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Transcript of Mushrooms Patagonia
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SEPTEMBER 2013AMERICAN METEOROLOGICAL SOCIETY |1319
AFFILIATIONS:WHITEMANUniversity of Utah, Salt Lake City,Utah; GARIBOTTIEl Chaltn, Argentina
CORRESPONDING AUTHOR: C. David Whiteman, Universityof Utah , 135 S. 1460 E , Rm. 819, Salt Lake City, UT 84112-0110
E-mail: [email protected]
DOI: 10.1175/BAMS-D-12-00167.1
2013 American Meteorological Society
2, and 3). While largely unknown to meteorologists,they pose challenges to climbers.
Rime mushrooms form when clouds and strongwinds engulf the terrain. Supercooled cloud dropletsare blown onto subfreezing surfaces and freeze rap-
Rime mushrooms, commonly called ice mush-rooms, build up on the upwind side of mountainsummits and ridges and on windward rock faces.
hese large, persistent, rounded or bulbous accretionsof hard rime range from pronounced mounds totowering projections with overhanging sides (Figs. 1,
Rime Mushrooms on Mountains
Description, Formation, and Impacts on MountaineeringBYC. DAVIDWHITEMANANDROLANDOGARIBOTTI
It was now my lead block, starting the 4th pitch, the bigrime-whale towered above me. I felt small and didntsee any good solutions other than venturing out into
the middle of it. Doing that would mean 100 meters of
severely overhanging face climbing on rime-covered ice.
I kept going up and my heart suddenly jumpedon the
right side of the mushroom a bluish half pipe appeared
winding its way upward. I have learned during my climbs
in Patagonia that very often, where the strong wind
forms mushrooms, it also grinds out half pipes and tun-
nels. Higher up, the half pipe shut downof course it
couldnt be this easy. My heart sank a little; it totally
closed, and above was a 3-meter, 45-degree roof of rimeleading out into the blue sky. Then I remembered the
option I had seen from below: I had seen a bluish glint on
the very belly of the beast. I decided to traverse left and
find the blue gold. We were not going down yet!
B-E , who, with Ole Lied, climbed a new
route, Venas Azules, on the South Face of Torre Egger in
the Cerro Fitz Roy massif of Patagonia in December 2011.
(Abridged and edited from its original version.) Bjorn-
Eivind died in a tragic climbing accident in Norway in
February 2012.
FIG. 1. Impressive rime mushrooms on the summitand west face of Cerro Torre, Argentina. The Ragni(Spider) route is indicated. It starts from the Col dela Esperanza (right) and ascends the bulky rime mush-room called El Elmo (the Helmet), then the west facethrough a series of rime mushrooms leading to thesummit mushroom. The mushroom just below thesummit is 50 m tall and hangs over the north, west, andsouth faces. The mushroom on the summit platformitself is 20 m tall and hangs over the north and eastfaces. (PHOTO: Rolando Garibotti)
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idly, making an opaque hard rime with air trappedbetween granular deposits. he mushrooms are mostfrequent and best developed on isolated summits andexposed ridges in stormy coastal areas. In describingrime mushrooms, their formation, where they have
been reported, and their impact on mountaineering,we will focus on Southern Patagonia. Climbers havedocumented very large, well-developed mushroomsthere (see acknowledgments).
COMPOSITION.As rime mushrooms persist,they are exposed to snowfall, graupel,rain, and drizzle. Meltfreeze cyclesand solar radiation can also affectthe consistency of the ice. In addition,rime mushrooms may incorporate
soft rime, clear rime, and even glaze.Soft rime forms when water vapordeposits onto a cold surface to pro-duce ice without changing to liquidfirst. Soft rime is feathery and whendeposited onto an existing snowpackis called surface hoar; on other objectsit is often called hoar frost. Unlikehard rime, soft rime forms duringclear skies and weak winds, and whennear-surface air is supersaturated withrespect to ice. It forms predominantly
at night. Clear rime or ice, contrary toits name, alternates opaque and clearlayers. Supercooled cloud dropletsfreeze as granules on impacted sur-faces to form opaque layers with less
air than hard rime. In clear layers,cloud droplets spread as a thin layer ofwater that then freezes. Whereas thethree types of rime are frozen clouddroplets,glaze, a smooth, compact,transparent layer of ice, forms whensupercooled rain or drizzle droplets,which are much larger than clouddroplets, coalesce and spread across asurface and then freeze.
