SeaWiFS HighlightsNovember 2002

SeaWiFS Views Aerosols from Santa Ana Winds

On Monday, November 25, 2002, SeaWiFS flew over the US West Coast and collected the data used to make these two images. The left-hand image is a quasi-true-color rendering of the information. Not much detail is visible in the water, but several other features can be made out. Dust and haze partly obscure southern California. (These aerosols were lofted by Santa Ana winds that were reported to top 75 miles per hour in places on Monday.) Several long smoke plumes drift westward across the Sacramento Valley from fires in the Sierra Nevada mountains. The mountain tops themselves are highlighted white with snow. Farther north, individual volcanoes are made visible by their snow caps.

By applying atmospheric corrections and other algorithms to the SeaWiFS data, one can bring out a wealth of detail in the chlorophyll distributions in the surface waters of the Pacific Ocean. In this pseudo-color depiction, purples and blues represent lower concentrations; cyan and green— moderate concentrations; and yellow, orange, and red—high concentrations. Note that the dust from southern California is thick enough in places that current algorithms are unable to determine chlorophyll concentrations in the water below.

POC: 970.2/Gene Feldman

gene@seawifs.gsfc.nasa.gov

SeaWiFS Views Aerosols from Santa Ana Winds

Sydney

Italy

November 25, 2002

Quasi-true-color Pseudo-color

ARCTIC SEA-ICE DRIFT FROM AMSR AND QUIKSCAT IMAGES

This is the first comparison of sea-ice drift maps derived by wavelet analysis using AMSR-E and QuikSCAT data since Aqua's launch on May 4, 2002. For better ice feature tracking, AMSR-E 89GHz data with 6.25km resolution are used in this study. The big gyre in the Chukchi/Beaufort/East Siberia Seas can be clearly identified in both results. The ice motion maps from QuikSCAT and AMSR-E agree each other pretty well. It looks like the ice motion map from AMSR-E data has more vectors in the area between north pole and greenland sea on this day which maybe becaused of higher resolution. Using this new high-resolution data set, more testing and calibration for different parameters in wavelet transform is underway. Since both results are comparable and complement to each other, merge of AMSR-E with QuikSCAT results by some data fusion techniques will definitely improve the sea-ice motion map with more complete coverage. AMSR and SeaWinds on-board of ADEOS-II is currently scheduled to be launched on December 14, 2002. We will be able to use and merge all AMSR-E, AMSR, SSM/I, QuikScat, and SeaWinds data by next spring for sea-ice motion and deformation study. Processing daily sea-ice motion maps and delivery of data products in a near-real time schedule for sea-ice community (e.g. NIC and CIS) has been proposed in a joint pathfinder project.

POC: Code 971/Antony Liu

Antony.A.Liu@nasa.gov

ARCTIC SEA-ICE DRIFT FROM AMSR AND QUIKSCAT IMAGES

Antony Liu and Yunhe ZhaoNASA Goddard Space Flight Center

AMSR QuikSCAT

Airborne Lidar Beach Mapping

Science Problem/Objective: Understanding coastline change as a result of major storm events.

Method: NASA/Wallops ATM Lidar sensor on NOAA’s Twin Otter with joint analysis with USGS.

Highlights: The Airborne Topographic Mapper (ATM) group at Wallops Flight Facility for the last five years has participated in a robust program in collaboration with the U.S. Geological Survey (USGS) Center for Coastal Geology in St. Petersburg, FL, to maintain reasonably current digital shoreline surveys of much of the coast of the continental U.S. During this time the entire coast from Portland, ME to Corpus Christi, TX has been surveyed except for the coastal Everglades and portions of the Mississippi Delta. All but ~100 km of the Pacific Coast has been surveyed. Most of these coastal areas have been surveyed two or more times. The preceding figure shows our most recent work, which has been used by the State of Louisiana for resource planning, as well as the USGS for storm modeling analysis. The upper figure displays color-coded elevation change. The lower figure is a mosaic of digital photos collected during our “pre” storm survey.

Earth Science Focus: Natural Hazards

POC: Bill KrabillWilliam.B.Krabill@nasa.gov

Recent Coastline Changes

For Raccoon Island, LA

Documented by NASA/GSFC ATM Lidar

in Collaboration with USGS

POC: Code 971/Robert BindschadlerRobert.A.Bindschadler@nasa.gov

A review article on the West Antarctic Ice Sheet appeared in the December 2002 issue ofScientific American. This article was written by Robert Bindschadler and Charles Bentley,regarded by many to be the leaders of conflicting views on the future of this large ice sheetand the consequent impact on sea level. While we don’t see our status as that of disputingleaders, we felt we could write an informative article that poses the knowns and unknowns onthis intriguing glaciological issue. We review the major achievements of the past 20 years ofresearch, many based on satellite remote sensing and accomplished at Goddard, and pose theuncertainties for future behavior of this mysterious ice sheet. New insights in how thesubglacial till control the speed of ice streams plays a central role in the article. While thepotential impact of this ice sheet is large (5 meters of sea level), major changes would have tobecome more widespread. Most troubling is the behavior of the poorly studied region drainedby the Pine Island and Thwaites Glaciers. Remote sensing has been the only means employedto study this area and it is expected that future sensors, most notably ICESat, will enable us tolearn more.

A Review Article from Scientific American on the West Antarctic Ice Sheet

Review article in December 2002 issueof Scientific Americanon the research, dynamicsand possible future of theWest Antarctic Ice Sheet(R. Bindschadler)

Beam-Filling Bias over the Different Climate Regimes

A.T.C. Chang, L.S. Chiu, and D.B. ShinHydrological Sciences Branch, NASA/GSFC andGeorge Mason University

A major error source in the satellite microwave estimation of rain is associated with the relatively largefootprint of microwave sensors compared to the spatial scale of rain elements. This “beam-filling” error is dueto the inhomogeneity of the rain field within the sensor footprint and the non-linearity of the rain (R) andbrightness temperature (Tb) relation.

We investigated the beam-filling error problem using co-located (TRMM) Microwave Imager (TMI) Tb andsurface rainfall and reflectivity profiles from the Precipitation Radar (PR) over the East and West Pacific. Thecoefficient of variation (CV), which is defined as the ratio of standard deviation to the average rain rate within aTMI footprint, was computed.

Figures 1 and 2 show the observed Tb as a function of rain rate at the 10, 19, 37 and 85 GHz (horizontalpolarization) for different CVs for the East and West Pacific, respectively. The difference in the R-Tb relationsfor different CV categories is consistent with earlier works on Global Atmospheric Research Program-AtlanticTropical Experiment (GATE) and Automatic Meteorological Data Acquisition System (AMeDAS) data and thebeam-filling correction formula proposed by Chiu et al. (1990). The difference between East and West Pacificis interpreted as the difference in the convective/stratiform partitioning of rainfall in these regions.

Chiu, L.S., G.R. North, D.A. Shout, and A. McConnell, Rain estimation from satellites: Effect of finite field ofview, JGR, 95, 2177-2185, 1990.

POC: 974.0/Al ChangAlfred.T.Chang@nasa.gov

Figure 1: Relationship of the Tb and rain rate as a function of averaged CV at 10, 19, 37,and 85 GHz (horizontal polarization) over the East Pacific.

Figure 2: Relationship of the Tb and rain rate as a function of averaged CV at 10, 19, 37,and 85 GHz (horizontal polarization) over the West Pacific.