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Lundquist, JD, Cayan DR, Dettinger MD.  2003.  Meteorology and hydrology in Yosemite National Park: A sensor network application. Information Processing in Sensor Networks, Proceedings. 2634( Zhao F, Guibas L, Eds.).:518-528., Berlin: Springer-Verlag Berlin Abstract

Over half of California's water supply comes from high elevations in the snowmelt-dominated Sierra Nevada. Natural climate fluctuations, global warming, and the growing needs of water consumers demand intelligent management of this water resource. This requires a comprehensive monitoring system across and within the Sierra Nevada. Unfortunately, because of severe terrain and limited access, few measurements exist. Thus, meteorological and hydrologic processes are not well understood at high altitudes. However, new sensor and wireless communication technologies are beginning to provide sensor packages designed for low maintenance operation, low power consumption and unobtrusive footprints. A prototype network of meteorological and hydrological sensors has been deployed in Yosemite National Park, traversing elevation zones from 1,200 to 3,700 m. Communication techniques must be tailored to suit each location, resulting in a hybrid network of radio, cell-phone, land-line, and satellite transmissions. Results are showing how, in some years, snowmelt may occur quite uniformly over the Sierra, while in others it varies with elevation.

Cayan, DR, Dettinger MD, Redmond K, McGabe G, Knowles N, Peterson DH.  2003.  The transboundary setting of California's water and hydropower systems - linkages between the Sierra Nevada, Columbia, and Colorado hydroclimates. Climate and water: transboundary challenges in the Americas. ( Diaz HF, Morehouse BJ, Eds.).:26., Dordrecht; Boston: Kluwer Academic Publishers Abstract
Knowles, N, Cayan DR.  2002.  Potential effects of global warming on the Sacramento/San Joaquin watershed and the San Francisco estuary. Geophysical Research Letters. 29   10.1029/2001gl014339   AbstractWebsite

[1] California's primary hydrologic system, the San Francisco estuary and its upstream watershed, is vulnerable to the regional hydrologic consequences of projected global climate change. Projected temperature anomalies from a global climate model are used to drive a combined model of watershed hydrology and estuarine dynamics. By 2090, a projected temperature increase of 2.1degreesC results in a loss of about half of the average April snowpack storage, with greatest losses in the northern headwaters. Consequently, spring runoff is reduced by 5.6 km(3) (similar to20% of historical annual runoff), with associated increases in winter flood peaks. The smaller spring flows yield spring/summer salinity increases of up to 9 psu, with larger increases in wet years.

Lundquist, JD, Cayan DR.  2002.  Seasonal and spatial patterns in diurnal cycles in streamflow in the western United States. Journal of Hydrometeorology. 3:591-603.   10.1175/1525-7541(2002)003<0591:saspid>;2   AbstractWebsite

The diurnal cycle in streamflow constitutes a significant part of the variability in many rivers in the western United States and can be used to understand some of the dominant processes affecting the water balance of a given river basin. Rivers in which water is added diurnally, as in snowmelt, and rivers in which water is removed diurnally, as in evapotranspiration and infiltration, exhibit substantial differences in the timing, relative magnitude, and shape of their diurnal flow variations. Snowmelt-dominated rivers achieve their highest sustained flow and largest diurnal fluctuations during the spring melt season. These fluctuations are characterized by sharp rises and gradual declines in discharge each day. In large snowmelt-dominated basins, at the end of the melt season, the hour of maximum discharge shifts to later in the day as the snow line retreats to higher elevations. Many evapotranspiration/infiltration-dominated rivers in the western states achieve their highest sustained flows during the winter rainy season but exhibit their strongest diurnal cycles during summer months, when discharge is low, and the diurnal fluctuations compose a large percentage of the total flow. In contrast to snowmelt-dominated rivers, the maximum discharge in evapotranspiration/infiltration-dominated rivers occurs consistently in the morning throughout the summer. In these rivers, diurnal changes are characterized by a gradual rise and sharp decline each day.

