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Ralph, FM, Neiman PJ, Wick GA, Gutman SI, Dettinger MD, Cayan DR, White AB.  2006.  Flooding on California's Russian River: Role of atmospheric rivers. Geophysical Research Letters. 33   10.1029/2006gl026689   AbstractWebsite

[1] Experimental observations collected during meteorological field studies conducted by the National Oceanic and Atmospheric Administration near the Russian River of coastal northern California are combined with SSM/I satellite observations offshore to examine the role of landfalling atmospheric rivers in the creation of flooding. While recent studies have documented the characteristics and importance of narrow regions of strong meridional water vapor transport over the eastern Pacific Ocean (recently referred to as atmospheric rivers), this study describes their impact when they strike the U. S. West Coast. A detailed case study is presented, along with an assessment of all 7 floods on the Russian River since the experimental data were first available in October 1997. In all 7 floods, atmospheric river conditions were present and caused heavy rainfall through orographic precipitation. Not only do atmospheric rivers play a crucial role in the global water budget, they can also lead to heavy coastal rainfall and flooding, and thus represent a key phenomenon linking weather and climate.

Ralph, FM, Prather KA, Cayan D, Spackman JR, DeMott P, Dettinger M, Fairall C, Leung R, Rosenfeld D, Rutledge S, Waliser D, White AB, Cordeira J, Martin A, Helly J, Intrieri J.  2016.  CalWater field studies designed to quantify the roles of atmospheric rivers and aerosols in modulating US West Coast precipitation in a changing climate. Bulletin of the American Meteorological Society. 97:1209-1228.   10.1175/bams-d-14-00043.1   AbstractWebsite

The variability of precipitation and water supply along the U.S. West Coast creates major challenges to the region’s economy and environment, as evidenced by the recent California drought. This variability is strongly influenced by atmospheric rivers (ARs), which deliver much of the precipitation along the U.S. West Coast and can cause flooding, and by aerosols (from local sources and transported from remote continents and oceans) that modulate clouds and precipitation. A better understanding of these processes is needed to reduce uncertainties in weather predictions and climate projections of droughts and floods, both now and under changing climate conditions.To address these gaps, a group of meteorologists, hydrologists, climate scientists, atmospheric chemists, and oceanographers have created an interdisciplinary research effort, with support from multiple agencies. From 2009 to 2011 a series of field campaigns [California Water Service (CalWater) 1] collected atmospheric chemistry, cloud microphysics, and meteorological measurements in California and associated modeling and diagnostic studies were carried out. Based on the remaining gaps, a vision was developed to extend these studies offshore over the eastern North Pacific and to enhance land-based measurements from 2014 to 2018 (CalWater-2). The dataset and selected results from CalWater-1 are summarized here. The goals of CalWater-2, and measurements to date, are then described.CalWater is producing new findings and exploring new technologies to evaluate and improve global climate models and their regional performance and to develop tools supporting water and hydropower management. These advances also have potential to enhance hazard mitigation by improving near-term weather prediction and subseasonal and seasonal outlooks.

Reisen, WK, Cayan D, Tyree M, Barker CA, Eldridge B, Dettinger M.  2008.  Impact of climate variation on mosquito abundance in California. Journal of Vector Ecology. 33:89-98.   10.3376/1081-1710(2008)33[89:iocvom]2.0.co;2   AbstractWebsite

Temporal variation in the abundance of the encephalitis virus vector mosquito, Culex tarsalis Coquillet, was linked significantly with coincident and antecedent measures of regional climate, including temperature, precipitation, snow pack, and the El Nino/Southern Oscillation anomaly. Although variable among traps, historical records that spanned two to five decades revealed climate influences on spring and summer mosquito abundance as early as the previous fall through early summer. Correlations between winter and spring precipitation and snow pack and spring Cx. tarsalis abundance were stronger than correlations with summer abundance. Spring abundance was also correlated positively with winter and spring temperature, whereas summer abundance correlated negatively with spring temperature and not significantly with summer temperature. Correlations with antecedent climate provide the opportunity to forecast vector abundance and therefore encephalitis virus risk, a capability useful in intervention decision support systems at local and state levels.

