Drought was a severe recurring phenomenon in Iraq over the past two decades due to climate change despite the fact that Iraq has been one of the most water-rich countries in the Middle East in the past.The Iraqi Kurdi...Drought was a severe recurring phenomenon in Iraq over the past two decades due to climate change despite the fact that Iraq has been one of the most water-rich countries in the Middle East in the past.The Iraqi Kurdistan Region(IKR)is located in the north of Iraq,which has also suffered from extreme drought.In this study,the drought severity status in Sulaimaniyah Province,one of four provinces of the IKR,was investigated for the years from 1998 to 2017.Thus,Landsat time series dataset,including 40 images,were downloaded and used in this study.The Normalized Difference Vegetation Index(NDVI)and the Normalized Difference Water Index(NDWI)were utilized as spectral-based drought indices and the Standardized Precipitation Index(SPI)was employed as a meteorological-based drought index,to assess the drought severity and analyse the changes of vegetative cover and water bodies.The study area experienced precipitation deficiency and severe drought in 1999,2000,2008,2009,and 2012.Study findings also revealed a drop in the vegetative cover by 33.3%in the year 2000.Furthermore,the most significant shrinkage in water bodies was observed in the Lake Darbandikhan(LDK),which lost 40.5%of its total surface area in 2009.The statistical analyses revealed that precipitation was significantly positively correlated with the SPI and the surface area of the LDK(correlation coefficients of 0.92 and 0.72,respectively).The relationship between SPI and NDVI-based vegetation cover was positive but not significant.Low precipitation did not always correspond to vegetative drought;the delay of the effect of precipitation on NDVI was one year.展开更多
Understanding the impact of anthropogenic climate change on drought is of great significance to the prevention of its adverse effects.Two drought indices,standardized precipitation index(SPI)and standardized precipita...Understanding the impact of anthropogenic climate change on drought is of great significance to the prevention of its adverse effects.Two drought indices,standardized precipitation index(SPI)and standardized precipitation evapotranspiration index(SPEI),are used here for the detection and attribution of autumn droughts in China,and for the exploration of the role played by the anthropogenic climate change.SPI is only related to precipitation,but SPEI involves both precipitation and potential evapotranspiration.For their trend’s spatial patterns,the historical simulations(including all forcings,noted as ALL)from 11 models of the Coupled Model Intercomparison Project phase 6,as an ensemble,are able to reproduce their observational counterpart.SPI shows wetting trend in the north of 35°N and drying trend in the south.SPEI shows drying trend in almost whole China.The drying trend in historical simulations ALL is significantly stronger,compared with the counterpart from the accompanying simulations(called NAT)with only natural forcings implemented.This result clearly indicates that anthropogenic climate change plays a dominant role in the enhancement of autumn drought in China.A more rigorous detection work is also performed with the signal’s fingerprint of ALL(and NAT)projected onto the observation and assessed with the background noise from no external-forcing control simulations.The trend pattern signal in ALL is significantly detected in observation for both SPI and SPEI,with a more pronounced signal in SPEI than in SPI,while the signal of NAT is not detected for neither SPI nor SPEI.Finally,extreme droughts(with indices beyond-2)are assessed in terms of probability ratio between ALL and NAT.It is shown that the anthropogenic precipitation change plays a leading role in the south of 35°N,while the anthropogenic temperature change leads in the north.展开更多
文摘Drought was a severe recurring phenomenon in Iraq over the past two decades due to climate change despite the fact that Iraq has been one of the most water-rich countries in the Middle East in the past.The Iraqi Kurdistan Region(IKR)is located in the north of Iraq,which has also suffered from extreme drought.In this study,the drought severity status in Sulaimaniyah Province,one of four provinces of the IKR,was investigated for the years from 1998 to 2017.Thus,Landsat time series dataset,including 40 images,were downloaded and used in this study.The Normalized Difference Vegetation Index(NDVI)and the Normalized Difference Water Index(NDWI)were utilized as spectral-based drought indices and the Standardized Precipitation Index(SPI)was employed as a meteorological-based drought index,to assess the drought severity and analyse the changes of vegetative cover and water bodies.The study area experienced precipitation deficiency and severe drought in 1999,2000,2008,2009,and 2012.Study findings also revealed a drop in the vegetative cover by 33.3%in the year 2000.Furthermore,the most significant shrinkage in water bodies was observed in the Lake Darbandikhan(LDK),which lost 40.5%of its total surface area in 2009.The statistical analyses revealed that precipitation was significantly positively correlated with the SPI and the surface area of the LDK(correlation coefficients of 0.92 and 0.72,respectively).The relationship between SPI and NDVI-based vegetation cover was positive but not significant.Low precipitation did not always correspond to vegetative drought;the delay of the effect of precipitation on NDVI was one year.
基金Supported by the National Key Research and Development Program of China(2018YFC1507704)。
文摘Understanding the impact of anthropogenic climate change on drought is of great significance to the prevention of its adverse effects.Two drought indices,standardized precipitation index(SPI)and standardized precipitation evapotranspiration index(SPEI),are used here for the detection and attribution of autumn droughts in China,and for the exploration of the role played by the anthropogenic climate change.SPI is only related to precipitation,but SPEI involves both precipitation and potential evapotranspiration.For their trend’s spatial patterns,the historical simulations(including all forcings,noted as ALL)from 11 models of the Coupled Model Intercomparison Project phase 6,as an ensemble,are able to reproduce their observational counterpart.SPI shows wetting trend in the north of 35°N and drying trend in the south.SPEI shows drying trend in almost whole China.The drying trend in historical simulations ALL is significantly stronger,compared with the counterpart from the accompanying simulations(called NAT)with only natural forcings implemented.This result clearly indicates that anthropogenic climate change plays a dominant role in the enhancement of autumn drought in China.A more rigorous detection work is also performed with the signal’s fingerprint of ALL(and NAT)projected onto the observation and assessed with the background noise from no external-forcing control simulations.The trend pattern signal in ALL is significantly detected in observation for both SPI and SPEI,with a more pronounced signal in SPEI than in SPI,while the signal of NAT is not detected for neither SPI nor SPEI.Finally,extreme droughts(with indices beyond-2)are assessed in terms of probability ratio between ALL and NAT.It is shown that the anthropogenic precipitation change plays a leading role in the south of 35°N,while the anthropogenic temperature change leads in the north.
