Using data published by RMOJ and Radio Meteor Observation Bulletin, “Activity Level index" every month in each region were calculated.
Activity Level Graphs with observing stations in Japan
What is “Activity Level" ?
This project adopts the new index which is “Activity Level" as relative value. This new index means how many times were echoes observed compared to background echo level. And two factors were considered. One is radiant factor. This factor is same as Visual observation which is 1/sin(h). Another is the elimination of error data.
You can see information of this method in research page.
The International Project for Radio Meteor Observation 2001-2003
* about this method in around 13th sheet
(H.Ogawa et al., The International Meteor Conference in 2003 )