By using a nine-layer global spectral model involving fuller parameterization of physical processes, with a rhomboidal truncation at wavenumber 15, experiments are performed in terms of two numerical schemes, one with...By using a nine-layer global spectral model involving fuller parameterization of physical processes, with a rhomboidal truncation at wavenumber 15, experiments are performed in terms of two numerical schemes, one with long-term mean coverage of Arctic ice (Exp.1), the other without the ice (Exp.2). Results indicate that the Arctic region is a heat source in Exp.2 relative to the case in Exp.1. Under the influence of the polar heat source simulated, there still exist stationary wavetrains that produce WA-EUP and weak PNA patterns in Northern winter. That either the Arctic or the tropical heat source can cause identical climatic effects is due to the fact that the anomaly of the Arctic ice cover will directly induce a south-propagating wavetrain, and bring about the redistribution of the tropical heat source / sink. The redistribution is responsible for new wavetrains that will exert impact on the global climate. The simulation results bear out further that the polar region in Exp.2 as a heat source, can produce, by local forcing, a pair of positive and negative difference centers, which circle the Arctic moving eastwards. Observed in the Northern Hemisphere extratropics is a 40-50 day oscillation in relation to the moving pair, both having the same period.展开更多
Populations at the low latitude limits of a species range(rear-edge populations)are often considered more vulnerable to climate change.However,their ability to track different environmental settings at a regional scal...Populations at the low latitude limits of a species range(rear-edge populations)are often considered more vulnerable to climate change.However,their ability to track different environmental settings at a regional scale has been widely overlooked,although this may be relevant to accurately assess their adaptive capacity to cope with ongoing changes.Here we tested whether the endemic African Chaffinch(Fringilla coelebs africana)tracks environmental changes(e.g.decreasing temperatures,snow cover)by rearranging their numbers between seasons(spring vs.winter)along the altitude gradients of its northwestern African range.We additionally tested whether these seasonal changes in abundance were paralleled by morphological variation,suggesting a process of population diversification.We assessed African Chaffinch abundance in tree covered farmland and woodland sites distributed along an altitude gradient in spring and winter.In addition,we captured and measured chaffinches within the study gradient to explore the patterns of morphological variation.Our results showed that chaffinches shifted to lowlands from snow covered highlands during winter.In addition,highland individuals showed longer and more concave wings than their lowland counterparts.These morphological traits are usually related to flight efficiency in migratory birds,which suggest the presence of altitudinal movements aimed to track the environmental seasonality caused by orography.These results suggest a potential role of altitudinal seasonality as a driver of regional diversification within the African Chaffinch populations,which could be occurring in other North African avian species given their relatively high endemicity in the region.The evolutionary and conservation implications of these displacements have been often overlooked despite they can shape the adaptive capacity of rear-edge bird populations to face the ongoing environmental changes in this peripheral area of the Palearctic.展开更多
The aim of this study was the spatial and temporal monitoring of soil erosion patterns in Iran.The G2 model was used,as an appropriate tool to provide the required month-time step country-wide soil loss maps and stati...The aim of this study was the spatial and temporal monitoring of soil erosion patterns in Iran.The G2 model was used,as an appropriate tool to provide the required month-time step country-wide soil loss maps and statistical outputs.The input parameters were derived with field surveys and remote sensing imagery(MODIS,SRTM,SPOT,and Sentinel-2 scenes).An innovation for G2 was the consideration of the snow cover effect on the rainfall erosivity.It was also the first time G2 was used to map such a big country like Iran on a country scale.The mean annual soil erosion in Iran was found to be 16.5 t ha−1,which is equal to about 2.7 billion tons of soil loss.In spatial terms,the highest soil loss values were found in the north,west and southwest part of Iran,in the steep slopes in Alborz and Zagros mountains.In temporal terms,the highest and lowest monthly erosion values of 3.2 and 0.09 t ha−1 correspond to January and July,respectively.展开更多
文摘By using a nine-layer global spectral model involving fuller parameterization of physical processes, with a rhomboidal truncation at wavenumber 15, experiments are performed in terms of two numerical schemes, one with long-term mean coverage of Arctic ice (Exp.1), the other without the ice (Exp.2). Results indicate that the Arctic region is a heat source in Exp.2 relative to the case in Exp.1. Under the influence of the polar heat source simulated, there still exist stationary wavetrains that produce WA-EUP and weak PNA patterns in Northern winter. That either the Arctic or the tropical heat source can cause identical climatic effects is due to the fact that the anomaly of the Arctic ice cover will directly induce a south-propagating wavetrain, and bring about the redistribution of the tropical heat source / sink. The redistribution is responsible for new wavetrains that will exert impact on the global climate. The simulation results bear out further that the polar region in Exp.2 as a heat source, can produce, by local forcing, a pair of positive and negative difference centers, which circle the Arctic moving eastwards. Observed in the Northern Hemisphere extratropics is a 40-50 day oscillation in relation to the moving pair, both having the same period.
基金contribution to the project CGL201785637-P(Life at the border:population differentiation of forest birds south of the Palearctic)granted by the Spanish Ministry of Science,Innovation and Universities。
文摘Populations at the low latitude limits of a species range(rear-edge populations)are often considered more vulnerable to climate change.However,their ability to track different environmental settings at a regional scale has been widely overlooked,although this may be relevant to accurately assess their adaptive capacity to cope with ongoing changes.Here we tested whether the endemic African Chaffinch(Fringilla coelebs africana)tracks environmental changes(e.g.decreasing temperatures,snow cover)by rearranging their numbers between seasons(spring vs.winter)along the altitude gradients of its northwestern African range.We additionally tested whether these seasonal changes in abundance were paralleled by morphological variation,suggesting a process of population diversification.We assessed African Chaffinch abundance in tree covered farmland and woodland sites distributed along an altitude gradient in spring and winter.In addition,we captured and measured chaffinches within the study gradient to explore the patterns of morphological variation.Our results showed that chaffinches shifted to lowlands from snow covered highlands during winter.In addition,highland individuals showed longer and more concave wings than their lowland counterparts.These morphological traits are usually related to flight efficiency in migratory birds,which suggest the presence of altitudinal movements aimed to track the environmental seasonality caused by orography.These results suggest a potential role of altitudinal seasonality as a driver of regional diversification within the African Chaffinch populations,which could be occurring in other North African avian species given their relatively high endemicity in the region.The evolutionary and conservation implications of these displacements have been often overlooked despite they can shape the adaptive capacity of rear-edge bird populations to face the ongoing environmental changes in this peripheral area of the Palearctic.
文摘The aim of this study was the spatial and temporal monitoring of soil erosion patterns in Iran.The G2 model was used,as an appropriate tool to provide the required month-time step country-wide soil loss maps and statistical outputs.The input parameters were derived with field surveys and remote sensing imagery(MODIS,SRTM,SPOT,and Sentinel-2 scenes).An innovation for G2 was the consideration of the snow cover effect on the rainfall erosivity.It was also the first time G2 was used to map such a big country like Iran on a country scale.The mean annual soil erosion in Iran was found to be 16.5 t ha−1,which is equal to about 2.7 billion tons of soil loss.In spatial terms,the highest soil loss values were found in the north,west and southwest part of Iran,in the steep slopes in Alborz and Zagros mountains.In temporal terms,the highest and lowest monthly erosion values of 3.2 and 0.09 t ha−1 correspond to January and July,respectively.
