Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data

The continuous 1992–2005 data set of the TOPEX Microwave Radiometer (TMR) has been reprocessed to provide global, zonal, and regional scale histories of overocean integrated water vapor (IWV) and cloud liquid water (CLW). Results indicate well-defined trends in IWV on global and hemisphere scales, with values of 1.8 ± 0.4%/decade (60°S–60°N), 2.4 ± 0.4%/decade (0–60°N), and 1.0 ± 0.5%/decade (0–60°S). The uncertainties represent 1 standard deviation of the regressed slope parameter adjusted for lag 1 autocorrelation. These results are comparable to earlier results based on analyses of the multiinstrument SSM/I ocean measurements beginning in 1988. For the 1992–2005 interval, comparisons between SSM/I- and TMR-derived IWV trends show remarkable agreement, with global trends differing by less than 0.3%/decade, comparable to the statistical uncertainty level and about one-sixth of the global TMR-derived trend. Latitudinal and regional analyses of IWV trends show large variability about the global mean, with synoptic scale variations of IWV trends ranging from ∼−8 to +8%/decade. Averaged over 5° latitude bands the IWV trends reveal a near zero minimum in the Southern Tropical Pacific and maximum values of ∼4%/decade over the 30–40N latitude band. Comparisons with band latitude averaged SST data over the same 1992–2005 interval roughly match a delta_IWV/delta_SST trend scaling of ∼11%/K, consistent with previously observed tropical and midlatitude seasonal variability. TMR-derived CLW trends are fractionally comparable to the IWV trends. The CLW values are 1.5 ± 0.6%/decade (60°S–60°N), 2.0 ± 0.8%/decade (0–60°N), and 1.1 ± 0.8%/decade (0–60°S). When scaled to global mean CLW derived from SSM/I and compared seasonally, the TMR CLW variations exhibit excellent tracking with the SSM/I results. Unlike IWV, however, the CLW statistical uncertainties do not likely reflect the dominant error component in the retrieved trends. The 1992–2005 CLW trend estimates were particularly sensitive to short-term trends in the first and last 2 years of the TMR archive. Additional errors difficult to quantify include strong aliasing effects from precipitation cells and uncertainties in the radiative transfer models utilized in the generation of the TMR CLW algorithm

Development Of An Improved Microwave Ocean Surface Emissivity Radiative Transfer Model

An electromagnetic model is developed for predicting the microwave blackbody emission from the ocean surface over a wide range of frequencies, incidence angles, and wind vector (speed and direction) for both horizontal and vertical polarizations. This ocean surface emissivity model is intended to be incorporated into an oceanic radiative transfer model to be used for microwave radiometric applications including geophysical retrievals over oceans. The model development is based on a collection of published ocean emissivity measurements obtained from satellites, aircraft, field experiments, and laboratory measurements. This dissertation presents the details of methods used in the ocean surface emissivity model development and comparisons with current emissivity models and aircraft radiometric measurements in hurricanes. Especially, this empirically derived ocean emissivity model relates changes in vertical and horizontal polarized ocean microwave brightness temperature measurements over a wide range of observation frequencies and incidence angles to physical roughness changes in the ocean surface, which are the result of the air/sea interaction with surface winds. Of primary importance are the Stepped Frequency Microwave Radiometer (SFMR) brightness temperature measurements from hurricane flights and independent measurements of surface wind speed that are used to define empirical relationships between C-band (4 - 7 GHz) microwave brightness temperature and surface wind speed. By employing statistical regression techniques, we develop a physical-based ocean emissivity model with empirical coefficients that depends on geophysical parameters, such as wind speed, wind direction, sea surface temperature, and observational parameters, such as electromagnetic frequency, electromagnetic polarization, and incidence angle

Aquarius L-Band Microwave Radiometer: Three Years of Radiometric Performance and Systematic Effects

The Aquarius L-band microwave radiometer is a three-beam pushbroom instrument designed to measure sea surface salinity. Results are analyzed for performance and systematic effects over three years of operation. The thermal control system maintains tight temperature stability promoting good gain stability. The gain spectrum exhibits expected orbital variations with 1f noise appearing at longer time periods. The on-board detection and integration scheme coupled with the calibration algorithm produce antenna temperatures with NEDT 0.16 K for 1.44-s samples. Nonlinearity is characterized before launch and the derived correction is verified with cold-sky calibration data. Finally, long-term drift is discovered in all channels with 1-K amplitude and 100-day time constant. Nonetheless, it is adeptly corrected using an exponential model

Data catalog for JPL Physical Oceanography Distributed Active Archive Center (PO.DAAC)

The Physical Oceanography Distributed Active Archive Center (PO.DAAC) archive at the Jet Propulsion Laboratory contains satellite data sets and ancillary in-situ data for the ocean sciences and global-change research to facilitate multidisciplinary use of satellite ocean data. Geophysical parameters available from the archive include sea-surface height, surface-wind vector, surface-wind speed, surface-wind stress vector, sea-surface temperature, atmospheric liquid water, integrated water vapor, phytoplankton pigment concentration, heat flux, and in-situ data. PO.DAAC is an element of the Earth Observing System Data and Information System and is the United States distribution site for TOPEX/POSEIDON data and metadata

