The ongoing loss of Arctic sea-ice cover has implications for the wider climate system. The detection and importance of the atmospheric impacts of sea-ice loss depends, in part, on the relative magnitudes of the sea-ice forced change compared to natural atmospheric internal variability (AIV). This study analyses large ensembles of two independent atmospheric general circulation models in order ...

We report preliminary results of an eeort to use variants of the Hidden Markov Models developed by speech researchers to characterize persistence and recurrence of atmospheric circulation patterns in a 36 year record of Northern Hemisphere 700-mb geopotential heights. Using a cross validation scheme, we t autoregressive hidden Markov models (ARHMMs) with a range of complexities , varying the au...

Egypt has recentely established a new precise geodetic framework based on the global WGS84 datum to furnish a national GPS-based reference system. For agricultural development along the Nile valley, the National Agricultural Cadastral Network (NACN) has been established with a precision of 1 part per million. However, the orthometric heights of the 112-station network have been computed utilizi...

High-fidelity geopotential calculation using spherical harmonics (SH) is expensive and relies on recursive non-parallel relations. Here, a global point mascon (PMC) model is proposed that is memory light, extremely simple to implement (at any derivative level), and is naturally amenable to parallelism. The gravity inversion problem is posed classically as a large and dense least squares estimat...

The recovery of a high resolution geopotential from satellite gradiometer observations motivates the examination of high performance computational techniques. The primary subject matter addresses specifically the use of satellite gradiometer and GPS observations to form and invert the normal matrix associated with a large degree and order geopotential solution. Memory resident and out-of-core p...

Successful satellite operations often depend on the ability to precisely determine the satellite’s position throughout it’s operational lifetime. Often, simplified models are used to reduce the computational complexity when producing an orbit determination solution. One example is the use of lower order gravitational terms when computing the state transition matrix. The US Naval Research Labora...