Scavia, D, Field JC, Boesch DF, Buddemeier RW, Burkett V, Cayan DR, Fogarty M, Harwell MA, Howarth RW, Mason C, Reed DJ, Royer TC, Sallenger AH, Titus JG.  2002.  Climate change impacts on US coastal and marine ecosystems. Estuaries. 25:149-164.   10.1007/bf02691304   AbstractWebsite

Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global air and ocean temperatures. The National Assessment of PotentiaI Consequences of Climate Variability and Change (NAST 2001) was based on a series of regional and sector assessments. This paper is a summary of the coastal and marine resources sector review of potential impacts on shorelines, estuaries, coastal wetlands, coral reefs, and ocean margin ecosystems. The assessment considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns; changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO(2). Increasing rates of sea-level rise and intensity and frequency of coastal storms and hurricanes over the next decades will increase threats to shorelines, wetlands, and coastal development. Estuarine productivity will change in response to alteration in the timing and amount of freshwater, nutrients, and sediment delivery. Higher water temperatures and changes in freshwater delivery will alter estuarine stratification, residence time, and eutrophication. Increased ocean temperatures are expected to increase coral bleaching and higher CO(2) levels may reduce coral calcification, making it more difficult for corals to recover from other disturbances, and inhibiting poleward shifts. Ocean warming is expected to cause poleward shifts in the ranges of many other organisms, including commercial species, and these shifts may have secondary effects on their predators and prey. Although these potential impacts of climate change and variability will vary from system to system, it is important to recognize that they will be superimposed upon, and in many cases intensify, other ecosystem stresses (pollution, harvesting, habitat destruction, invasive species, land and resource use, extreme natural events), which may lead to more significant consequences.

Westerling, AL, Gershunov A, Cayan DR, Barnett TP.  2002.  Long lead statistical forecasts of area burned in western US wildfires by ecosystem province. International Journal of Wildland Fire. 11:257-266.   10.1071/wf02009   AbstractWebsite

A statistical forecast methodology exploits large-scale patterns in monthly U.S. Climatological Division Palmer Drought Severity Index (PDSI) values over a wide region and several seasons to predict area burned in western US. wildfires by ecosystem province a season in advance. The forecast model, which is based on canonical correlations, indicates that a few characteristic patterns determine predicted wildfire season area burned. Strong negative associations between anomalous soil moisture (inferred from PDSI) immediately prior to the fire season and area burned dominate in most higher elevation forested provinces, while strong positive associations between anomalous soil moisture a year prior to the fire season and area burned dominate in desert and shrub and grassland provinces. In much of the western US., above- and below-normal fire season forecasts were successful 57% of the time or better, as compared with a 33% skill for a random guess, and with a low probability of being surprised by a fire season at the opposite extreme of that forecast.

Auad, G, Miller AJ, Roads JO, Cayan D.  2001.  Pacific Ocean wind stress and surface heat flux anomalies from NCEP reanalysis and observations: Cross-statistics and ocean model responses. Journal of Geophysical Research-Oceans. 106:22249-22265.   10.1029/2000jc000264   AbstractWebsite

Wind stresses and surface heat fluxes over the Pacific Ocean from the National Center for Environmental Prediction (NCEP) reanalysis and the comprehensive Ocean-Atmosphere Data Set (COADS) (blended with FSU tropical wind stresses) are compared over a common time interval (1958-1997) in their statistics anal in the responses that they induce in sea surface temperature (SST) and heat storage when used to force an ocean model. Wind stress anomalies from the two data sets are well correlated in the midlatitude extratropics, especially in the highly sampled North Pacific. In the tropics and subtropics, low correlations were found between the two wind stress data sets. The amplitudes of the stress variations of the two data sets are similar in midlatitudes, but in the tropics NCEP wind stresses are weaker than the LOADS/FSU stresses, especially on interannual timescales. Surface heat flux anomalies from the two data sets are well correlated on interannual and shorter timescales in the North Pacific Ocean poleward of 20 degreesN, but they are poorly correlated elsewhere and on decadal timescales. In the extratropics the amplitudes of the heat flux variations of the two data sets are comparable, but in the tropics the NCEP heat fluxes are weaker than those of CORDS. Ocean model hindcasts driven by bath data sets are also compared: The midlatitude SST hindcasts were superior when using the NCEP flux anomalies while tropical SST hindcasts were equally skillful for the two hindcasts when considering all climatic timescales. The spatial and temporal sampling rates of the LOADS observations and their consequent impacts on constraining the NCEP reanalysis appear to be the main factors controlling the results found here.

