Analysis of Warm Season Precipitation and Wind Flow Within Hubbard Brook Experimental Forest

It has been theorized that climate change may alter orographic processes by shifting atmospheric circulation patterns and increasing the frequency of extreme weather events, potentially intensifying precipitation in mountainous regions. This study aims to quantify these effects within the Hubbard Brook Experimental Forest in New Hampshire. We analyzed 15-minute precipitation data from two rain gauges positioned on opposing sides of Hubbard Brook Experimental Forest during the warm season (April 1st to September 30th) over a 50-year period from 1970-2019. The analysis involved determining maximum precipitation rates for storm events as defined by a pre-existing storm event dataset and calculating the 90th, 95th, and 99th percentile rain rates. Storm events were categorized into common (recorded by both gauges) and unique (recorded by only one gauge). ERA5 wind reanalysis data for two 5-year periods (2000-2004 and 2015-2019) were used to examine wind patterns at the 10m, 925mb, 850mb, and 700mb levels. Results indicated that annual warm season total precipitation amount as well as frequency of precipitation observations increased over the study period. It was determined that veering wind patterns were present during storm events in both periods, with winds shifting westward and exhibiting reduced variability from 2015-2019 compared to 2000-2004. It was determined that storm events unique to one rain gauge showed greater variability in wind direction than common events. Additionally, higher maximum precipitation rates were associated with more westerly low-level wind flows. These findings underscore the influence of orographic processes on precipitation patterns and highlight changes in wind characteristics over time.