Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water de...Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water demand.Iran,with large climatic variability,is experiencing a serious water crisis due to limited water resources and inefficient agriculture.In order to overcome the issue of uneven distribution of weather stations,gridded Climatic Research Unit(CRU)data was applied to analyze the changes in potential evapotranspiration(PET),effective precipitation(EFFPRE)and WREQ.Validation of data using in situ observation showed an acceptable performance of CRU in Iran.Changes in PET,EFFPRE and WREQ were analyzed in two 30-a periods 1957-1986 and 1987-2016.Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast,more significant in summer and spring.However,EFFPRE decreased in the southeast,northeast,and northwest,especially in winter and spring.Analysis of annual trends revealed an upward trend in PET(14.32 mm/decade)and WREQ(25.50 mm/decade),but a downward trend in EFFPRE(-11.8 mm/decade)over the second period.Changes in PET,EFFPRE and WREQ in winter have the impact on the annual trend.Among climate variables,WREQ showed a significant correlation(r=0.59)with minimum temperature.The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran.With all changes in PET and WREQ,immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.展开更多
发展了一种同化窗口为1个月的陆面气温推广三维变分资料同化方法,并建立了逐日资料到月平均资料的观测算子。作为对该同化方法的初步检验,以2000年1月中国陆地区域时间分辨率低、空间分辨率较高且在高原地区与台站观测资料比较接近的CRU...发展了一种同化窗口为1个月的陆面气温推广三维变分资料同化方法,并建立了逐日资料到月平均资料的观测算子。作为对该同化方法的初步检验,以2000年1月中国陆地区域时间分辨率低、空间分辨率较高且在高原地区与台站观测资料比较接近的CRU(Climate Research Unit)月平均陆面气温资料作为观测,以时间分辨率高、空间分辨率较低且在高原地区与台站资料有较大误差的NCEP逐日气温资料作为背景场,采用背景误差协方差矩阵(简称B矩阵)的两种简化对角形式进行同化试验,得到高时空分辨率的格点陆面气温分析场,并进行对比分析和均方根误差检验。结果显示,由两种简化形式得到的逐日资料和月平均资料的质量均得到改善,在我国东南和中部大部分地区与台站观测基本一致,在青藏高原、新疆等台站稀疏地区与地形对应良好,为M-SDGVM模型或其他陆面过程模式高质量陆面气象驱动场的准备提供了一种新的手段。尤其在B矩阵中考虑了方差逐日变化的简化形式所得到的分析场整体上要优于不考虑的,这为最终在B矩阵中考虑协方差(即对推广三维变分同化不作简化)进一步改进同化效果打下了基础。展开更多
With rising population,decline in soil productivity and land-based conflicts,the per-capita land availability for cultivation is rapidly decreasing within Benue State,a largely agrarian and small-holder setting.This s...With rising population,decline in soil productivity and land-based conflicts,the per-capita land availability for cultivation is rapidly decreasing within Benue State,a largely agrarian and small-holder setting.This study attempts a local-level support for the actualisation of Sustainable Development Goal Number 2(“end hunger,achieve food security and improved nutrition,and promote sustainable agriculture”)by 2030.Using Multi-Criteria Decision Making(MCDM)method,remote sensing data from Climate Research Unit(CRU)and in-situ data from Nigeria Meteorological Agency(NIMET)were analyzed by GIS techniques to map the suitability of rice cultivation in the study area,with the integration of Normalized Difference Vegetation Index(NDVI),land cover,slope,temperature,precipitation and soil parameters(cation exchange capacity,pH,bulk density,organic carbon).We apply the various statistical parameters that include mean spatial NDVI;correlation coefficient,standard deviation and Root Mean Square(RMS)between CRU and NIMET data.Spatial regression trend analysis is conducted between CRU precipitation and NDVI and between CRU temperature and NDVI from 1985 to 2015.The results reveal that NDVI in highly suitable rice planting regions is higher than marginally suitable regions except in the months of October and November,which shows that the highly suitable regions will yield better than the marginally suitable regions during the dry season.Additionally,NDVI is seasonally bimodal in response to precipitation,meaning that vegetation vigor is more dependent on precipitation than temperature.Finally,the correlation coefficient,standard deviation and RMS between CRU and NIMET precipitation data shows 0.42,108,and 110,respectively,while these three factors between CRU and NIMET temperature data shows 0.88,1.60,and 0.86,respectively.In conclusion,the MCDM approach reveals that upland is more suitable for rice cultivation in Benue State when comparing with the area provided by the Global Land Cover and National Mappings Organization(GLCNMO)data.展开更多
