Allgemeine Meteorologie

Liljequist, Gösta H.; Cehak, Konrad

doi:10.1007/978-3-322-83675-5

Cited by 19 publications

(7 citation statements)

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“…(2) The albedo on ice walls of the outer margin is increased to 0.75 in the east‐north‐east sector (between 45° and 90°; clockwise) and the southwest sector (between 200° and 250°; clockwise) in order to account for the advection of relatively moist air, as reflected in the spatial distribution of annual precipitation with two maxima in these aspects of the mountain [ Coutts , 1969]. Advection of moist air leads to formation of hoar frost on objects facing the flow of the moist air mass, a typical and well‐known process in mountain meteorology [e.g., Liljequist and Cehak , 1994; Whiteman , 2000], and one we observed on Kibo. In the combined model, the higher albedo not only expresses increased reflectivity of solar radiation on the affected ice walls but again parameterizes other factors, e.g., changed small‐scale cloud conditions in this case.…”

Section: Resultssupporting

confidence: 57%

Solar‐radiation‐maintained glacier recession on Kilimanjaro drawn from combined ice‐radiation geometry modeling

2003

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In the context of investigating modern glacier recession on Kilimanjaro, which began around 1880, this study addresses the glacier regime of the vertical ice walls that typically form the margins of Kilimanjaro's summit glaciers. These walls have suffered a continuous lateral retreat during the twentieth century. To evaluate the role of solar radiation in maintaining glacier recession on Kilimanjaro, a radiation model is applied to an idealized representation of the 1880‐ice cap. The combined process‐based model calculates the spatial extent and geometry of the ice cap for various points in time after 1880. Support for input data and fundamental assumptions are provided by an automatic weather station that has operated on the summit's Northern Icefield since February 2000. Even in a simple climatic scenario only forced with an annual cycle of clouds, the basic evolution in spatial distribution of ice bodies on the summit is modeled well. The Northern and Southern Icefields form in characteristic east‐west orientation, which verifies the basic idea behind the model. Forcing the model with further climate‐related phenomena improves the results. It then additionally reproduces the Eastern Icefield, the third big ice entity on the summit. This study qualitatively demonstrates that solar radiation is the main climatic parameter maintaining modern glacier recession on Kilimanjaro summit, but also suggests that retreat on the inner ice cap margin might have been supported by a secondary energy source. The need for additional field measurements is emphasized in order to better understand the complex processes of glacier‐climate interaction on Kilimanjaro.

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Section: Resultssupporting

confidence: 57%

Solar‐radiation‐maintained glacier recession on Kilimanjaro drawn from combined ice‐radiation geometry modeling

2003

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“…Aerosol was included as in the default settings of the radiation transfer module following Elterman et al [1968] with a total aerosol optical density OD = 0.34 at λ = 340 nm. The surface albedo was assumed to be 0.1 ∀ λ, which is the value for the ocean surface and which lies between the minimum (0.05) and maximum (0.2) values for land surface [ Liljequist and Cehak , 1984]. 31 layers (z(1) = 0.5 km, Δz = 0.5 km) were used so that the J values could be calculated for the center of each aircraft altitude bin used later in the box model.…”

Section: Model Descriptionmentioning

confidence: 99%

Influence of summertime deep convection on formaldehyde in the middle and upper troposphere over Europe

et al. 2006

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[1] We present HCHO measurements performed during the Upper Tropospheric Ozone: Processes Involving HO x and NO x (UTOPIHAN) II aircraft campaign over centralwestern Europe and the northwestern Mediterranean region in 2003 and 2004. We compare these with box model and three-dimensional (3-D) chemistry-transport model results for ''background'' and ''convective'' conditions. Generally, we obtain good agreement between the model and measurement data, although the 3-D model tends to underestimate HCHO near the tropopause, whereas the box model tends to slightly overestimate HCHO for the background case. Sensitivity simulations indicate that the most important factors determining HCHO concentrations are the abundances of NO, reactive hydrocarbons (e.g., isoprene), CH 3 OOH, CH 3 OH, and acetone and also the level of irradiance. In the middle and upper troposphere the most important HCHO production term is the reaction of CH 3 O 2 with NO (68 ± 10%, including a contribution of 38 ± 7% from CH 4 oxidation), followed by the destruction of CH 3 OOH by OH and photolysis (14 ± 2%), and the reaction of CH 3 OH with OH (14 ± 8%). HCHO loss is dominated by photolysis rather than by the reaction with OH, except in the upper tropospheric convective case, where the loss by OH contributes about 50%. Our measurements furthermore indicate that convective transport of H 2 O 2 can be very efficient.

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“…These Santa Ana winds typically develop from October to March as a result of a pressure gradient between high‐pressure systems over the Great Basin, roughly between the Rocky Mountains and the Sierra Nevada, and low pressure over the Pacific. Cool and dry air is heated and relative humidity further reduced by adiabatic compression on its descent from the high‐elevation Great Basin, and the resulting winds are channeled by the mountain ranges toward openings in the California coastal range [ Liljequist and Cehak , 1984; Westerling et al , 2004]. Because of these Santa Ana conditions, relative humidity dropped below 10% in many mountainous areas of southern California on 25 October, and in San Diego's coastal areas between 0400 and 1400 UTC on 26 October (NOAA Cooperative Institute for Regional Prediction (CIRP)), causing widespread critical low fuel moisture and little nighttime humidity recovery.…”

Section: Meteorological Conditionsmentioning

confidence: 99%

Trace gas and particulate emissions from the 2003 southern California wildfires

Mühle

Lueker

et al. 2007

J. Geophys. Res.

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[1] In October 2003, thirteen major wildfires in southern California burned more than 300,000 hectares of mainly chaparral biome. High-precision in situ trace gas and particle measurements of the wildfire plumes in La Jolla, California, showed a high degree of correlation among carbon dioxide (CO 2 ), methane (CH 4 ), nonmethane hydrocarbons, and methyl halide mixing ratios, as well as with particle number concentrations (10-300 nm and 500-2500 nm aerodynamic diameter). Aerosol time-of-flight mass spectrometry of individual aerosol particles (50-2500 nm range) showed that 70-85% had typical biomass burning signatures (levoglucosan coupled with potassium). Only 5-18% of particles in the 50-300 nm range had vehicle signatures. Molar trace gas enhancement ratios (ERs) versus ethane and CO 2 were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N 2 O and CH 3 CCl 3 versus CO 2 were determined, but correlations were poor. No significant CH 2 Cl 2 or CHCl 3 emissions were detected. CO 2 emissions from the nearby Cedar fire were estimated both with a simple Lagrangian atmospheric transport model and a burned area approach and extrapolated to 11 Tg CO 2 for the total burned area in southern California. Total CO 2 , CH 4 , C 2 -hydrocarbons, benzene, toluene, methyl chloride, methyl iodide, and PM 2.5 emissions were $0.2-3.5% of yearly global extratropical forest fire emissions and more than 28% of CH 4 , C 6 H 6 , and PM 2.5 2003 San Diego and South Coast Air Basins anthropogenic emissions. Particle distributions and single particle chemistry are discussed. PM 2.5 considerably exceeded the EPA short-term exposure limit.

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Allgemeine Meteorologie

Cited by 19 publications

References 0 publications

Solar‐radiation‐maintained glacier recession on Kilimanjaro drawn from combined ice‐radiation geometry modeling

Solar‐radiation‐maintained glacier recession on Kilimanjaro drawn from combined ice‐radiation geometry modeling

Influence of summertime deep convection on formaldehyde in the middle and upper troposphere over Europe

Trace gas and particulate emissions from the 2003 southern California wildfires

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