Multiscale Local Forcing of the Arabian Desert Daytime Boundary Layer, and Implications for the Dispersion of Surface-Released Contaminants

Thomas T. Warner National Center for Atmospheric Research,* and Program in Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado

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Rong-Shyang Sheu National Center for Atmospheric Research,* Boulder, Colorado

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Abstract

Four 6-day simulations of the atmospheric conditions over the Arabian Desert during the time of the 1991 detonation and release of toxic material at the Khamisiyah, Iraq, weapons depot were performed using a mesoscale model run in a data-assimilation mode. These atmospheric simulations are being employed in a forensic analysis of the potential contribution of the toxic material to so-called Gulf War illness. The transport and concentration of such surface-released contaminants are related strongly to the planetary boundary layer (PBL) depth and the horizontal wind speed in the PBL. The product of the PBL depth and the mean wind speed within it is referred to as the ventilation and is used as a metric of the horizontal transport within the PBL. Thus, a corollary study to the larger forensic analysis involves employing the model solutions and available data in an analysis of the multiscale spatial variability of the daytime desert PBL depth and ventilation as they are affected by surface forcing from terrain elevation variations, coastal circulations, and contrasts in surface physical properties.

The coarsest computational grid spanned the entire northern Arabian Desert and surrounding areas of the Middle East, and represented the large-scale PBL modulation by the orography. The PBL depths were greatest over the high elevations of the western Arabian Peninsula and over the Zagros Mountains in western Iran and were shallowest over water bodies and the lower elevations in the Tigris–Euphrates Valley. Higher-resolution grids in the nest (the smallest grid increment was 3.3 km) showed that the PBL depth minimum in the Tigris–Euphrates Valley was likely a consequence of compensating subsidence associated with the thermally forced daytime upward motion over the Zagros Mountains to the east in Iran, with possible contributions from an elevated mixed layer. Further local modulation of the daytime desert PBL occurred as a result of the inland penetration of the coastal sea-breeze circulation on the west side of the Persian Gulf, where PBL depths were suppressed as far as 100 km inland. On the finest scales, significant PBL-depth variability resulted from surface thermal differences associated with contrasts between barren desert and partially vegetated desert.

The average 1500 LT ventilation over the Arabian Desert for the 6-day period varied spatially from less than 4000 m2 s−1 to over 24 000 m2 s−1. This range represents over a factor-of-6 variation in the ability of the atmosphere to transport contaminants away from a source region.

Corresponding author address: Thomas T. Warner, NCAR/RAP, P.O. Box 3000, Boulder, CO 80307-3000.

warner@ucar.edu

Abstract

Four 6-day simulations of the atmospheric conditions over the Arabian Desert during the time of the 1991 detonation and release of toxic material at the Khamisiyah, Iraq, weapons depot were performed using a mesoscale model run in a data-assimilation mode. These atmospheric simulations are being employed in a forensic analysis of the potential contribution of the toxic material to so-called Gulf War illness. The transport and concentration of such surface-released contaminants are related strongly to the planetary boundary layer (PBL) depth and the horizontal wind speed in the PBL. The product of the PBL depth and the mean wind speed within it is referred to as the ventilation and is used as a metric of the horizontal transport within the PBL. Thus, a corollary study to the larger forensic analysis involves employing the model solutions and available data in an analysis of the multiscale spatial variability of the daytime desert PBL depth and ventilation as they are affected by surface forcing from terrain elevation variations, coastal circulations, and contrasts in surface physical properties.

The coarsest computational grid spanned the entire northern Arabian Desert and surrounding areas of the Middle East, and represented the large-scale PBL modulation by the orography. The PBL depths were greatest over the high elevations of the western Arabian Peninsula and over the Zagros Mountains in western Iran and were shallowest over water bodies and the lower elevations in the Tigris–Euphrates Valley. Higher-resolution grids in the nest (the smallest grid increment was 3.3 km) showed that the PBL depth minimum in the Tigris–Euphrates Valley was likely a consequence of compensating subsidence associated with the thermally forced daytime upward motion over the Zagros Mountains to the east in Iran, with possible contributions from an elevated mixed layer. Further local modulation of the daytime desert PBL occurred as a result of the inland penetration of the coastal sea-breeze circulation on the west side of the Persian Gulf, where PBL depths were suppressed as far as 100 km inland. On the finest scales, significant PBL-depth variability resulted from surface thermal differences associated with contrasts between barren desert and partially vegetated desert.

The average 1500 LT ventilation over the Arabian Desert for the 6-day period varied spatially from less than 4000 m2 s−1 to over 24 000 m2 s−1. This range represents over a factor-of-6 variation in the ability of the atmosphere to transport contaminants away from a source region.