Nemani, RR, White MA, Cayan DR, Jones GV, Running SW, Coughlan JC, Peterson DL.  2001.  Asymmetric warming over coastal California and its impact on the premium wine industry. Climate Research. 19:25-34.   10.3354/cr019025   AbstractWebsite

Climatic changes over coastal California from 1951 to 1997 may have benefited the premium wine industry, as seen in higher quality wines and larger grape yields. Observed temperature warming trends were asymmetric, with greatest warming at night and during spring. Warming was associated with large increases in eastern Pacific sea surface temperatures (SST) and amounts of atmospheric water vapor. Although the average annual temperature warming trend was modest (1.13degreesC/47 yr), there was a 20 d reduction in frost occurrence and a 65 d increase in frost-free growing season length. In the Napa and Sonoma valleys, warmer winter and spring temperatures advanced the start of the growing season by 18 to 24 d, and enhanced atmospheric water vapor resulted in a 7% reduction in evaporative demand. Given the strong coupling between Pacific SSTs and the coastal California climate, and because regional-scale SSTs persist for 6 to 12 mo, additional research may allow the possibility of predicting vintage quantity and quality from previous winter conditions.

Cayan, DR, Kammerdiener SA, Dettinger MD, Caprio JM, Peterson DH.  2001.  Changes in the onset of spring in the western United States. Bulletin of the American Meteorological Society. 82:399-415.   10.1175/1520-0477(2001)082<0399:citoos>;2   AbstractWebsite

Fluctuations in spring climate in the western United States over the last 4-5 decades are described by examining changes in the blooming of plants and the timing of snowmelt-runoff pulses. The two measures of spring's onset that are employed are the timing of first bloom of lilac and honeysuckle bushes from a long-term cooperative phenological network, and the timing of the first major pulse of snowmelt recorded from high-elevation streams. Both measures contain year-to-year fluctuations, with typical year-to year fluctuations at a given site of one to three weeks. These fluctuations are spatially coherent, forming regional patterns that cover most of the west. Fluctuations in lilac first bloom dates are highly correlated to those of honeysuckle, and both are significantly correlated with those of the spring snowmelt pulse. Each of these measures, then, probably respond to a common mechanism. Various analyses indicate that anomalous temperature exerts the greatest influence upon both interannual and secular changes in the onset of spring in these networks. Earlier spring onsets since the late 1970s are a remarkable feature of the records, and reflect the unusual spell of warmer-than-normal springs in western North America during this period. The warm episodes are clearly related to larger-scale atmospheric conditions across North America and the North Pacific, but whether this is predominantly an expression of natural variability or also a symptom of global warming is not certain.

White, WB, Cayan DR, Dettinger MD, Auad G.  2001.  Sources of global warming in upper ocean temperature during El Nino. Journal of Geophysical Research-Oceans. 106:4349-4367.   10.1029/1999jc000130   AbstractWebsite

Global average sea surface temperature (SST) from 40 degreesS to 60 degreesN fluctuates +/-0.3 degreesC on interannual period scales, with global warming (cooling) during El Nino (La Nina). About 90% of the global warming during El Nino occurs in the tropical global ocean from 20 degreesS to 20 degreesN, half because of large SST anomalies in the tropical Pacific associated with El Nino and the other half because of warm SST anomalies occurring over similar to 80% of the tropical global ocean. From examination of National Centers for Environmental Prediction [Kalnay et al., 1996] and Comprehensive Ocean-Atmosphere Data Set [Woodruff et al., 1993] reanalyses, tropical global warming during El Nino is associated with higher troposphere moisture content and cloud cover, with reduced trade wind intensity occurring during the onset phase of EI Nino. During this onset phase the tropical global average diabatic heat storage tendency in the layer above the main pycnocline is 1-3 Wm(-2) above normal. Its principal source is a reduction in the poleward Ekman heat flux out of the tropical ocean of 2-5 Wm(-2). Subsequently, peak tropical global warming during El Nino is dissipated by an increase in the flux of latent heat to the troposphere of 2-5 W m(-2), with reduced shortwave and longwave radiative fluxes in response to increased cloud cover tending to cancel each other. In the extratropical global ocean the reduction in poleward Ekman heat flux out of the tropics during the onset of El Nino tends to be balanced by reduction in the flux of latent heat to the troposphere. Thus global warming and cooling during Earth's internal mode of interannual climate variability arise from fluctuations in the global hydrological balance, not the global radiation balance. Since it occurs in the absence of extraterrestrial and anthropogenic forcing, global warming on decadal, interdecadal, and centennial period scales may also occur in association with Earth's internal modes of climate variability on those scales.

