My conversation with Peck was suspended when a lecture began on the subject of the algae that live in snow and feed on the nutrients in it. The organic material the algae excrete may support colonies of bacteria, and the algae themselves serve as food for several varieties of snowworms. Sometimes algae are so prevalent that the snow turns red or yellow or blue; the colored snow may exude the smell of fresh watermelon. The lecture revealed one more novel element in the unfolding dynamic of snow—the fact that snow is an ecosystem. By the time the lecture began, Peck had gotten as far on his sheets of legal paper as "1979—Thomas Carroll to direct operational program in Minneapolis, MN." He was, it seemed clear, just getting going.
The strategic snow command
There is a certain cast to the people who attend meetings of the Western Snow Conference. It is not, of course, exhibited universally, though I suspect that it would clearly emerge if one were somehow to add everyone together and take the mean. They are mostly men and mostly at the lower end of middle age. They seem to be independent-minded, friendly, physically fit. They are given to calling precipitation "precip," and partial to neatly trimmed facial hair and the kind of casual clothing one associates with people who do enlightened and brainy things outdoors. Formality never exceeds a bolo tie, the color of whose string indicates regional affiliation. The design of the clasp tends to reflect the year of one's first attendance at the Snow Conference; there were clasps around me going back to the 1940s.
One senses that there may be something of a division inside the Western Snow Conference between a younger generation that holds a firm faith in what new technology can accomplish and an older generation that idealizes tramping about in snowshoes with a Mount Rose sampler. Even so, the nature of the work brings out a bit of the mountain man in almost everyone. I cautioned one hydrologist, who was about to make the harrowing drive up the mesa to nearby Los Alamos, "Hold on to your hat. It's pretty steep." He looked at me as if to say, "I could do steep in my sleep."
No one intends to give up the traditional manual outdoor snow surveys. Not only are they part of the romance that drew many people into the field to begin with, but, more important, they contribute an indispensable something for which, in this age of remote sensing, a specialized term has been developed: "ground truth." With respect to the specific variable of water content, snow surveys set a standard that other methods can only measure themselves against. Many of James Church's original snow-survey courses in the Sierra Nevada are loyally maintained to this day.
Still, the forecasting business has made some important advances during the past few decades (a period known to some as the Second Golden Age of Hydrology). In addition to the 1,600 or so traditional mountain snow courses that the Soil Conservation Service and other agencies continue to run, the SCS operates 550 SNOTEL (for "snow telemetry") sites in mountainous areas throughout the West, each with an array of snow pillows, precipitation gauges, and sensors to record temperature and sometimes other variables, such as wind speed and soil moisture. Information is brought back to headquarters by means of "meteor-burst transmission": a request signal from one of the two SNOTEL master stations is bounced to remote sites not off a satellite but off the ionized trails of some of the billions of tiny meteors that enter the earth's atmosphere every day; the remote stations bounce back their most recent data in the same way. Forecasting agencies still send out on paper monthly state-by-state bulletins, but increasingly all the relevant data is available electronically, often in real time or near-real time.
Actually, the term "data" is beginning to sound a little limited. The National Weather Service in its publications refers to what it inclusively calls "airborne and satellite snow-cover products." I spoke with Thomas Carroll, who was the chairman of the executive committee of the Santa Fe meeting, and who since 1979 has been the director of the weather service's National Operational Hydrologic Remote Sensing Center, which is based in Minneapolis. For much of North America the center functions as a kind of Strategic Snow Command. The NWS, Carroll said, runs snow courses after a fashion—more than 1,850 of them, in twenty-six states and seven Canadian provinces. Each one is about ten miles long and is monitored by aircraft. The basic idea behind these very long snow courses is relatively simple. The earth's surface emits natural gamma radiation from trace elements of potassium, uranium, and thorium in the soil. That radiation is attenuated by the amount of water in the snow. An estimate of water content can be obtained along any of the established flight lines by comparing a background reading previously made over bare ground with a fresh reading made over the same piece of ground under snow.
There are limitations. "All methodologies have deficiencies," Carroll said, and he frankly ticked off the ones that characterize his flight-line network. "One, we have to fly close to the ground —five hundred feet—so we can only fly in good weather. Two, flying close to the ground means that terrain is also a problem. We can do some mountain areas, but we can't do others. Three, when the snowpack gets above eight, ten, twelve feet, the gamma-radiation technique turns to mush. The biggest limitation of all is the cost. It takes a lot of money to fly airplanes."
The snow-water-equivalent estimates from overflights, like those derived from any snow course, represent only samples. But already it is possible to merge, using computer models, sample surveys of every kind with continent-wide snow-cover imaging obtained by microwaves from satellites. The images will be getting better. Last October the space shuttle Endeavour made its second series of experimental investigations (the first was in April) with a new radar system capable of looking at the snowpack. A powerful multipurpose remote-sensing platform called the Earth Observing System, consisting of several integrated satellites, is scheduled to go into operation in 1998, with a $7 billion array of earth-monitoring equipment that will make the present Landsat satellite seem like a stereoscope in a Victorian parlor.
