By using occurrence years of great drought in Shaoyang district in recent 20 years,the time sequence was established,and by gray disaster prediction theory,the possible great drought years in future in Shaoyang distri...By using occurrence years of great drought in Shaoyang district in recent 20 years,the time sequence was established,and by gray disaster prediction theory,the possible great drought years in future in Shaoyang district were predicted. The results showed that one quasi-periodic of great drought occurrence in Shaoyang district is 2 years,the next great drought years are 2010,2012 and 2015. Gray prediction drought theory will provide scientific basis for drought resistance work in Shaoyang district.展开更多
The Great Plains region of the United States is susceptible to drought of all kinds including meteorological/climatological, agricultural, hydrological, and socioeconomic. Drought conditions in the region span varying...The Great Plains region of the United States is susceptible to drought of all kinds including meteorological/climatological, agricultural, hydrological, and socioeconomic. Drought conditions in the region span varying spatial and temporal scales and the causes include: 1) certain synoptic conditions that favor drought such as mid-tropospheric ridging over the drought-affected area and a weak low-level jet;2) sea surface temperature anomalies and associated teleconnections;3) land-atmosphere coupling;and 4) anthropogenic effects. While drought can span as few as a couple of months, the most severe droughts can occur at the decadal scale such as the 1930s Dust Bowl, the worst drought in recent history from a societal standpoint. Such droughts in the Great Plains have widespread impacts on agriculture, water resources, human health, and the economy.展开更多
This study analyzes the spatio-temporal distribution of daily rainfall data from 13 stations in the country of Senegal located in the North-West of Africa. These data, covering the period 1950-2010, are extracted from...This study analyzes the spatio-temporal distribution of daily rainfall data from 13 stations in the country of Senegal located in the North-West of Africa. These data, covering the period 1950-2010, are extracted from the database of the Regional Study Center for the Improvement of Drought Adaptation (CERAAS). They allow to calculate, in each station, dry episodes and their sequences and the results reveal a latitudinal variability of class 1 breaks (1 - 3 days) with the highest values recorded in the south. Unlike the class 2 episodes (greater or equal than 15 days), the latitudinal gradient is less pronounced but they are more frequent in the north. For most of the regions studied, a break in the trend towards an increase in dry sequences can be noted, most often at the beginning of the 1970s, which coincides with the start of the great drought of the 1970s decade. For all sites, the frequency of dry episodes of class 1 (1 - 3 days) exceeds 70%. The frequency of class 2 of dry episodes (greater or equal than 15 days) decreased from 30% in 1951-1970 to 18% in 1991-2010 in the region of Thiès;from 25% in 1951-1970 to 20% in 1991-2010 in Louga;from 22% in 1951-1970 to 18% in 1991-2010 in Tamba;23% in 1951-1970 to 15% in 1991-2010 in Ziguinchor;25% in 1951-1970 to 16% in 1991-2010 in Kolda;22% in 1951-1970 to 18% in 1991-2010 in Diourbel and finally 20% in 1951-1970 to 17% in 1991-2010 in Fatick. Over the whole period of study, the spatial distribution of the number of dry periods in class 1 is higher in the South than in the Center and in the North of Senegal. For class 2 breaks, the latitudinal gradient is less pronounced and the minimum number of dry periods in this class is recorded in the south, especially in Ziguinchor. However, the maximum is observed in the Center. In the Northern region (Saint-Louis), classes 3 and 4 are much more frequent. This spatial variability of rainfall breaks is clearly associated with the rainfall gradient between the North and the South. The temporal evolution of the numbers of each class intrinsically follows the evolution of the ITCZ.展开更多
文摘By using occurrence years of great drought in Shaoyang district in recent 20 years,the time sequence was established,and by gray disaster prediction theory,the possible great drought years in future in Shaoyang district were predicted. The results showed that one quasi-periodic of great drought occurrence in Shaoyang district is 2 years,the next great drought years are 2010,2012 and 2015. Gray prediction drought theory will provide scientific basis for drought resistance work in Shaoyang district.
文摘The Great Plains region of the United States is susceptible to drought of all kinds including meteorological/climatological, agricultural, hydrological, and socioeconomic. Drought conditions in the region span varying spatial and temporal scales and the causes include: 1) certain synoptic conditions that favor drought such as mid-tropospheric ridging over the drought-affected area and a weak low-level jet;2) sea surface temperature anomalies and associated teleconnections;3) land-atmosphere coupling;and 4) anthropogenic effects. While drought can span as few as a couple of months, the most severe droughts can occur at the decadal scale such as the 1930s Dust Bowl, the worst drought in recent history from a societal standpoint. Such droughts in the Great Plains have widespread impacts on agriculture, water resources, human health, and the economy.
文摘This study analyzes the spatio-temporal distribution of daily rainfall data from 13 stations in the country of Senegal located in the North-West of Africa. These data, covering the period 1950-2010, are extracted from the database of the Regional Study Center for the Improvement of Drought Adaptation (CERAAS). They allow to calculate, in each station, dry episodes and their sequences and the results reveal a latitudinal variability of class 1 breaks (1 - 3 days) with the highest values recorded in the south. Unlike the class 2 episodes (greater or equal than 15 days), the latitudinal gradient is less pronounced but they are more frequent in the north. For most of the regions studied, a break in the trend towards an increase in dry sequences can be noted, most often at the beginning of the 1970s, which coincides with the start of the great drought of the 1970s decade. For all sites, the frequency of dry episodes of class 1 (1 - 3 days) exceeds 70%. The frequency of class 2 of dry episodes (greater or equal than 15 days) decreased from 30% in 1951-1970 to 18% in 1991-2010 in the region of Thiès;from 25% in 1951-1970 to 20% in 1991-2010 in Louga;from 22% in 1951-1970 to 18% in 1991-2010 in Tamba;23% in 1951-1970 to 15% in 1991-2010 in Ziguinchor;25% in 1951-1970 to 16% in 1991-2010 in Kolda;22% in 1951-1970 to 18% in 1991-2010 in Diourbel and finally 20% in 1951-1970 to 17% in 1991-2010 in Fatick. Over the whole period of study, the spatial distribution of the number of dry periods in class 1 is higher in the South than in the Center and in the North of Senegal. For class 2 breaks, the latitudinal gradient is less pronounced and the minimum number of dry periods in this class is recorded in the south, especially in Ziguinchor. However, the maximum is observed in the Center. In the Northern region (Saint-Louis), classes 3 and 4 are much more frequent. This spatial variability of rainfall breaks is clearly associated with the rainfall gradient between the North and the South. The temporal evolution of the numbers of each class intrinsically follows the evolution of the ITCZ.
