1,566 research outputs found

    Four dimensional observations of clouds from geosynchronous orbit using stereo display and measurement techniques on an interactive information processing system

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    Simultaneous Geosynchronous Operational Environmental Satellite (GOES) 1 km resolution visible image pairs can provide quantitative three dimensional measurements of clouds. These data have great potential for severe storms research and as a basic parameter measurement source for other areas of meteorology (e.g. climate). These stereo cloud height measurements are not subject to the errors and ambiguities caused by unknown cloud emissivity and temperature profiles that are associated with infrared techniques. This effort describes the display and measurement of stereo data using digital processing techniques

    Wind resource assessment using weather research and forecasting model. A case study of the wind resources at Havøygavlen wind farm

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    The need for energy increases globally due to rapid expansion of population and prosperity. To meet this demand while decreasing carbon emission and eventually transition out fossil fuel, efficient utilization of wind power is prominent. This study evaluates the performance of the Weather Research and Forecast model (WRF) with respect to wind speed and wind direction. The area of the study is the northernmost wind farm site in the world, Havøygavlen. It is located just about 50 kilometers southwest of the North cape, consisting of a complex and coastal terrain. The model simulation period was the entire year of 2017, and the resulting estimates where compared to on-site data measured at hub height at each of the 16 turbines located at the site. In terms of forecasting capability, the Model was evaluated using correlation, Root Mean Square Error and Bias. The assessment showed little agreement and implementing finer resolution displayed no apparent improvements. The estimate was particularly vulnerable to sudden changes in wind speed, and performed more accurately in periods of low to moderate wind speeds. Annual weather resource assessment of the site was performed using box plots, annual average wind maps and wind speed histograms. The model is unsuccessful at capturing the high complexity of the terrain, ultimately leading to an underestimation of the wind resources. However, enhanced domain resolution improved the predictive performance, which agreed adequately with the on-site measurements. Furthermore, the annual average wind maps provided valuable knowledge about the local wind patterns surrounding the site. Annual wind roses and wind fields at specific times of high wind speed occurrence was used to evaluate the model’s estimated wind direction. Enhanced domain resolution showed improved directional stability and ability to capture the terrain’s effect on the wind before arriving at the site. As a preliminary wind resource tool, the model performs sufficiently, despite the complex terrain of the studied area

    Surface properties of Mars' polar layered deposits and polar landing sites

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    On December 3, 1999, the Mars Polar Lander and Mars Microprobes will land on the planet's south polar layered deposits near (76°S, 195°W) and conduct the first in situ studies of the planet's polar regions. The scientific goals of these missions address several poorly understood and globally significant issues, such as polar meteorology, the composition and volatile content of the layered deposits, the erosional state and mass balance of their surface, their possible relationship to climate cycles, and the nature of bright and dark aeolian material. Derived thermal inertias of the southern layered deposits are very low (50–100 J m^(−2) s^(−1/2) K^(−1)), suggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice. The landing site region is smoother than typical cratered terrain on ∼1 km pixel^(−1) Viking Orbiter images but contains low-relief texture on ∼5 to 100 m pixel^(−1) Mariner 9 and Mars Global Surveyor images. The surface of the southern deposits is older than that of the northern deposits and appears to be modified by aeolian erosion or ablation of ground ice

    Martian clouds observed by Mars Global Surveyor Mars Orbiter Camera

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    We have made daily global maps that cover both polar and equatorial regions of Mars for Ls 135°–360° and 0°–111° using the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red and blue wide-angle swaths taken from May 1999 to January 2001. We study the seasonal distribution of condensate clouds and dust clouds during roughly 1 Martian year using these daily global maps. We present the development and decay of the tropical cloud belt and the polar hoods, the spatial and temporal distributions of lee waves and spiral clouds, and an unusual “aster” cloud above the volcanoes, consisting of rays around a central disk, like the flower. The tropical cloud belt contains mostly fibrous clouds during northern spring/early summer and convective clouds during middle/late northern summer. The detailed development and decay of the tropical cloud belt is nonuniform in longitude. Two distinct stormy periods in late summer precede the formation of the north and south circumpolar hoods. The north polar storms in late summer resemble baroclinic frontal systems on Earth but contain both dust and condensate clouds. Spiral clouds occur only in the northern high latitudes and only during northern spring and summer. The north polar hood displays a stationary wave number two structure during the fall and winter. The south polar hood has fewer streak clouds and lee wave clouds than the north polar hood. During this particular year the lee wave cloud abundance in the south had two peaks (in early fall and late winter), and the lee wave cloud abundance in the north had one peak (in early fall)

    Data registration and integration requirements for severe storms research

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    Severe storms research is characterized by temporal scales ranging from minutes (for thunderstorms and tornadoes) to hours (for hurricanes and extra-tropical cyclones). Spatial scales range from tens to hundreds of kilometers. Sources of observational data include a variety of ground based and satellite systems. Requirements for registration and intercomparison of data from these various sources are examined and the potential for operational forecasting application of techniques resulting from the research is discussed. The sensor characteristics and processing procedures relating to the overlay and integrated analysis of satellite and surface observations for severe storms research are reviewed

    Tropospheric forcing of the boreal polar vortex splitting in January 2003

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    e dynamical evolution of the relatively warm stratospheric winter season 2002–2003 in the Northern Hemisphere was studied and compared with the cold winter 2004–2005 based on NCEP-Reanalyses. Record low temperatures were observed in the lower and middle stratosphere over the Arctic region only at the beginning of the 2002–2003 winter. Six sudden stratospheric warming events, including the major warming event with a splitting of the polar vortex in mid-January 2003, have been identified. This led to a very high vacillation of the zonal mean circulation and a weakening of the stratospheric polar vortex over the whole winter season. An estimate of the mean chemical ozone destruction inside the polar vortex showed a total ozone loss of about 45 DU in winter 2002–2003; that is about 2.5 times smaller than in winter 2004–2005. Embedded in a winter with high wave activity, we found two subtropical Rossby wave trains in the troposphere before the major sudden stratospheric warming event in January 2003. These Rossby waves propagated north-eastwards and maintained two upper tropospheric anticyclones. At the same time, the amplification of an upward propagating planetary wave 2 in the upper troposphere and lower stratosphere was observed, which could be caused primarily by those two wave trains. Furthermore, two extratropical Rossby wave trains over the North Pacific Ocean and North America were identified a couple of days later, which contribute mainly to the vertical planetary wave activity flux just before and during the major warming event. It is shown that these different tropospheric forcing processes caused the major warming event and contributed to the splitting of the polar vortex
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