Satellite altimetry for hydrological purpose

As a new spatial measuring technic developed in 1970s, altimetry was designed to determine the sea surface height based on spatial technology, electronic technology and microwave technology. It also plays an important role in geodesy and oceanography; meanwhile, it can provide all-weather and repetitious measurements in global region for the studying of variation of SSH, earth gravity field, ocean circulation as well as submarine topography. In addition, real-time data can also be provided for the field of weather forecast, ocean circulation forecast and wave forecast in globally. Satellite radar altimetry, well known as TOPEX/POSEIDON, JASON, ENVISAT, which have been originally designed to measure global ocean surface height, nowadays, also demonstrated with great potential for applications of inland water body studies. Therefore, the main task of this study is to analyze and summarize the relevant theory and technology of altimetry waveform, waveform retracking methods based on the investigative research up to now. And above all, data used in this study is Topex geophysical data and sensor data from 1992 until 2002 provided by NASA (http://podaac.jpl.nasa.gov/). The main content of this study are listed as follows: - Discuss the theory and process of altimeter waveform, and distinguish the real waveforms from ideal ones. - Waveform classification based on different shapes. - Automatic waveform filter is designed to move out noisy data. - The most popular retracking methods (OCOG, Threshold, 5β) are compared and evaluated with respect to different groups of waveform. And finally an optimal Lake level height is to be generated by sufficient combing all the above retracking methods. - Generate time series of Lake level height (from 10Hz data) in selected water bodies; evaluate the result by comparison with in-situ gauge data

Tendance et variabilité de la vapeur d'eau atmosphérique : un enjeu pour l'étude du niveau moyen océanique

La mesure du niveau de la mer par altimétrie satellitaire est perturbée par la présence de vapeur d'eau dans l'atmosphère. Un radiomètre micro-onde, sur les missions altimétriques, est chargé de corriger les mesures de ces perturbations. Les exigences quant à la qualité de cette correction, appelée correction troposphérique humide, sont particulièrement fortes pour l'étude des changements climatiques. Cette thèse a pour objet l'étude des corrections troposphériques humides utilisées dans le cadre des missions altimétriques Jason-1 et Envisat. L'objectif est de caractériser les incertitudes liées à la correction et d'identifier les potentielles anomalies présentes. L'étude faire ressortir une potentielle dérive dans l'étalonnage du radiomètre de la mission Jason-1 après 2008. Pour la mission Envisat, l'analyse met en avant des biais régionaux à l'approche des côtes. Ces derniers sont probablement liés au traitement de la donnée radiométrique.Measurements of the sea surface height are disturbed by the presence of water vapor in the atmosphere. A microwave radiometer, on altimetric missions, is used to correct the measurements from theses disturbances. Requirements on the quality of this correction, called the wet tropospheric correction, are stringent for the survey of climate changes. This thesis concerns the monitoring of the wet tropospheric correction used in the altimetry missions, Jason-1 and Envisat. The aim is to characterize uncertainties related to this correction and to identify potential anomalies. The analysis brings out a potential drift in the radiometer used on Jason-1, after 2008. For the Envisat missions, the presence of biases near coastlines suggests processing related issues

Literature analysis of SWOT mission from geodetic perspective

Satellite radar altimeter has been used for nearly twenty years to observe the variety of the global ocean surface topography. It has advanced our understanding of global ocean circulation and sea level change. However the conventional radar altimeter can not resolve the submesoscale features in the oceans because of its large spacing between satellite ground tracks and coarse ground resolution. On the other hand altimetry technique is expected to be able to observe large rivers, lakes and monitor the storage of freshwater on land. These new challenges require a new technique and a new mission. In 2016 a satellite mission called Surface Water and Ocean Topography (SWOT) will be launched by NASA and CNES according to plan. This term paper will summarize the general measurement principle, orbit design issues and applications of SWOT in the literature.Die Satelliten-Radar-Altimetrie wird seit fast zwanzig Jahren zur Beobachtung der Änderung der globalen Ozeanoberflächentopografie verwendet. Sie hat unser Verständnis von globaler Ozeanzirkulation und Meeresspiegeländerung verbessert. Die konventionale Radar-Altimetrie kann jedoch die Merkmale von Ozeanen wegen ihrer großen Distanz zwischen Bodenspuren und grober Bodenauflösung nicht im Submesoskalenbereich auflösen. Auf der anderen Seite wird erwartet, dass die Altimetrie die Beobachtung großer Flüsse und Seen sowie die Überwachung der Süßwasserspeicherung an Land ermöglicht. Diese Herausforderung verlangt eine neue Mission mit neuer Technik. Im Jahre 2016 soll nach den Plänen von NASA und CNES eine neue Satellitenmission namens Surface Water and Ocean Topography (SWOT) gestartet werden. Diese Studienarbeit fasst das in der Literatur beschriebene grundlegende Messprinzip, das Bahndesign und einigen Anwendungen von SWOT zusammen