Monday, 13 January 2020: 10:45 AM
105 (Boston Convention and Exhibition Center)
Our field campaign of aircraft observations had successfully been conducted over the UAE regions in the summer of 2017. This campaign has mainly two objectives. First, in situ measurements contribute to investigation on microphysical processes in seeded and unseeded clouds as well as elucidation of the mechanism responsible for precipitation augmentation. Secondly, the field observation data is useful to validate numerical simulations of cloud and precipitation and to improve the accuracy and reliability of numerical models. We had deployed two aircraft whose base was Al Ain International Airport, as well as one ground-based observation site next to the aircraft hangar. One aircraft for in situ measurements was B200T operated by Diamond Air Service Inc., Japan, and the other for cloud seeding was C-90 operated by UAE National Center of Meteorology (NCM). We performed 14 research flights (~30 hours in total) from September 5 to 24, 2017. Thirteen of the B200T flights were coordinated with the C-90 flights. As one of the flight patterns, seeding plumes generated from the C-90 were sampled and measured with the instrumented B200T which followed the C-90. We collected basic data for background (BG) aerosols and seeding plume particles generated by CaCl2 hygroscopic (HYG) flares, silver iodide (AgI) flares, or simultaneously generated by the both types.
In order to investigate cloud seeding effects, the B200T measured the evolution of aerosols and cloud particles from cloud base to upper levels before and after the C-90's flare seeding. Based on the same strategy and method as in previous studies on Japanese field campaigns, the flight data quality check and data analysis have been processed, and results of initial cloud droplet size distributions in terms of the seeding signatures are shown from several cases. In general, there were no significant broadening of cloud droplet size spectra in any cases.
Except for the seeding experiments, several flights provided us in situ measurements of natural clouds. We sometimes encountered relatively developed clouds whose top temperature was warmer than -10 C, and most of such clouds had ice crystals and graupels. Those basic data will be useful to fully understand the mechanism of cloud and ice formation over the UAE regions and to verify the numerical simulations of cloud and precipitation.
In order to conduct an effective and efficient cloud seeding experiment, it is necessary to obtain the physico-chemical properties of BG aerosols in the atmosphere and to observe their spatial and temporal distributions before the experiment. The vertical profiles of aerosol number concentrations (corrected for STP conditions) showed rather constant below cloud base height. The IN and CCN abilities of BG aerosols are also essential information to accurately simulate cloud formation and precipitation development. The analysis of number concentrations of INP and CCN is shown from a few cases. The INP concentrations were typically ranged on the order of 1 to 10 L-1 and there were no significant height dependency. The CCN concentrations were typically several hundreds cm-3_stp and generally depended on the space and time.
In order to investigate cloud seeding effects, the B200T measured the evolution of aerosols and cloud particles from cloud base to upper levels before and after the C-90's flare seeding. Based on the same strategy and method as in previous studies on Japanese field campaigns, the flight data quality check and data analysis have been processed, and results of initial cloud droplet size distributions in terms of the seeding signatures are shown from several cases. In general, there were no significant broadening of cloud droplet size spectra in any cases.
Except for the seeding experiments, several flights provided us in situ measurements of natural clouds. We sometimes encountered relatively developed clouds whose top temperature was warmer than -10 C, and most of such clouds had ice crystals and graupels. Those basic data will be useful to fully understand the mechanism of cloud and ice formation over the UAE regions and to verify the numerical simulations of cloud and precipitation.
In order to conduct an effective and efficient cloud seeding experiment, it is necessary to obtain the physico-chemical properties of BG aerosols in the atmosphere and to observe their spatial and temporal distributions before the experiment. The vertical profiles of aerosol number concentrations (corrected for STP conditions) showed rather constant below cloud base height. The IN and CCN abilities of BG aerosols are also essential information to accurately simulate cloud formation and precipitation development. The analysis of number concentrations of INP and CCN is shown from a few cases. The INP concentrations were typically ranged on the order of 1 to 10 L-1 and there were no significant height dependency. The CCN concentrations were typically several hundreds cm-3_stp and generally depended on the space and time.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner