Climate changes caused by human activities are characterized by global warming and changes in regional hydrological cycle and precipitation.As the link between climate and human society,it is essential to understand the change of precipitation.As the most important contributors to global warming in recent decades,anthropogenic carbon dioxide(CO2)and black carbon(BC)play significant roles in driving the regional hydrological cycle.However,most of the previous studies on the precipitation changes induced by CO2 and BC focused on tropics and monsoon regions.The influences and their differences of CO2 and BC on the precipitation in Northern Hemisphere mid-latitudes(NHML)have not been paid enough attention.With global warming,the annual range of precipitation increases.However,few studies investigate the influence of CO2 and BC on annual range of precipitation.In this thesis,nine global climate models under the framework of the Precipitation Driver Response Model Intercomparison Project(PDRMIP)are used to compare the NHML precipitation and annual range of precipitation in typical regions responses to a tenfold increase in BC and a doubling of CO2,respectively.The main conclusions are as follows:(1)Comparative analyses of sensitivity experiments show that the NHML precipitation changes induced by BC and CO2distinctly differ in trends and seasons.The increased BC will reduce the NHML precipitation,especially in summer,whereas the doubled CO2will enhance the regional precipitation,mainly in winter.The differences between the BC and CO2 induced NHML precipitation changes are most significant in Central Asia(35°N-50°N,50°E-90°E)and central North America(35°N-50°N,75°W-125°W).(2)Analyses of moisture budget indicate that BC decreases the precipitation in NHML mainly by dynamic effect,while CO2 enhances the precipitation by thermodynamic effect.NHML has the largest warming because of the high concentration of BC,resulting in a decrease in the meridional temperature gradient(MTG)between the middle and low latitude.The decrease of MTG weakens the zonal winds in the middle and lower latitudes,decreasing the zonal water vapor flux and then precipitation.The global warming induced by the increase of CO2 is relatively uniform and has little influence on the temperature and MTG in NHML.However,the increased CO2 enhances water vapor in NHML,which leads to the increase of zonal water vapor flux and precipitation.(3)CO2 and BC have different influences on the annual range of precipitation.Increased CO2 enhances the annual range of precipitation in some tropical and temperate regions,while BC decreases it.The most significant differences are observed in Northeast East Asia(NEEA:28°N-53°N,122°E-140°E)and Northeast Pacific(NEP:23.5°N-45°N,125°W-153°W).The distinct annual range of precipitation responses mainly depend on the change of maximum precipitation effected by regional atmospheric circulation.The maximum precipitation in NEEA occurs in summer.Increased BC will induce anticyclonic anomaly,decreasing maximum precipitation and annual range of precipitation,while CO2 will enhance the southerly flow carrying water vapor,increasing maximum precipitation and annual range.The maximum precipitation in NEP occurs in winter.Increased BC(CO2)will lead to anticyclonic(cyclonic)anomaly,decreasing(increasing)maximum precipitation and annual range of precipitation. |