Changes In Summer Precipitation Events Over China Under The Future Low Warming Target With Transient And Equilibrium Experiment

This paper uses the Common Earth System Model(CESM)model to predict the global warming threshold and stability(1.5/2 ?)and its different warming in the global transient and stable arrivals at 1.5/2 ?.The response to the extreme events in China during the process,and focused on the possible causes of differences in future summer precipitation changes.The results show that:(1)Compared with 1986-2005,the temperature over China region rises by about 1.2?/1.9 ? in the 1.5?/2? equilibrium experiment;the number of heat wave days increases by about 15/25 days;the number of frost days decreases by about 10 / 15 days;precipitation intensity increased by 6%/7%;maximum precipitation for five consecutive days increased by 10%/14%.For the transient experiment,the annual maximum temperature in China increased by about 1.3?/2.3? at 1.5?/2 ? warming target;the number of heat wave days increased by about 15/28 days;the number of frost days decreased by about 12/19 days;The precipitation intensity increased by 3%/6%;the annual maximum daily precipitation increased by 8%/13%;the maximum precipitation for five consecutive days increased by 7%/11%.Under the same warming target,the increase of transient experiment is more obvious than that of equilibrium experiment on extreme temperature,especially in the northwest,Qinghai-Tibet Plateau,and Northeast China,but the changes of extreme precipitation events are opposite.the increase of equilibrium experiment is more obvious than that of transient experiment,and the sensitivity areas are in the southwest and southeast regions of China.(2)Using the moist budget diagnose to analyze the mechanism of summer precipitation difference in China with transient and equilibrium experiment.For the southeastern region of China(21-29°N,112-125°E)in the equilibrium and transient experiments at 1.5? warming target,the dynamic term dominated by vertical velocity are about 0.7 and 0.4 mm/ d,and the thermal term corresponding to the increase in moist content by temperature increase contribute to about 0.3 and 0.2 mm/d.That is to say,the contribution of the dynamic term in the southeast region plays a leading role in the two experiments,which is about twice the contribution of the thermal conditions.The diagnosis of 500 hPa temperature advection indicate that the zonal wind advection difference in the mid-latitude region(especially near 30°N)is the main reason for the southeast precipitation in equilibrium experiment to be stronger than that of transient experiments.(3)Analysis of the heating effect of visible heat source on the upper atmosphere in summer,it is found that the abnormal heating of the upper atmosphere in equilibrium experiment makes the intensity of South Asia high increase obviously,causing the west wind increased near 30°N,and the corresponding high-level divergence is obviously strengthened,and its lower layer Corresponding to strong convergence and vertical ascending motion,the dynamic conditions for precipitation in southern China are maintained.The diagnosis of vorticity manufacturing rate to the subtropical high shows that compared with the transient experiment,the spatial distribution of vorticity anomalies contributes to the westward and southward expansion of subtropical high.Finally,the southwesterly wind on the west side of the subtropical high is strengthened,so that the water vapor transport in the Yangtze River Basin is strengthened and precipitation is increased.