Characterization of Virginia’s Climate

The study aims to characterize the general temperature climate of Virginia. It uses the National Oceanic and Atmospheric Administration’s (NOAA) nClimGrid-Daily dataset, a gridded dataset (2.5 arcminute resolution) of temperature and precipitation in the contiguous United States. Gridded data facilitates analysis of spatial characteristics by providing evenly-spaced data, compared to data from irregularly-spaced weather observations. The study examines daily high, low, and average temperatures for 1991-2020, a thirty-year time period which is standard in defining an area’s climatology. Preliminary analysis is confined to coldest and hottest months, January and July. In addition to monthly means, the temperatures of extreme hot and cold days are of interest because of the effects of extreme events on health, transportation, and other aspects of society and ecology. Therefore, this study includes 5th and 95th percentile values as measures of extremes, and it examines geographical features of individual extreme heat events in Virginia. Contours of uniform temperature align southwest to northeast, with the coldest temperatures occurring in the Blue Ridge/Appalachian Mountains, and January having a larger temperature range than July. Across these metrics the daily high (daytime) temperature range in January is slightly smaller than the daily low (nighttime) range. Most notably, coastal moderation is more apparent at night than during the day, indicating that the warming effects of coastal moderation are more influential than its cooling effect on Virginia’s climate. This characteristic is also found in comparing the days and nights of July, further supporting the finding. The effects of topography (lower temperature at higher elevation) are greater in July than in January. By utilizing the nClimGrid-Daily dataset, this study identified general climatic patterns in Virginia and found unique characteristics in Virginia’s day-night cycle as well as the seasons.