Deep Convective Clouds over the Northern Pacific and Their Relationship with Oceanic Cyclones

Based on combined CloudSat/CALIPSO detections, the seasonal occurrence of deep convective clouds （DCCs） over the midlatitude North Pacific （NP） and cyclonic activity in winter were compared. In winter, DCCs are more frequent over the central NP, from approximately 30~N to 45~N, than over other regions. The high frequencies are roughly equal to those occurring in this region in summer. Most of these DCCs have cloud tops above a 12 km altitude, and the highest top is approximately 15 km. These wintertime marine DCCs commonly occur during surface circulation conditions of low pressure, high temperature, strong meridional wind, and high relative humidity. Further, the maximum probability of DCCs, according to the high correlation coefficient, was found in the region 10^-20~ east and 5^-10~ south of the center of the cyclones. The potential relationship between DCCs and cyclones regarding their relative locations and circulation conditions was also identified by a case study. Deep clouds were generated in the warm conveyor belt by strong updrafts from baroclinic flows. The updrafts intensified when latent heat was released during the adjustment of the cyclone circulation current. This indicates that the dynamics of cyclones are the primary energy source for DCCs over the NP in winter.

Using Satellite Data to Analyze the Initiation and Evolution of Deep Convective Clouds

In this study, two deep convective cloud cases were analyzed in detail to study their initiation and evolution. In both cases, all deep convective clouds were positioned at the rear of the cold front cloud bands and propagated backward. Satellite data showed that prior to initiation of the deep convective clouds, thermodynamic and moist conditions were favorable for their formation. In the morning, a deep convective cloud at the rear of cold front cloud band propagated backward, the outflow boundary of which created favorable conditions for initiation. An additional deep convective cloud cluster moved in from the west and interacted with the outflow boundary to develop a mesoscale convective system(MCS) with large, ellipse-shaped deep convective clouds that brought strong rainfall. The initiation and evolution of these clouds are shown clearly in satellite data and provide significant information for nowcasting and short-term forecasting.

Comparison of Aerosol Effects on Simulated Spring and Summer Hailstorm Clouds

Numerical simulations are carried out to investigate the effect of cloud condensation nuclei（CCN） concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are：（1） The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration;（2） Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles;（3） As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail;（4） When the CCN concentration increases, the amount of total precipitation lessens,while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of icephase precipitation. The differences between the two storms include：（1） An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case;（2） Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case;（3） An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.

An Algorithm to Detect Tropical Deep Convective Clouds Through AMSU-B Water Vapor Channels

An algorithm to detect tropical deep convective clouds and deep convective overshootings based on the measurements from the three water vapor channels （1833GHz± 1GHz, 183.3GHz±3GHz and 183.3GHz±7GHz） of the Advanced Microwave Sounding Unit-B （AMSU-B） is presented. This algorithm is an improved version of the method of Hong et al. （2005）. The proposed procedure is based on the statistical analysis of seven years＇ （2001-2007） measurements from AMSU-B on NOAA-16. From the 1-d histograms of the brightness temperature of the three water vapor channels and the 2-d histograms of the brightness temperature dif- ference between these channels, new thresholds for brightness temperature differences and the brigb.tness temperature of chamM 18 （183.3 GHz 4-1 GHz） are suggested. The new algorithm is employed to investigate the mean distribution of tropical deep convective clouds and convective overshootings from 30＇S to 30＇N for the years 2001 to 2007. The major concentration of deep convective clouds and convective overshootings is found over the Intertropical Convergence Zone （ITCZ）, the South Pacific Convergence Zone （SPCZ）, tropical Africa, South America, the Indian Ocean and Indonesia ruth an average fraction of 0.4%. In terms of these clouds we identity, the secondary Intertropical Convergence Zone located in the eastern South Pacific and parallel to the main ITCZ in the North Pacific. The convective overshooting is more frequently observed over land than over the ocean.

Analysis of Airplane Precipitation Operation on Embedded Convective Clouds in Hunan Province

Based on NCEP 1°×1° reanalysis data, ground encryption houdy precipitation, FY-2E stationary satellite and Doppler radar data, the structural characteristics of precipitation clouds in Hunan Province and the effects of airplane precipitation operation were analyzed. The results show that under the effects of low-pressure system and southwest monsoon, Hunan was rich in water vapor, which was beneficial to the maintaining of precipitation clouds. During the process of the artificial precipitation operation over Hunan Province, convection developed vigorously, and precipita- tion was strong in the south of the province; embedded convective clouds were dominant and precipitation was weak in the east of the province. Cloud optical thickness correlated with ground precipitation positively. After catalyzing, echo at high altitudes responded firstly, and the echo intensi- ty increased gradually; the response of low-altitude echo lagged behind that of high-altitude echo. It shows that catalysis could lead to increase of upper precipitation particles in size and quantity. As time goes on, upper precipitation particles descended to low altitudes, so that echo intensity in- creased at low altitudes. It is clearly seen that catalysis could lead to increase of echo intensity and prolong the lifetime of target clouds to improve the area of strong echo zone, showing obvious positive catalytic effect. At the same time, houdy average precipitation in the affected region tended to increase stably and was obviously more than that of the contrast region where hourly average precipitation reduced gradually with time. The changing trend of hourly average precipitation in the affected region correlated positively with the response of radar echo.

