Increasing heavy concentrated Meiyu precipitation over the Yangtze–Huaihe river valley (YHRV) during recent years has been previously reported. In fact, the concentrated Meiyu rainfall occurring in a small region or a certain period easily results in floods, thus it is worthy to analyze the heterogeneity of Meiyu rainfall over YHRV. In this study, we use both of precipitation concentration period (PCP) and precipitation concentration degree (PCD) based on vector analysis to identify the heterogeneity of Meiyu rainfall over YHRV. On the climatological mean, the concentrated heavy precipitation occurs in late summer over the Yangtze River Delta, where is usually suffered by floods. The dominant two patterns of PCP and PCD variations are northeast–southwest dipole pattern, homogeneous anomalies and homogeneous variation, north–south dipole pattern, respectively. In addition, the relationship on heterogeneity of Meiyu rainfall with sea surface temperature (SST) and the low level summer intraseasonal oscillation (ISO) are investigated. Two key regions of SST activities are found: Bay of Bengal (BOB) and Equatorial eastern Pacific. From BOB, more abundant water vapor has been brought. On the El Niño-Southern Oscillation variation, it is closely relative with PCD–PC1 during the decaying phase of El Niño, while PCP–PC2 is accompanied with developing phase of La Nina events, suggesting a negative feedback of PCP–PC2 on the Niño3.4 SST, and changes to positive during the later winter. On the ISO activities, the robust regions are located over the high-latitude areas, which are closely related with northeastern cold vortex. The north “cold and dry” air southwardly invaded with the lower-level strong warm air in the rainy area, and easily formed an “upper-wet and lower-dry” unstable layer. Under the trigger of the upward motion, the concentrated heavy rainfall easily occurred over YHRV. In all, the homogeneity variation of the concentrated heavy precipitation over YHRV is closely associated with both of the heating forcing (SST) and dynamical atmospheric forcing (low-level ISO). 相似文献
This study analyzes the impact of anthropogenic climate change in the hydroclimatology of Senegal with a focus over the lake of Guiers basin for the middle (2041–2060) and late twenty-first century (2080–2099). To this end, high-resolution multimodel ensemble based on regional climate model experiments considering two Representative Concentration Pathways (RCP4.5 and RCP8.5) is used. The results indicate that an elevated warming, leading to substantial increase of atmospheric water demand, is projected over the whole of Senegal. In the Lake basin, these increases in potential evapotranspiration (PE) range between 10 and 25 % in the near future and for RCP4.5 while for the far future and RCP8.5, they exceed 50 %. In addition, mean precipitation unveils contrasting changes with wetter (10 to 25 % more) conditions by the middle of the century and drier conditions (more than 50 %) during the late twenty-first century. Such changes cause more/less evapotranspiration and soil moisture respectively during the two future periods. Furthermore, surface runoff shows a tendency to increase in most areas amid few locations including the Lake basin with substantial reduction. Finally, it is found that while semi-arid climates develop in the RCP4.5 scenario, generalized arid conditions prevail over the whole Senegal for RCP8.5. It is thus evident that these future climate conditions substantially threaten freshwater availability for the country and irrigated cropping over the Lake basin. Therefore, strong governmental politics are needed to help design response options to cope with the challenges posed by the projected climate change for the country.