Stahle, DW, Therrell MD, Cleaveland MK, Cayan DR, Dettinger MD, Knowles N.  2001.  Ancient Blue Oaks reveal human impact on San Francisco Bay salinity. EOS Trans. AGU. 82:141,144-145. Abstract
Biondi, F, Gershunov A, Cayan DR.  2001.  North Pacific decadal climate variability since 1661. Journal of Climate. 14:5-10.   10.1175/1520-0442(2001)014<0005:npdcvs>;2   AbstractWebsite

Climate in the North Pacific and North American sectors has experienced interdecadal shifts during the twentieth century. A network of recently developed tree-ring chronologies for Southern and Baja California extends the instrumental record and reveals decadal-scale variability back to 1661. The Pacific decadal oscillation (PDO) is closely matched by the dominant mode of tree-ring variability that provides a preliminary view of multiannual climate fluctuations spanning the past four centuries. The reconstructed PDO index features a prominent bidecadal oscillation, whose amplitude weakened in the late 1700s to mid-1800s. A comparison with proxy records of ENSO suggests that the greatest decadal-scale oscillations in Pacific climate between 1706 and 1977 occurred around 1750, 1905, and 1947.

White, WB, Cayan DR.  2000.  A global El Nino-Southern Oscillation wave in surface temperature and pressure and its interdecadal modulation from 1900 to 1997. Journal of Geophysical Research-Oceans. 105:11223-11242.   10.1029/1999jc900246   AbstractWebsite

Zonal wavenumber frequency spectra of sea surface temperature (SST) anomalies along the equator in the Indo-Pacific basin For the 98 years from 1900 to 1997 and of surface temperature (ST) and sea level pressure (SLP) anomalies extending around the globe along 10 degrees N for the 48 years from 1950 to 1997 display significant peak spectral energy density for standing and eastward propagating waves of 3-7 year periods and 120 degrees-360 degrees zonal wavelengths, The global standing wave is the familiar Southern Oscillation, but the global propagating wave represents a new paradigm for the El Nino-Southern Oscillation (ENSO). Global distributions of the phase velocities for this global ENSO wave finds covarying SLP and ST anomalies propagating eastward along the mean path of the Intertropical Convergence Zone (ITCZ), with the global zonal wavenumber 1 (2) component taking similar to 4 (6) years to cross the tropical Indian, Pacific, and Atlantic Oceans at a zonal average speed of 90 degrees (60 degrees) longitude per year. Along this path the interannual SST acid SLP anomalies are directly out of phase. Since thermocline depth anomalies underneath the ITCZ in the Pacific Ocean propagate westward [White et al. 1985], we view the global ENSO wave as a slow coupled SST wave trapped onto the ITCZ. Separating the global ENSO wave from the Southern Oscillation using complex empirical orthogonal function analysis finds the amplitude of the propagating wave to be half that of the standing wave, with the former (latter) accounting for one third (two thirds) of the interannual variability in Nino-3 SST and SLP indices during the 1980s. The global ENSO wave is shown to be responsible for the eastward propagation of covarying zonal surface wind and thermocline depth anomalies across the equatorial Pacific Ocean and through this mechanism is able to influence both the phasing and intensity of El Nino. Examining the persistence of the global ENSO wave from 1900 to 1997 finds it and the intensity of El Nino in the eastern equatorial Pacific Ocean modulated by interdecadal change, Both were strong (weak or absent) during decades of global tropical cooling (warming).