Corresponding author address: Thomas T. Warner, NCAR/RAP, P.O. Box 3000, Boulder, CO 80307-3000.

warner@ucar.edu

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  • Bader, D. C., and T. B. McKee, 1983: Dynamical model simulation of the morning boundary layer development in deep mountain valleys. J. Climate Appl. Meteor.,22, 341–351.

  • Bagnold, R. A., 1954: The Physics of Blown Sand and Desert Dunes. Methuen, 265 pp.

  • Benjamin, S. G., and N. L. Seaman, 1985: A simple scheme for objective analysis in curved flow. Mon. Wea. Rev.,113, 1184–1198.

  • Blackadar, A. K., 1976: Modeling the nocturnal boundary layer. Preprints, Third Symp. on Atmos. Turbulence, Diffusion, and Air Quality, Raleigh, NC, Amer. Meteor. Soc, 46–49.

  • Blackadar, A. K., 1979: High resolution models of the planetary boundary layer. Advances in Environmental Science and Engineering, Vol. 1, J. Pfafflin and E. Ziegler, Eds., Gordon and Breach, 50–85.

  • Blake, D. W., T. N. Krishnamurti, S. V. Low-Nam, and J. S. Fein, 1983: Heat low over the Saudi Arabian Desert during May 1979 (Summer MONEX). Mon. Wea. Rev.,111, 1759–1775.

  • Carlson, T. N., and F. H. Ludlam, 1968: Conditions for the formation of severe local storms. Tellus,20, 203–226.

  • Davis, C., H.-M. Hsu, T. Keller, A. Shantz, T. Warner, J. Bowers, and E. Astling, 1998: A meso-γ-scale real time forecasting system suitable for regions of complex terrain. Preprints, 12th Conf. on Numerical Weather Prediction, Phoenix, AZ, Amer. Meteor. Soc., 223–225.

  • Davis, C., T. Warner, E. Astling, and J. Bowers, 1999: Development and application of an operational, relocatable, mesogamma-scale weather analysis and forecasting system. Tellus,51A, 710–727.

  • Dudhia, J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. J. Atmos. Sci.,46, 3077–3107.

  • Dudhia, J., 1993: A nonhydrostatic version of the Penn State–NCAR Mesoscale Model: Validation tests and the simulation of an Atlantic cyclone and cold front. Mon. Wea. Rev.,121, 1493–1513.

  • Greeley, R., and J. D. Iverson, 1985: Wind as a Geological Process on Earth, Mars, Venus and Titan. Cambridge University Press, 333 pp.

  • Grell, G. A., 1993: Prognostic evaluation of assumptions used by cumulus parameterizations. Mon. Wea. Rev.,121, 764–787.

  • Grell, G. A., J. Dudhia, and D. R. Stauffer, 1994: A description of the Fifth Generation Penn State/NCAR Mesoscale Model (MM5). NCAR Tech. Note, NCAR/TN 398+STR, 138 pp. [Available from Milli Butterworth, UCAR Communications, P.O. Box 3000, Boulder, CO, 80307-3000.].

  • Hacker, J. M., 1988: The spatial distribution of the vertical energy fluxes over a desert lake area. Aust. Meteor. Mag.,36, 235–243.

  • Hong, S.-Y., and H.-L. Pan, 1996: Nonlocal boundary layer vertical diffusion in a medium-range forecast model. Mon. Wea. Rev.,124, 2322–2339.

  • Humes, K. S., W. P. Kustas, and D. C. Goodrich, 1997: Spatially distributed sensible heat flux over a semiarid watershed. Part I:Use of radiometric surface temperatures and a spatially uniform resistance. J. Appl. Meteor.,36, 281–292.

  • Jury, W. A., J. Letey Jr., and L. H. Stolzy, 1981: Flow of water and energy under desert conditions. Water in Desert Ecosystems, D. D. Evans and J. L. Thames, Eds., Dowden, Hutchinson and Ross, 92–113.

  • Kimura, F., and T. Kuwagata, 1995: Horizontal heat fluxes over complex terrain computed using a simple mixed-layer model and a numerical model. J. Appl. Meteor.,34, 549–558.

  • Kuwagata, T., and F. Kimura, 1995: Daytime boundary layer evolution in a deep valley. Part I: Observations in the Ina Valley. J. Appl. Meteor.,34, 1082–1091.

  • Lee, J. A., 1991a: The role of desert shrub size and spacing on wind profile parameters. Phys. Geograph.,12, 72–89.

