Gravity wave activities in Tibet observed by COSMIC GPS radio occultation

The Gravity waves activities in the Tibetan Plateau are very complex with different effects and natures that are not clear due to the lack of high resolution data from space and also from ground. In this paper,using COSMICGPS radio occultation data from 2006 to 2014, the atmospheric gravity waves activities and climatologic behaviors in Tibetan stratosphere are studied and analyzed, which show different characteristics. Most of the gravity waves with potential energy(Ep) at altitude of 17-24 km are associated with mountain waves. A good correlation between gravity wave activities and zonal wind flow is found. The distribution of gravity wave(GW) activities in Tibet is strongly connected with zonal wind variation and topography. GW activities are enhanced in winter seasons and decreased in summer seasons since strong western winds persist at all heights of the Tibetan troposphere. The gravity waves generated in the Tibetan area are mostly related to the orography of the area. The vertical wavelengths of GWS are shorter.Gravity waves in the Northwest have different vertical wavelengths in the Southeastern part of Tibetan Plateau, and dominant wavelengths are 3-5 km in the Northwest and 2-3 km in the Southeast,respectively. In the summer, the Northwestern part is the main source of wave generation while in the winter the GW is generated almost from all peaks of the Tibetan Plateau. Gravity waves in the region are clearly related to deep convection, which can also be proved by the inverse relation of Outgoing long wave radiation(OLR) and potential energy(Ep).

Global Statistical Study of Ionospheric Waves Based on COSMIC GPS Radio Occultation Data

Extracting and parameterizing ionospheric waves globally and statistically is a longstanding problem. Based on the multichannel maximum entropy method（MMEM） used for studying ionospheric waves by previous work, we calculate the parameters of ionospheric waves by applying the MMEM to numerously temporally approximate and spatially close global-positioning-system radio occultation total electron content profile triples provided by the unique clustered satellites flight between years 2006 and 2007 right after the constellation observing system for meteorology, ionosphere, and climate（COSMIC） mission launch. The results show that the amplitude of ionospheric waves increases at the low and high latitudes（~0.15 TECU） and decreases in the mid-latitudes（~0.05 TECU）. The vertical wavelength of the ionospheric waves increases in the mid-latitudes（e.g., ~50 km at altitudes of 200–250 km） and decreases at the low and high latitudes（e.g., ~35 km at altitudes of 200–250 km）.The horizontal wavelength shows a similar result（e.g., ~1400 km in the mid-latitudes and ~800 km at the low and high latitudes）.

Ionospheric disturbances following the March 2015 geomagnetic storm from GPS observations in China

When strong solar activities and geomagnetic storms happen, satellite communications and navigation system will be strongly disturbed. It is of great significance to monitor ionospheric disturbances,because empirical models cannot capture ionospheric anomalous disturbances well. Nowadays, dualfrequency GPS(Global Positioning System) observations can be used to estimate the ionospheric total electron content, correct the ionospheric delay and analyze the response of the ionosphere to geomagnetic storms. In this paper, the ionospheric response to the geomagnetic storm occurred in March 2015 is investigated using GPS observations provided by Crustal Movement of Observation Network of China. The result shows that this storm increases the electron density in the ionosphere quickly and disrupts the structure of the northern equatorial anomaly region at the beginning. In the main process stage, compared with that in the quite periods, the VTEC(Vertical Total Electron Content)around the longitude of 120°E decreases by 50% and the amount of depletion is larger in the high latitude region than that in the low latitude region. We also find the height of the peak electron density in F2 layer increases during the geomagnetic storm from the electron density profiles derived from GPS occultation mission.