality. The comparisons of the sensible heat fluxes for four coordinate rotation methods to fluxes before correction indicate that the PF10 scheme is the best to preserve consistency between fluxes. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source


Ye Q.,Jiangxi Agricultural University | Ye Q.,China Agricultural University | Yang X.-G.,China Agricultural University | Liu Z.-J.,China Agricultural University | And 5 more authors.
Journal of Integrative Agriculture | Year: 2014

Based on climate data from 254 meteorological stations, this study estimated the effects of climate change on rice planting boundaries and potential yields in the southern China during 1951-2010. The results indicated a significant northward shift and westward expansion of northern boundaries for rice planting in the southern China. Compared with the period of 1951-1980, the average temperature during rice growing season in the period of 1981-2010 increased by 0.4°C, and the northern planting boundaries for single rice cropping system (SRCS), early triple cropping rice system (ETCRS), medium triple cropping rice system (MTCRS), and late triple cropping rice system (LTCRS) moved northward by 10, 30, 52 and 66 km, respectively. In addition, compared with the period of 1951-1980, the suitable planting area for SRCS was reduced by 11% during the period of 1981-2010. However, the suitable planting areas for other rice cropping systems increased, with the increasing amplitude of 3, 8, and 10% for ETCRS, MTCRS and LTCRS, respectively. In general, the light and temperature potential productivity of rice decreased by 2.5%. Without considering the change of rice cultivars, the northern planting boundaries for different rice cropping systems showed a northward shift tendency. Climate change resulted in decrease of per unit area yield for SRCS and the annual average yields of ETCRS and LTCRS. Nevertheless, the overall rice production in the entire research area showed a decreasing trend even with the increasing trend of annual average yield for MTCRS. © 2014 Chinese Academy of Agricultural Sciences. Source


Ye Q.,Jiangxi Agricultural University | Ye Q.,China Agricultural University | Yang X.,China Agricultural University | Dai S.,University of Nebraska - Lincoln | And 4 more authors.
Agricultural Water Management | Year: 2015

Rice is one of the main crops grown in southern China. Global climate change has significantly altered the local water availability and temperature regime for rice production. In this study, we explored the influence of climate change on suitable rice cropping areas, rice cropping systems and crop water requirements (CWRs) during the growing season for historical (from 1951 to 2010) and future (from 2011 to 2100) time periods. The results indicated that the land areas suitable for rice cropping systems shifted northward and westward from 1951 to 2100 but with different amplitudes. The land areas suitable for single rice-cropping systems (SRCS) and early double rice-cropping systems (EDRCS) decreased, whereas the land areas suitable for middle double rice-cropping systems (MDRCS) and late double rice-cropping systems (LDRCS) expanded significantly. Among the rice-cropping systems, the planting area suitable for SRCS was the largest during the historical period (1951-1980), whereas the suitable planting area for LDRCS was the largest during the future period (2070-2100). Spatially, the water requirement of rice during the growing season exhibited a decreasing trend from southeast to northwest from 1951 to 2010. Temporally, the regional water requirement of rice during the growing season decreased from 720mm (1951-1980) to 700mm (1981-2010) as a result of solar radiation and evapotranspiration. However, the water requirement was predicted to increase from 1027mm (2011-2040) to 1150mm (2071-2100). During the past six decades, the planting area suitable for double rice-cropping systems increased by 2.7×104km2 and, consequently, the CWR and irrigation water requirement (IWR) increased by 1.1×1010 and 8.8×109m3, respectively. In addition, under A1B scenarios, the CWR and IWR of double rice-cropping systems are expected to increase by 1.6×1011 and 1.2×1011m3, respectively, from 2071-2100 compared with the historical period of 1951-1980. The regional CWR and IWR were predicted to increase respectively by 8% and 6% from 2011 to 2040, by 17% and 19% from 2041 to 2070, and by 20% and 24% from 2071 to 2100 compared with 1951-1980. These increases can be attributed to climate warming, which expands the suitable planting area for multiple-cropping systems and extends the growing season for late-maturing rice varieties. Our study aims to provide a scientific guide for planning future cropping systems and optimizing water management in the southern rice cropping region of China. © 2015. Source


Liu L.,Nanjing University | Liu L.,Guizhou Key Laboratory of Mountainous Climate and Resources | Wang T.,Nanjing University | Li Z.,Nanjing University | And 4 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2011

To meet the requirements of regional atmospheric environment management, we brought forward the concept of air resource and the estimation and assessment methods. A case study was conducted for the west coast of Taiwan Strait. Based on the analysis of climate characteristics and various weather systems associated with high levels of air pollution occurring in this area, both regional and local meteorological fields were simulated with the Weather Research and Forecasting (WRF) model. The key factors that affected air resource significantly were selected from the meteorological fields and turbulence parameters. They acted as evaluating indicators of regional air resource. Each of the factors was classified and then graded to determine the weighted coefficient. The total scores of air resource in west Strait were estimated from the weighted sum of the respective factor scores. The levels of air resource were determined subsequently. Finally, spatial distribution of the overall scores and the levels of air resource were obtained. It showed that the air resource over the Strait was of the top grade (5) with the score 18. The grades in the rest were of 2 to 4 with the scores 14 to 18. In general, the air resource in the coastal area was most abundant, inland flat less and mountainous area the least, showing an inhomogeneous pattern. The results indicated that the method proposed in this paper was a reasonable solution to assess regional air resource. There will be a great application prospect for regulation and management of the atmospheric environment. Source


Ye Q.,China Agricultural University | Ye Q.,Jiangxi Agricultural University | Yang X.-G.,China Agricultural University | Dai S.-W.,China Agricultural University | And 3 more authors.
Journal of Integrative Agriculture | Year: 2013

The spatiotemporal characteristics of hydrothermal resources in southern rice production area of China have changed under the background of climate change, and this change would affect the effectiveness of hydrothermal resources during local rice growing period. According to the cropping system subdivision in southern rice production area of China during 1980s, this study used climate data from 254 meteorological stations and phonological data from 168 agricultural observation stations in the south of China, and adopted 6 international evaluation indices about the effectiveness of hydrothermal resources to analyze the temporal and spatial characteristics of hydrothermal resources during the growing period of single cropping rice system and double cropping rice system for 16 planting zones in the whole study area. The results showed that: in southern rice production area of China, the effectiveness of thermal resources of single cropping rice area (SCRA) was less than that of double cropping rice area (DCRA), whereas the effectiveness of thermal resources of both SARA and DCRA showed a decreasing trend. The index value of effective precipitation satisfaction of SCRA was higher than that of DCRA, nevertheless the index value of effective precipitation satisfaction of both SCRA and DCRA showed a decreasing trend. There was a significant linear relationship between effective thermal resource and water demand, likely water demand increased by 18 mm with every 100°C d increase of effective heat. Effective precipitation satisfaction index (EPSI) showed a negative correlation with effective heat, yet showed a positive correlation with effective precipitation. EPSI reduced by 1% when effective heat resource increased by 125°C d. This study could provide insights for policy makers, land managers or farmers to improve water and heat resource uses and rationally arrange rice production activities under global climate change condition. © 2013 Chinese Academy of Agricultural Sciences. Source

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