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Monthly temperature and precipitation data from 41 global climate models (GCMs) of the Coupled Model Intercomparison Project Phase 5 (CMIP5) were compared to observations for the 20th century, with a focus on the U.S. Pacific Northwest (PNW) and surrounding region. A suite of statistics, or metrics, was calculated, including correlation and variance of mean seasonal spatial patterns, amplitude of seasonal cycle, diurnal temperature range, annual- to decadal-scale variance, long-term persistence, and regional teleconnections to El Niño Southern Oscillation (ENSO). Performance, or credibility, was assessed based on the GCMs' abilities to reproduce the observed metrics. GCMs were ranked in their credibility using two...
Wildfires periodically burn large areas of chaparral and adjacent woodlands in autumn and winter in southern California. These fires often occur in conjunction with Santa Ana weather events, which combine high winds and low humidity, and tend to follow a wet winter rainy season. Because conditions fostering large fall and winter wildfires in California are the result of large-scale patterns in atmospheric circulation, the same dangerous conditions are likely to occur over a wide area at the same time.Furthermore, over a century of watershed reserve management and fire suppression have promoted fuel accumulations, helping to shape one of the most conflagration-prone environments in the world [Pyne, 1997]. Combined...
Abstract (from http://journals.ametsoc.org/doi/abs/10.1175/WCAS-D-15-0042.1): Drought is a natural part of the historical climate variability in the northern Rocky Mountains and high plains region of the United States. However, recent drought impacts and climate change projections have increased the need for a systematized way to document and understand drought in a manner that is meaningful to public land and resource managers. The purpose of this exploratory study was to characterize the ways in which some federal and tribal natural resource managers experienced and dealt with drought on lands managed by the U.S. Department of the Interior (DOI) and tribes in two case site examples (northwest Colorado and southwest...
While significant progress has been made in seasonal climate prediction in recent years, summertime mid-latitude climate prediction remains problematic [e.g., Gershunov and Cayan, 2003]. Several previous studies have explored the skill of Pacific Sea Surface Temperatures (PSST) in the seasonal prediction of various atmospheric variables [e.g., Barnett and Preisendorfer, 1987],but few have focused on the value of PSST in forecasting summer conditions [e.g., Douville, 2003].Advances in summertime temperature forecasts are important for planning in different economic sectors, such as the energy industry. This issue is especially important in California, where the summer peak energy demand is about 50% higher than that...
Most regional ocean models that use discharge as part of the forcing use relatively coarse river discharge data sets (1°, or ∼110 km) compared to the model resolution (typically 1/4° or less), and do not account for seasonal changes in river water temperature. We introduce a new climatological data set of river discharge and river water temperature with 1/6° grid spacing over the Arctic region (Arctic River Discharge and Temperature; ARDAT), incorporating observations from 30 Arctic rivers. The annual mean discharge for all rivers in ARDAT is 2817 ± 330 km3 yr−1. River water temperatures range between 0 °C in winter to 14.0–17.6 °C in July, leading to a long-term mean monthly heat flux from all rivers of 3.2 ± 0.6...
The atmospheric water balance over the upper Colorado River is evaluated twice daily for the seven winter seasons 1957?1963. The atmospheric water balance yields the exchange of water and water vapor at the earth-atmosphere interface through the observation of the spatial and time distributions and fluxes of water vapor in the atmosphere over the basin. The quantity precipitation minus evaporation is determined as a residual of the computation and is accumulated for daily and seasonal values. In addition, a natural period analysis is performed; the natural periods are delineated by homogeneity in the parameter precipitation minus evaporation. The dry periods are shown to exhibit a seasonal trend in evaporation rate...
Recent research has suggested that changes in temperature and precipitation events due to climate change have had a significant impact on the availability and timing of streamflow. In this study, monthly temperature and precipitation data collected over 29 climate divisions covering the entire Colorado River basin and monthly natural flow data from 29 U.S. Geological Survey (USGS) gauge locations along the Colorado River are investigated for trend or step changes using parametric and nonparametric statistical tests. Temperature increases are persistent (at least 10 climate divisions over 6 months in trend analysis) throughout the year over the Colorado River basin, whereas precipitation only notably increased over...
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Drylands cover 40% of the global terrestrial surface and provide important ecosystem services. While drylands as a whole are expected to increase in distribution and aridity in coming decades, temperature and precipitation forecasts vary by latitude and geographic region suggesting different trajectories for tropical, subtropical, and temperate drylands. Uncertainty in the future of tropical and subtropical drylands is well constrained, whereas soil moisture and ecological droughts, which drive vegetation productivity and composition, remain poorly understood in temperate drylands. Here we show that, over the 21st century, temperate drylands may contract by a third, primarily converting to subtropical drylands,...
Most regional ocean models that use discharge as part of the forcing use relatively coarse river discharge data sets (1°, or ∼110 km) compared to the model resolution (typically 1/4° or less), and do not account for seasonal changes in river water temperature. We introduce a new climatological data set of river discharge and river water temperature with 1/6° grid spacing over the Arctic region (Arctic River Discharge and Temperature; ARDAT), incorporating observations from 30 Arctic rivers. The annual mean discharge for all rivers in ARDAT is 2817 ± 330 km3 yr−1. River water temperatures range between 0 °C in winter to 14.0–17.6 °C in July, leading to a long-term mean monthly heat flux from all rivers of 3.2 ± 0.6...
We evaluate the ability of global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) to reproduce observed seasonality and interannual variability of temperature over the Caribbean, and compare these with simulations from atmosphere-only (AMIP5) and previous-generation CMIP3 models. Compared to station and gridded observations, nearly every CMIP5, CMIP3 and AMIP5 simulation tends to reproduce the primary inter-regional features of the Caribbean annual temperature cycle. In most coupled model simulations, however, boreal summer temperature lags observations by about 1 month, with a similar lag in the simulated annual cycle of sea surface temperature (SST), and a systematic...