Bremen 2017 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 13: Erdnaher Weltraum

EP 13.1: Hauptvortrag

Donnerstag, 16. März 2017, 16:30–17:00, GW2 B2880

Is there a solar 27-day signature in tropospheric clouds? — •Christian von Savigny¹, Kai-Uwe Eichmann², Christoph Hoffmann¹, and Martin Langowski¹ — ¹Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Greifswald, Germany — ²Institut für Umweltphysik, Universität Bremen, Bremen, Germany

Solar 27-day signatures have been identified in many different middle atmospheric parameters. In contrast, little is known about potential solar-driven 27-day signatures in the troposphere. Recent studies suggest the existence of a solar-driven 27-day signature in outgoing longwave radiation (OLR) - particularly in the tropical pacific region - and attribute it to a 27-day signature in tropospheric clouds. In this contribution we employ OLR data in combination with tropospheric cloud top height observations with the SCIAMACHY instrument on the Envisat satellite to investigate the presence of potential solar-driven 27-day variations. We concentrate on low latitudes, where earlier studies identified potential 27-day signatures. We find OLR and cloud top altitudes generally to be highly anti-correlated, as expected. We also find coherent variations in cloud top height in the Indian and Pacific Ocean region with amplitudes of up to 2 km and with periods generally in the 30 - 60 day range. These periods are indicative of the Madden-Julian-Oscillation (MJO). Although we cannot entirely rule out the possibility that part of the observed variability is related to the solar 27-day cycle, it appears more likely that quasi 27-day signatures in OLR and cloud parameters are driven by the MJO.