Gershunov, A, Barnett TP, Cayan DR, Tubbs T, Goddard L.  2000.  Predicting and downscaling ENSO impacts on intraseasonal precipitation statistics in California: The 1997/98 event. Journal of Hydrometeorology. 1:201-210.   10.1175/1525-7541(2000)001<0201:padeio>;2   AbstractWebsite

Three long-range forecasting methods have been evaluated for prediction and downscaling of seasonal and intraseasonal precipitation statistics in California. Full-statistical, hybrid-dynamical-statistical and full-dynamical approaches have been used to forecast Fl Nino-Southern Oscillation (ENSO)-related total precipitation, daily precipitation frequency, and average intensity anomalies during the January-March season. For El Nino winters, the hybrid approach emerges as the best performer, while La Nina forecasting skill is poor. The full-statistical forecasting method features reasonable forecasting skill for both La Nina and El Nino winters. The performance of the full-dynamical approach could not be evaluated as rigorously as that of the other two forecasting schemes. Although the full-dynamical forecasting approach is expected to outperform simpler forecasting schemes in the long run, evidence is presented to conclude that, at present, the full-dynamical forecasting approach is the least viable of the three, at least in California. The authors suggest that operational forecasting of any intraseasonal temperature, precipitation, or streamflow statistic derivable from the available-records is possible now for ENSO-extreme years.

Pandey, GR, Cayan DR, Dettinger MD, Georgakakos KP.  2000.  A hybrid orographic plus statistical model for downscaling daily precipitation in northern California. Journal of Hydrometeorology. 1:491-506.   10.1175/1525-7541(2000)001<0491:ahopsm>;2   AbstractWebsite

A hybrid (physical-statistical) scheme is developed to resolve the finescale distribution of daily precipitation over complex terrain. The scheme generates precipitation by combining information from the upper-air conditions and From sparsely distributed station measurements: thus, it proceeds in two steps. First, an initial estimate of the precipitation is made using a simplified orographic precipitation model. It is a steady-state, multilayer, and two-dimensional model following the concepts of Rhea, The model is driven by the 2.5 degrees x 2.5 degrees gridded National Oceanic and Atmospheric Administration-National Centers for Environmental Prediction upper-air profiles, and its parameters are tuned using the observed precipitation structure of the region, Precipitation is generated assuming a forced lifting of the air parcels as they cross the mountain barrier following a straight trajectory. Second, the precipitation is adjusted using errors between derived precipitation and observations from nearby sites. The study area covers the northern half of California, including coastal mountains, central valley, and the Sierra Nevada. The model is run for a 5-km rendition of terrain for days of January-March over the period of 1988-95. A jackknife analysis demonstrates the validity of the approach. The spatial and temporal distributions of the simulated precipitation field agree well with the observed precipitation, Further, a mapping of model performance indices (correlation coefficients, model bias, root-mean-square error, and threat scores) from an array of stations from the region indicates that the model performs satisfactorily in resolving daily precipitation at 5-km resolution.

Peterson, DH, Smith RE, Dettinger MD, Cayan DR, Riddle L.  2000.  An organized signal in snowmelt runoff over the western United States. Journal of the American Water Resources Association. 36:421-432.   10.1111/j.1752-1688.2000.tb04278.x   AbstractWebsite

Daily-to-weekly discharge during the snowmelt season is highly correlated among river basins in the upper elevations of the central and southern Sierra Nevada (Carson, Walker, Tuolumne, Merced, San Joaquin, Kings, and Kern Rivers). In many cases, the upper Sierra Nevada watershed operates in a single mode (with varying catchment amplitudes). In some years, with appropriate lags, this mode extends to distant mountains. A reason for this coherence is the broad scale nature of synoptic features in atmospheric circulation which provide anomalous insolation and temperature forcings that span a large region, sometimes the entire western U.S. These correlations may fall off dramatically, however, in dry years when the snowpack is spatially patchy.

Dettinger, MD, Cayan DR, McCabe GM, Marengo JA.  2000.  Multiscale streamflow variability associated with El Nino/Southern Oscillation. El Nino and the southern oscillation: multiscale variability and global and regional impacts. ( Diaz HF, Markgraf V, Eds.).:113-146., Cambridge; New York, NY: Cambridge University Press Abstract
Cayan, DR, Redmond KT, Riddle LG.  1999.  ENSO and hydrologic extremes in the western United States. Journal of Climate. 12:2881-2893.   10.1175/1520-0442(1999)012<2881:eaheit>;2   AbstractWebsite

