CHANGES IN PRECIPITATION REGIMES IN THE UNITED STATES

This study aims to investigate how climate change has affected precipitation patterns in the US. Precipitation provides us with freshwater, the most vital resources for life; but it also brings damages from extreme storms and flooding. There are three major mechanisms of precipitation in the United States: (1) frontal storms dominate during colder months from late fall to early spring and generally last for longer periods of time; (2) convective storms or “pop-up thunderstorms” are more common during late spring and summer, and typically bring more intense rainfall for shorter period of time, and (3) precipitation due to orographic lifting in mountainous regions. The objectives of this study are to establish (1) if precipitation regimes have changed in the United States in the past 60 years as a result of climate change, and (2) if changes in precipitation patterns are similar for different types of storms and (3) if changes in precipitation patterns are similar in different climate regions. For this purpose, we used hourly and daily precipitation data from 1900 through 2010 collected from National Climate Data Center and US Historical Climatology Network to look for trends in the frequency and intensity of storms of various durations, and examine the statistical significance of these trends. The investigation is conducted in GIS in order to examine spatial variations of such changes.