Combination patterns of precipitation and its concentration degree determining the risk of dengue outbreaks in China

The amount and distribution of precipitation can determine dengue risk by affecting mosquito breeding;however,previous studies failed to incorporate this bivariate characteristic to examine dengue fever transmission.In the present research,nationwide data on daily dengue cases in China between January 2005 and December 2020 were obtained,and the top 12 cities accounting for 78%of total cases were selected for analysis.Precipitation patterns were quantified by weekly precipitation and precipitation concentration degree(PCD).On the basis of the combinations of both parameters,the exposure-response relationships of precipitation with dengue risk were established using generalised additive models,and the high-dengue-risk thresholds of precipitation patterns were further identified.Dengue burden was assessed by calculating attributable dengue cases.For the same amount of precipitation,the dispersed precipitation in the pre-summer rainy season leads to a higher dengue risk in autumn.The weekly precipitation of 100-150 mm and PCD of 0.2-0.4 constitute the highest risk scenario,and the average frequency of precipitation associated with dengue risk in 2013-2020 is 1.6 times higher than that in 2005-2012.A total of 3093 attributable dengue cases are identified.From 2005 to 2020,the amount of dispersed precipitation increased in southern and southwestern China and posed high dengue risks in central China.This study has improved the understanding of the health impacts of irregular rainfall under climate change.Our approach to identifying thresholds provides information for early warning systems and helps reduce the risk of dengue transmission in the long run.

Analysis of Intra-annual Heterogeneous Characteristics of Precipitation in Shaoguan City

Based on the daily precipitation data between 1965 and 2009 from 8 rainfall stations in Shaoguan City,the indexes of precipitation concentration degree（ PCD） and precipitation concentration period（ PCP） were calculated. And then inverse distance weighted（ IDW） interpolation method was used to analyze the heterogeneous distribution characteristics of inter-annual precipitation by introducing the spatial distribution of annual mean values,variable coefficients,correlation coefficients with annual precipitation,change trends and composite analysis. The results showed that PCD was mainly decreasing from southeast to northwest in spatial distribution,long-term average annual values of PCP were distributed in the first ten days of June at most region. Annual precipitation increased as PCD increased in southern region,but the change trend was the opposite in northern region. Annual precipitation increased as PCP lagged in most region. PCD and PCP mainly appeared upward trend. Composite analysis of PCD in more-precipitation years was similar to less-precipitation years in spatial distribution,but the PCD in less-precipitation years was higher.Seen from the mean in the whole region,PCP in more-precipitation years lagged about 20 days behind those in less-precipitation years. The research can provide basis for the production of agriculture and industry as well as disaster prevention and reduction.