Frequency distributions of daily precipitation in winter and daily stream flow from late winter to early summer, at several hundred sites in the western United States, exhibit strong and systematic responses to the two phases of ENSO. Most of the stream flows considered are driven by snowmelt. The Southern Oscillation index (SOI) is used as the ENSO phase indicator. Both modest (median) and larger (90th percentile) events were considered. In years with negative SOI values (El Nino), days with high daily precipitation and stream flow are more frequent than average over the Southwest and less frequent over the Northwest. During years with positive SOI values (La Nino), a nearly opposite pattern is seen. A more pronounced increase is seen in the number of days exceeding climatological 90th percentile values than in the number exceeding climatological 50th percentile values, for both precipitation and stream flow. Stream flow responses to ENSO extremes are accentuated over precipitation responses. Evidence suggests that the mechanism for this amplification involves ENSO-phase differences in the persistence and duration of wet episodes, affecting the efficiency of the process by which precipitation is converted to runoff. The SOI leads the precipitation events by several months,and hydrologic lags (mostly through snowmelt) delay the stream flow response by several more months. The combined 6-12-month predictive aspect of this relationship should be of significant benefit in responding to flood (or drought) risk and in improving overall water management in the western states.

Weinheimer, AL, Kennett JP, Cayan DR.  1999.  Recent increase in surface-water stability during warming off California as recorded in marine sediments. Geology. 27:1019-1022.   10.1130/0091-7613(1999)027<1019:riisws>;2   AbstractWebsite

Warming of surface waters in the California Current since the 1950s has coincided with a significant decline in zooplankton volume. This has been attributed to reduced upwelling of nutrient-rich waters caused by increased thermal stratification across the thermocline. Proxy microfossil evidence preserved in the Santa Barbara Basin suggests that stability increased early in the 1900s, intensified after the early 1940s, and became well established by 1960. Accumulation of up-welled radiolarians in the basin has steadily declined since 1900, while oxygen isotopes in surface-dwelling planktonic foraminifera reflect increasing surface temperatures. Comparison of the delta(18)O records between surface and thermocline-dwelling planktonic foraminifera reveals that the temperature difference between surface and thermocline water has increased during the twentieth century. Instrumental records of surface and thermocline temperatures, monitored since 1950, support these results. This evidence suggests that relaxation of North Pacific anticyclonic gyre circulation deepened isopycnics, causing onshore movement of warmer, less saline waters and reduced upwelling of cool, nutrient-rich waters.

Biondi, F, Perkins DL, Cayan DR, Hughes MK.  1999.  July temperature during the second millennium reconstructed from Idaho tree rings. Geophysical Research Letters. 26:1445-1448.   10.1029/1999gl900272   AbstractWebsite

An 858-year proxy record of July temperature for east-central Idaho shows multi-decadal periods of extreme cooling centered around AD 1300, 1340, 1460, and after AD 1600. These cold intervals are interrupted by prolonged warm spells in the early 1400s, late 1500s, and in the 1930s. The spatial signature of the paleoclimate record is centered on the north-central Rockies and central Great Plains, and expands over North America following a wave-like pattern. Neither instrumental nor proxy data in Idaho northeast valleys show unusual warming during the twentieth century. Climate episodes over the last three centuries are in broad agreement with the Greenland borehole temperature history. Low-frequency patterns are consistent with other northern hemisphere tree-ring records for the late Holocene, and provide a chronology of warm and cold intervals during the Little Ice Age.

Pandey, GR, Cayan DR, Georgakakos KP.  1999.  Precipitation structure in the Sierra Nevada of California during winter. Journal of Geophysical Research-Atmospheres. 104:12019-12030.   10.1029/1999jd900103   AbstractWebsite

Influences of upper air characteristics along the coast of California upon wintertime (November-April) precipitation in the Sierra Nevada are investigated. Precipitation events in the Sierra Nevada region occur mostly during wintertime, irrespective of station location (leeside or windside) and elevation. Most precipitation episodes in the region are associated with moist southwesterly winds (coming from the southwest direction) and also tend to occur when the 700-mbar temperature at the upwind direction is close to -2 degrees C. This favored wind direction and temperature signify the importance of both moisture transport and orographic lifting in augmenting precipitation in the region. By utilizing the observed dependency of the precipitation upon the upper air conditions, a linear model is formulated to quantify the precipitation observed at different sites as a function of moisture transport. The skill of the model increases with timescale of aggregation, reaching more than 50% variance explained at an aggregation period of 5-7 days. This indicates that upstream air moisture transport can be used to estimate the precipitation totals in the Sierra Nevada region.