Reverdin, G, Cayan D, Dooley HD, Ellett DJ, Levitus S, Dupenhoat Y, Dessier A.  1994.  Surface salinity of the North Atlantic: Can we reconstruct its fluctuations over the last one hundred years? Progress in Oceanography. 33:303-346.   10.1016/0079-6611(94)90021-3   AbstractWebsite

Surface samples have been collected in the North Atlantic in the past one hundred years for determining the ocean salinity and its temperature. A large share of the data we have used were collected by merchant vessels or weather ships of European countries and to a large extent are listed in reports, in particular in the Bulletin Hydrographique. We investigate whether these data are relevant for determining low frequency fluctuations of the sea surface salinity. We find many crossings in the 1920s for which salinity is anomalously high compared with the climatology or with other crossings collected on the same ship line. These anomalies are indicative of a contamination of the sample. By examining hydrographic data, reports and recent experience in collection and storage in sea water, we can attribute these large errors to unclean buckets where salt crystals dissolve into the sample and to breathing of the samples during the storage. Each of these stages contributes in estimating a too large salinity and adds to the scatter of the measurements. To further investigate these errors we compare the surface salinity and temperature for each monitoring program with nearby hydrographic casts, mostly in the eastern Atlantic. We find large differences between the various monitoring programs of different periods, and we use comparisons to empirically correct the data. Unfortunately, the number of comparisons is often too small resulting in a large uncertainty in these corrections, in particular before 1914 and for the UK and German monitoring programs before 1939 which exhibit the largest average bias in the 1920s. Despite this, we find that surface samples provide a useful complement to the hydrographic station data for investigating low-frequency variability of upper ocean waters. In the two areas where we did construct these time series: the Faeroe-Shetland Channel and the eastern Atlantic near 50-degrees-N, the surface data critically reduce the aliasing caused by insufficient sampling by the hydrographic casts. Both areas present minimum salinities around 1910 and in the late 1970s.

Reverdin, G, Cayan D, Kushnir Y.  1997.  Decadal variability of hydrography in the upper northern North Atlantic in 1948-1990. Journal of Geophysical Research-Oceans. 102:8505-8531.   10.1029/96jc03943   AbstractWebsite

We investigate the variability of the North Atlantic subarctic gyre in recent decades from time series of station temperature and salinity. Decadal variability stronger at the surface is identified, which exhibits vertical coherence over a layer deeper than the late winter mixed layer. In the northwestern Atlantic, it corresponds to the layer with a component of water from the Arctic Ocean or from the Canadian Arctic. The spatial coherence of the signal is investigated. An empirical orthogonal function decomposition of lagged time series indicates that a single pattern explains 70% of the variance in upper ocean salt content, corresponding to a propagating signal from the west to the northeast in the subarctic gyre. The most likely interpretation is that the salinity signal originates in the slope currents of the Labrador Sea and is diffused/advected eastward of the Grand Banks over the near western Atlantic. In the northwestern Atlantic, temperature fluctuations are strongly correlated to salinity fluctuations and are aligned along the average T-S characteristics. This signal suggests large variations in the outflow of fresh, cold water in the slope current, and is strongly correlated with ice cover. A basin scale atmospheric circulation of weakened westerlies at 55 degrees N, weaker northwesterlies west of Greenland and weaker southerlies over the central and eastern North Atlantic is associated with the high salinity and warm water phase of the first principal component. This circulation pattern leads fluctuations in the northeast Atlantic and lags those in the northwestern part of the basin. The wind indices also suggest that the fluctuations of the fresh water outflow occur during intervals of anomalously northerly winds, either east of Greenland (1965, 1968-1969) or off the Canadian Archipelago (1983-1984).

Rick, TC, Sillett TS, Ghalambor CK, Hofman CA, Ralls K, Anderson RS, Boser CL, Braje TJ, Cayan DR, Chesser RT, Collins PW, Erlandson JM, Faulkner KR, Fleischer R, Funk WC, Galipeau R, Huston A, King J, Laughrin L, Maldonado J, McEachern K, Muhs DR, Newsome SD, Reeder-Myers L, Still C, Morrison SA.  2014.  Ecological change on California's Channel Islands from the Pleistocene to the Anthropocene. Bioscience. 64:680-692.   10.1093/biosci/biu094   AbstractWebsite

Historical ecology is becoming an important focus in conservation biology and offers a promising tool to help guide ecosystem management. Here, we integrate data from multiple disciplines to illuminate the past, present, and future of biodiversity on California's Channel Islands, an archipelago that has undergone a wide range of land-use and ecological changes. Our analysis spans approximately 20,000 years, from before human occupation and through Native American hunter-gatherers, commercial ranchers and fishers, the US military, and other land managers. We demonstrate how long-term, interdisciplinary research provides insight into conservation decisions, such as setting ecosystem restoration goals, preserving rare and endemic taxa, and reducing the impacts of climate change on natural and cultural resources. We illustrate the importance of historical perspectives for understanding modern patterns and ecological change and present an approach that can be applied generally in conservation management planning.

