Does Strong Tropospheric Forcing Cause Large-Amplitude Mesospheric Gravity Waves? A DEEPWAVE Case Study

On 4 July 2014, during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), strong low-level horizontal winds of up to 35 m s−1 over the Southern Alps, New Zealand, caused the excitation of gravity waves having the largest vertical energy fluxes of the whole campaign (38 W m−2). At the same time, large-amplitude mesospheric gravity waves were detected by the Temperature Lidar for Middle Atmospheric Research (TELMA) located at Lauder (45.0°S, 169.7°E), New Zealand. The coincidence of these two events leads to the question of whether the mesospheric gravity waves were generated by the strong tropospheric forcing. To answer this, an extensive data set is analyzed, comprising TELMA, in situ aircraft measurements, radiosondes, wind lidar measurements aboard the DLR Falcon as well as Rayleigh lidar and advanced mesospheric temperature mapper measurements aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V. These measurements are further complemented by limited area simulations using a numerical weather prediction model. This unique data set confirms that strong tropospheric forcing can cause large-amplitude gravity waves in the mesosphere, and that three essential ingredients are required to achieve this: first, nearly linear propagation across the tropopause; second, leakage through the stratospheric wind minimum; and third, amplification in the polar night jet. Stationary gravity waves were detected in all atmospheric layers up to the mesosphere with horizontal wavelengths between 20 and 100 km. The complete coverage of our data set from troposphere to mesosphere proved to be valuable to identify the processes involved in deep gravity wave propagation

Characteristics of tropical cyclones in the North Atlantic and East Pacific.

In this dissertation, I present a series of investigations to expand our understanding of TCs in the East Pacific and North Atlantic basins. First, I developed and applied a climatological tool that quickly and succinctly displays the spread of historical TC tracks for any point in the North Atlantic basin. This tool is useful in all parts of a basin because it is derived from prior storm motion trajectories and summarily captures the historical synoptic and mesoscale steering patterns. It displays the strength of the climatological signal and allow for rapid qualitative comparison between historical TC tracks and NWP models. Second, I have used a robust statistical technique to quantify the relationships between fifteen different metrics of TC activity in nine ocean basins and twelve climate indices of the leading modes of atmospheric and oceanic variability. In a thorough, encyclopedic manner, over 12,000 Spearman rank correlation coefficients were calculated and examined to identify relationships between TCs and their environment. This investigation was not limited to the East Pacific or North Atlantic, and new climatic associations were found between seasonal levels of TC activity and the major climate indices across the nine basins. This information is critical to forecasters, economists, actuaries, energy traders, and societal planners who apply knowledge of levels of TC activity on intraseasonal to interdecadal timescales. The statistics are also valuable to climatologists seeking to understand how regional TC frequency will change as the global climate warms. Third, I have examined the leading intraseasonal mode of atmospheric and oceanic variability, the Madden-Julian Oscillation (MJO), and discovered statistically significant relationships with the frequency of TC genesis, intensification, and landfall over the nine basins. Like the significance of the longer-period oscillations to the frequency of TC activity on intraseasonal and longer timescales, these results are highly relevant to the problem of short-term (one- to two-week) predictability of TC activity. These three investigations demonstrate the utility of historical datasets across a wide range of applications, from short-term forecasting to climate studies. In this way, the results highlighted in this dissertation represent a significant and positive contribution to meteorology. Collectively, they reveal multiple characteristics of TCs in the East Pacific and North Atlantic and provide greater understanding of the complex interactions between TCs and their surrounding larger-scale environment

Adaptive Orthogonal Matrix-Valued Wavelets and Compression of Vector-Valued Signals

Wavelet transforms using matrix-valued wavelets (MVWs) can process the components of vector-valued signals jointly, and thus offer potential advantages over scalar wavelets. For every matrix-valued scaling filter, there are infinitely many matrix-valued wavelet filters corresponding to rotated bases. We show how the arbitrary orthogonal factor in the choice of wavelet filter can be selected adaptively with a modified SIMPLIMAX algorithm. The 3×3 orthogonal matrix-valued scaling filters of length 6 with 3 vanishing moments have one intrinsic free scalar parameter in addition to three scalar rotation parameters. Tests suggest that even when optimising over these parameters, no significant improvement is obtained when compared to the naive scalar-based filter. We have found however in an image compression test that, for the naive scaling filter, adaptive basis rotation can decrease the RMSE by over 20%

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

The 1995 Science Information Management and Data Compression Workshop

This document is the proceedings from the 'Science Information Management and Data Compression Workshop,' which was held on October 26-27, 1995, at the NASA Goddard Space Flight Center, Greenbelt, Maryland. The Workshop explored promising computational approaches for handling the collection, ingestion, archival, and retrieval of large quantities of data in future Earth and space science missions. It consisted of fourteen presentations covering a range of information management and data compression approaches that are being or have been integrated into actual or prototypical Earth or space science data information systems, or that hold promise for such an application. The Workshop was organized by James C. Tilton and Robert F. Cromp of the NASA Goddard Space Flight Center

Statistical characteristics of MST radar echoes and its interpretation

Two concepts of fundamental importance are reviewed: the autocorrelation function and the frequency power spectrum. In addition, some turbulence concepts, the relationship between radar signals and atmospheric medium statistics, partial reflection, and the characteristics of noise and clutter interference are discussed

Mountain Wave Propagation under Transient Tropospheric Forcing: A DEEPWAVE Case Study

The impact of transient tropospheric forcing on the deep vertical mountain wave propagation is investigated by a unique combination of in-situ and remote-sensing observations and numerical modeling. The temporal evolution of the upstream low-level wind follows approximately a cos2 shape and was controlled by a migrating trough and connected fronts. Our case study reveals the importance of the time-varying propagation conditions in the upper troposphere, lower stratosphere (UTLS). Upper-tropospheric stability, the wind profile as well as the tropopause strength affected the observed and simulated wave response in the UTLS. Leg-integrated along-track momentum fluxes (−MFtrack) and amplitudes of vertical displacements of air parcels in the UTLS reached up to 130 kN m−1 and 1500 m, respectively. Their maxima were phase-shifted to the maximum low-level forcing by ≈ 8 h. Small-scale waves (λx ≈ 20–30 km) were continuously forced and their flux values depended on wave attenuation by breaking and reflection in the UTLS region