Rime mushrooms, like the snow in asnowpack, are thus heterogeneous andconstantly in dynamic equilibrium,with energy and mass exchanges andwater phase changes at the atmo-sphereice boundary and metamorphicchanges within the rime formation.
METEOROLOGICAL CONDITIONS.hehigher the total mass of supercooled cloud droplets ina unit cloud volume and the higher the wind speeds,the larger the rate of accumulation of rime.
he rate of increase of rime mass on an obstacle
can be approximated by
dM/dt= wU A [kg s1], (1)
where w is the supercooled liquid water content(kg m3) of the cloud, Uis wind velocity (m s1),Ais
FIG. 2. Rime mushrooms in a range of sizes cover the summit of TorreEgger in the Cerro Torre Massif, Argentina. Climbers Ole Leid andBjrn-Eivind rtun have reached the summit after completing a newroute named Venas Azules. (PHOTO: Jorge Ackermann)
FIG. 3. Rime mushrooms on Cerro Torre. (PHOTO: Rolando Garibotti)
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the area of the obstacle perpendicularto the wind, and is the dropletob-stacle collision efficiency (a numberbetween 0 and 1).
he dropletobstacle collision
efficiency is less than 1 because thewind splits around the obstacle; somecloud droplets do not collide with theobstacle. he collision eff iciencies onrime mushrooms are not known, butcan be expected to vary across thesurface of an obstacle. According toN. H. Fletcher and others, the meanliquid water content of stratus, stra-tocumulus, and cumulus clouds isgenerally between 0.15 to 0.9 g m3. Ifa 1-m2obstacle were perpendicular toa 10 m s1wind, with a collision efficiency of 0.1, andthe liquid water content were 0.3 g m 3, then rimewould build up at the rate of 26 kg per day.
While the mass of a rime accretion is the same asthe mass of the supercooled water droplets hittingthe obstacle, the density of rime is lower than that ofliquid water because of the air spaces. he amountof air incorporatedand therefore the densityde-pends on wind speed, ambient temperature, dropletdiameter, and liquid water content. As reported byW. C. Macklin, the density of rime typically varies
from that of solid ice, 900 kg m3, down to 100 kg m3.Using the example of a rime mass buildup of 26 kg perday, which would produce a water depth of 2.6 cm, andassuming the rime density were 600 kg m3, the 24-hrime buildup on the surface would be 4.3 cm deep. Inthis example, rime would accumulate rather rapidly.
he WMOs International Cloud Atlasstates thatsupercooled droplets are most likely in a cloud atsubfreezing temperatures from about 2 to 10C.At 0 to 2C, the heat liberated when the dropletsfreeze can warm the impacted surface, resulting in
water running off and forming clear rime ratherthan lower-density hard rime. Depending on windspeed and cloud liquid water content, this processcan occur over a range of subfreezing temperatures(Mazin et a l. 2001), but it is most likely at tempera-
FIG. 4. Reported permanent or semipermanent rime mushrooms.
FIG. 5. The snowy northern Patagonian Ice Cap is225 km north-northwest of Cerro Torre (CT) in theCerro Fitz Roy Massif. The Southern Patagonian Ice Cap extends from northwest of CT southward. Soundingsfrom the Puerto Montt (PM), Comodoro Rivadavia (CR), and Punta Arenas (PA) radiosonde stations are takenregularly at 1200 UTC and occasionally at 0000 UTC. Each station had more than 10,900 radiosonde ascents.Monthly means are determined by averaging the separately determined 0000 and 1200 UTC monthly means.[Background image from Google Maps.]
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tures near freezing. Below 10C, the probabilityincreases that cloud droplets wil l freeze rather thanremain supercooled, because more ice nuclei becomeactivated and the supercooled droplets are more
likely to come into contact with frozen precipitation
particles. he mass of supercooled liquid water in-creases as air with temperatures below 0C is forcedupward by steep mountains.
