Quantifying the Effect of the Upper Atmospheric Electric Potential on Lower Atmospheric Temperature and Pressure

Weather and climate prediction are inevitably limited by incomplete knowledge of the Earth system and its external influences. One under-explored and consequently controversial area of research is the meteorological influence of the Sun through processes other than direct radiation, such as variations in the Earth-ionosphere electric potential in the global electric circuit driven by solar wind-magnetosphere-ionosphere interactions. Previous work has suggested that a relationship exists (often termed the Mansurov effect) but previous correlations have been indirect and the effects most likely underestimated. BAS has considerable expertise in the measurement and understanding of the ionospheric electric potential pattern using the Super Dual Auroral Radar Network (SuperDARN). We propose to use 15 years of SuperDARN electric potential measurements from both the northern and southern hemispheres to conduct the most comprehensive analysis to date of the relationship between the ionospheric electric potential and atmospheric temperature and pressure. If this analysis confirms a significant relationship then its consequences for weather and climate will be assessed by studying the climatologies for different ionospheric potential states and evaluating the possible effects on atmospheric modes like the North Atlantic Oscillation.

Scientific mechanisms are often viewed as controversial, or not important, because they have been poorly measured or are poorly understood. Only with a full understanding of such mechanisms can their scientific, economic, and societal impact be properly assessed. The effect of solar variability on climate is presently a very high-profile area of scientific research with sceptics of anthropogenic climate change often exploiting the poorly-understood nature of many of these mechanisms to support the view that natural variability can explain the unprecedented warming of the last 50 years. It is only by having a clear quantitative understanding of all the mechanisms by which solar variability affects the Earth's climate that some closure can be brought to these arguments, and the uncertainty in climate change scenarios can be reduced.

There is presently a low level of understanding of the solar influence on weather and climate. According to the Intergovernmental Panel on Climate Change (IPCC 2007) "More research on climate is needed before the magnitude of solar effects on climate can be stated with certainty". The IPCC focuses on the effects of changing solar irradiance. It is now well known that total solar irradiance, which provides heat input to the lower atmosphere and oceans, varies by ~0.1% through the solar cycle. In addition, ultraviolet irradiance, which affects stratospheric ozone production and temperature, varies by a few percent. The effects of these irradiance mechanisms on climate have now been well modelled and it has been shown that they can result in significant climate effects if present over a long time interval or if there are non-linear responses that give amplifying feedbacks. The IPCC also note that there might be other mechanisms though which the Sun can couple to the Earth's climate. These include such mechanisms as the effect of energetic particle precipitation on stratospheric ozone, and the effect of solar-driven variations in the global electric circuit (GEC) on lower atmosphere temperature and pressure. NERC also identifies, within its climate theme, that there is a need to "improve understanding of natural variability and the link with climate change", and that there is a need for "the inclusion of a wider range of processes" in climate models.

This proposal aims to provide a quantitative measure of the influence of solar variability on weather and climate, through variations in the ionospheric electric potential and consequently in the global electric circuit. Measurements and monitoring of the global electric circuit have been neglected in recent decades, which has prevented the testing of the basic hypotheses except for some limited regions or by using historical data.

Hence, we envisage the impacts of the project to be:

(i) Quantitative measures of the effect of variations in the ionospheric electric potential on atmospheric pressure and temperature and atmospheric pressure systems like the North Atlantic Oscillation that will provide input for weather and climate modellers at institutes such as the Met Office or ECMWF.

(ii) Raising the profile of the GEC (and its possible effects on weather and climate) within the climate and general science community.

(iii) Ultimately, a reduction in the uncertainty in climate change scenarios (e.g., input to IPCC).