Climate and Weather Monitoring at Fort Larned National Historic Site: Water Year 2022

The sandstone buildings, Fort Larned National Historic Site, Kansas.

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Overview

Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems and across the Southern Plains (Woodhouse and Overpeck 1998). Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.

At Fort Larned National Historic Site (Figure 1), Southern Plains Network scientists study how ecosystems may be changing by taking measurements of key resources, or “vital signs,” year after year—much as a doctor keeps track of a patient’s vital signs. This long-term ecological monitoring provides early warning of potential problems, allowing managers to mitigate them before they become worse. At Fort Larned National Historic Site, we monitor climate, among other vital signs.

Reporting is by water year (WY), which begins in October of the previous calendar year and goes through September of the water year (e.g., WY2022 runs from October 2021 through September 2022). This article reports the results of climate monitoring at Fort Larned National Historic Site in WY2022.

Reference: Woodhouse, C. A., and J. T. Overpeck. 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society 79(12): 2693–2714. https://doi.org/10.1175/1520-0477(1998)079%3C2693:YODVIT%3E2.0.CO;2.

Figure 1. Weather station near Fort Larned National Historic Site.

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Fort Larned National Historic Site, Kansas

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Climate and Weather

There is often confusion over the terms “weather” and “climate.” In short, weather describes instantaneous meteorological conditions (e.g., it’s currently raining or snowing, it’s a hot or frigid day). Climate reflects patterns of weather at a given place over longer periods of time (seasons to years). Climate is the primary driver of ecological processes on earth. Climate and weather information provide context for understanding the status or condition of other park resources.

Methods

A National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather station (Larned 2 KS # 144531) has been operational 5.8 miles (9.3 km) east of Fort Larned National Historic Site since 2009 (see Figure 1). The station typically provides a reliable climate dataset. However, in WY2022 it was missing data on 29 days. As a substitute, climate analyses in this year’s report use 30-year averages (1991–2020) and gridded surface meteorological (GRIDMET) data from the location of the visitor center at the park. Subsequent reports may revert to the weather stations as the data source depending on future data quality.

GRIDMET is a spatial climate dataset at a 4-km resolution that is interpolated using weather station data, topography, and other observational and modeled land surface data. Temperature and precipitation estimated from GRIDMET may vary from actual weather at a particular location, depending on the availability of weather station data and the difference in elevation between the location of interest and that assigned to a grid cell. Data from both weather station and GRIDMET are accessible through Climate Analyzer.

Results for Water Year 2022

Precipitation

Annual precipitation at Fort Larned National Historic Site in WY2022 was 20.69″ (52.6 cm; Figure 2), 5.04″ (12.8 cm) less than the 1991–2020 annual average. The precipitation deficit primarily occurred in November, December, February, April, June, and August, which had monthly rainfall totals that were 0.68″ to 2.53″ below the 1991–2020 monthly averages.

Air Temperature

The mean annual maximum temperature at Fort Larned National Historic Site in WY2022 was 71.6°F (22.0°C), 2.7°F (1.5°C) above the 1991–2020 average. The mean annual minimum temperature in WY2022 was 42.6°F (5.9°C), 0.3°F (0.2°C) below the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2022 differed by as much as 10.7°F (5.9°C; see December as an example) from the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures were generally warmer than average for the entire year, except in January and February. Mean monthly minimum temperatures were more variable relative to monthly averages, with temperatures near average during several months and cooler than average from January–April.

Figure 2. Climogram showing monthly precipitation and mean maximum and minimum air temperatures in water year 2022 (WY2022) and the 1991–2020 averages at Fort Larned National Historic Site. Data source: GRIDMET via climateanalyzer.org.

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Drought

Reconnaissance drought index (Tsakiris and Vangelis 2005) provides a measure of drought severity and extent relative to the long-term climate. It is based on the ratio of average precipitation to average potential evapotranspiration (the amount of water loss that would occur from evaporation and plant transpiration if the water supply was unlimited) over short periods of time (seasons to years). The reconnaissance drought index for Fort Larned National Historic Site indicates that WY2022 was drier than the 1991–2022 average from the perspective of both precipitation and potential evapotranspiration (Figure 3).

Reference: Tsakiris G., and H. Vangelis. 2005. Establishing a drought index incorporating evapotranspiration. European Water 9: 3–11.

Figure 3. Reconnaissance drought index for Fort Larned National Historic Site, water years 1991–2022. Drought index calculations are relative to the time period selected (1990–2022). Choosing a different set of start/end points may produce different results. Data source: GRIDMET via climateanalyzer.org.

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Authors: Kara Raymond, Andy Ray

Please cite this report as
Raymond, K., and A. Ray. 2023. Climate and Weather Monitoring at Fort Larned National Historic Site: Water Year 2022. Southern Plains Network, National Park Service, Pecos, New Mexico.