Roche, JW, Rice R, Meng XD, Cayan DR, Dettinger MD, Alden D, Patel SC, Mason MA, Conklin MH, Bales RC.  2019.  Climate, snow, and soil moisture data set for the Tuolumne and Merced river watersheds, California, USA. Earth System Science Data. 11:101-110.   10.5194/essd-11-101-2019   AbstractWebsite

sWe present hourly climate data to force land surface process models and assessments over the Merced and Tuolumne watersheds in the Sierra Nevada, California, for the water year 2010-2014 period. Climate data (38 stations) include temperature and humidity (23), precipitation (13), solar radiation (8), and wind speed and direction (8), spanning an elevation range of 333 to 2987 m. Each data set contains raw data as obtained from the source (Level 0), data that are serially continuous with noise and nonphysical points removed (Level 1), and, where possible, data that are gap filled using linear interpolation or regression with a nearby station record (Level 2). All stations chosen for this data set were known or documented to be regularly maintained and components checked and calibrated during the period. Additional time-series data included are available snow water equivalent records from automated stations (8) and manual snow courses (22), as well as distributed snow depth and co-located soil moisture measurements (2-6) from four locations spanning the rain-snow transition zone in the center of the domain. Spatial data layers pertinent to snowpack modeling in this data set are basin polygons and 100 m resolution rasters of elevation, vegetation type, forest canopy cover, tree height, transmissivity, and extinction coefficient. All data are available from online data repositories (https://doi.org/10.6071/M3FH3D).

Rodo, X, Ballester J, Cayan D, Melish ME, Nakamura Y, Uehara R, Burns JC.  2011.  Association of Kawasaki disease with tropospheric wind patterns. Scientific Reports. 1   10.1038/srep00152   AbstractWebsite

The causal agent of Kawasaki disease (KD) remains unknown after more than 40 years of intensive research. The number of cases continues to rise in many parts of the world and KD is the most common cause of acquired heart disease in childhood in developed countries. Analyses of the three major KD epidemics in Japan, major non-epidemic interannual fluctuations of KD cases in Japan and San Diego, and the seasonal variation of KD in Japan, Hawaii, and San Diego, reveals a consistent pattern wherein KD cases are often linked to large-scale wind currents originating in central Asia and traversing the north Pacific. Results suggest that the environmental trigger for KD could be wind-borne. Efforts to isolate the causative agent of KD should focus on the microbiology of aerosols.

Rodo, X, Curcoll R, Robinson M, Ballester J, Burns JC, Cayan DR, Lipkin WI, Williams BL, Couto-Rodriguez M, Nakamura Y, Uehara R, Tanimoto H, Morgui JA.  2014.  Tropospheric winds from northeastern China carry the etiologic agent of Kawasaki disease from its source to Japan. Proceedings of the National Academy of Sciences of the United States of America. 111:7952-7957.   10.1073/pnas.1400380111   AbstractWebsite

Evidence indicates that the densely cultivated region of northeastern China acts as a source for the wind-borne agent of Kawasaki disease (KD). KD is an acute, coronary artery vasculitis of young children, and still a medical mystery after more than 40 y. We used residence times from simulations with the flexible particle dispersion model to pinpoint the source region for KD. Simulations were generated from locations spanning Japan from days with either high or low KD incidence. The postepidemic interval (1987-2010) and the extreme epidemics (1979, 1982, and 1986) pointed to the same source region. Results suggest a very short incubation period (<24 h) from exposure, thus making an infectious agent unlikely. Sampling campaigns over Japan during the KD season detected major differences in the microbiota of the tropospheric aerosols compared with ground aerosols, with the unexpected finding of the Candida species as the dominant fungus from aloft samples (54% of all fungal strains). These results, consistent with the Candida animal model for KD, provide support for the concept and feasibility of a windborne pathogen. A fungal toxin could be pursued as a possible etiologic agent of KD, consistent with an agricultural source, a short incubation time and synchronized outbreaks. Our study suggests that the causative agent of KD is a preformed toxin or environmental agent rather than an organism requiring replication. We propose a new paradigm whereby an idiosyncratic immune response, influenced by host genetics triggered by an environmental exposure carried on winds, results in the clinical syndrome known as acute KD.