In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five ...In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five tropical cyclones(TCs) in 2013. The results show that the ice-phase clouds of a mature TC are mainly above 5 km. With increasing altitude, the cloud droplet effective radius decreases, and the particle number concentration increases. Ice water content first increases and then decreases with increasing height. In the eye area, in addition to the well-known warm-core area, another warm core is also apparent around the eye at a height of 8 to 15 km. The horizontal distribution of precipitation is characterized by large-scale stratiform precipitation mixed with independent convective precipitation. The height of precipitation is mostly below 7.5 km, and the heavy rain is mainly below 5 km. When the peripheral convective clouds are strong enough, ice particles would be generated, thus providing conditions that are favourable for the formation of precipitation below.展开更多
This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in ...This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018,based on the observations from the aircraft,the Suomi National Polar-Orbiting Partnership(NPP)satellite,and the high-resolution Himawari-8(H8)satellite.The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region.This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat,resulting in strengthened updrafts,enhanced radar echoes,higher cloud tops,and more and larger precipitation particles.In contrast,in the stratiform cloud region,after the Silver Iodide(AgI)seeding,the radar echoes become significantly weaker at heights close to the seeding layer,with the echo tops lowered by 1.4–1.7 km.In addition,a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km,and features such as icing seeding tracks appear.These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part.The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding;while in the stratiform region,a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding,which moves along the wind direction as width increases.展开更多
To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed ...To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed in this study. The results demonstrated that the vertical distribution of the aerosol number concentration（N_a） was similar to that of the clean rural continent. The average aerosol effective diameter（D_e） was maintained at approximately 0.4 μm at all levels. The data obtained during cloud penetrations showed that there was a progressive increase in the cloud droplet concentration（N_c） and liquid water content（LWC） from outside to inside the clouds, while the Nawas negatively related to the Ncand LWC at the same height. The fluctuation of the N_a, Ncand LWC during cloud penetration was more obvious under polluted conditions（Type 1） than under clean conditions（Type 2）. Moreover, the wet scavenging of cloud droplets had a significant impact on the accumulation mode of aerosols, especially on particles with diameters less than 0.4 μm. The minimum wet scavenging coefficient within the cloud was close to 0.02 under Type 1 conditions, while it increased to 0.1 under Type 2 conditions,which proved that the cloud wet scavenging effect under Type 1 conditions was stronger than that under Type 2 conditions.Additionally, cloud droplet spectra under Type 1 conditions were narrower, and their horizontal distributions were more homogeneous than those under Type 2 conditions.展开更多
Long-term observational data indicated a decreasing trend for the amount of autumn precipitation(i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s(~ 5.6% per decade). To examine the cause of ...Long-term observational data indicated a decreasing trend for the amount of autumn precipitation(i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s(~ 5.6% per decade). To examine the cause of the decreasing trend, the mechanisms associated with the change of autumn precipitation were investigated from the perspective of water vapor transportation, atmospheric stability and cloud microphysics. Results show that the decrease of convective available potential energy(i.e. 12.81 J kg-1/ decade) and change of cloud microphysics, which were closely related to the increase of aerosol loading during the past twenty years, were the two primary factors responsible for the decrease of autumn precipitation. Our results showed that increased aerosol could enhance the atmospheric stability thus weaken the convection. Meanwhile, more aerosols also led to a significant decline of raindrop concentration and to a delay of raindrop formation because of smaller size of cloud droplets. Thus, increased aerosols produced by air pollution could be one of the major reasons for the decrease of autumn precipitation. Furthermore, we found that the aerosol effects on precipitation in autumn was more significant than in other seasons, partly due to relatively more stable synoptic systems in autumn. The impact of large-scale circulation dominant in autumn and the dynamic influence on precipitation was more important than the thermodynamic activity.展开更多
基金Young Scientists Fund of National Natural Science Foundation of China Grant(41505013,41575017)Natural Science Foundation of Shandong Province(BS2015HZ019)
文摘In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five tropical cyclones(TCs) in 2013. The results show that the ice-phase clouds of a mature TC are mainly above 5 km. With increasing altitude, the cloud droplet effective radius decreases, and the particle number concentration increases. Ice water content first increases and then decreases with increasing height. In the eye area, in addition to the well-known warm-core area, another warm core is also apparent around the eye at a height of 8 to 15 km. The horizontal distribution of precipitation is characterized by large-scale stratiform precipitation mixed with independent convective precipitation. The height of precipitation is mostly below 7.5 km, and the heavy rain is mainly below 5 km. When the peripheral convective clouds are strong enough, ice particles would be generated, thus providing conditions that are favourable for the formation of precipitation below.
