The Study in Context

"On 26 March 1999, a complex snowfall event occurred across the southern Appalachian region, producing unexpectedly heavy snowfall amounts [defined here as 10 cm (4 in.) or more of snow within 12 h]. The heavy snowfall totaled 20–30 cm (8–12 in.) across the Smoky Mountains and 10–15 cm (4–6 in.) across other portions of southwest North Carolina, northeast Tennessee, and southwest Virginia (Fig. 1 ). Across the Great Tennessee Valley, downwind of the Smoky Mountains (Fig. 2 ), the heavy snowfall occurred in a narrow north-to-south band. During the initial part of the event (between 0900 and 1400 UTC), satellite and radar images revealed an interesting aspect to this event in that the precipitation was organized in west-to-east-oriented bands that propagated to the north". (Gaffin, D.M., S.S. Parker, and P.D. Kirkwood, 2003: An Unexpectedly Heavy and Complex Snowfall Event across the Southern Appalachian Region. Wea. Forecasting, 18, 224–235.)

"There is much evidence of recent changes to the hydrological cycle with impacts on precipitation patterns across the planet, especially during the late twentieth century (e.g., Oki and Kanae 2006). Coinciding with these changes, some climate modes have also undergone substantial shifts, such as the annular modes in both hemispheres (e.g., Fyfe et al. 1999; Thompson et al. 2000), the North Atlantic Oscillation (e.g., Hurrell 1995), and the El Niño–Southern Oscillation (ENSO) (e.g., Fedorov and Philander 2000). In addition, key drivers of precipitation, such as sea surface temperature (e.g., Levitus et al. 2000) and sea level pressure (e.g., Gillett et al. 2003; Marshall 2003) are showing widespread changes over recent decades. The goal of this study is to examine late twentieth-century New Zealand precipitation trends and their association to changes in Southern Hemisphere climate modes." (Ummenhofer, C.C., A. Sen Gupta, and M.H. England, 2009: Causes of Late Twentieth-Century Trends in New Zealand Precipitation. J. Climate, 22, 3–19.)

"According to the results of Kelly et al. (1985, p. 1999), severe thunderstorm winds (either gusts >25 m s–1, or damage-related reports) account for approximately 61% of the total number of severe thunderstorm reports (i.e., hail and wind) across the United States. Although a few studies provide insight into the convective modes associated with severe winds at the surface (e.g., Bluestein and Jain 1985; Johns and Hirt 1987; Atkins and Wakimoto 1991), comparatively little is known about the relative frequency of parent convective systems that produce these severe and damaging winds. With the sparse population and observation network over the northern High Plains (NHP)—herein defined as the area west of the central Dakotas and central Nebraska, and east of the Rocky Mountains (Fig. 1 )—even less is known about the relative significance, frequency, and mode of severe convective windstorms over this area.." (Klimowski, B.A., M.J. Bunkers, M.R. Hjelmfelt, and J.N. Covert, 2003: Severe Convective Windstorms over the Northern High Plains of the United States. Wea. Forecasting, 18, 502–519

"Winds within the lowest few hundred meters above the earth’s surface, hereinafter referred to as low-level winds, are the means by which the pollution emitted by anthropogenic activities near the earth’s surface is transported and dispersed. It is still challenging to accurately simulate low-level winds for air quality-related applications (such as air quality prediction and the State Implementation Plans for air quality control) that involve complex topography because of the complicated processes involved in the interaction between the atmosphere and the earth’s surface. Recently, applying the Weather and Research Forecasting (WRF) Model (Skamarock et al. 2005) to air quality problems has become increasingly attractive because of its well-designed mass-conserved numeric schemes and the state-of-the-art land surface model, both of which are essential for the simulation of the mesoscale, orographically forced atmospheric flows. Effort has been taken within the Earth System Research Laboratory (ESRL) of the National Oceanic and Atmospheric Administration (NOAA) to apply the WRF Model to air quality applications in California in order to, in part, assess the skills of the WRF Model in reproducing locally forced meteorological conditions. Successful simulation of these conditions for cases where they can be validated against observations gives confidence that the model can be used to make inferences about meteorological processes described by the model in regions of sparse or no data." (Michelson, S.A., and J.W. Bao, 2008: Sensitivity of Low-Level Winds Simulated by the WRF Model in California’s Central Valley to Uncertainties in the Large-Scale Forcing and Soil Initialization. J. Appl. Meteor. Climatol., 47, 3131–3149.)