TOPOGRAPHIC AND GEOGRAPHIC FAC-TORS.opography affects the formation of rimemushrooms. Elevation is important because windsare commonly stronger at higher elevations, as are thesubfreezing temperatures required for supercooleddroplets. owering, isolated peaks in particular oftencreate cap cloudsthat expose upper slopes to super-
cooled droplets.Mountains force approaching air masses to rise,resulting in cooling. his orographic lifting producesthe cloud condensate necessary for rime accretion ifthe approaching air mass is moist enough and thelifting altitude is sufficient to form a cloud base belowthe summit. If sidewalls are steep, air close to the peakascends rapidly, adding significantly to the cloudcondensate by enlarging existing cloud droplets andinitiating the formation of new droplets. he rapidascent leaves little time for the droplets to freeze. heincrease in the size and number of cloud droplets
FIG. 6. Monthly mean ERA-Interim reanalysis of 70-kPageopotential heights in MSL (solid lines with labels),wind vectors (25 m s 1west wind vector shown inlegend), and isotachs (colors in legend) for the higherlatitudes of the Southern Hemisphere in (a) Jan and(b) Jul. Patagonia is at about 70W longitude.
FIG. 7. Monthly 70-kPa (a) vector-average wind directionsand (b) arithmetic-average wind speeds (m s1) at PuertoMontt, Comodoro Rivadavia, and Punta Arenas. In (a):estimated wind direction (dashed line) over the Pacificcoast at the latitude of Cerro Torre (CT). In (b): esti-mated wind speeds for the same location (dashed line)and the estimated standard deviations (vertical blacklines). See Fig. 5 for site locations and abbreviations.
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produced by orographic lifting, as well as the increasein wind speed with elevation, increase rime accretionswith altitude on a mountain. On a smaller scale, thebulbous shape might be produced by the increase ofwind speed with height near the ground, increasingrime accretion with height on obstacles.
opographic irregularities often channel air risingon the upwind side of a mountain. Wind speeds in-
crease when air is channeled, enhancing rime mush-room formation where the ascending air goes throughgullies and over ridges and summit plateau edges.
Location is also significant. Rime mushroomsare more likely where large-scale weather patternsproduce low clouds and persistent high winds froma predominant direction. Downwind of a body ofwater that remains unfrozen year round and is largeenough to supply significant moisture, summits favorpersistent mushrooms if they are high enough abovethe water for lifted air to cool sufficiently.
WHERE RIME MUSHROOMS ARE FOUND.Rime mushrooms are familiar primarily tomountain climbers, so we searched for them inthe Ameri can Alpine Journa l (1929 to present;www.americanalpineclub.org/p/aaj). We also useda Google Internet search and discussions with well-traveled climbers. he number of reports was small(about four dozen), and our resulting map (Fig. 4)may be biased because most communications werewith climbers who have extensive experience inPatagonia.
he southern spine of the Andean Cordillera iswell known for rime mushroom formation. Rimemushrooms have also been reported in the coastalranges of North and South America, on the Ant-arctic Peninsula, on the South Shetland and South
Georgia islands of the Southern Ocean, in northernScandinavia, and in portions of the Himalayas im-pacted by the Asian summer monsoon. he highestsummits in the Himalayas have a more continen-tal climate and are more likely to build up snowcornices downwind of obstacles rather than rimemushrooms on the upwind side. Many locationswhere heavy accumulations of seasonal rime arereported do not experience large or persistent rimemushrooms, which cannot be sustained through thesummer in temperate climates.
CONDITIONS IN SOUTHERN PATAGO-NIA.Patagonia is a geographic (rather than political)name for a large region in southern Argentina andChile. Southern Patagonia includes two well-knownAndean landscapes: the Cerro Fitz Roy massif inArgentina and the orres del Paine massif in Chile.hese high mountains are separated from the PacificOcean by the Southern Ice Cap, the largest ice fieldin the Southern Hemisphere outside of Antarctica,with an area of about 16,800 km2(Fig. 5) and a meanelevation of about 1,500 m MSL. he Southern Ice
FIG. 8. Monthly mean LCLs at Comodoro Rivadavia,Punta Arenas, and Puerto Montt, and estimated LCLover the Pacific coast at the latitude of Cerro Torre(CT). For reference, the elevation of Cerro Torres
summit is 3,128 m MSL. See Fig. 5 for site locationsand abbreviations.
FIG. 9. Altitude of the 2C isotherm as a function ofmonth of year at Puerto Montt, Comodoro Rivadavia,and Punta Arenas, based on radiosonde data. Alsoshown are the estimated altitudes of the 2 and 10C
isotherms at the Pacific coast at the latitude of CerroTorre (CT), obtained by a latitudinal interpolationbetween Puerto Montt and Punta Arenas. The hori-zontal gray line indicates the altitude of Cerro Torressummit. See Fig. 5 for site locations and abbreviations.
