This project has two parts: (1) passive microwaves and (2) photogrammetry, Landsat and SAR imagery.

(1) Passive microwave data were obtained from the Defense Meteorological Satellite Platform (DMSP) and the Special Sensor Microwave Imager (SSMI). These data are being used to map the hemispheric extent of snow cover with a spatial resolution of 30 km. Because the microwave radiation emanates from the ground beneath the snow as well as from the snow itself, the relationship between microwave brightness temperature and snow characteristics is complex. We have focused on a traverse across Alaska from the Pacific Ocean at 58°N, south of Alaska, to 73°N in the Arctic Ocean north of Alaska. Our data set spans the all-time record low temperature period in January 1989 through the all-time high temperature period in February 1989.

Variables include the surface temperature, the moisture content and the general nature of the upper layers of rock and soil, the amount of snow cover and the extent of depth-hoar crystal development within it, the presence of ice lenses in the snow, and any liquid water present in the snow. The hope still persists that microwave brightness temperature can be interpreted to obtain snow depth and liquid water content, but the complications are sobering and in addressing them we expect to learn more about the overall soil-snow system and how it interacts. During the past two years we have learned that vegetation plays a major role in controlling the passive microwave signal received by the satellite. Indeed, the vegetation map by A.W. Kuchler (U.S.G.S. National Atlas, sheet No. 89) agrees very well with the patterns of microwave brightness temperatures. Our paper presented at the 50th Eastern Snow Conference deals with this.

A persistent anomaly, of unexpectedly low brightness temperature (approximately 45 K lower than surrounding values) is present in the data sets in the northern foothills of the Brooks Range during each year of the study. The exact location of the anomaly varies slightly from year to year. We have investigated several possible explanations for this anomaly but so far without success.

(2) The 1993 and 1994 photogrammetry was successful over the summit of Mt. Wrangell. It was paid for by the U.S. Geological Survey and the Alaska Division of Geological and Geophysical Surveys.

Analysis of ice volume changes in the North Crater (1 km diameter) of Mt. Wrangell, based on photogrammetric, digital data of cross sections, 20 m apart, are still underway.

In addition, we have made orthophoto maps of the glacier termini, paying special attention to parts that are advancing on the northeast flank of the mountain. The local nature of the advancing termini have been verified by examining Landsat imagery from 1973 and 1986.

The possibility of identifying facies boundaries on Mt. Wrangell with SAR imagery, as mentioned in this report in connection with Greenland, has proven to be successful. A publication on this subject is in preparation.

NASA Grant NAG4-887: Scientific personnel, C. S. Benson; D. K. Hall (NASA Goddard Space Flight Center); M. Sturm (CRREL).