Stratospheric response to intraseasonal changes in incoming solar radiation

Superposed epoch analysis of meteorological reanalysis data is used to demonstrate a significant connection between intraseasonal solar variability and temperatures in the stratosphere. Decreasing solar flux leads to a cooling of the tropical upper stratosphere above 7 hPa, while increasing solar flux leads to a warming of the tropical upper stratosphere above 7 hPa, after a lag of approximately 6-10 days. Late winter (February-March) Arctic stratospheric temperatures also change in response to changing incoming solar flux in a manner consistent with that seen on the 11 year timescale: 10-30 days after the start of decreasing solar flux, the polar cap warms during the easterly phase of the quasi-biennial oscillation. In contrast, cooling is present after decreasing solar flux during the westerly phase of the quasi-biennial oscillation (though it is less robust than the warming during the easterly phase). The estimated composite mean changes in Northern Hemisphere upper stratospheric (~ 5 hPa) polar temperatures exceed 8 K and are potentially a source of intraseasonal predictability for the surface. These changes in polar temperature are consistent with the changes in wave driving entering the stratosphere.