Solar Activity and Regional Streamflow
Kansas District, U.S. Geological Survey
AUTHOR: Charles A. Perry, Research Hydrologist
Variations of Solar Activity Affect Regional Hydro-climate
This research focuses on the hypothesis that variations in solar activity affect regional streamflow. Variations in solar activity may control the amount of energy that reaches the Earth’s surface. These variations in solar energy may help create ocean temperature anomalies that can persist for years and move with the ocean currents. The ocean temperature anomalies can have an effect on meteorological factors such as atmospheric vorticity and moisture, both important for precipitation formation. Varying amounts of precipitation controls the regional hydrology including streamflow, groundwater, and lake levels.
Variations in solar activity are manifested in the magnetic structure of the Sun, total solar irradiance, and the strength of the solar wind. Solar wind speed and density directly affect the flux of galactic cosmic rays to the Earth and variations in the Earth’s geomagnetic field. Each of these parameters varies on an approximate 11-year cycle than can range from 9 to 14 years in length which over time displays a unique “fingerprint.” The long-term streamflow record of the Mississippi River at St. Louis, Missouri exhibits a similar “fingerprint.” The historic records of the geomagnetic index aa and 36 month moving averages of Mississippi River streamflow are compared in the following graph.
Comparison of the 36-month moving average of the Mississippi River streamflow and the Geomagnetic Index AA. Streamflow has been lagged 34 years after the Geomagnetic data.
The mechanism responsible for the linkage is thought to involve five important processes:
- Variable solar activity causes variation in total solar irradiance (energy) that reaches the top of the Earth’s atmosphere. Variable solar activity controls the flux of galactic cosmic rays which may affect the formation of low-level clouds that control atmospheric albedo (reflectance).Variations in total solar energy reaching the Earth’s surface are amplified by changes in atmospheric albedo;
- The variable solar energy is absorbed by tropical oceans creating large pools with different amounts of stored energy;
- Pools of ocean water with varying amounts of stored energy are transported by major ocean currents (Ocean Conveyor Belt) to other global locations where;
- Differential evaporation rates from oceanic areas alter global atmospheric pressure patterns (i.e., jetstream position and associated atmospheric vorticity);
- These patterns dictate regional precipitation and temperature distribution and, consequently, the regional hydrology.
This mechanism is outlined in two papers (Perry, 2006) and (Perry, 2007), and is shown schematically below.
All rivers in the United States appear to follow the solar signal as seen in the graph below which compares the 1st principle component of U.S. Streamflow (courtesy Greg McCabe, USGS) with a Cosmic Ray/Total Solar Irradiance combination index.
For more information contact:
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, Kansas 66049-3839