Malvinas Current Blooms - 23 Dec 04 Gene Feldman NASA GSFC, Laboratory for Hydrospheric Processes, SeaWiFS Project Office The final downlink of SeaWiFS data to NASA occurred at 12:52 AM (EST) on December 24, The sensor remains in good health, but NASA's contract with ORBIMAGE, the provider of the data, has ended.ORBIMAGE

Atmospheric Correction for SWE Estimation Using GHz Radiometric Measurements James R. Wang NASA GSFC, Laboratory for Hydrospheric Processes, Microwave Sensors The satellite radiometric measurements (e.g., SSM/I, AMSR-E) near 19 and 37 GHz (either horizontal or vertical polarization) have been used for the estimation of snow water equivalent (SWE) or snow depth (SD). The effect of atmospheric absorption has been ignored thus far, because both 19 and 37 GHz channels lie in the window region of the microwave absorption spectrum. Because the atmospheric absorption is different between 19 and 37 GHz, this effect must be accounted for a consistent estimation of SD (or SWE) at low and high elevations. Plot (a) above shows this effect in terms of brightness temperature (T b ) difference between 19 and 37 GHz at altitudes (1 and 4 km), which is a measure of SD, as a function of the T b difference at surface. There is a 23% correction factor between surface and at 4 km altitude. Over Tibet Plateau where the elevation is as high as 5.5 km (see elevation map in plot (b)), the correction factor would be about 30%, which is quite significant. Plots (c) and (d) show the effect of this atmospheric correction, using Aqua AMSR-E measurements; plot (c) gives the estimated SD without atmospheric correction, and plot (d), with atmospheric correction. It’s quite clear that the correction is fairly significant. These preliminary results were presented in AGU fall 2004 meeting in San Francisco, in collaboration with National Snow and Ice Data Center (R. Armstrong, M. Brodzik, J. Wang, et al).

(a) (c) (b) (d)

Guiding the South Pole Traverse The National Science Foundation is attempting to establish a heavy-vehicle over-ice traverse route from McMurdo Station to the South Pole. At NSF’s request, Robert Bindschadler (Code 970) was asked to steer the traverse party through a series of dangerous crevasses that had halted the traverse and threatened both the safety of the field team and the viability of the traverse route. Using ASTER imagery, Bindschadler identified waypoints that guided the traverse across the 80-mile section of the ice shelf in just two days without encountering a single crevasse. crevasses ASTER image: January 4, 2002 revised route planned route Photo of crevasse on Amery Ice Shelf, Antarctica (by J. Bassis)

Global Land Surface Water Use Efficiency Bhaskar J. Choudhury NASA GSFC, Laboratory for Hydrospheric Processes, Hydrological Sciences Water use efficiency is defined as the ratio of annual carbon accumulation by plant communities and total evaporation or transpiration. This efficiency is considered to be a highly significant indicator of ecosystem performance. A biophysical process- based model, combining energy and water balance equations, with carbon assimilation determining stomatal control on transpiration, has been used, together with 60 consecutive months of geo-coded and synchronous observations, to calculate components to total evaporation (transpiration, soil evaporation, and interception).

This figure shows the ratio of annual total carbon accumulation per unit area and annual total evaporation (i.e., sum of transpiration, soil evaporation, and evaporation of intercepted water) in units of depth of water evaporated per unit area.