William Teng

Tropical Rainfall Measuring Mission (TRMM) Precipitation Data and Services for Research and Applications

Precipitation is a critical component of the Earths hydrological cycle. Launched on 27 November 1997, TRMM is a joint U.S.–Japan satellite mission to provide the first detailed and comprehensive dataset of the four-dimensional distribution of rainfall and latent heating over vastly undersampled tropical and subtropical oceans and continents (40°S–40°N). Over the past 14 years, TRMM has been a major data source for meteorological, hydrological, and other research and application activities around the world. This short article describes how the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) provides TRMM archive and nearreal- time precipitation datasets and services for research and applications. TRMM data consist of orbital data from TRMM instruments at the sensors resolution, gridded data at a range of spatial and temporal resolutions, subsets, ground-based instrument data, and ancillary data. Data analysis, display, and delivery are facilitated by the following services: (1...

Developing an Online Information System Prototype for Global Satellite Precipitation Algorithm Validation and Intercomparison

Abstract Over the decades, significant progress has been made in satellite precipitation product development. In particular, temporal resolution and timely availability have been improved by blended techniques. The resulting products, including near-real-time precipitation products, are widely used in various research and applications. However, the lack of support for user-defined areas or points of interest poses a major obstacle to quickly gaining knowledge of product quality and behavior on a local or regional scale. Current online operational intercomparison and validation services have not addressed this issue adequately. This paper describes an ongoing work to develop an online information system prototype for global satellite precipitation algorithm validation and intercomparison, to overcome current shortcomings by providing dynamic and customized information to users on the expected bias and accuracy of the products, and to give algorithm developers a better understanding of the strengths and wea...

Analysis of Spatial Similarities Between NEXRAD and NLDAS Precipitation Data Products

Precipitation is one of the key inputs for hydrological modeling. Although the Multisensor Precipitation Estimator (MPE) from NEXRAD (Next Generation Radar) and the NLDAS (North American Land Data Assimilation System) precipitation data have been extensively used in various hydrological and climatic studies, there has been no systematic investigation of the spatial similarities and differences between them, based on long-term time series data over a large spatial region. In this study, six years of hourly and daily precipitation time series data from NEXRAD and NLDAS were investigated for their spatial similarities, over a subregion of the Ohio River basin. Three spatial metrics were used: Cohens Kappa coefficient, Forecast Quality Index (FQI), and displacement-based Forecast Quality Measure (FQM). The three metrics were also applied to the two data products after stratification by season (warm, cold). Results show that significant differences exist between NEXRAD MPE and NLDAS. Analyses and discussions are presented on possible causes of the dissimilarities. In addition, results show that a single metric cannot adequately represent their spatial characteristics. The three metrics are complementary to each other and, when used jointly, can provide a more complete picture of the similarities and differences between the two precipitation products. However, if a single metric is desired, then a more comprehensive one needs to be developed to effectively account for magnitude, distance, shape, and neighborhood effects.

Developing GIOVANNI-based online prototypes to intercompare TRMM-related global gridded-precipitation products

New online prototypes have been developed to extend and enhance the previous effort by facilitating investigation of product characteristics and intercomparison of precipitation products in different algorithms as well as in different versions at different spatial scales ranging from local to global without downloading data and software. Several popular Tropical Rainfall Measuring Mission (TRMM) products and the TRMM Composite Climatology are included. In addition, users can download customized data in several popular formats for further analysis. Examples show product quality problems and differences in several monthly precipitation products. It is seen that differences in daily and monthly precipitation products are distributed unevenly in space and it is necessary to have tools such as those presented here for customized and detailed investigations. A simple time series and two area maps allow the discovery of abnormal values of 3A25 in one of the months. An example shows a V-shaped valley issue in the Version 6 3B43 time series and another example shows a sudden drop in 3A25 monthly rain rate, all of which provide important information when the products are used for long-term trend studies. Future plans include adding more products and statistical functionality in the prototypes. We developed online tools for intercomparing global precipitation products.We included 3-hourly, daily, and monthly precipitation products.We included research and near-real-time products in both Version 6 and Version 7.Basic functions help discover data quality issues and differences in products.Several data formats are available for data download and for further analysis.

