HR: 1340h
AN: A23C-0962    [Abstracts]
TI: Dependence Of Cloud And Precipitation Developments On Cloud Condensation Nuclei Concentrations And Thermodynamic Conditions-A Modeling And Observational Study
AU: * Yang, H
EM: loveatm@yonsei.ac.kr
AF: Department of Atmospheric Sciences, Yonsei University, Seoul, 120-749 Korea, Republic of
AU: Yum, S
EM: ssyum@yonsei.ac.kr
AF: Department of Atmospheric Sciences, Yonsei University, Seoul, 120-749 Korea, Republic of
AB: Thermodynamic conditions, which can be represented by convective available potential energy (CAPE), and cloud condensation nuclei (CCN) concentrations, which vary greatly depending on geographical locations and air mass changes, are important factors that determine cloud and precipitation development. How precipitation efficiency is affected by these two factors is investigated using a two dimensional cloud model with detailed (using hydrometeor size bins) cloud microphysics and an observation analysis. Two different CCN concentrations, representing maritime and continental environments, are used as input CCN data and the model is run on eight thermodynamic conditions that are selected from observational soundings. Model run results showed that small CAPE conditions developed a shallow cloud with negligible precipitation when continental CCN were used while maritime CCN produced somewhat deeper clouds with significant precipitation. In case of strong convection (large CAPE), the sensitivity of the precipitation rate to the CCN concentrations was relatively low. In general both maritime and continental clouds produced significant precipitation but continental, rather than maritime, clouds were deeper and eventually produced stronger updrafts. Another important factor is found to be the altitude difference of lifting condensation level (LCL) and freezing level (FL). Some thermodynamic soundings with a large CAPE but a deep FL-LCL did not produce significant rain, because the cloud could not penetrate the FL and thus ice process was prohibited. This demonstrates that appearance of ice phase precipitating particle is important in initiating heavy rain. As an effort to find some observational support for these model results, 6-hourly sounding data at one Korean weather station and the hourly precipitation data from a nearby (20 km apart) Automatic Meteorological Observing Station (AMOS) were analyzed for the year 2002. Among the 1460 rawinsonde soundings, only 30 cases were classified as related to an isolated convective precipitation event, for which the measured CAPE could be used as an indicator of convective activity. Analysis of these cases showed that there was more rain for thinner FL-LCL (colder season) than deeper FL-LCL (warmer season) for similar CAPE, probably because of high FL and thus lack of ice process. However, no information was available for CCN concentrations that are associated with the cases selected here. Further analyses of observational data will be presented at the conference.
DE: 3310 Clouds and cloud feedbacks
DE: 3311 Clouds and aerosols
DE: 3314 Convective processes
DE: 3354 Precipitation (1854)
DE: 3367 Theoretical modeling
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005