气溶胶-降水相互作用是大气科学的热点问题，也一直是国际研究的重点和难点问题。前人研究多关注气溶胶对降水量年代际或日降水特征的影响，很少有研究以降水事件为时间尺度；研究多着重单一区域而缺乏多区域对比研究，不同区域气溶胶对降水特征的影响是否一致、如何影响以及影响程度等问题仍然是不明确的；同时中国东部大城市人口密集，气溶胶污染严重，因此在中国华北地区、长江三角洲及珠江三角洲研究气溶胶对降水特征的影响具有重要科学意义。

为了深入研究气溶胶对降水特征的影响，弥补前人研究的不足，本文基于高精度的气溶胶(PM_2.5质量浓度)、降水、气象数据，研究了不同区域气溶胶对降水触发时间、峰值时间、强度、峰值强度及时长的影响，明确了对流和层状降水对气溶胶的不同响应，并分别检验了在不同湿度、低层大气稳定度及风切变情景中气溶胶对降水特征的影响是否一致，主要研究结果如下：

1) 高气溶胶浓度推迟华北地区降水高频时段(降水频率高于日平均降水频率的时段)，但延长降水高频时段的时长，使得华北地区降水高频时段开启时间(14时)晚于长三角(11时)及珠三角(11时)地区，但总时长为8-9小时，相差无几；除了气溶胶浓度的差异，气溶胶类型(吸收型和散射型)也使得不同区域降水触发(峰值)时间对气溶胶响应不同。华北地区气溶胶浓度高，吸收型气溶胶主导，对大气加热效应明显，使得高频时段中降水触发时间提前3小时，珠江三角洲相反表现为推迟2小时，而长江三角洲无论浓度还是吸收型气溶胶占比均处于两者之间，降水时间受气溶胶影响不明显。气溶胶辐射作用在一天中不同时段作用不同，其对降水特征的影响也存在差异。

2) 各地区弱降水(峰值)强度对气溶胶的响应均不明显；在华北和长三角地区，一天中气溶胶加热大气的时段强降水强度也被气溶胶增强，而在珠三角恰恰相反，这可能与湿度有关，降水强度和降水峰值强度对气溶胶的响应基本一致；强降水强度对气溶胶响应的变化节点与温度对气溶胶响应变化的节点一致，而降水峰值强度则对垂直上升速度的变化更敏感，但均能体现出气溶胶对降水强度的影响。气溶胶能缩短时长不超过5小时的降水事件的降水时长。

3) 层状降水概率高于对流降水，但对流降水发展高度及强度均高于层状降水。层状降水受气溶胶影响较小。对流降水触发、峰值时间以及降水时长对气溶胶的响应基本与结论(1)中的一致，不同之处在于气溶胶推迟长三角午后对流降水触发时间1小时，但提前珠三角午后对流降水峰值时间1小时。强对流降水强度和峰值强度对气溶胶响应基本一致，均为垂直上升速度为负的时段气溶胶促进对流降水强度，而垂直上升速度为正时则抑制对流降水强度。

4) 湿度有利于降水发生，能够提前降水时间，延长降水时长，但气溶胶对降水的影响在高湿度中被削弱，适当的湿度能够增强降水强度，但过大的湿度对降水强度不利。低层大气稳定度改变降水触发(峰值)时间日变化特征，高低层大气稳定度抑制降水强度；不同低层大气稳定度下，气溶胶对降水时间和强度的影响依然明显存在，但对降水时长和高低层大气稳定度时降水触发(峰值)时间影响复杂较难判断。风切变抑制气溶胶效应，对降水触发(峰值)时间的影响与气溶胶相反，其推迟华北地区降水触发(峰值)时间峰值3小时，推迟长三角1小时，提前珠三角2小时，风切变基本表现为抑制降水(峰值)强度。

The issue of aerosol-precipitation interaction is a hot in atmospheric science and has always been the focus and difficulty of international research. Previous studies have focused on the influence of aerosols on the inter-decadal or daily precipitation characteristics, and few studies have taken precipitation events as the time scale. It is still unclear that whether the influence of aerosols on precipitation characteristics is consistent, how to influence and what the degree of influence is, in different regions. Simulately, the large cities are densely populated and aerosol pollution is serious in eastern China. Therefore, it is necessary to study the influence of aerosol on precipitation in North China Plain (NCP), Yangtze River Delta (YRD) and Pearl River Delta (PRD).