Comparison Analysis of Continuous Severe Convection Weather in the West of Shandong Based on Multi-scale Data

Based on conventional observation data, NCEP reanalysis data, wind profiler radar, Doppler radar, and satellite cloud image data, two times of severe convection weather in the west of Shandong Province during June 13-14 in 2016 were analyzed. The results are shown as follows： firstly, the convection on the night of June 13 was stronger than that on the afternoon of June 14. The two times of severe convection weather generated under the circulation background of upper cold vortex. There was northwest air current at high altitudes and warm wet advection at low altitudes. Severe convection weather was triggered by low-level shear lines and surface convergence lines on June 13 and by weak cold air at 700 hPa on June 14 respectively. Secondly, there was certain water vapor transport and convergence before the occurrence of severe convection, and it was warm and wet at low altitudes but dry and cold at high altitudes; there was convergence at low altitudes and divergence at middle and high altitudes. 0 ℃ layer was at about 4 000 m, and-20 ℃ layer was at about 7 000 m. Thirdly, radar echo intensity was larger than 45 dBZ when severe convection happened, and it reached above 60 dBZ at an elevation of 1.5°, while middle strong echo zone overhung weak echo zone at low altitudes. Vertically integrated liquid（VIL） was up to 20 kg/m^2, and mesocyclone generated in strong echo zone; there was bow echo on the night of June 13, and VIL was higher than that on June 14. In wind profiler data, strong vertical wind shear and fluctuation of wind direction had denotative meaning to the occurrence of severe convection weather. Fourthly, hail, gale and other severe convection weather happened in front of long and narrow cold cloud zone and convective cloud clusters as well as in southwestern TBB gradient zone.

A Review of Cloud-Resolving Model Studies of Convective Processes

Convective processes affect large-scale environments through cloud-radiation interaction, cloud micro- physical processes, and surface rainfall processes. Over the last three decades, cloud-resolving models （CRMs） have demonstrated to be capable of simulating convective-radiative responses to an imposed large-scale forcing. The CRM-produced cloud and radiative properties have been utilized to study the convective- related processes and their ensemble effects on large-scale circulations. This review the recent progress on the understanding of convective processes with the use of CRM simulations, including precipitation processes; cloud microphysical and radiative processes; dynamical processes; precipitation efficiency; diurnal variations of tropical oceanic convection; local-scale atmosphere-ocean coupling processes; and tropical convective-radiative equilibrium states. Two different ongoing applications of CRMs to general circulation models （GCMs） are discussed： replacing convection and cloud schemes for studying the interaction between cloud systems and large-scale circulation, and improving the schemes for climate simulations.

Numerical Simulation of Microphysics in Meso-β-Scale Convective Cloud System Associated with a Mesoscale Convective Complex

Numerical simulation of meso-β-scale convective cloud systems associated with a PRE-STORM MCC case has been carried out using a 2-D version of the CSU Regional Atmospheric Modeling System (RAMS) nonhydrostatic model with parameterized microphysics. It is found that the predicted meso-r-scale convective phenomena arc basically unsteady under the situation of strong shear at low-levels, while the meso-β-scale convective system is maintained up to 3 hours or more. The meso -β- scale cloud system exhibits characteristics of a multi-celled convective storm in which the meso-r-scale convective cells have lifetime of about 30 min. Pressure perturbation depicts a meso-low after a half hour in the low levels. As the cloud system evolves, the meso-low intensifies and extends to the upshear side and covers the entire domain in the mid-lower levels with the peak values of 5-8 hPa. Temperature perturbation depicts a warm region in the middle levels through the entire simulation period. The meso-r-scale warm cores with peak values of 4-8 ℃ are associated with strong convective cells. The cloud top evaporation causes a stronger cold layer around the cloud top levels.Simulation of microphysics exhibits that graupel is primarily concentrated in the strong convective cells forming the main source of convective rainfall after one hour of simulation time. Aggregates are mainly located in the stratiform region and decaying convective cells which produce the stratiform rainfall. Riming of the ice crystals is the predominant precipitation formation mechanism in the convection region, whereas aggregation of ice crystals is the predominant one in the stratiform region, which is consistent with observations. Sensitivity experiments of ice-phase mierophysical processes show that the microphysical structures of the convective cloud system can be simulated better with the diagnosed aggregation collection efficiencies.

