This study examines the inter-annual variability of rainfall and Mean Sea Level Pressure (</span><span style="font-family:Verdana;">M</span><span style="font-family:Verdana;"&g...This study examines the inter-annual variability of rainfall and Mean Sea Level Pressure (</span><span style="font-family:Verdana;">M</span><span style="font-family:Verdana;">SLP) over west Africa based on analysis of the Global Precipitation</span><span style="font-family:""><span style="font-family:Verdana;"> Climatology Project (GPCP) and National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis respectively. An interconnection is found in this region, between Mean Sea Level Pressure (MSLP) anomaly (over Azores and St. Helena High) and monthly mean precipitation during summer (June to September: JJAS). We also found that over northern Senegal (15</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">N</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">17</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">N;17</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">W</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">13</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">W) the SLP to the north is strong;the wind converges at 200</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">hPa corresponding to the position of the African Easterly Jet (AEJ) the rotational wind 700</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">hPa (corresponding to the position of the African Easterly Jet (AEJ) coming from the north-east is negative. In this region, th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 展开更多
The three measurement periods: the TOMS Nimbus-7 TOMSN7L3 v008 from 1978 to 1993, the TOMS EP TOMSEPL3 v008 from 1996 to 2005 and the OMI OMTO3d v003 from 2004 to 2008 have allowed the presence of dust to be observed ...The three measurement periods: the TOMS Nimbus-7 TOMSN7L3 v008 from 1978 to 1993, the TOMS EP TOMSEPL3 v008 from 1996 to 2005 and the OMI OMTO3d v003 from 2004 to 2008 have allowed the presence of dust to be observed in the 10°North to 20°North latitudinal band (10 - 20 band) of Africa. The 10 - 20 band has a permanent dust presence. The AERONET data show AOD peaks exceeding 2 in Senegal and Niger (on an AOD scale). The statistical study reveals intra-annual relationships in deposition. In Senegal, a significant deposition is observed.展开更多
文摘This study examines the inter-annual variability of rainfall and Mean Sea Level Pressure (</span><span style="font-family:Verdana;">M</span><span style="font-family:Verdana;">SLP) over west Africa based on analysis of the Global Precipitation</span><span style="font-family:""><span style="font-family:Verdana;"> Climatology Project (GPCP) and National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis respectively. An interconnection is found in this region, between Mean Sea Level Pressure (MSLP) anomaly (over Azores and St. Helena High) and monthly mean precipitation during summer (June to September: JJAS). We also found that over northern Senegal (15</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">N</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">17</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">N;17</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;">W</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">13</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">W) the SLP to the north is strong;the wind converges at 200</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">hPa corresponding to the position of the African Easterly Jet (AEJ) the rotational wind 700</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">hPa (corresponding to the position of the African Easterly Jet (AEJ) coming from the north-east is negative. In this region, th
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
文摘The three measurement periods: the TOMS Nimbus-7 TOMSN7L3 v008 from 1978 to 1993, the TOMS EP TOMSEPL3 v008 from 1996 to 2005 and the OMI OMTO3d v003 from 2004 to 2008 have allowed the presence of dust to be observed in the 10°North to 20°North latitudinal band (10 - 20 band) of Africa. The 10 - 20 band has a permanent dust presence. The AERONET data show AOD peaks exceeding 2 in Senegal and Niger (on an AOD scale). The statistical study reveals intra-annual relationships in deposition. In Senegal, a significant deposition is observed.