In order to study the influence of aerosol on precipitation fully and make up for the shortcomings of previous studies, this study investigates the influence of aerosol on the start time, peak time, intensity, peak intensity and duration of precipitation in different regions, based on the high-resolution precipiataion, aerosol (PM2.5 mass concentration) and meteorological data from June–August (summer) in the years 2015 to 2020. The different responses of convective and stratiform precipitation to aerosol are studied. The effects of aerosol on precipitation in different humidity, low tropospheric stability and wind shear are investigated. Interesting results have been found with the following seven important points:

1) The high frequency period of precipitation is delayed and prolonged by high aerosols concentration in NCP, so the start time of high frequency period of precipitation in NCP (14 o’clock) is later than in YRD (11 o’clock) and PRD (11 o’clock) but the durations are similar. Except the different aerosol concentration, different aerosol types (absorbing and scattering) make the influences of aerosol on the start (peak) time of precipitation are different in NCP, YRD and PRD. The start time of precipitation is ahead 3 hours in NCP but delayed 2 hours in PRD by aerosols in high frequency period of precipitation and the start time of precipitation in YRD shows no response to aerosol. The reason is that the aerosol heats atmosphere strongly in NCP, which is because the aerosol concentration in NCP is high and the absorbing aerosol is dominant in NCP. The concentration of aerosol and aerosol type of PRD is opposite to NCP. The concentration of aerosol and aerosol type of YRD is between of NCP and PRD, so the start (peak) time of precipitation in YRD is little affected by aerosol. The influences of aerosol radiation effect on precipitation characteristics are different in different periods of the day.

2) The response of weak precipitation (peak) intensity to aerosol is weak. When the aerosol heats atmosphere, the heavy precipitation intensity is strengthened by aerosol in NCP and YRD, but is suppressed in PRD, which is related to humidity possibly. The response of precipitation intensity to aerosol is consistent with precipitation peak intensity. The nodes of heavy precipitation intensity are consistent with that of temperature response to aerosol, while the peak intensity of precipitation is more sensitive to the change of vertical updraft velocity. Aerosol can shorten the duration of precipitation when their durations are less than 5 hours.

3) The frequency of stratiform precipitation is higher than convective precipitation. The occurrence altitude of convective precipitation and convective precipitation rate are higher than that for stratiform precipitation. The convective precipitation is more sensitive to aerosol than stratiform precipitation. For convective precipitation, the responses of the start time, peak time and duration of precipation to aerosol are similar except that the start time is delayed 1 hours in YRD, but the peak time is ahead 1 hours in PRD.

4) Humidity is beneficial to precipitation, which can advance the start (peak) time of precipitation and prolong the duration of precipitation events, but the influence of aerosol on precipitation is weakened when the humidity is high. Too much humidity is unfavorable to the intensity of precipitation. The low tropospheric stability (LTS) can modify the characteristics of start (peak) time of precipitation of diurnal change. High LTS suppresses the intensity of precipitation. Under different LTS, the influences of aerosol on start time, and intensity of precipitation are significant. However, the influences of aerosol on duration of precipitation and peak time under high LTS are complex. Vertical wind shear (WS) inhibits the aerosol effect on precipitation and the influences of WS on the start (peak) time of precipitation are opposite to that of aerosol. WS delays the start (peak) time of precipitation in NCP by 3 hours, delays that in YRD by 1 hours and advances that in PRD by 2 hours. WS can suppress the (peak) intensity of precipitation.