Project Details
Projekt
Impact of planetary waves and solar proton events on long-term variations of noctilucent clouds II
Applicant
Professor Christian von Savigny, Ph.D.
Subject Area
Atmospheric Science
Term
from 2007 to 2013
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 42779644
The polar summer mesopause regions in both hemispheres feature the recurring occurrence of optically thin H2O clouds known as noctilucent clouds (NLCs) or polar mesospheric clouds (PMCs). NLCs were studied intensively by many groups in the recent past, mainly because these clouds are potentially early indicators of global change. However, the validity of the proposed mechanisms leading to long-term changes in NLCs, i.e., a negative temperature trend due to increased radiative cooling by CO2 and a positive trend in upper mesospheric H2O caused by CH4 oxidation was not yet demonstrated convincingly. Moreover, there are several other processes and mechanisms that may introduce long-term and solar cycle variations in NLCs. This project aims at improving our understanding of several of these other processes that may have a significant impact on the geographical distribution of NLCs and their long-term variation, but which are only poorly understood or not understood at all. These processes are (a) planetary wave perturbations of NLCs, (b) pre- cipitation of solar energetic particles, (c) short-term variations in solar irradiance, and (d) recently discovered interhemispheric coupling processes affecting the thermal conditions at the polar summer mesopause. These processes drive the strong variability in NLCs and will be studied using a suite of satellite observations (SBUV, SCIAMACHY/Envisat, OSIRIS/Odin, OMI/Aura) of NLCs, middle atmospheric temperature and H2O abundance (MLS/Aura, SABER/TIMED, SCIAMACHY/Envisat). In collaboration with different CAWSES and non-CAWSES partners model simulations of chemical, thermal and dynamical effects of solar proton events will be used in particular to improve our understanding of the physical mechanisms leading to NLC depletion during and after solar proton events.
DFG Programme
Priority Programmes
International Connection
USA
Participating Persons
Dr. Heinrich Bovensmann; Professor Dr. John Philip Burrows; Dr. Matthew DeLand