As we discussed satellites, Tom Carroll repeated, "All methodologies have deficiencies." The advantage of microwaves, Carroll said, is that they can see through clouds. The disadvantage is that they can show with confidence only the areal extent of the snowpack. They are much less able, given the present state of technology, to extract accurate information about water content. "That's a big problem," Carroll said. "Big problem." Even so, he went on, just being able to see the areal extent of the snow cover can make an important difference. Consider what happened in 1983 in the Colorado River basin. Forecasters knew from sampling that the water content of the snowpack was running about 200 percent of normal—"There was a lot of snow all over the shop"—and were expecting much more than the usual runoff. Typically what happens in the West is that the lower elevations warm up before the higher elevations, and the runoff is therefore gradual, drawn out over time: what is known as a "soft landing." In 1983 there was very little early-spring runoff. Scattered local reports indicated that the lower snowpack was still in place, but no one had any idea of the vast size of the phenomenon. The weather stayed cold all through the spring, and then a weather system moved in and warmed the entire snowpack all at once. Big problem. "If we'd had a program then to monitor areal extent of snow cover," Carroll said, "we'd have noticed the anomalies in the lower elevations. We could have been more responsive."
Being "responsive" in this case would have meant releasing water from reservoirs downstream to accommodate the coming torrent. As it was, in 1983 the Colorado River spilled over the top of the Hoover Dam, creating a western version of Niagara Falls. Flooding in the Colorado basin did not end until autumn. Looking back at newspaper accounts, I noted with satisfaction that the federal official charged with overseeing the Colorado River dams was named Plummer.
The future of snow
For all the improvements in detection, though, there remains something fundamentally unsatisfying about the forecasting endeavor. One hydrologist I met at the Snow Conference meeting resorted to a medical analogy. We have gone, he said, from the equivalent of Laennec's wooden tube to the stethoscope to the electrocardiogram in the space of a generation, but, as with the human body, we still don't know many fundamental things about snow. Nor do we understand its relation to weather and to climate—the dynamics of climate being one of the perennials on the "must figure out" list of science. And although, as in medicine, we can predict the likely course and consequence of certain conditions once they arrive, we find it a lot harder to predict the onset of many of those conditions very far in advance.
That is one of the tasks for the future. The Snow Conference meeting offered glimpses of some avenues of research. One paper speculated about a possible relationship between the size of the Himalayan snowpack in a given year and the size and timing of the subsequent monsoon. Another paper sought to document a link between the periodic El Nino warming trend and diminished snowfall in the Pacific Northwest, a link that would have practical significance for forecasters if the onset of El Nino could consistently be determined in advance. (I overheard someone behind me snort and say, "Yeah, but try telling water-conservation officials that you think there's going to be a shortage because of the barometric pressure in Tahiti.") Several papers looked ahead to what would probably happen to precipitation and snowmelt in certain locales in the event of global warming. One of them, which assumed a 3 degrees Celsius increase in average temperature, concluded that the volume of precipitation in the Sierra Nevada would not be much affected but the timing of the snowmelt would: nearly a third of the precipitation that would ordinarily appear as runoff in springtime, when farmers can use it right away, would appear as runoff in wintertime instead, meaning significant losses for watersheds that don't have adequate means of storage.
Even as global climate and large-scale circulation patterns affect snowfall, snowfall has a considerable impact in return, given that gains and losses of energy in the atmosphere are what swirl air masses around the planet. There is no natural surface on earth with a higher albedo—reflective power—than fresh snow. A field of planted farmland may reflect back as little as three percent of shortwave solar radiation. The Mojave Desert may reflect as much as 30 percent, sea ice as much as 40 percent. Fresh snow may reflect fully 95 percent. Rather than being retained as heat, the sun's energy is sent back where it came from. The melting of a winter's worth of snow takes so much energy that even though the sun in the Northern Hemisphere is at its most intense in June, the atmosphere remains cooler than it "ought" to be until August.
All the earth sciences began as applied sciences, spurred by basic considerations of economics and survival. In helping to organize the Western Snow Conference, James E. Church expressed the hope that the study of snow might be broadened beyond the pragmatic and the empirical. To some extent this is happening. Snow studies are, of course, still pragmatic, sometimes in ways that those in the so-called progressive conservation movement of the late nineteenth and early twentieth centuries would never have anticipated. In the current period of drought, for instance, utility companies and water authorities are conducting cloud-seeding experiments in many areas of the West as part of an attempt to see if more snow can be put on the peaks. (Such efforts in the past resulted in some well-publicized legal tangles when snow suddenly fell in an unexpected place.) Snowmelt forecasting will also play a big role as states throughout the West, under various mandates, begin to restore depleted rivers and lakes. To the list of competing uses for the snowpack's water, in other words, we must now add another.
As I prepared to leave Santa Fe, the space shuttle Endeavour was high overhead, in the midst of a successful ten-day test of its new radar. I drove north out of town to the banks of the Rio Grande, which flows through a broad plain between the Jemez and the Sangre de Cristo mountains. The snow in the lower elevations had begun to melt, and the river, though it was still shallow and slow-moving, had begun to rise. According to the newspaper that morning, the Sangre de Cristo Water Company's reservoirs in the Santa Fe Canyon, which trap the spring snowmelt and were now nearly full, would be releasing water into the Rio Grande in a matter of weeks. Looking up, I could see the alpine snowpack—still intact, and, on average, about ten feet deep, according to information I had received from the Soil Conservation Service. Or, as I might have put it at another time, "The snow 120." The cottonwoods along the Rio Grande displayed the haze of fuzzy lime-green they briefly exhibit every spring, reminding me that this was exactly the time of year that Horace had been writing about: "The snows have dispersed, now grass returns to the fields and leaves to the trees."
All those former needles and sheaths, those cups and bullets, those dendrites and stellar crystals—they were dispersed, or dispersing, to be sure. But, fortunately for all of us, they would be back.