| dc.description.abstract | Warm clouds perform a key role in the system of weather and climate. It has a considerable impact on radiative forcing and also precipitation properties. Knowledge about their raindrop size distribution (RSDs) is useful in realizing rain integral-parameters and in the understanding of precipitation microphysics. Unfortunately, as a result of the discontinuity of spatiotemporal observation, obtaining a detailed process that occurs in warm clouds is still challenging. The characteristics of rain microphysical of warm precipitating clouds on Taiwan Island are still not specifically investigated. The objective of this study is to identify the characteristics of the raindrop size distribution of warm precipitating cloud in Northern Taiwan. This research also aims to reveal how the warm cloud properties relate to the alteration in rainfall intensity and how the changes relate to their drop size distribution in Northern Taiwan during the winter season from December 2017 to January 2018. The observations and analyses are based on the space-borne satellite observation (Himawari-8/9) and in-situ surface Joss-Waldvogel Disdrometer (JWD) datasets.
This study found that warm precipitating clouds observed from optically medium clouds with a preferred value of Cloud Effective Radius (CER) of 20 - 30 µm, Cloud Liquid Water Path (CLWP) of 130 - 400 g m-2, and Cloud Top Pressure (CTP) of 440 – 560 hPa. Its raindrop size features consist of higher concentration of small raindrops rather than middle and large drops with a larger mean weighted diameter (Dm), higher total number concentration (NT), narrower and more-isolated intercept parameter (log10Nw), with smaller and more homogenous of shape (µ) and slope (Λ) parameters as the rain intensity become stronger.
The cloud-precipitation regimes show obvious discriminating features only on specific of the pair of the investigated cloud with the raindrops parameters, such as COT with Dm and NT; CER with Dm, NT, and log10Nw; and CLWP with Dm, µ and Λ. The result shows Dm substantially increase as CLWP increase, whereas it decreases for COT and become homogenous when CER is getting larger. In contrast, NT decreases with COT, while for CER shows a unimodal trend for NT and log10Nw with peaks of 20 - 30 µm. µ and Λ are monotonically decreased and tends to be constant as the CLWP increased. These results indicate the usefulness of these cloud parameters on specific selected raindrop parameters. | en_US |