A COMPREHENSIVE ANALYSIS OF INTERACTIONS BETWEEN MESO-SCALE CONVECTIVE CLOUD CLUSTERS IN TYPHOONS AND MESOSCALE HEAVY RAINS

In this paper, time and space distribution regularity of meso-scale heavy rains in five selected typhoons which landed at Fujian from 1996 to 1998 has been analyzed. Besides, with hourly digitized satellite infrared imagery, the features of the mesoscale are revealed for the genesis and evolution of mesoscale convective systems in typhoons. It indicates that the intensity of mesoscale storms is closely connected with the temperature and the area of the coldest cloud cluster. The heavy rainfall usually emerges on the eastern side of the mesoscale convective cloud clusters, where the cloud mass is developing and with a dense gradient and big curvature of isoline of the cloud top temperature.

Observational Evidence of High Ice Concentration in a Shallow Convective Cloud Embedded in Stratiform Cloud over North China

In this study we observed the microphysical properties, including the vertical and horizontal distributions of ice particles,liquid water content and ice habit, in different regions of a slightly supercooled stratiform cloud. Using aircraft instrument and radar data, the cloud top temperature was recorded as higher than -15℃, behind a cold front, on 9 September 2015 in North China. During the flight sampling, the high ice number concentration area was located in the supercooled part of a shallow convective cloud embedded in a stratiform cloud, where the ambient temperature was around -3℃. In this area,the maximum number concentrations of particles with diameter greater than 100 μm and 500 μm（N_（100） and N_（500）） exceeded 300 L-（-1） and 30 L-（-1）, respectively, and were related to large supercooled water droplets with diameter greater than 24 μm derived from cloud–aerosol spectrometer probe measurements. The ice particles types in this region were predominantly columnar, needle, graupel, and some freezing drops, suggesting that the occurrence of high ice number concentrations was likely related to the Hallett–Mossop mechanism, although many other ice multiplication processes cannot be totally ruled out.The maximum ice number concentration obtained during the first penetration was around two to three orders of magnitude larger than that predicted by the Demott and Fletcher schemes when assuming the cloud top temperature was around-15℃.During the second penetration conducted within the stratiform cloud, N_（100） and N_（500） decreased by a factor of five to ten, and the presence of columnar and needle-like crystals became very rare.

GENERATION AND DEVELOPMENT OF MESOSCALE CLOUD ON HEAVY RAIN BELT ON THE PERIPHERY OF TYPHOON 9608 (Herb)

Typhoon-induced heavy rains are mostly studied from the viewpoint of upper-level westerly troughs. It is worthwhile to probe into a case where the rain is caused by tropical cyclone system, which is much heavier. During August 3 ~ 5, 1996, an unusually heavy rainstorm happened in the southwest of Hebei province. It was caused by 3 mesoscale convective cloud clusters on the periphery of a tropical cyclone other than the direct effects of a westerly trough. Generating in a weak baroclinic environment that is unstable with high energy, the cloud clusters were triggered off for development by unstable ageostrophic gravity waves in the low-level southeast jet stream on the periphery of the typhoon. There was a vertical circulation cell with horizontal scale close to 1000 km between the rainstorm area and westerly trough in northeast China. As shown in a computation of the Q vector of frontogenesis function, the circulation cell forms a mechanism of transforming energy between the area of interest and the westerly trough system farther away in northeast China. Study of water vapor chart indicates that high-latitude troughs in the northeast portion of the rain migrate to the southeast to enhance anti-cyclonic divergence in upper-level convection over the area of heavy rain and cause rain clusters, short-lived otherwise, to develop vigorously. It is acting as an amplifier in this case of unusually strong process of rain.

Study on Causes of a Local Heavy Rainstorm Process in Shandong Province

Based on conventional meteorological observation data, NECP 1°×1° reanalysis data, precipitation data from automatic weather stations on the ground, FY- 2E satellite cloud images, and so forth, the circulation background, formation mechanism and features of a satellite cloud image of a local heavy rainstorm process in Shandong Province during August 8-9 in 2010 were analyzed. The results showed that the slow eastward movement of short-wave trough at middle and high latitudes, the stable maintenance of the subtropical high and ground cyclone, and the strong development of extra low-level southeast flow were large-scale circulation back- grounds of occurrence of the rainstorm; the rainstorm generated under the effects of mesoscale echo clusters or echo belts and mesoscale convective cloud clusters; precipitation mainly happened in periods when convective cloud clusters generated, developed and matured, and short-time heavy precipitation mainly appeared in the west, southwest and south of convective cloud clusters; extra low-level southeast flow was very conducive to the occurrence of short-time heavy precipitation; mesoscale convective systems rose in the whole troposphere, and the constant enhancement of low-level θse frontal zone provided favorable unstable energy for the occurrence of convective heavy rainfall.

