M a n a g e m e n t

a n d

A n a l y s i s

o f

S n o w,

A v a l a n c h e

a n d

C l i m a t e

D a t a

The May 1 and June 1 SWE fractions have markedly de-
creased (figures 4, 10,5,11),23% and 32%, respectively.
Maysnowestimatesaredowninalmostallelevation
zones.In the May elevation zones, 70% of the yearly per-
cent changes are supported with 95% confidence.
The day of maximum SWEhas also changed, occurring
about a week earlieroverall,with a stronger influence in
the lower elevations.In areas between 1500 and 2500 m,
the snow accumulation peaks about 2 weeks earlierthan
before,with40%ofthese estimatessupported by95%
confidence (figure 2).

ACKNOWLEDGMENTS

TammyJohnsonwishestothankTomPainterandTom
Albright formany useful discussions.Fundingforthis re-
search was provided by NASA's Earth Observing System.

REFERENCES

Aguado, E.,1990: Elevational andlatitudinal patterns of snow
accumulationdeparturesfromnormalintheSierraNevada,
Theoretical Applied Climatology,42 , 177-185.

Aguado, E., D. Cayan, L. Riddle, and M. Roos, 1992: Climatic
fluctuations and thetiming of West Coast Streamflow,Journal
of Climate,5(12), 1468-1483.

Barry, R.G., J.-M.Fallot, andR.L. Armstrong, 1995: Twentieth-
century Variability in Snow-cover Conditions and Approaches
toDetectingandMonitoringChanges:StatusandProspects ,
Progress in Physical Geography ,19(4), 520-532.

Dettinger, M.D., and D.R. Cayan, 1995: Large-scale atmospheric
forcingof recent trends towardearlysnowmelt runoff in Cali-
fornia,Journal of Climate,8 , 606-623.

LettenmaierD.P. and T.Y. Gan, 1990: Hydrologic Sensitivities
of the Sacramento-San JoaquinRiver Basin, California,toGlo-
bal Warming,Water Resources Research ,26(1), 69-86.

Mitchell, J.F.B., S. Manabe, V. Meleshkoand T. Tokioka (Eds),
1990: EquilibriumClimate Changeand its implication for the
future.InClimate Change:TheIPCCScientificAssessment,
Houghton, J.T., G.J. Jenkins, and J.J. Ephraums (Eds), Cambridge,
Cambridge University Press, 131-172.

Pupacko,A.,1993:VariationsinNorthernSierraNevada
Streamflow: Implications of Climate Change,Water Resources
Bulletin,29(2), 283-290.

Roos,M.,1991:ATrendofDecreasingSnowmeltRunoffin
Northern California , Proceedings of the 59 ^thWestern Snow Con-
ference , Juneau, Alaska, 29-36.

Tsuang, B.J. and J.A. Dracup, 1991: Effect of Global Warming on
Sierra Nevada Mountain Snow Storage,Proceedings of the 59 ^th
Western Snow Conference,Juneau, Alaska, 17-27.

Wahl, K.L.,1991: Is April toJulyRunoff ReallyDecreasing in
theWesternUnitedStates?,Proceedingsofthe59 ^thAnnual
Western Snow Conference , Juneau, Alaska, 67-78.

6