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Cap supports numerous glaciers that calve icebergsinto a network of fjords along Chiles Pacific coast thatcome as close as 60 km to the Cerro Fitz Roy massif.
Cerro orre (49.29S, 73.10W, 3,128 m MSL), onthe eastern edge of the Southern Patagonian Ice Capin Argentinas Los Glaciares National Park, is, likethe Swiss Matterhorn, one of the iconic mountainsof the world. It was long thought to be unclimbable,and has a rich climbing history. It is also the moun-tain with the best-known rime mushrooms. Cerroorre and the Cerro Fitz Roy massif are the focus of
the following analysis and discussion. We used twosources of meteorological data. First, a long-termcombined modelobservation dataset provides meanhemispheric charts at 70 kPa (700 mb) for 19892005(ERA-Interim Reanalysis, Dee et al. 2011). Second,radiosonde data for 19752012 for three Chilean andArgentine radiosonde stations that surround Cerroorre provide additional information about winds(Fig. 5). Analyses will focus on the 70-kPa pressurelevel because it is at about the same elevation as Cerroorres summit.
Winds.he key feature of the Southern Patagonianclimate was described in a 1953 Journal of Glaciol-ogy article by Dr. Louis Lliboutry of the Universityof Chile, a member of the 195152 French AlpineExpedition to the Cerro Fitz Roy area, as the verystrong and almost incessant wind, which oftenreaches 100 km h1on the crests, with gusts of150180 km h1.
Both high wind speeds (Eq. 1) and consistent winddirections can be seen in the mean January and Julyupper-air charts (Fig. 6a,b), with a circumpolar vortex
extending northward over the Southern Ocean intoPatagonia in both months. No strong mean troughsor ridges perturb the wind direction, indicating thatthe mean winds are westerly. Monthly mean winddirections at 70 kPa at the three radiosonde stations(Fig. 7a)confirm that winds in Patagonia are con-sistently from a narrow range of westerly directions.hese are some of the strongest sustained winds on
Earth, which is why latitudes between 40 and 50Sare known as the Roaring Forties.
here are seasonal variations in wind strength,if not direction, across Patagonia. In the summer(January, Fig. 6a), a narrow band of especially strongwesterly jet winds at about 55S strikes the tip ofSouth America. In winter (July, Fig. 6b), the heightlines are distributed more evenly across the latitudezone between the edges of the Antarctic continent and30S, indicating more consistent wind speeds acrossPatagonia. hus, summer winds are stronger than
winter winds over the southern tip of South America(Fig. 7b, Punta Arenas) but weaker than winter windsat more northerly latitudes (Fig. 7b, Puerto Montt).he winds at Cerro orre are probably somewhatstronger than indicated for the coast (Fig. 7b) becauseof the speedup effect, which strengthens winds as theycross a mountain barrier (note the color change overthe Andes in Fig. 6). Winds probably exceed 28 m s1(95 km h1) a signif icant fraction of the time.
Clouds and precipitation.he west side of the south-ern Andes is frequently enveloped in clouds as the
FIG. 10. The summit rime mushroom on Monte Sarmien-to, Tierra del Fuego, illustrates the rough surfacetexture of rime mushrooms. (PHOTO: Ralf Gantzhorn) FIG. 11. Rime mushrooms form below the West Ridge
route on Punta Herron, in the Cerro Fitz Roy massifof Argentine Patagonia. These overhanging mush-rooms sometimes break and fall onto the rocks below.(PHOTO: Rolando Garibotti)
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cool, moist air from the coast coolsand condenses to form clouds. hiscloudiness is enhanced by stormsystems carried around the SouthernOcean in the circumpolar vortex. For
the clouds to envelop the summits, thecloud base must form below the sum-mit elevations. he mean monthlylifting condensation levels (LCLs) orcloud base heights at coastal stations(Fig. 8) are lowest in winter, highestin summer, but consistently belowthe Cerro orre summit all year.Latitudinal interpolation betweenthe Puerto Montt and Punta Arenassuggests that the mean monthly cloudbase heights west of Cerro orre rangefrom about 600 m MSL in summer to250 m MSL in winter. he low LCLsindicate that Cerro orre is withoutclouds on few days. At ComodoroRivadavia on the drier east side of thecontinent, the LCLs and cloud basesare much higher.
