[14] Ideas for new applications 2

[14-2] March 1, 14:50-15:10

Assimilation Experiment of Weather Diary Data Using an LETKF System

Panduka Neluwala (Department of Civil Engineering, The University of Tokyo), Kinya Toride (Department of Civil and Environmental Engineering, University of California), and Kei Yoshimura (Institute of Industrial Science, The University of Tokyo and Atmosphere and Ocean Research Institute, The University of Tokyo)


Personal diaries provide useful information about the historical weather when the modern instrumental observations were absent. This study focused on the 18th -19th century and aims to use the Japanese diaries to assimilate weather information in a General Spectral Model (GSM). Although diaries tend to have a short description of daily weather conditions which make challenging to accomplish our goal, a recent study showed the potential to use these data with idealized experiments. This study further extended the idealized experiments towards assimilating diary data. We utilized Japan Meteorological Agency (JMA) observation data during the modern period, and 17 stations were considered over Japan representing the availability of diaries during the 18th -19th century. Local Ensemble Transformed Kalman Filter (LETKF) system was used for assimilating observations to the GSM. To incorporate the observation limitations, we assimilated only zero precipitation days and daily average total cloud column percentage after categorizing into 10%, 50% and 80% categories representing weather description of sunny, partially cloudy and cloudy in diaries. A random error of 2 (mm/day) and 30% was added respectively to zero rainfall events and to cloud observations to represent observation uncertainties. The comparison of results indicated that assimilation of data improved the assimilated as well as other atmospheric fields.

  Presentation file: 14_2_P.Neluwala.pdf