Relative Humidity Characteristic Analysis of Henan Tobacco-Growing Areas in Recent 35 Years

The temporal-spatial distribution and variation features of ten-day relative humidity and the relationship between relative humidity and other meteorological factors in Henan tobacco-growing areas were analyzed using data from 41 stations over the years of 1971-2005 in Henan,adopting the methods of linear trend,Mann-Kendall test and wavelet analysis.Results indicated that during period April and September,the ten-day average relative humidity and ten-day maximum humidity and ten-day minimum have a significantly increasing trend.Abrupt changes took place from mid-to-late June to early or middle July and it showed high.The ten-day relative humidity was mainly 80% from mid-July to early September and other times it was mainly 60%~80%.Two cycles of relative humidity exist with periods of 3,6 and the former tended to evidently,what was more,the two periods showed localization.Relative humidity tended to rising in tobacco growth period and it was too high in maturation period.The relative humidity in different tobacco-growing areas in Henan ranked as south Henan,central Henan,west Henan and the variation of relative humidity in different growth period was root elongation stage,vigorous growth and stage maturing stage.There was a significantly positive correlation between relative humidity and rainfall,and significant negative correlation between relative humidity and sunshine duration,evaporation.The correlation between relative humidity and temperature was not significant.