Air crests the Andes and descends and warmson the east side, forming a rain shadow. hus, largevariations in precipitation occur across the Andesat this latitude. he Pacific coast west of the Fitz
Roy massif receives an estimated 4,0005,000 mmof precipitation per year, sustaining the SouthernIce Cap and ice to fjords and to valley glaciers onboth east and west sides of the Andes. In contrast,in the rain shadow Coyhaique (45.6S, 72.1W,310 m MSL) and Cochrane (47.2S, 72.6W, 182 mMSL) receive only 1,200 and 730 mm of annual pre-cipitation, respectively (www.meteochile.cl/climas/climas_undecima_region.html).
Supercooled cloud water.he elevations of the 2 and
10C isothermsthe preferred temperature range forsupercooled dropletsvary diurnally, seasonally, and
geographically. A northsouth gradient in monthlymean heights of the 2 and 10C isotherms occursalong the west coast of South America between PuertoMontt and Punta Arenas (Fig. 9). hese isotherms arehighest in February and lowest in August. he 2Cisotherm ranges between 1,396 and 2,775 m MSLwellbelow the elevation of Cerro orre in all months. hemonthly mean altitude of the 10C isotherm variesbetween 2,801 and 4,270 m MSLabove the altitudeof Cerro orre in all months except June through Sep-
tember. his places the summit of Cerro orre firmlyin the 2 to 10C range, in which rime formation isfavored during 8 months of the year. For comparison,at the east side of the continent, the height of the 2C
isotherm at Comodoro Rivadavia is depressed by upto 500 m relative to Puerto Montt in summer and byseveral hundred meters in winter and fall.
MOUNTAINEERING CHALLENGES.Becauseof the persistent cloudiness and strong winds in thePatagonian Andes, climbers often spend weeks in abase camp or in the nearby town of El Chaltn waitingfor good weather. Windows of good weather may bebrief, forcing climbers to return to base to wait outbad weather and then to reascend known pitches to
continue the climb. In the summer of 200910, theweather was completely uncooperative and not asingle climber ascended Cerro orre.
Forecasting good weather periods in the CerroFitz Roy massif is difficult because of the lack of me-teorological data and the consequent difficulties ininitializing and assimilating data into meteorologicalmodels. Improved Internet access from El Chaltn tolarge-scale weather forecasts has greatly improvedthe chances for successful climbs and has allowedsome climbers to travel to Patagonia only when goodweather is anticipated.
FIG. 12. The route to the summit of Cerro Torre from the west iscompletely blocked by rime mushrooms. Here, two climbers, one ontop of the mushroom to the right and one on the face of the summitmushroom, are climbing Cerro Torre in 2012, a relatively dry year.(PHOTO: Colin Haley)
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Once on the mountain, climbers are concernedabout the anchorage, surface characteristics, andinternal cohesion of rime mushrooms. he icy baseof permanent or semipermanent rime mushrooms
secures them to the underlying rock. A persistentrime mushroom builds up over many weather cyclesand is thus affected by seasonal and daily variationsin the type and extent of temperature, cloud, precipi-tation, and sometimes even riming. he exterior ofthe mushroom is generally harder than the interiorbut can be brittle, friable, or unconsolidated. heinternal consistency ranges from hard veins in ahoneycomb-like structure to a popcorn textureor even cotton candy (Fig. 10). While mushroomscan persist for a long time, they can also fracture,
causing unpredictable ice falls (Fig. 11). Because aparticular rime formation is highly variable overtime and space, the value of advice from previousclimbers is limited.
he underlying rock and solid ice is generallyunreachable for solid hand and footholds or devicesto secure the climber against falls. Snow pickets canbe placed in the rime, but they are often insecure.
When rime mushrooms form on summit blocks(Fig. 12), routes must go over or through them, prefer-ably in vertical creases or gullies separating pillow-like sections. Nearly vertical tunnels sometimes form
in rime mushrooms (Fig. 13) andare preferred ascent routes, as theirinteriors are often solid ice. It is notknown how these tunnels form (theymay be created between converging
mushrooms), but wind clearly helpskeep the tunnels open. Where suit-able natural tunnels are absent andthe mushroom surface is dangerous,the climber can tunnel underneaththe mushrooms surface to be bettersecured against falls (Fig. 14).1
CONCLUSIONS.Rime mush-rooms have never been investigatedscientifically, and there are manyopen questions. While the Cerro FitzRoy region of Southern Patagoniaexemplifies the conditions favorablefor permanent but ever-changing rimemushrooms, analysis of other areasknown for rime mushrooms couldhelp define the range of conditionssuitable for their formation. Meteo-
rologically, the airflow dynamics and microphysicalaspects would be of particular interest. Further studywill be limited by the remoteness of these areas andthe lack of meteorological data.
