Global Positioning System Reference
In-Depth Information
possible non-chemical effects, such as dynamical changes of vertical ion motions induced by
winds and E×B drifts, tides and waves in the mesosphere/lower thermosphere (MLT)
region, which can be dynamically coupled upward to generate ionospheric perturbations
and oscillations.
Ground-based and space borne GPS observations have been widely used in atmospheric
sounding, including sensing tropopsheric precipitable water vapor (PWV), ionospheric total
electron content (TEC) and atmospheric profile information (e.g., pressure, temperature,
humidity, tropopause and ionospheric electron density). These observations have facilitated
greater advancements in meteorology, climatology, numerical weather model, atmospheric
science and space weather (e.g., Jin et al., 2007; Jin et al., 2009; Schmidt, et al. 2010). For
example, the dual frequency ground GPS array could detect ionospheric response and its
processes during large geomagnetic storms (Jin et al., 2008). Meanwhile, ground GPS also
observed the plasma bubbles and retrieved reliable propagation characteristics of the
depletions without assumptions about the mapping of the depletion along magnetic field
lines to large latitudinal distances, comparable with airglow data (Haase et al., 2011).
Additionally, space-borne GPS receivers have proven very successful in making high
vertical resolution and global atmospheric measurements using the radio occultation (RO)
technique The existing GPS radio occultation (RO) missions have been widely used to
estimate the detailed vertical profile information, including pressure, temperature, gravity
waves and sporadic E-layers as well as their variation characteristics, particularly six
satellites of the Taiwan/US FORMOSAT-3/COSMIC (FORMOsa SATellite mission-
3/Constellation Observing System for Meteorology, Ionosphere and Climate) mission with
more than 2000 radio occultation profiles per day. Schmidt et al. (2010) was the first to
observe upper tropospheric warming and lower stratospheric cooling using GPS RO data
(2001-2009). Although a number of progresses in atmospheric and ionospheric sensing have
been made using GPS RO missions in the past few years, they still do not satisfy actual
requirements for short-time scales and higher temporal-spatial resolution monitoring
together with ground GNS observations. For instance, the tropospheric or ionospheric
profile information cannot be directly estimated from GPS tomography due to the lack of
enough line-of-sight GPS signals passing each grid cell (Jin et al., 2006 and 2008; Nesterov
and Kunitsyn, 2011). Moreover, most current RO satellite missions are approaching their
end of operations. With the increase of future GNSS satellite constellations and more GNSS
RO missions, the goal of improved temporal-spatial resolution will enable more detailed
profile information and evolution processes of the atmosphere and ionosphere.
5. Acknowledgement
This work was supported by the Shanghai Pujiang Talent Program, National Natural
Science Foundation of China (Grant No.11043008) and Key Direction Project of Chinese
Academy of Sciences (Grant No. KJCX2- EW-T03).
6. References
Austen, J. R.; S. J. Franke, and C. H. Liu, Application of computerized tomography
techniques to ionospheric research, in Radio Beacon contributions to the study of
ionization and dynamics of the ionosphere and to corrections to geodesy and
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