Rossby-wave driven stirring of the UTLS - a detailed view on the intricately layered structure by the 3-D imaging limb-sounder GLORIA

Abstract:

The Gimballed Limb Radiance Imager of the Atmosphere (GLORIA) is a new instrument that combines a classical Fourier transform spectrometer (FTS) with a 2-D detector array. Imaging allows the spatial sampling to be improved by up to an order of magnitude when compared to a limb scanning instrument. GLORIA is designed to operate on various high altitude research platforms. The instrument is a joint development of the German Helmholtz Large Research Facilities Karlsruhe Institute of Technology (KIT) and Research Centre Juelich (FZJ). GLORIA builds upon the heritage of KIT and FZJ in developing and operating IR limb sounders (MIPAS, CRISTA).

In Summer 2012, GLORIA was an integral part of the first large missions for the German research aircraft HALO dedicated to atmospheric research, TACTS and ESMVAL. The data span latitudes from 80°N to 65°S and include several tomographic flight patterns that allow the 3-D reconstruction of observed air masses.

We provide an overview of the heterogeneous structure of the upper troposphere/lower stratosphere (UTLS) as observed over Europe. Retrieved water vapor and ozone are used to identify the tropospheric or stratospheric character of air masses and can thus be used to visualize the multi-species 2-D (and partly 3-D) chemical structure of the UTLS. A highly intricate structure is found consisting often of fine-scale layers extending only several hundred meters in the vertical. These horizontally large-scale structures are thus below the typical vertical resolution of current chemistry climate models.

Trajectory studies reveal the origin of the filaments to be Rossby wave-breaking events over the Pacific and Atlantic that cause tropical air stemming from the general area of the Asian monsoon to be mixed across the jet-stream into the subtropical lowermost stratosphere.

These results demonstrate a rich spatial structure of the UTLS region at the subtropical jet, where the tropopause break is perturbed by breaking Rossby waves. The frequency of such observations seems to indicate that such a highly heterogeneous state is a regular occurrence for the UTLS in summer over Europe. Further tomographic processing of GLORIA data will deliver further 3-D snapshots of stirred filaments.