ACKNOWLEDGMENTS. Johanna Whiteman pro-vided expert editorial assistance. Editor Jeff Rosenfeld
suggested this venue for the art icle and made suggestionsfor reducing the article size. Climbers Camilo Rada,
Ralf Gantzhorn, Colin Haley, Gregory Crouch, SimonGarrod, Jorge Ackermann, Damien Gildea, Simn Elas,
Hayden Kennedy, Ole Lied, Lionel Daudet, homasUlrich, homas Senf, Jon Walsh, and Josh Whar ton pro-
1In addition to rime mushrooms, simple rime on rock faces
can chal lenge climbers. Newly deposited rime or winter
rime that has not been through meltfreeze cycles can be
easily cleared away. Clearing rime that has gone through
one or more meltfreeze cycles is more difficult , unless it has
been loosened by rising temperatures. On steep rock faces,
warming air and rock may cause rime-falls. Water flowing
from melting rime on a rock face may subsequently freeze
in cracks or chimneys, forming verglas. Tis thin layer of
brittle, clear ice is attached to the rock or separated from it
by an air gap through which water drained as the underlying
rock was heated by solar radiation or by stored heat from the
rock mass.
FIG. 13. Colin Haley entering the base of a 50-m-long natural tun-nel through the ice mushrooms on the west face of Cerro Torre in2005. This tunnel was used by other climbers in 2005 through 2008or later but was absent in 2011. Reports of such tunnels date back tothe mid-1980s. (PHOTO: Rolando Garibotti)
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vided mushroom descriptions and photographs. Kevinrenberth and Dennis Shea at the National Center for
Atmospheric Science and Jeff Massey at the University ofUtah assisted with Fig. 6. Wesley Harrison compiled rimemushroom reports and produced Fig. 4. Matt Jeglum is
thanked for useful discussions and a review of an earlyversion of this art icle. his research was partia lly funded
by the National Science Foundation under grants AM-0938397 and AGS-0837870, and by the Office of Naval
Research Award # N00014-11-1-0709, Mountain errainAtmospheric Modeling and Observations (MAER-HORN) Program.
FOR FURTHER READING
Crouch, G., 2001: Enduring Patagonia. Random House,225 pp.
Dee, D. P., and Coauthors, 2011: he ERA-Interimreanalysis: Configuration and performance of thedata assimilation system. Quart. J. Roy. Meteor. Soc.,137, 553597.
Fletcher, N. H., 1962: The Physics of Rain Clouds. Cam-bridge University Press, 390 pp.
Kearney, A., 1993: Mountaineering in Patagonia . heMountaineers, 143 pp.
Lliboutry, L., 1953: Snow and ice in the Monte Fitz Royregion (Patagonia).J. Glaciol., 2, 255261.
Macklin, W. C., 1962: he density and structure of iceformed by accretion. Quart. J. Roy. Meteor. Soc., 88,3050.
Mazin, I. P., A. V. Korolev, A. Heymsfield, G. A. Isaac,and S. G. Cober, 2001: hermodynamics of icecylinder measurements of liquid water content insupercooled clouds.J. Atmos. Oceanic Technol., 18,543558.
Mazzoni, E., A. Coronato, and J. Rabassa, 2010: heSouthern Patagonian Andes: he largest mountainice cap of the Southern Hemisphere. Geomorphologi-
cal Landscapes of the World, P. Migon, Ed., Springer,111121.
Whiteman, C. D., 2000:Mountain Meteorology: Funda-mentals and Applications. Oxford University Press,355 pp.
World Meteorological Organization, 1975: International
Cloud Atlas, Vol I. Manual on the Observation ofClouds and Other Meteors. WMO No. 407, 155 p.
FIG. 14. Jorge Ackermann climbing above a tunnel/halfpipe that he has dug in one of Cerro Torres notoriousmushrooms. Climbers have adapted their axes with
heart-shaped or shovel-like attachments for use onrime formations to improve purchase and facilitatedigging. Obviously, while digging tunnels, the leadclimber should position the belayer to protect againstcascades of rime ice particles and ice chunks. (PHOTO:Rolando Garibotti)