基金supported by the National Key Research and Development Project(Grant No.2019YFA0606803,2016YFA0601704)the National Natural Science Foundation of China(Grant No.41925022)+1 种基金the Innovation and Development Project of China Meteorological Administration(CXFZ2022J036)the Science and Technology Development Fund of Hubei Meteorological Bureau(Grant No.2017Y06,2017Y07,2016Y06,2019Y10).
文摘This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018,based on the observations from the aircraft,the Suomi National Polar-Orbiting Partnership(NPP)satellite,and the high-resolution Himawari-8(H8)satellite.The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region.This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat,resulting in strengthened updrafts,enhanced radar echoes,higher cloud tops,and more and larger precipitation particles.In contrast,in the stratiform cloud region,after the Silver Iodide(AgI)seeding,the radar echoes become significantly weaker at heights close to the seeding layer,with the echo tops lowered by 1.4–1.7 km.In addition,a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km,and features such as icing seeding tracks appear.These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part.The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding;while in the stratiform region,a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding,which moves along the wind direction as width increases.
基金jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05100304)the Chinese Natural Science Foundation (Grant No. 41005073)
文摘To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed in this study. The results demonstrated that the vertical distribution of the aerosol number concentration（N_a） was similar to that of the clean rural continent. The average aerosol effective diameter（D_e） was maintained at approximately 0.4 μm at all levels. The data obtained during cloud penetrations showed that there was a progressive increase in the cloud droplet concentration（N_c） and liquid water content（LWC） from outside to inside the clouds, while the Nawas negatively related to the Ncand LWC at the same height. The fluctuation of the N_a, Ncand LWC during cloud penetration was more obvious under polluted conditions（Type 1） than under clean conditions（Type 2）. Moreover, the wet scavenging of cloud droplets had a significant impact on the accumulation mode of aerosols, especially on particles with diameters less than 0.4 μm. The minimum wet scavenging coefficient within the cloud was close to 0.02 under Type 1 conditions, while it increased to 0.1 under Type 2 conditions,which proved that the cloud wet scavenging effect under Type 1 conditions was stronger than that under Type 2 conditions.Additionally, cloud droplet spectra under Type 1 conditions were narrower, and their horizontal distributions were more homogeneous than those under Type 2 conditions.
基金National Basic Research Program of China(2012CB955301)
文摘Long-term observational data indicated a decreasing trend for the amount of autumn precipitation(i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s(~ 5.6% per decade). To examine the cause of the decreasing trend, the mechanisms associated with the change of autumn precipitation were investigated from the perspective of water vapor transportation, atmospheric stability and cloud microphysics. Results show that the decrease of convective available potential energy(i.e. 12.81 J kg-1/ decade) and change of cloud microphysics, which were closely related to the increase of aerosol loading during the past twenty years, were the two primary factors responsible for the decrease of autumn precipitation. Our results showed that increased aerosol could enhance the atmospheric stability thus weaken the convection. Meanwhile, more aerosols also led to a significant decline of raindrop concentration and to a delay of raindrop formation because of smaller size of cloud droplets. Thus, increased aerosols produced by air pollution could be one of the major reasons for the decrease of autumn precipitation. Furthermore, we found that the aerosol effects on precipitation in autumn was more significant than in other seasons, partly due to relatively more stable synoptic systems in autumn. The impact of large-scale circulation dominant in autumn and the dynamic influence on precipitation was more important than the thermodynamic activity.