文摘Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water demand.Iran,with large climatic variability,is experiencing a serious water crisis due to limited water resources and inefficient agriculture.In order to overcome the issue of uneven distribution of weather stations,gridded Climatic Research Unit(CRU)data was applied to analyze the changes in potential evapotranspiration(PET),effective precipitation(EFFPRE)and WREQ.Validation of data using in situ observation showed an acceptable performance of CRU in Iran.Changes in PET,EFFPRE and WREQ were analyzed in two 30-a periods 1957-1986 and 1987-2016.Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast,more significant in summer and spring.However,EFFPRE decreased in the southeast,northeast,and northwest,especially in winter and spring.Analysis of annual trends revealed an upward trend in PET(14.32 mm/decade)and WREQ(25.50 mm/decade),but a downward trend in EFFPRE(-11.8 mm/decade)over the second period.Changes in PET,EFFPRE and WREQ in winter have the impact on the annual trend.Among climate variables,WREQ showed a significant correlation(r=0.59)with minimum temperature.The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran.With all changes in PET and WREQ,immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.
文摘发展了一种同化窗口为1个月的陆面气温推广三维变分资料同化方法,并建立了逐日资料到月平均资料的观测算子。作为对该同化方法的初步检验,以2000年1月中国陆地区域时间分辨率低、空间分辨率较高且在高原地区与台站观测资料比较接近的CRU(Climate Research Unit)月平均陆面气温资料作为观测,以时间分辨率高、空间分辨率较低且在高原地区与台站资料有较大误差的NCEP逐日气温资料作为背景场,采用背景误差协方差矩阵(简称B矩阵)的两种简化对角形式进行同化试验,得到高时空分辨率的格点陆面气温分析场,并进行对比分析和均方根误差检验。结果显示,由两种简化形式得到的逐日资料和月平均资料的质量均得到改善,在我国东南和中部大部分地区与台站观测基本一致,在青藏高原、新疆等台站稀疏地区与地形对应良好,为M-SDGVM模型或其他陆面过程模式高质量陆面气象驱动场的准备提供了一种新的手段。尤其在B矩阵中考虑了方差逐日变化的简化形式所得到的分析场整体上要优于不考虑的,这为最终在B矩阵中考虑协方差(即对推广三维变分同化不作简化)进一步改进同化效果打下了基础。
文摘With rising population,decline in soil productivity and land-based conflicts,the per-capita land availability for cultivation is rapidly decreasing within Benue State,a largely agrarian and small-holder setting.This study attempts a local-level support for the actualisation of Sustainable Development Goal Number 2(“end hunger,achieve food security and improved nutrition,and promote sustainable agriculture”)by 2030.Using Multi-Criteria Decision Making(MCDM)method,remote sensing data from Climate Research Unit(CRU)and in-situ data from Nigeria Meteorological Agency(NIMET)were analyzed by GIS techniques to map the suitability of rice cultivation in the study area,with the integration of Normalized Difference Vegetation Index(NDVI),land cover,slope,temperature,precipitation and soil parameters(cation exchange capacity,pH,bulk density,organic carbon).We apply the various statistical parameters that include mean spatial NDVI;correlation coefficient,standard deviation and Root Mean Square(RMS)between CRU and NIMET data.Spatial regression trend analysis is conducted between CRU precipitation and NDVI and between CRU temperature and NDVI from 1985 to 2015.The results reveal that NDVI in highly suitable rice planting regions is higher than marginally suitable regions except in the months of October and November,which shows that the highly suitable regions will yield better than the marginally suitable regions during the dry season.Additionally,NDVI is seasonally bimodal in response to precipitation,meaning that vegetation vigor is more dependent on precipitation than temperature.Finally,the correlation coefficient,standard deviation and RMS between CRU and NIMET precipitation data shows 0.42,108,and 110,respectively,while these three factors between CRU and NIMET temperature data shows 0.88,1.60,and 0.86,respectively.In conclusion,the MCDM approach reveals that upland is more suitable for rice cultivation in Benue State when comparing with the area provided by the Global Land Cover and National Mappings Organization(GLCNMO)data.