Gershunov, A, Barnett TP, Cayan DR.  1999.  North Pacific interdecadal oscillation seen as factor in ENSO-related North American climate anomalies. EOS Trans. AGU. 80:25-30. Abstract
White, WB, Cayan DR, Lean J.  1998.  Global upper ocean heat storage response to radiative forcing from changing solar irradiance and increasing greenhouse gas/aerosol concentrations. Journal of Geophysical Research-Oceans. 103:21355-21366.   10.1029/98jc01477   AbstractWebsite

We constructed gridded fields of diabatic heat storage changes in the upper ocean from 20 degrees S to 60 degrees N from historical temperature profiles collected from 1955 to 1996. We filtered these 42 year records for periods of 8 to 15 years and 15 to 30 years, producing depth-weighted vertical average temperature (DVT) changes from the sea surface to the top of the main pycnocline. Basin and global averages of these DVT changes reveal decadal and interdecadal variability in phase across the Indian, Pacific, Atlantic, and Global Oceans, each significantly correlated with changing surface solar radiative forcing at a lag of 0 +/- 2 years. Decadal and interdecadal changes in global average DVT are 0.06 degrees +/- 0.01 degrees K and 0.04 degrees K +/- 0.01 degrees K, respectively, the same as those expected from consideration of the Stefan-Boltzmann radiation balance (i.e., 0.3 degrees K per W m(-2)) in response to 0.1% changes in surface solar radiative forcing of 0.2 W m(-2) and 0.15 W m(-2), respectively. Global spatial patterns of DVT changes are similar to temperature changes simulated in coupled ocean-atmosphere models, suggesting that natural modes of Earth's variability are phase-locked to the solar irradiance cycle. A trend in global average DVT of 0.15 degrees K over this 42 year record cannot be explained by changing surface solar radiative forcing. But when we consider the 0.5 W m(-2) increase in surface radiative forcing estimated from the increase in atmospheric greenhouse gas and aerosol (GGA) concentrations over this period [Intergovernmental Panel on Climate Change, 1995], the Stefan-Boltzmann radiation balance yields this observed change. Moreover, the sum of solar and GGA surface radiative forcing can explain the relatively sharp increase in global and basin average DVT in the late 1970's.

White, WB, Cayan DR.  1998.  Quasi-periodicity and global symmetries in interdecadal upper ocean temperature variability. Journal of Geophysical Research-Oceans. 103:21335-21354.   10.1029/98jc01706   AbstractWebsite

Recent studies find interannual (i.e., 3 to 7 year), decadal (i.e., 9 to 13 year), and interdecadal (i.e., 18 to 23 year) periodicities, and a trend dominating global sea surface temperature (SST) and sea level pressure (SLP) variability over the past hundred years, with the interdecadal signal dominating sub-El Nino-Southern Oscillation (ENSO) frequencies. We isolate interdecadal frequencies in SST and SLP records by band passing with a window admitting 15 to 30 year periods. From 1900 to 1989, the rms of interdecadal-filtered SST and SLP anomalies is largest in the extratropics and eastern boundaries. First-mode empirical orthogonal functions (EOFs) explain about half the interdecadal variance in both variables, with the tropical warn phase peaking near 1900, 1920, 1940, 1960, and 1980. From 1955 to 1994, EOF spatial patterns of interdecadal SST, SLP, and 400m temperature (T400) anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins, with tropical and eastern ocean SSTs warmer (cooler) than normal, covarying with stronger (weaker) extratropical westerly winds, cooler (warmer) SSTs in western-central subarctic and subantarctic frontal zones (SAFZs), stronger (weaker) subtropic and subarctic gyre circulations in North Pacific and North Atlantic Oceans, and warmer (cooler) basin and global average SSTs of 0.1 degrees C or so. Evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative, also characterized by reflection and translation symmetries. During the tropical warm phase, cool SST anomalies along western-central SAFZs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation, the latter conducting extratropical SST anomalies into the tropics. A delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution.