Statistical Analysis on Daily Variations of Birch Pollen Amount with Climatic Variables in Sapporo

Abstract

Birch pollen mainly causes springtime allergy-related diseases, birch pollinoses, widely known in high-latitude countries. By utilizing the observation in Sapporo from 2001 to 2011, we found that the daily pollen amount almost follows the log-normal distribution with its characteristic time-scale of several days. The pollen amount itself was therefore taken as a major predictor for its day-to-day variations. Another predictor was chosen from climatic variables that were possibly related to the pollen amount such as temperature, rainfall, sunshine duration, wind, relative humidity, rainfall, and daily temperature difference to explain daily variations of the pollen amount. A resulting statistical equation with two independent predictors of lagged pollen amount and diurnal temperature range based on the multiple regression analysis provided a reasonable hindcast prediction with the correlation coeffcient with observation being 0.80. Moreover, the equation was better fitted to the observations in abundant years than in poor-yield years.