Historical trends of rain and air temperature in the Dominican Republic

The present work aims to characterize trends in air temperature and precipitation from the late 1930s to 2007 in the Dominican Republic, establishing whether some climate change patterns can be identified in the distribution of climate types of this country. The time series to be analysed present many quality issues and challenges, essentially due to abundance of missing data and inhomogeneous measurements. A number of statistical corrections have hence been applied: time series have been first filtered, then homogenized with respect to purposely built reference series, then completed through multiple imputation. Trend estimation has finally been performed on the annual and monthly scale. The analysis of homogenized and imputed series shows that significant trends occurred since 1930s, both in rain and air temperature. A pattern in the distribution of rain trends is evident in the country during the period 1939-2007, which reflects the influence of the orographic structure of the country on the atmospheric dynamics that dominate in the Caribbean region: significant negative annual trends are detectable in leeward areas, behind the main mountainous chains, while positive trends are generally evident in windward regions, exposed to trade winds. All the analysed series demonstrate an increase in air temperature: in Santo Domingo, minimum air temperature increased 3.0 +/- 0.5 degrees C since 1936, while the maximum air temperature increased 1.8 +/- 0.4 degrees C in the same period. Furthermore, an increase of rain erosivity can be detected on the South coast of the country, in some areas of the Cordillera Central and in the Northeast. Another important result is the increase of potential evapotranspiration, while significant uniform trends cannot be identified for extreme events.