Comparisons of Reflectivities from the TRMM Precipitation Radar and Ground-Based Radars

Given the decade long and highly successful Tropical Rainfall Measuring Mission (TRMM), it is now possible to provide quantitative comparisons between ground-based radars (GRs) with the space-borne TRMM precipitation radar (PR) with greater certainty over longer time scales in various tropical climatological regions. This study develops an automated methodology to match and compare simultaneous TRMM PR and GR reflectivities at four primary TRMM Ground Validation (GV) sites: Houston, Texas (HSTN); Melbourne, Florida (MELB); Kwajalein, Republic of the Marshall Islands (KWAJ); and Darwin, Australia (DARW). Data from each instrument are resampled into a three-dimensional Cartesian coordinate system. The horizontal displacement during the PR data resampling is corrected. Comparisons suggest that the PR suffers significant attenuation at lower levels especially in convective rain. The attenuation correction performs quite well for convective rain but appears to slightly over-correct in stratiform rain. The PR and GR observations at HSTN, MELB and KWAJ agree to about 1 dB on average with a few exceptions, while the GR at DARW requires +1 to -5 dB calibration corrections. One of the important findings of this study is that the GR calibration offset is dependent on the reflectivity magnitude. Hence, we propose that the calibration should be carried out using a regression correction, rather than simply adding an offset value to all GR reflectivities. This methodology is developed towards TRMM GV efforts to improve the accuracy of tropical rain estimates, and can also be applied to the proposed Global Precipitation Measurement and other related activities over the globe

Development of a new global rain model for radio regulation

Signal attenuation due to rain scatter is the dominant fade mechanism on the majority of high-capacity microwave telecommunications links, both terrestrial and Earth-space. These links carry a large proportion of the information that underpins the way modern life functions and is a vital component of national infrastructure. Many studies have established the virtuous cycle that exists between the development of telecommunications infrastructure and economic growth. Therefore, it is important that rain fade models exist for the design and optimisation of telecommunications networks, globally, but especially in developing countries.A set of internationally recognised and agreed radio propagation models is maintained by the International Telecommunications Union - Radiocommunication Sector (ITU-R) in the form of Recommendations. A fundamental input parameter to many of these models is the point one-minute rain rate exceeded for 0.01% (about 50 minutes) of an average year. Historically, the collection of one-minute rain rates has been rare and so very few regions of the world have measured this important parameter. Where local data are not available, the full distribution of one-minute rain rates, including the 0.01% exceeded rate, can be obtained from Rec. ITU-R P.837-7. The input parameters to this Recommendation are the average monthly temperatures and rain accumulations.The network of meteorological stations is very sparse in equatorial developing countries. This limits the reliability of monthly rain accumulation statistics. ITU-R models are validated against DBSG3: the database of link and meteorological measurements maintained by ITU-R Study Group 3. However, there is very little data from the Tropics in DBSG3. Therefore, there are legitimate concerns that the ITU-R P.837-7 model may not work accurately in the Tropics.This thesis uses rain rates derived from the satellite Earth observation Tropical Rain Measuring Mission, TRMM, to estimate point one-minute rain rate distributions in the Tropics. Two distinct uses of these data have been tested. Initially, the measured distributions of TRMM rain rates were used to estimate rain distributions in the Tropics. A method was developed to transform TRMM rain rate distributions to those needed for radio systems, based on UK rain radar data. In many cases, this method performed better than Rec. ITU-R P.837-7, particularly with databases of rain rates not included in DBSG3. To extend the work to global application, TRMM data were used to estimate the monthly rain rate distributions conditional upon monthly temperature and accumulation, as used in Rec. ITU-R P.837-7. These were then used to replace the analytic distributions in the Recommendation. The method worked well on several databases of measurements, but appeared to be biased in temperate regions. The measured TRMM conditional distributions were replaced by curve-fit approximations and a hybrid method was developed that combined the standard Rec. ITU-R P.837-7 prediction with the curve-fit TRMM prediction. This algorithm performed as well as or better than Rec. ITU-R P.837-7 for most test databases and at most time percentages.The direct use of satellite Earth observation data to produce distributions of point one-minute rain rates is a radical departure from methods used before. This thesis has shown the potential of satellite-based measurements to replace the current methods based on downscaling numerical weather prediction output. In the future when more satellite data are available, spanning the globe, this suggests that direct use of satellite data will become standard

Remote Sensing of Precipitation: Part II

Precipitation is a well-recognized pillar in the global water and energy balances. The accurate and timely understanding of its characteristics at the global, regional and local scales is indispensable for a clearer insight on the mechanisms underlying the Earth’s atmosphere-ocean complex system. Precipitation is one of the elements that is documented to be greatly affected by climate change. In its various forms, precipitation comprises the primary source of freshwater, which is vital for the sustainability of almost all human activities. Its socio-economic significance is fundamental in managing this natural resource effectively, in applications ranging from irrigation to industrial and household usage. Remote sensing of precipitation is pursued through a broad spectrum of continuously enriched and upgraded instrumentation, embracing sensors which can be ground-based (e.g., weather radars), satellite-borne (e.g., passive or active space-borne sensors), underwater (e.g., hydrophones), aerial, or ship-borne. This volume hosts original research contributions on several aspects of remote sensing of precipitation, including applications which embrace the use of remote sensing in tackling issues such as precipitation estimation, seasonal characteristics of precipitation and frequency analysis, assessment of satellite precipitation products, storm prediction, rain microphysics and microstructure, and the comparison of satellite and numerical weather prediction precipitation products

Ocean Remote Sensing with Synthetic Aperture Radar

The ocean covers approximately 71% of the Earth’s surface, 90% of the biosphere and contains 97% of Earth’s water. The Synthetic Aperture Radar (SAR) can image the ocean surface in all weather conditions and day or night. SAR remote sensing on ocean and coastal monitoring has become a research hotspot in geoscience and remote sensing. This book—Progress in SAR Oceanography—provides an update of the current state of the science on ocean remote sensing with SAR. Overall, the book presents a variety of marine applications, such as, oceanic surface and internal waves, wind, bathymetry, oil spill, coastline and intertidal zone classification, ship and other man-made objects’ detection, as well as remotely sensed data assimilation. The book is aimed at a wide audience, ranging from graduate students, university teachers and working scientists to policy makers and managers. Efforts have been made to highlight general principles as well as the state-of-the-art technologies in the field of SAR Oceanography

Marshall Space Flight Center Research and Technology Report 2017

This report features over 60 technology development and scientific research efforts that collectively aim to enable new capabilities in spaceflight, expand the reach of human exploration, and reveal new knowledge about the universe in which we live. These efforts include a wide array of strategic developments: launch propulsion technologies that facilitate more reliable, routine, and cost effective access to space; in-space propulsion developments that provide new solutions to space transportation requirements; autonomous systems designed to increase our utilization of robotics to accomplish critical missions; life support technologies that target our ability to implement closed-loop environmental resource utilization; science instruments that enable terrestrial, solar, planetary and deep space observations and discovery; and manufacturing technologies that will change the way we fabricate everything from rocket engines to in situ generated fuel and consumables

Innovation: Key to the future

The NASA Marshall Space Flight Center Annual Report is presented. A description of research and development projects is included. Topics covered include: space science; space systems; transportation systems; astronomy and astrophysics; earth sciences; solar terrestrial physics; microgravity science; diagnostic and inspection system; information, electronic, and optical systems; materials and manufacturing; propulsion; and structures and dynamics

Research and technology, 1993. Salute to Skylab and Spacelab: Two decades of discovery

A summary description of Skylab and Spacelab is presented. The section on Advanced Studies includes projects in space science, space systems, commercial use of space, and transportation systems. Within the Research Programs area, programs are listed under earth systems science, space physics, astrophysics, and microgravity science and applications. Technology Programs include avionics, materials and manufacturing processes, mission operations, propellant and fluid management, structures and dynamics, and systems analysis and integration. Technology transfer opportunities and success are briefly described. A glossary of abbreviations and acronyms is appended as is a list of contract personnel within the program areas

Space Photovoltaic Research and Technology 1995

The Fourteenth Space Photovoltaic Research and Technology conference was held at the NASA Lewis Research Center from October 24-26, 1995. The abstracts presented in this volume report substantial progress in a variety of areas in space photovoltaics. Technical and review papers were presented in many areas, including high efficiency GaAs and InP solar cells, GaAs/Ge cells as commercial items, high efficiency multiple bandgap cells, solar cell and array technology, heteroepitaxial cells, thermophotovoltaic energy conversion, and space radiation effects. Space flight data on a variety of cells were also presented