Development of observed meteorological database to understand the deposition and dispersion processes over Fukushima and Kanto plain of Japan in March 2011

Abstract:

Meteorological simulations and understanding of the distribution of radioactive compounds depends on the accurate simulation of precipitation and on information regarding the timing of the emission of these radioactive pollutants from the power plant. Furthermore, three-dimensional rain drop and even fog information should be essentially important for understanding the wet deposition processes, since the initial drizzle is not measured by the tipping bucket-type raingauge.

We have developed various meteorological information links (http://www.chikyu.ac.jp/akiyo/firis/) and original radar and precipitation data will be released from the page. Here we present various radar images that we have prepared for March 2011. We prepared three-dimensional radar reflectivity of the C-band radar of JMA in every 10 minutes over all Kanto Plain centered at Tokyo and Fukushima prefecture centered at Sendai. We have released images of each altitude (1km interval) for 15^th - 16^thand 21th March (http://sc-web.nict.go.jp/fukushima/). The vertical structure of the rainfall is almost the same at 4km with the surface and sporadic high precipitation is observed at 6 km height for 15-16th. While, generally precipitation pattern that is similar to the surface is observed at 5km height on 21th.

On the other hand, an X-band radar centered at Fukushima university is also used to know more localized raindrop patterns at zenith angle of 4 degree. We prepared 10-minutes/120m mesh precipitation patterns for March 15^th, 16^th, 17^th, 18^th, 20^th, 21th, 22th and 23th. Quantitative estimate is difficult from this X-band radar, but localized structure, especially for the rain-band along Nakadori (middle valley in Fukushima prefecture), that is considered to determine the highly contaminated zone, is observed with only this X-band radar in the mid-night (JST) of 15^th. We will show the movie of how precipitation systems were moved at the meeting.

We are preparing rain/snow amount information and fog information during March 2011, and are going to compare them with atmospheric electricity fields that can be used for the index of dry deposition. The comprehensive datasets will reveal how the pollutants were moved and deposited, and will be used to improve atmospheric transport models.