Engineering topics

Olson, Bill

Publications and source records attributed to Olson, Bill.

5 records

NASA NTRS2019

The Combined Radar-Radiometer Algorithm — GPM Version 06X

The primary motivation behind the Version 6X (V06X) Combined Radar-Radiometer Algorithm (CORRA) is to utilize high-sensitivity mode (HS) Ka-band data that had been moved to locations in the outer part of the GPM Dual-Frequency Precipitation Radar (DPR) swath on May 21, 2018. Presented at the Precipitation Measurement Missions (PMM) meeting are statistics of CORRA precipitation estimates across both the inner and outer portions of the DPR swath for the purpose of identifying potential discontinuities caused by the new HS data. Although none are found, further investigation reveals possible biases caused by assumptions regarding radar pulse attenuation within the ground clutter of the DPR.

Olson, Bill↗

NASA NTRS2011

NEWS Climatology Project: The State of the Water Cycle at Continental to Global Scales

NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the NEWS Water and Energy Cycle Climatology project is to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project is a multiinstitutional collaboration with more than 20 active contributors. This presentation will describe results of the first stage of the water budget analysis, whose goal was to characterize the current state of the water cycle on mean monthly, continental scales. We examine our success in closing the water budget within the expected uncertainty range and the effects of forcing budget closure as a method for refining individual flux estimates.

Rodell, Matthew↗

NASA NTRS2007

NEWS Integration: Observations

This viewgraph presentation reviews The NASA Energy and Water Cycle Study (NEWS) methodology and integration of data products from remote sensing observations. The contents include: 1) Theme Objective; 2) Scope of Current Theme-related NEWS investigation; 3) Progress; 4) Anticipated Accomplishments (near-term and long-range); 5) Assessment of Overall Science Value (to NEWS and Earth Science in general); and 6) Outstanding Issues.

remote sensing↗

NASA NTRS2002

High-Resolution Simulation of Hurricane Bonnie (1998): Microphysics Validation using TRMM Data

A simulation of Hurricane Bonnie (1998) has been performed using multiple grid nesting to 2 km grid spacing. The simulation is initialized with large-scale analysis fields from the European Center for Medium Range Forecasts and with a bogus vortex inserted via four-dimensional variational data assimilation. The simulation reproduces well the storm intensity, the wavenumber 1 asymmetry of the precipitation field, the occurrence of deep convective towers within the eyewall, and the presence of broad stratiform precipitation regions. Radar and microwave observations from TRMM are used to validate the simulation. Result show excessive graupel production and, to some extent, excessive precipitation production in general by the model. Additional simulations are conducted (and validated by TRMM data) to test parameters and assumptions within the microphysics parameterizations including particle size distributions, particle densities, and assumptions that impact the partitioning of precipitation mass between graupel and snow.

Starr, David OC.↗

NASA NTRS2001

Space-Time Characteristics of Rainfall Diurnal Variations

The space-time features of rainfall diurnal variation of precipitation are systematically investigated by using the Tropical Rainfall Measuring Mission (TRMM) precipitation products retrieved from TRMM microwave imager (TMI), precipitation radar (PR) and TMI/PR combined algorithms. Results demonstrate that diurnal variability of precipitation is obvious over tropical regions. The dominant feature of rainfall diurnal cycle over, ocean is that there is consistent rainfall peak in early morning, while there is a consistent rainfall peak in mid-late afternoon over land. The seasonal variation on intensity of rainfall diurnal cycle is clearly evidenced. Horizontal distributions of rainfall diurnal variations indicate that there is a clearly early-morning peak with a secondary peak in the middle-late afternoon in ocean rainfall at latitudes dominated by large-scale convergence and deep convection. There is also an analogous early-morning peak in land rainfall along with a stronger afternoon peak forced by surface heating. Amplitude analysis shows that the patterns and its evolution of rainfall diurnal cycle are very close to rainfall distribution pattern and its evolution. These results indicate that rainfall diurnal variations are strongly associated with large-scale convective systems and climate weather systems. Phase studies clearly present the regional and seasonal features of rainfall diurnal activities. Further studies on convective and stratiform rainfall show different characteristics of diurnal cycles. Their spatial and temporal variations of convective and stratiform rainfall indicate that mechanisms for rainfall diurnal variations vary with time and space.

Yang, Song↗