SeaWiFS Views Six Years of Data 970.2/Gene Feldman, NASA GSFC, Laboratory for Hydrospheric Processes, Office for Global Carbon Studies Launched on August 1, 1997, SeaWiFS began collecting global data operationally in mid-September and has continued to perform flawlessly for the past six years. The image above is the average ocean chlorophyll a concentration as derived from SeaWiFS since launch. What is clear from this image is the tight coupling between the physical and chemical processes in the ocean and their resulting biological signature. What SeaWiFS has allowed us to do as never before, is to not only monitor the short-term spatial and temporal variability in the ocean's biology, but to have the first well-calibrated, long-term data set that allows us to quantify the ocean's biological response to global change. Images and digital data sets are available that are based upon the SeaWiFS climatology for seven different geophysical parameters at a number of different temporal scales. One of the interesting insights that came out of the generation of this chlorophyll a climatology is the identification of the region of the world's oceans that has the lowest chlorophyll concentration. That area, slightly west of Easter Island in the South Pacific (centered at 26 degrees South and 115 degrees West) had an average concentration of milligrams chlorophyll a per cubic meter.

SeaWiFS Views Six Years of Data

ICESat - Animations of Ice Sheet Elevation Data 971/Chris Shuman, NASA GSFC, Laboratory for Hydrospheric Processes, Oceans and Ice Branch Animations of elevation data acquired during ICESat’s two 2003 operational phases have been prepared by C. Shuman (971) with support by V. Suchdeo (NVI, 971). Elevations are indicated by color-coded elevation ranges and missing data are shown as gaps in all the progressively plotted tracks (both 8-day and 91 day repeat patterns). Data acquired to date from both the Laser 1 and the first Laser 2 mission phases (2/20/03 to 3/29/03 and 9/25/03 to 11/18/03, respectively) are available and show the gradual development of the elevation database that is ICESat’s primary mission goal. The animations show, among other things, the significantly denser coverage resulting from Laser 2’s 91 day exact repeat pattern and longer operational period, the impact of heavy cloud cover along the Greenland and Antarctic coastlines (especially in southern Greenland and along the Bellingshausen and Amundsen Seas), the general topographic form of the two great polar ice sheets, and even the location of specific nunataks in West Antarctica. All data available has been incorporated with more recent tracks overprinting older tracks for exact repeats; this gradually fills in gaps resulting from clouds. No attempt has been made to filter anomalies at this point. The animation files are too large to incorporate in these powerpoint slides (>100 mb) and will be shown as separate movies. It may be possible to size them appropriately for web-based display but that is not currently an option.

ICESat - Animations of Ice Sheet Elevation Data Animations of ICESat elevation data (stills shown here) have been prepared by C. Shuman (971) with support by V. Suchdeo (NVI, 971)

Areal Water Equivalent of Snow in the Upper Yangtze River Basin Using Microwave Satellite Data A.T.C. Chang and J.C. Shi Hydrological Sciences Branch, NASA/GSFC and University of California, Santa Barbara Snow is a major source of water supply, and is important in generating hydropower. Snow is also a major component of the global energy and water balance cycles. Routine measurements on the ground of snow depth and snow water equivalent (SWE) are very sparse. However, satellite observations of microwave radiation from snow can be used to estimate SWE under most weather conditions since naturally upwelling microwave radiation is not strongly affected by clouds. Most importantly, the measurable interaction of microwaves with snowpacks make them ideal for snowpack monitoring. A reasonably robust semi-empirical radiative transfer model has been used to infer the snow water equivalent from Nimbus-7 SMMR observations at about 25 km x 25 km spatial resolution: SWE = 4.8 (T 18V – T 37V ) mm Few verifications of large SWE estimates have been possible thus far due to the sparse snow gauge data. Thus, an alternative method using a simple water balance model has been used to verify the microwave-derived SWE estimates from the upper Yangtze River Basin (using averaged data from 8 years). Stream Flow = Precipitation – Evaporation + Snow Melting Preliminary results show that the passive microwave derived SWE compares well with a water balance model analysis.

90E105E 25N 35N Major River Basins in China Upper Yangtze River Basin SMMR Derived Snow Water Equivalent SWE area ~ 693,715 km 2, GPCP area ~ 866,962 km 2

Water Balance Estimates Stream Flow: Cuntang ( ’ E, ’ N) Precipitation: GPCP monthly x grid Evaporation: 60% of precipitation Snow Melting: Monthly SWE difference (February to July) 1:1 Feb Mar Ap r May Jun Jul

Snow radar tests on Southern Ocean sea ice 975/Thorsten Markus, NASA/GSFC, Laboratory for Hydrospheric Processes, Microwave Sensors Branch (in collaboration with Prasad Gogineni, U. Kansas, Lawrence, KS and Vicky Lytle, Australian Antarctic Division, Hobart, Australia) Snow depth on sea ice is a standard EOS Aqua AMSR-E product but validation is extremely difficult as no other remote sensor at this time can measure this quantity and direct in-situ are very difficult given the harsh environment and the remote location. Therefore, an airborne radar that can measure the snow on spatial scales comparable to the AMSR-E footprint is currently under development. The Australian Antarctic Division conducted a research vessel cruise in September/October 2003 with an emphasis on AMSR sea ice validation. Part of this cruise was also dedicated to the testing of a radar prototype that was mounted on a sled. The radar was tested on thirteen 100m and 500m long transects in the vicinity of the ship which consisted of a variety of sea ice and snow conditions. Initial results look very promising and have proven the concept. The next steps are the refinement of data processing and modifications for the airborne system.

Snow radar tests on Southern Ocean sea ice Thorsten Markus, Code 975, NASA/GSFC (in collaboration with Prasad Gogineni, U. Kansas, Lawrence, KS and Vicky Lytle, Australian Antartic Division, Hobart, Australia)