Plan of the Field Observation in the Tokyo Metropolitan Area: Lifecycle of Cumulonimbus Experiment (LCbEX)

Disasters caused by local heavy rainfall, tornadoes, hail, and lightning are serious social problems especially in urban areas in Japan. It is known that these phenomena are associated with developed cumulonimbi (Cb). The understanding of development mechanism and development of prediction method are needed for the reduction of these disasters.

National Research Institute for Earth Science and Disaster Prevention (NIED), Japan started field observation of lifecycle of Cb (Lifecycle of Cb Experiment: LCbEx I) in the Tokyo Metropolitan Area from 2011 using a Ka-band Doppler radar, two X-band polarimetric radars, and stereo photography, etc. A case study of early development stage of Cb was carried out with Ka-band Doppler radar data (Sakurai et al. 2012) and the thermodynamical retrieval using sector volume scan data by two X-band polarimetric radars at 1 to 2 min interval. Furthermore it was shown that the data assimilation of cloud liquid water content (latent heat) and potential temperature deviation had important effects to prediction of Cb development using cloud resolving model.

In 2013 and 2014, ten microwave radiometers, three Doppler lidars, and five Ka-band radars were additionally set up in the Tokyo Metropolitan Area covered by the X-band polarimetric radars for the observation of environment of cumulus (Cu) initiation and Cb development, and cloud before precipitation. We can get information on water vapor, wind field in the clear air, and non-precipitating cloud, respectively. All data can be collected and processed in real-time in the NIED.

Development of estimation method not based on statistical methods of vertical profile of water vapor and other parameters is one of issues related to microwave radiometer measurements. Three of the Ka-band radars have polarimetric capability that is thought to be useful for data quality control and detection of ice crystals. Precise estimation of cloud liquid water content is one of issues and the comparison with in-situ measurements is planned.

The field observation (LCbEx II) using these new remote sensors will be started from the summer season in 2015 for the understanding of development process including initiation of Cu and early stage of Cb development, precipitation formation process from cloud, and prediction of Cb development using an NWP model and data assimilation.