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  • Author or Editor: C. P. Bahrmann x
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J. M. Schneider, D. K. Fisher, R. L. Elliott, G. O. Brown, and C. P. Bahrmann

Abstract

A network of automated soil water and temperature systems, installed at 21 locations in Oklahoma and Kansas in 1996 and 1997, is providing hourly profiles of soil temperature and water at eight depths, from 0.05 to 1.75 m below the surface, in twin profiles 1 m apart. Dubbed the Soil Water and Temperature System (SWATS), these systems are an addition to the extended facilities of the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Program's Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site. Average spacing between SWATS systems is about 75 km. The SWATS network is one of three overlapping soil water networks in the region but is unique in depth of deployment, providing observations of available soil water through most of the rooting zone of SGP pastures and prairies. A description of the SWATS sensor and network, calibration and data verification, and example time series from the first 3 yr of operation are presented. Perusal of the time series reveals systematic spatial and seasonal variations in soil water profile characteristics. These spatiotemporal variations are interpreted as the integrated response in varying soils to antecedent soil water and recent precipitation, under varying mixes of vegetation determined by climatic gradients in precipitation, with impacts from local pasture management.

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J. Verlinde, J. Y. Harrington, G. M. McFarquhar, V. T. Yannuzzi, A. Avramov, S. Greenberg, N. Johnson, G. Zhang, M. R. Poellot, J. H. Mather, D. D. Turner, E. W. Eloranta, B. D. Zak, A. J. Prenni, J. S. Daniel, G. L. Kok, D. C. Tobin, R. Holz, K. Sassen, D. Spangenberg, P. Minnis, T. P. Tooman, M. D. Ivey, S. J. Richardson, C. P. Bahrmann, M. Shupe, P. J. DeMott, A. J. Heymsfield, and R. Schofield

The Mixed-Phase Arctic Cloud Experiment (M-PACE) was conducted from 27 September through 22 October 2004 over the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) on the North Slope of Alaska. The primary objectives were to collect a dataset suitable to study interactions between microphysics, dynamics, and radiative transfer in mixed-phase Arctic clouds, and to develop/evaluate cloud property retrievals from surface-and satellite-based remote sensing instruments. Observations taken during the 1977/98 Surface Heat and Energy Budget of the Arctic (SHEBA) experiment revealed that Arctic clouds frequently consist of one (or more) liquid layers precipitating ice. M-PACE sought to investigate the physical processes of these clouds by utilizing two aircraft (an in situ aircraft to characterize the microphysical properties of the clouds and a remote sensing aircraft to constraint the upwelling radiation) over the ACRF site on the North Slope of Alaska. The measurements successfully documented the microphysical structure of Arctic mixed-phase clouds, with multiple in situ profiles collected in both single- and multilayer clouds over two ground-based remote sensing sites. Liquid was found in clouds with cloud-top temperatures as cold as −30°C, with the coldest cloud-top temperature warmer than −40°C sampled by the aircraft. Remote sensing instruments suggest that ice was present in low concentrations, mostly concentrated in precipitation shafts, although there are indications of light ice precipitation present below the optically thick single-layer clouds. The prevalence of liquid down to these low temperatures potentially could be explained by the relatively low measured ice nuclei concentrations.

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R. A. Peppler, C. P. Bahrmann, J. C. Barnard, J. R. Campbell, M.-D. Cheng, R. A. Ferrare, R. N. Halthore, L. A. HeiIman, D. L. Hlavka, N. S. Laulainen, C.-J. Lin, J. A. Ogren, M. R. Poellot, L. A. Remer, K. Sassen, J. D. Spinhirne, M. E. Splitt, and D. D. Turner

Drought-stricken areas of Central America and Mexico were victimized in 1998 by forest and brush fires that burned out of control during much of the first half of the year. Wind currents at various times during the episode helped transport smoke from these fires over the Gulf of Mexico and into portions of the United States. Visibilities were greatly reduced during favorable flow periods from New Mexico to south Florida and northward to Wisconsin as a result of this smoke and haze. In response to the reduced visibilities and increased pollutants, public health advisories and information statements were issued by various agencies in Gulf Coast states and in Oklahoma.

This event was also detected by a unique array of instrumentation deployed at the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains Cloud and Radiation Testbed and by sensors of the Oklahoma Department of Environmental Quality/Air Quality Division. Observations from these measurement devices suggest elevated levels of aerosol loading and ozone concentrations during May 1998 when prevailing winds were favorable for the transport of the Central American smoke pall into Oklahoma and Kansas. In particular, aerosol extinction profiles derived from the ARM Raman lidar measurements revealed large variations in the vertical distribution of the smoke.

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