Global distribution of Cloud Droplet Effective Radius from POLDER Measurement
Abstract
The cloud droplet size distribution is a key parameter in calculating the radiative forcing of liquid clouds. The retrieval of cloud droplet size via Polarization and Directionality of the Earth's Reflectance (POLDER) is able to obtain the effective radii (CDR) and effective variance (EV) simultaneously. The impact of cloud horizontal inhomogeneity can lead to large uncertainties in the retrieval. For example, the sub-grid-scale variability in the CDR biases both the CDR and EV estimates. On the other hand, the variability in the CDR reshapes the observed rainbow structures and results in a lot of retrievals being inaccessible. It is also found that the retrieval is accurate with less directional sampling along the cloudbow region and is largely free of random noise. Therefore, higher-resolution retrievals provide much more successful droplet size distribution estimates and reduce the biases introduced by the effects of horizontal inhomogeneity in clouds. Using the POLDER data of 2008, the retrieval of cloud size distribution is performed in a resolution of 75 km × 75 km measurements, and unlike the operational procedure, the measurements in the primary rainbow region (137-145◦) are used to ensure retrievals of large droplet (>15µm) and to reduce the uncertainties caused by cloud heterogeneity.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMPP41A2238S
- Keywords:
-
- 0321 Cloud/radiation interaction;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 0429 Climate dynamics;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES