Radar Imaging in Challenging Scenarios from Smart and Flexible Platforms

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Global Precipitation Measurement

This chapter begins with a brief history and background of microwave precipitation sensors, with a discussion of the sensitivity of both passive and active instruments, to trace the evolution of satellite-based rainfall techniques from an era of inference to an era of physical measurement. Next, the highly successful Tropical Rainfall Measuring Mission will be described, followed by the goals and plans for the Global Precipitation Measurement (GPM) Mission and the status of precipitation retrieval algorithm development. The chapter concludes with a summary of the need for space-based precipitation measurement, current technological capabilities, near-term algorithm advancements and anticipated new sciences and societal benefits in the GPM era

Simulations of Infrared Radiances Over a Deep Convective Cloud System Observed During TC4: Potential for Enhancing Nocturnal Ice Cloud Retrievals

Retrievals of ice cloud properties using infrared measurements at 3.7, 6.7, 7.3, 8.5, 10.8, and 12.0 microns can provide consistent results regardless of solar illumination, but are limited to cloud optical thicknesses tau 20, the 3.7 - 10.8 microns and 3.7 - 6.7 microns BTDs are the most sensitive to D(sub e). Satellite imagery appears consistent with these results. Keywords: clouds; optical depth; particle size; satellite; TC4; multispectral thermal infrare

Use of Dual Polarization Radar in Validation of Satellite Precipitation Measurements: Rationale and Opportunities

Dual-polarization weather radars have evolved significantly in the last three decades culminating in the operational deployment by the National Weather Service. In addition to operational applications in the weather service, dual-polarization radars have shown significant potential in contributing to the research fields of ground based remote sensing of rainfall microphysics, study of precipitation evolution and hydrometeor classification. Furthermore the dual-polarization radars have also raised the awareness of radar system aspects such as calibration. Microphysical characterization of precipitation and quantitative precipitation estimation are important applications that are critical in the validation of satellite borne precipitation measurements and also serves as a valuable tool in algorithm development. This paper presents the important role played by dual-polarization radar in validating space borne precipitation measurements. Starting from a historical evolution, the various configurations of dual-polarization radar are presented. Examples of raindrop size distribution retrievals and hydrometeor type classification are discussed. The quantitative precipitation estimation is a product of direct relevance to space borne observations. During the TRMM program substantial advancement was made with ground based polarization radars specially collecting unique observations in the tropics which are noted. The scientific accomplishments of relevance to space borne measurements of precipitation are summarized. The potential of dual-polarization radars and opportunities in the era of global precipitation measurement mission is also discussed

EM 2000 Microbathymetric and HYDROSWEEP DS-2 Bathymetric Surveying – a Comparison of Seafloor Topography at Porcupine Bank, west of Ireland

One of the latest discoveries in the world oceans are carbonate structures in the North-East Atlantic. In the frameworks of several European projects, the research vessel POLARSTERN and underwater robot VICTOR 6000 were engaged to explore these areas. The data described in this thesis were collected during the expedition ARK XIX/3 between 16 - 19th June 2003. Bathymetric and microbathymetric data in parts of the Pelagia Province, located on the northern Porcupine Bank, west of Ireland, were measured with two multibeam sonar systems deployed at different distances from the bottom. The four compared models come from a KONGSBERG SIMRAD EM 2000 multibeam sonar system and an ATLAS ELEKTRONIK HYDROSWEEP DS-2 multibeam sonar system. After necessary corrections of the data, digital terrain models were created, subtracted and correlated using appropriate software. This thesis begins with a description of the historical background of bathymetry, followed by a description of the principles of navigation and underwater navigation, inertial navigation systems, and the calibration of these systems. Systematic errors will be pointed out. It examines the measurement principles of the echo sounders used on the ARK XIX/3a expedition and accompanying necessary procedures, such as CTD measurements. A discussion of how the data are processed from raw data to edited results, and the effects of the errors, follows. One chapter is dedicated to a comparison and interpretation of the data. Sidescan, mosaic and PARASOUND data from the Hedge and Scarp Mounds are introduced as complementary information

Interaction between aerosols and the mesoscale convective systems over the tropical continents

Presence of aerosols in the upper troposphere can have significant impacts on the Earth’s radiative energy budget. However, the aerosol–cloud relationship represents the largest uncertainty in the radiative energy budget. Relationships between aerosols and the mesoscale convective systems (MCSs) are complicated and difficult to ascertain, due in large part to inadequate availability of satellite datasets until recent years. Variation of aerosol impacts with meteorological parameters and the relative influence of these parameters on the convective strength of the MSCs can also be attributed to limited detectability of aerosol invigoration effects. To address the interaction between aerosol and the MCSs, I first address the influence of MCS on the distribution of the aerosols, which is poorly known on a global scale. Then, I investigate the influence of aerosol on MCSs. This dissertation addresses these problems by collocating a suite of geostationary and polar orbital satellites at three different phases of their convective lifecycle. First, I estimate the extent of upper tropospheric aerosol layers (UT ALs) surrounding the MCSs and explore the relationships between UT AL extent and the morphology, location, and developmental stages of collocated MCSs in the tropics over equatorial Africa, South Asia, and the Amazon basin between June 2006 and June 2008. I identify that the most extensive UT ALs over equatorial Africa are associated with the mature MCSs, while the most extensive UT ALs over South Asia and the Amazon basin are associated with the growing MCSs. Convective aerosol transport over Amazonia is weaker than that observed over the other two regions despite similar transport frequencies, likely due to smaller sizes and shorter mean lifetimes of Amazonian MCSs. Variations in UT ALs in the vicinity of tropical MCSs are primarily explained by variations in the horizontal sizes of the associated MCSs and are not related to aerosol loading in the lower troposphere. Relationships between convective properties and aerosol transport are relatively weak during the decaying stage of convective development. Then I estimate the relative influence of aerosols and other meteorological parameters on MCS strength and longevity using collocated samples of MCSs from January 2003 to June 2008. The results show that relative humidity (RH) and convective available potential energy (CAPE) have the strongest impacts on MCS lifetime and enhance the lifetime of the MCSs by 6-36 hours when other parameters such as vertical wind shear (VWS) and aerosols are kept constant. Aerosols also enhance the convective lifetime of MCSs, however at a much weaker rate (6-24h) and only when RH and VWS are high. Moreover, aerosol influence on convective lifetime is detected during the mature and decaying phases only. At the continental scale, aerosols explain 20-27% of the total variance of MCSs’ lifetime over equatorial South America, but explain only 8% of the same over equatorial Africa. South Asian MCSs are more strongly influenced by meteorological parameters and MCS-associated aerosols when they are over the ocean than when over the land since most MCSs form and develop over the oceans. After that, I estimate the influence of aerosols and other meteorological parameters on MCSs’ rain rate (RR). Results show that an increase in aerosol concentration enhance IWC and suppress RR and LH during all three phases of convective lifetime. Increasing aerosol concentrations suppress RR at the rate of -0.38 mm/h and -0.47 mm/h during the growing, decaying phases when VWS is high and at a rate of -0.30 mm/h during the mature phase when RH is low. Meteorological parameters such as VWS and RH have significant effects on these aerosol influences. The suppression of RR is also associated with a decrease in latent heat released by large hydrometeors. Aerosols explain 16%, 23%, and 29% of RR’s variance during the growing, mature and decaying phases, respectively, as estimated by a multiple linear regression method. Consequently, aerosols enhance IWC of the MCSs inside the anvil up to 0.72, 1.41, 0.82 mg/m3 and enhance the total integrated reflectivity of the larger-sized ice particles up to 8, 11, and 18 dBZ in the convective core regions during the growing, mature and decaying phases, respectively. In contrast, changes (one standard deviation) in CAPE and RH enhance the RR up to 0.35 mm/h. This dissertation study provides the first satellite based global tropical assessment of the relative influences of aerosols and meteorological conditions on MCSs’ lifetime, rain rate, and IWC and the mutual dependence of these influences. It also shows how aerosols influence the rain rate, cloud ice and lifetime of the MCSs, varying within their lifecycle and between different tropical continents ranging from humid equatorial South America during wet season and big monsoonal systems over South Asia to relatively dry equatorial Africa with high aerosol loading. In doing so, this work has also advanced our capability to evaluate whether or not aerosols could increase convective lifetime by suppressing rain rate and invigorating the MCSs on climate scale and what are the favorable meteorological conditions for aerosol to affect the lifetime of the MCSs. Our results also provide an interpretive framework for devising and evaluating numerical model experiments that can examine relationships between convective properties and ALs transported in the upper troposphere. In the future, we would like to investigate the influence of different meteorological parameters and aerosols on extra tropical MCSs and on self-aggregation of convection.Geological Science

A Physical Model to Estimate Snowfall over Land using AMSU-B Observations

In this study, we present an improved physical model to retrieve snowfall rate over land using brightness temperature observations from the National Oceanic and Atmospheric Administration's (NOAA) Advanced Microwave Sounder Unit-B (AMSU-B) at 89 GHz, 150 GHz, 183.3 +/- 1 GHz, 183.3 +/- 3 GHz, and 183.3 +/- 7 GHz. The retrieval model is applied to the New England blizzard of March 5, 2001 which deposited about 75 cm of snow over much of Vermont, New Hampshire, and northern New York. In this improved physical model, prior retrieval assumptions about snowflake shape, particle size distributions, environmental conditions, and optimization methodology have been updated. Here, single scattering parameters for snow particles are calculated with the Discrete-Dipole Approximation (DDA) method instead of assuming spherical shapes. Five different snow particle models (hexagonal columns, hexagonal plates, and three different kinds of aggregates) are considered. Snow particle size distributions are assumed to vary with air temperature and to follow aircraft measurements described by previous studies. Brightness temperatures at AMSU-B frequencies for the New England blizzard are calculated using these DDA calculated single scattering parameters and particle size distributions. The vertical profiles of pressure, temperature, relative humidity and hydrometeors are provided by MM5 model simulations. These profiles are treated as the a priori data base in the Bayesian retrieval algorithm. In algorithm applications to the blizzard data, calculated brightness temperatures associated with selected database profiles agree with AMSU-B observations to within about +/- 5 K at all five frequencies. Retrieved snowfall rates compare favorably with the near-concurrent National Weather Service (NWS) radar reflectivity measurements. The relationships between the NWS radar measured reflectivities Z(sub e) and retrieved snowfall rate R for a given snow particle model are derived by a histogram matching technique. All of these Z(sub e)-R relationships fall in the range of previously established Z(sub e)-R relationships for snowfall. This suggests that the current physical model developed in this study can reliably estimate the snowfall rate over land using the AMSU-B measured brightness temperatures