The Sevilleta’s climate is characterized by an intriguing combination of abundant sunshine, low humidity, and high variability for most meteorological factors. The site exists at the boundary between several major air mass zones that contribute to the dynamics of the local climate. The annual temperature/precipitation cycle of the Sevilleta is characterized by the dry, cold, winter months of December through February with a transition into a warmer, windy, but still generally dry, spring period from March to May. Spring is usually followed by a hot, dry early June which is followed by the hot but wetter months of July and August as a consequence of the arrival of the summer “monsoons”. Monsoon precipitation typically occurs as intense thunderstorms often accounting for a majority of the annual moisture. The monsoon’s moisture and temperatures ebb during September, and fall is characterized by moderate temperatures with drying from October through November. The monsoon moisture is less variable from year to year and accounts for a majority of the annual precipitation, while the non-monsoon moisture of the fall-winter-spring months is lower, more variable and strongly linked to the El Niño Southern Oscillation (ENSO) cycle.
Meteorological data have been collected at the Sevilleta since 1989 by a network of automated stations. There are currently 10 complete meteorological stations located across the refuge that quantify the spatially and temporally variable temperature and precipitation common on the Sevilleta, particularly during monsoon season. In 2003 the National Oceanic and Atmospheric Administration (NOAA) installed a National Climate Reference (USCRN) station adjacent to the Sevilleta Field Station. This system has more accurate temperature and precipitation instrumentation. In addition, Natural Resources Conservation Service (NRCS) installed a Soil Climate Analysis Network (SCAN) station that provides a more complete set of soil temperature and soil moisture readings than other meteorological stations at the Sevilleta. A few partial weather stations that primarily measure temperature and precipitation have been added over time. More recently tipping-bucket rain gauges with HOBO data loggers were installed near experiments to provide better spatial accuracy of precipitation inputs.Each meteorological station continuously measures the following: air temperature, relative humidity, mean wind speed, mean vectored wind speed, mean vectored wind direction, maximum and minimum wind speeds, total solar radiation and precipitation. Most stations also monitor soil temperature (1 and 10 cm depth) and soil moisture potential (10 and 30 cm depth). Through time most of the stations were equipped with Time Domain Reflectometry (TDR) probes that provide a measure of volumetric soil moisture in the top 30 cm. Summaries of all variables are output on an hourly basis; precipitation is also output on a 1-minute basis during periods of rain. VHF radio communication with the meteorological stations has recently been replaced by wireless communication systems that allow access via the Internet.