  • Lee, J. A., 1991b: Near-surface wind flow around desert shrubs. Phys. Geograph.,12, 140–146.

  • Lieman, R., and P. Alpert, 1992: Investigation of the temporal and spatial variations of PBL height over Israel. Air Pollution Modeling and its Application, Vol. IX, G. Kallos, Ed., Plenum, 231–239.

  • Malek, E. and G. E. Bingham, 1997: Partitioning of radiation and energy balance components in an inhomogeneous desert valley. J. Arid Environ.,37, 193–207.

  • Malek, E., G. E. Bingham, and G. D. McCurdy, 1990: Evapotranspiration from the margin and moist playa of a closed desert valley. J. Hydrol.,120, 15–34.

  • Malek, E., G. E. Bingham, D. Orr, and G. D. McCurdy, 1997: Annual mesoscale study of water balance in a Great Basin heterogeneous desert valley. J. Hydrol.,191, 223–244.

  • Oke, T. R., 1987: Boundary Layer Climates. 2d ed. Methuen, 435 pp.

  • Otterman, J., 1989: Enhancement of surface–atmosphere fluxes by desert-fringe vegetation through reduction of surface albedo and of soil heat flux. Theor. Appl. Climatol.,40, 67–79.

  • Seaman, N. L., F. L. Ludwig, E. G. Donall, T. T. Warner, and C. M. Bhumralker, 1989: Numerical studies of urban planetary boundary layer structure under realistic synoptic conditions. J. Appl. Meteor.,28, 760–781.

  • Seaman, N. L., D. R. Stauffer, and A. M. Lario-Gibbs, 1995: A multiscale four-dimensional data assimilation system applied in the San Joaquin Valley during SARMAP. Part I: Modeling design and basic performance characteristics. J. Appl. Meteor.,34, 1739–1761.

  • Shultz, P., and T. T. Warner, 1982: Characteristics of summertime circulations and pollutant ventilation in the Los Angeles Basin. J. Appl. Meteor.,21, 672–682.

  • Stauffer, D. R., and N. L. Seaman, 1990: Use of four-dimensional data assimilation in a limited-area mesoscale model. Part I: Experiments with synoptic data. Mon. Wea. Rev.,118, 1250–1277.

  • Stauffer, D. R., N. L. Seaman, and F. S. Binkowski, 1991: Use of four-dimensional data assimilation in a limited-area mesoscale model. Part II: Effects of data assimilation within the planetary boundary layer. Mon. Wea. Rev.,119, 734–754.

  • Stauffer, D. R., N. L. Seaman, T. T. Warner, and A. M. Lario, 1993: Application of an atmospheric simulation model to diagnose air pollution transport in the Grand Canyon region of Arizona. Chem. Eng. Comm.,121, 9–25.

  • Steedman, R. A., and Y. Ashour, 1976: Sea breezes over northwest Arabia. Tellus,28, 299–306.

  • Stensrud, D. J., 1993: Elevated residual layers and their influence on surface boundary layer evolution. J. Atmos. Sci.,50, 2284–2293.

  • Sullivan, R. J., 1987: Comparison of aeolian roughness measured in a field experiment and in a wind tunnel simulation. M.S. thesis, Arizona State University, 136 pp.

  • Taylor, C. M., F. Said, and T. Lebel, 1997: Interactions between the land surface and mesoscale rainfall variability during HAPEX-Sahel. Mon. Wea. Rev.,125, 2211–2227.

  • Vogelezang, D. H. P., and A. A. M. Holtslag, 1996: Evaluation and model impacts of alternative boundary-layer height formulations. Bound.-Layer. Meteor.,81, 245–269.

  • Warner, T. T., Y.-H. Kuo, J. D. Doyle, J. Dudhia, D. R. Stauffer, and N. L. Seaman, 1992: Nonhydrostatic, mesobeta-scale real-data simulations with the Penn State University/National Center for Atmospheric Research Mesoscale Model. Meteor. Atmos. Phys.,49, 209–227.

  • Westphal, D. L., and Coauthors, 1999: Meteorological reanalyses for the study of Gulf War illnesses: Khamisiyah case study. Wea. Forecasting,14, 215–241.

  • Whiteman, C. D., 1982: Breakup of temperature inversions in deep mountain valleys: Part I. Observations. J. Appl. Meteor.,21, 270–289.

  • Zhang, D.-L., and R. A. Anthes, 1982: A high-resolution model of the planetary boundary layer—Sensitivity tests and comparisons with SESAME-79 data. J. Appl. Meteor.,21, 1594–1609.

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