A GPS/MET Sounding through an Intense Upper-Level Front

Abstract

A Global Positioning System Meteorology (GPS/MET) proof-of-concept experiment became a reality on 3 April 1995. A small satellite carrying a modified GPS receiver was launched into earth orbit to demonstrate the feasibility of active limb sounding of the earth's neutral atmosphere and ionosphere using the radio occultation method. On 22 October 1995, a GPS/MET occultation took place over northeastern China where a dense network of radiosonde observations was available within an hour of the occultation. The GPS/MET refractivity profile shows an inflection, and the corresponding temperature retrieval displays a sharp temperature inversion around 310 mb. Subjective analyses based on radiosonde observations indicate that the GPS/MET occultation went through a strong upper-level front. In this paper, the GPS/MET sounding is compared with nearby radiosonde observations to assess its accuracy and ability to resolve a strong mesoscale feature. The inflection in the refractivity profile and the sharp frontal inversion seen in the GPS/MET sounding were verified closely by a radiosonde located about 150 km to the east of the GPS/MET occultation site. A similar frontal structure was also found in other nearby radiosonde observations. These results showed that high-quality GPS/MET radio occultation data can be obtained even when the occultation goes through a sharp temperature gradient associated with an upper-level front. 1. Introduction A small satellite (MicroLab 1) carrying a global positioning system (GPS) receiver, modified to sound the atmosphere, was launched on 3 April 1995. This instrument is the centerpiece of a proof-of-concept experiment to demonstrate the feasibility of sensing the terrestrial atmosphere by the GPS limb-sounding method (Fjeldbo et al. 1971; Melbourne et al. 1994). Ware et al. (1996) reviewed the theory and history of this experiment and presented preliminary results obtained from this GPS meteorology (GPS/MET) experiment. They compared 11 representative temperature

Seasonal and Longitudinal Variations in the Tropical Tropopause Observed with the GPS Occultation Technique (GPS/MET)

“…Rocken et al (1997) conducted a comprehensive study on the validation of GPS/MET temperature profiles compared with data from other independent sources, such as radiosondes and other satellite measurements including TOVS (TIROS operational vertical sounder), GOES (Geostationary Operational Environmental Satellite), MLS (Microwave Limb Sounder) and HALOE (Halogen Occultation Experiment) on board LIARS (Upper Atmosphere Research Satellite), as well as model analyses at NCEP (National Center for Environmental Prediction) and ECMWF (European Center for Medium Range Weather Forecasts). Comparing a GPS/MET temperature profile with a nearby radiosonde sounding, Kuo et al (1998) reported that GPS/MET detected a detailed temperature profile including a sharp temperature inversion associated with an upper-level front.…”

GPS meteorology project of Japan —Exploring frontiers of geodesy—

“…The project also supports analysis of the middle atmospheric dynamics by using the temperature data retrieved by GPS occultation techniques in the space-based GPS meteorology project now conducted in the University Corporation for Atmospheric Research (UCAR) of the United States Rocken et al, 1997b;Kuo et al, 1998). Nishida and Tsuda (1998) have found that the GPS occultation data can describe meso-scale temperature perturbations in the stratosphere with a vertical scale ranging from 2 to 10 km, which seem to be caused by atmospheric waves.…”

A Practical Algorithm for LEO Orbit Determination

“…Another testing quantity for method (1) is the phase/range (R) combination: (7) where the ionospheric term, ⌬ Iono (t), is again assumed to display slow temporal variations, so that any significant jump in the tested quantity would indicate a cycle slip. Since this combination, including the pseudorange measurement, has relatively higher noise compared with equation (6), it is useful for detecting larger cycle slips.…”