Tropical Rainfall Measuring Mission Data and Access Tools

The Tropical Rainfall Measuring Mission (TRMM), jointly sponsored by the National Aeronautics and Space Administration (NASA) of the United States and the Japanese Aerospace Exploration Agency (JAEA, formally National Space Development Agency (NASDA) of Japan), is the first coordinated international satellite mission to study tropical and sub-tropical rain systems. The TRMM provides visible, infrared, and microwave observations of tropical and subtropical rain systems, as well as lightning and cloud and radiation measurements. The satellite observations are complemented by ground radar and rain gauge measurements to validate satellite rain estimation algorithms (Simpson, 1988). Several field experiments have taken place for validating the algorithms and advancing the physics of precipitation systems.

GIS and data interoperability at the NASA Goddard DAAC

The NASA Goddard Space Flight Center (GSFC) Earth Sciences (GES) Distributed Active Archive Center (GDAAC) is developing a number of related Web capabilities that will enable it to make its vast amounts of satellite remote sensing data more easily accessible and integrated by users, regardless of differing formats (i.e., interoperable data), and thus effect a wider distribution and use of NASA remote sensing data. Two approaches were adopted, one focused on facilitating use of the data and the other on facilitating access to the data. An automated system was developed to operationally convert selected GDAAC data into GIS formats and to distribute the GIS-compatible data to a network of Remote Sensing Information Partners. The second approach provides online, interactive capabilities for GIS data searching, visualization, mapping, and analysis; access to ancillary data; and retrieval of data (in various formats) or results of analysis of the data. Specific ongoing efforts include a WebGIS, a WMT-DODS (Web Mapping Testbed-Distributed Oceanographic Data System) server, and an Open GIS Consortium (OGC)-compliant client. These related capabilities could be variously integrated into coherent, application-driven, interoperable, data access systems, which will allow a much larger and more diverse user community to make use of GDAAC data, greatly increase the information density of the data accessed by users, and enable a greater diversity of potential applications of GDAAC data.

The Effects of Laterite and Associated Terrain Components on PBMR Response in HAPEX-Sahel

Abstract Terrain characteristics such as roughness and vegetation have been shown to significantly affect the interpretation of microwave brightness temperatures ( T B s ) for mapping soil moisture. This study, a part of the 1992 HAPEX-Sahel experiment (Hydrologic Atmospheric Pilot Experiment in the Sahel), aimed to determine the effects of laterite and associated terrain components (i.e. vegetation, soil, and exposed water bodies) on the T B of the Pushbroom Microwave Radiometer (PBMR, L-band, 21 cm wavelength), using the NS001 Thematic Mapper Simulator data as a surrogate for ground data. Coincident PBMR and NS001 data acquired from the high altitude (about 1500 m) long transect flights were processed to obtain T B s and radiances, respectively. The transects covered a range of moisture conditions. For this preliminary evaluation, no atmospheric corrections were applied, and the data sets were aligned by matching the acquisition times of the data records. NS001 pixels (about 4 m) were averaged to approximate the resolution of the PBMR (about 450 m), before their flight line data were compared. The laterite plateaux were found to have a surprisingly strong effect on the PBMR T B response. T B variations along the flight line could largely be explained by a combination of density and dielectric properties of laterite. The effect of surface moisture was distinguishable from the laterite effect, with the distinction apparently related to the occurrence of ephemeral pools of water after rainfall. Model simulated T B s agreed reasonably well with the observed T B s .

Workshop Examines Ways to Channel a Flood of Hydrological Data ; Collaborative Energy and Water Cycle Information Services Workshop; Greenbelt, Maryland, 15–16 June 2010

Blizzards, floods, droughts, and heat waves from January to July 2010 brought into sharp focus a primary expected manifestation of global climate change: significant alteration of Earths hydrological cycle. Increased numbers of extreme events, and longer-term and larger-scale precipitation pattern shifts that will stress both natural ecosystems and human societal norms, are anticipated as consequences of this alteration. For 25 years, NASA has orbited satellite sensors providing data on Earths interconnected energy and hydrologic systems; new missions for this purpose are scheduled to launch in coming years, including the Global Precipitation Measurement mission in 2013. These missions, and complementary studies, have produced large and steadily increasing volumes of data, either archived at NASA data centers or held by investigators, particularly those in the NASA Energy and Water Cycle Study (NEWS) program. This increasing volume has induced a data management dilemma: Investigators encounter an increasingly complex process to locate, access, and utilize such data, especially when seeking to combine heterogeneous data sets for innovative research.