BWMO recently designed and built several cloud chambers specifically for the cloud physics and weather modification research. There are three small cloud chambers (~8 m3) that are connected sequentially to study the cloud mixing and entrainment processes, which are called “Triplets”. Other than the Triplets, a large expansion chamber (70 m3 in volume and 14 m high) was also built to simulate cloud and rain formation, cloud seeding effect and cloud electrification effect on clouds, and to obtain CCN and Ice Nuclei (IN) concentrations. This chamber was named “Beijing Aerosol and Cloud Interaction Chamber” (BACIC, pronounced as “basic”). The “tallness” is the advantage of BACIC. Unlike most cloud chambers, the 14 m vertical dimension of BACIC allows the rain formation processes to be studied in controlled experimental environments.
Experiment of cloud formation under natural background aerosol condition
Since getting aerosol samples from UAE to China for the experiments is impractical (sample volume and aging problems), local background aerosols will be used for the experiments. The mixtures of these particles will be injected into the chamber through the aerosol injection system in a controlled concentration. An expansion procedure will be conducted at the same time to mimic either warm or mixed-phase clouds. The aerosol PSD, cloud droplet PSD, and environmental conditions will be continuously monitored throughout the cloud lifetime.
Experiment of hygroscopic and glaciogenic seeding on cloud
Based on the cloud formation experiment, hygroscopic seeding materials will be introduced into the chamber at two different times for the warm cloud case to test the effect. In the first scenario, seeding particles will be injected together with the background aerosols to study the competition effect of seeding materials. In the second scenario, seeding particles will be introduced after the cloud is formed to investigate effects of in-cloud seeding. Similar experiments will be conducted for mixed-phase cloud with AgI particles as seeding agents.
Experiment of cloud formation by AgI deposition nucleation
The BACIC will be configured to keep a condition that is subsaturated respect to water but supersaturated respect to ice in an appropriate temperature range. The AgI particles will then be introduced into the chamber to study if new clouds can be formed in the clear air.
The BACIC (Beijing Aerosol and Cloud Interaction Chamber) in BWMO CLOUD Base (Cloud Laboratory and Observational Utilities Deployment Base) is a laboratory tool for investigating aerosol physical processes that have strong impacts on cloud microphysics, weather modification and aerosol-cloud-climate interactions. The chamber (70 m3 in volume and 14 m high, see Table 1 for specifications) can be operated over a wide range of atmospheric conditions throughout the troposphere and stratosphere under which water clouds, mixed-phase clouds, cirrus clouds are formed. The BACIC chamber is designed to operate at variable pressure (0.01-1000 hpa), temperature (-223.5 K to 303.2K), and humidity conditions including super-saturations with respect to ice and liquid water. A unique feature of the BACIC is the large temperatures range with operation at reduced pressure and a comprehensive set of trace gas, aerosol and cloud instrumentations. The available observational instruments for the BACIC are listed in Table 2. The schematic of the BACIC is illustrated in Figure. 1 for one side.
|
Shape |
Cylinder |
|
Size |
Diameter: 2.6m / Height: 14m |
|
Volume/inner surface |
70 m3 / 118.4 m2+ |
|
Surface to volume ratio |
1.69 m |
|
Wall material |
Stainless steel |
|
Temperature |
223.5-303.2K |
|
Operating Pressure |
0.01 hpa-1000 hpa |
Table 2. List of instrumentations currently in BWMO CLOUD Base for the BACIC chamber
Instrument | Function |
DMT atomizer | Generation of aerosol particles |
TSI (3938) | Measurement of the aerosol size distribution from 10 nm to 600 nm |
TSI (3321) | Measurement of the aerosol size distribution from 500 nm to 20 μm |
DMT cloud condensation nucleus counter (CCN-100) | Measurement of the cloud condensation nucleus number concentarion |
Colorado State University continuous flow diffusion chamber | Real time measurement of number concentration of ice nucleus |
DMT Fog Monitor (FM-120) | Droplet-laden ambient air and produces size distributions in the range from 2 – 50 µm |
Hygroscopicity Tandem Differential Mobility Analyzer (Brechtel -3002) | Real-time particle size and relative humidity dependent hygroscopic growth and number distribution measurement |
HR-TOF-AMS | Size and chemical mass loading information in real-time for non-refractory sub-micron aerosol particles |
Ion Chromatograph | Measurement of water soluble chemical mass concentration |
Trace Gas | Measurement of SO2, NOx, CO, O3 and H2O2 |
Single particle soot photometer (DMT, SP2) | Detection of aerosol particles through their scattering signal and quantification of the soot content through incandescence |
DMT Photoacoustic （PASS-3） | Measurement of absorption and scattering of aerosol at three wavelengths |
Thermistor array | Measurement of T spatial profile in the chamber |