Thermal Ionization Method of Modifying the Atmospheric Processes

The paper discusses the influence of ions on the formation of clouds, precipitation and thunderstorm electricity. Thermal ionization method is based on two core concepts： electrical micro- and macro-instability of clouds. Cloud droplets increase in sizes in the ascending air under the influence of electric micro-instability. Macro-instability is responsible for the formation of space charges in convective clouds. Artificial rainfall and discharge of space charges of clouds may be caused by means of the electrical modification techniques. The key role in these processes belongs to thermionic production of artificial light and heavy ions, which are formed as the result of applying a pyrotechnic composition of potassium-magnesium compounds. Negative ions are hydrated and adsorbed by cloud droplets leading to their growth and further rainfall. An artificial ionized channel allows to change cloud conductivity, which prevents clouds from accumulating thunderstorm electricity. Electrical methods of cloud modification can be used for the artificial induction of precipitation, prevention of natural hazards, thunderstorms, tornadoes and heavy rains.

Analysis of a Local Rainstorm in Central Inner Mongolia

Based on conventional observation data,satellite cloud image data and new generation Doppler radar data,the local rainstorm weather situation and physical quantities in Ulanqab City from 08:00 to 20:00 on June 24,2019 were analyzed by means of synoptic methods.The results show that the local rainstorm was caused by the forward trough system and the convergence of warm and cold air,and triggered by the low-level jet and the surface convergence line.The splitting and merging of cloud clusters in satellite cloud images and strong radar echoes had a good guiding effect on short-term heavy precipitation.

Ensemble Cloud Model Application in Simulating the Catastrophic Heavy Rainfall Event

An attempt has been made in the present research to simulate a deadly flash-flood event over the City of Skopje,Macedonia on 6 August 2016.A cloud model ensemble forecast method is developed to simulate a super-cell storm’s initiation and evolutionary features.Sounding data are generated using an ensemble approach,that utilizes a triple-nested WRF model.A three-dimensional(3-D)convective cloud model(CCM)with a very fine horizontal grid resolution of 250-m is initialized,using the initial representative sounding data,derived from the WRF 1-km forecast outputs.CCM is configured and run with an open lateral boundary conditions LBC,allowing explicit simulation of convective scale processes.This preliminary study showed that the ensemble approach has some advantages in the generation of the initial data and the model initialization.The applied method minimizes the uncertainties and provides a more qualitative-quantitative assessment of super-cell storm initiation,cell structure,evolutionary properties,and intensity.A high-resolution 3-D run is capable to resolve detailed aspects of convection,including high-intensity convective precipitation.The results are significant not only from the aspect of the cloud model’s ability to provide a qualitative-quantitative assessment of intense precipitation but also for a deeper understanding of the essence of storm development,its vortex dynamics,and the meaning of micro-physical processes for the production and release of large amounts of precipitation that were the cause of the catastrophic flood in an urban area.After a series of experiments and verification,such a system could be a reliable tool in weather services for very short-range forecasting(now-casting)and early warning of weather disasters.

The behavior of deep convective clouds over the warm pool and connection to the Walker circulation

As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared. The DCC intensity and area varies more significantly in the Indian Ocean than the western Pacific sector, while the DCC frequency is comparable in both sectors at the seasonal scale. Although the Indian Ocean sector is strongly dominated by the seasonal evolution, the interannual variations in the two sectors are comparable for all three DCC properties(frequency, intensity, and area). Besides,Walker circulation is closely correlated with the interannual variability of DCCs in both sectors. The Walker circulation strengthens(weakens) as the DCCs shift eastward(westward) over the Indian Ocean sector and westward(eastward) over the western Pacific sector. When more or stronger DCCs occur over the Indian Ocean sector(western Pacific sector), the Walker circulation becomes stronger(weaker) and shifts westward(eastward). Interestingly, the response of the Walker circulation to DCC variability over the warm pool is asymmetry. The asymmetry response of the Walker circulation to the negative and positive DCC anomaly may be related to the non-linearity internal variability of the atmosphere. DCCs over the Indian Ocean sector have a much weaker nonlinear correlation with the Walker circulation than DCCs over the western Pacific sector.