Globalna analiza atmosferskih refrakcijskih profilov iz prekrivanj radijskih signalov COMSIC GPS

Atmospheric refractivity is a function of temperature, pressure and water vapor. The refractivity retrieved from the GNSS radio occultation soundings has fine vertical resolution and high accuracy, so it can be used to improve the accuracy of numerical weather prediction models and in climate and meteorological research. This study evaluates differences of refractivity from the COSMIC against radiosondes (RS) at different atmospheric levels, latitudes and seasons. Then temporal and global spatial distribution patterns of the COSMIC refractivity are analyzed at the atmospheric levels of 925 and 300 hPa. The results indicate that the COSMIC and RS refractivities are in generally good agreement. The differences between COSMIC and RS refractivity decrease with increasing height in the troposphere above 300 hPa, and the differences are very small above the tropopause. The COSMIC-RS differences exhibit distinct latitudinal and seasonal variation.The global COSMIC refractivity at 925 hPa is the highest in the tropics, and it decreases with increasing latitude in the NH and SH. However, the refractivity at the atmospheric levels of 300 hPa is just the opposite. Refractivity anomalies relative to the annual mean values in January and July are significant, whereas the differences are not as large in the transitional seasons of April and October.Atmosferska refrakcija je odvisna od temperature, tlaka in vodne pare. Iz GNSS ocenjena refrakcija ima dovolj dobro vertikalno ločljivost in točnost, da jo lahko vključimo v numerične modele napovedi vremena ter uporabimo v meteoroloških in klimatskih raziskavah. V študiji smo ovrednotili razlike med modelom refrakcije, pridobljenim iz sistema COSMIC, in izračuni iz podatkov vertikalne radiosondaže, in sicer za različne višine, geografske širine in letne čase. Analizirali smo časovne in globalne prostorske porazdelitvene vzorce atmosferske refrakcije na podlagi podatkov COSMIC za atmosferske ravni, kjer zračni tlak znaša 925 hPa in 300 hPa. Rezultati so pokazali, da je ocenjena refrakcija v splošnem podobna oceni iz podatkov radiosond. Razlika se značilno manjša z višino, ko je v troposferi tlak nad 300 hPa, nad tropopavzo pa so razlike komaj še zaznavne. Izrazite razlike med oceno refrakcije iz podatkov COSMOS oziroma podatkov, pridobljenih z radiosondami, se kažejo s spreminjanjem geografske širine in z letnim časom. Globalna refrakcija COSMIC na višini, kjer je tlak 825 hPa, je najvišja v tropskem pasu ter se manjša proti severni in južni hemisferi. V atmosferi na višini, kjer je tlak 300 hPa, je z refrakcijo ravno nasprotno. Anomalije refrakcije glede na srednjo letno vrednost so večje v januarju in juliju, manjše pa v aprilu in oktobru

New features of the Moon revealed and identified by CLTM-s01

Previous analyses showed a clear asymmetry in the topography, geological material distribution, and crustal thickness between the nearside and farside of the Moon. Lunar detecting data, such as topography and gravity, have made it possible to interpret this hemisphere dichotomy. The high-resolution lunar topographic model CLTM-s01 has revealed that there still exist four unknown features, namely, quasi-impact basin Sternfeld-Lewis (20 degrees S, 232 degrees E), confirmed impact basin Fitzgerald-Jackson (25 degrees N, 191 degrees E), crater Wugang (13 degrees N, 189 degrees E) and volcanic deposited highland Yutu (14 degrees N, 308 degrees E). Furthermore, we analyzed and identified about eleven large-scale impact basins that have been proposed since 1994, and classified them according to their circular characteristics

Lunar topographic model CLTM-s01 from Chang'E-1 laser altimeter

More than 3 million range measurements from the Chang'E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang'E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25A degrees (similar to 7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, respectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (-1.777, -0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings

Chang'E-1 orbiter discovers a lunar nearside volcano: YUTU Mountain

In the day time of the Moon surface, the strong illumination from high altitude and high albedo rate radical craters will introduce the illumination effect on observing the nearby low altitude, low albedo rate and shallow small slop rate area seriously, and even can "hide" the later area from the light. Based on the lunar global topography model obtained by Chang'E-1 mission, and by comparing with the lunar gravity model, a volcano named "YUTU Mountain" has been identified. It is a volcano with diameter of similar to 300 km and height of similar to 2 km located at (14 degrees N, 308 degrees E) in Oceanus Procellarum. Besides, the DEM of another volcano named "GUISHU Mountain" in the same area has been improved. This new discovery will benefit the study of lunar magmatism and volcanism evolution in the nearside of the Moon

CEGM02: An improved lunar gravity model using Chang'E-1 orbital tracking data

Using Chang'E-1 orbital tracking data, in combination with orbital tracking data of SELENE, Lunar Prospector, and historical spacecraft, a lunar gravity field model denoted CEGM02 is developed. Analyses show that due to its higher orbit altitude (200 km), tracking data of Chang'E-1 contribute to the long wavelengths of the lunar gravity field. When compared to SGM100h, formal error of CEGM02 coefficients below degree 5 is reduced by a factor of about 2. Lunar mean moment of inertia is found to be 0.393466 +/- 0.000065, which can be served as a strong constraint in lunar internal structure research. Lunar potential Love number k(2) is estimated to be 0.0242 +/- 0.0004 (ten times the formal error), which may provide better constraints on lunar interior by combination with lunar moments of inertia. (C) 2011 Elsevier Ltd. All rights reserved