Kansas climate basics: Part 3 -- Precipitation trends over the last 121 years
(Editor’s note: The following article is one in a series of articles in the Agronomy eUpdate that examines the historical record of temperature and precipitation in Kansas. The methods used to do this analysis of temperature trends in Kansas is explained in the introductory article in this series, from eUpdate No. 571, May 20, 2016. – Steve Watson)
Precipitation trends in Kansas
Precipitation in Kansas is highly variable from year to year, with the statewide annual average from a low of 17.3 inches in 1956 to a high of 43.7 inches in 1951 (Fig. 1). From the western third to the eastern third of Kansas, long-term mean annual precipitation totals (over the last 121 years) were 20.2 inches, 26.0 inches, and 37.2 inches (Fig. 1). Over the last two decades, annual amounts of precipitation have increased. Due to larger year-to-year variability, however, the long-term annual precipitation does not show any statistically significant increase or decrease at the 95% confidence levels.
Figure 1. Kansas annual precipitation time series over 1895 to 2015: Western Kansas (top panel); Central Kansas (middle); and Eastern Kansas precipitation variations (bottom). The black lines are period-of-record mean over 1895 to 2015 (inclusive). A 9-point moving average was used to provide an indication of multi-year trends (blue lines). When trends are statistically significant the trend rates are displayed. All adjusted p values are shown.
For the state as a whole, the seasonal means of precipitation are nearly 20 inches during spring (March-April-May) and summer (June-July-August) seasons combined. The fall (September-October-November) and winter (December-January-February) seasons only contribute about 9.5 inches (Fig. 2). The winter season’s mean is less than 2.8 inches, with small year-to-year variations.
There were no statistically significant trends in any of seasons at 95% confidence level. Precipitation rates did show statistically significant increases in eastern and central Kansas, however, at the 90% confidence level. Seasonally, only spring precipitations showed a statistically significant increase rate at the 90% confidence level.
Figure 2. Kansas seasonal precipitation time series over 1895 to 2015, from top to bottom panels: Spring, summer, fall, and winter precipitation variations. The black lines are period-of-record means over 1895 to 2015 (inclusive). A 9-point moving average was used to provide an indication of multi-year trends (blue lines). When trends are statistically significant the trend rates are displayed. All adjusted p values are shown.
Xiaomao Lin, State Climatologist, Department of Agronomy
John Harrington Jr., Department of Geography
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist