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Xiaozhen Xiong, Dan Lubin, Wei Li, and Knut Stamnes

function of cloud droplet size. However, in the polar regions, the surface is covered by snow/ice most of the time throughout the year, and visible solar radiation in AVHRR channel 1 (0.58–0.68 μ m) that is reflected by clouds over a bright snow/ice surface is not as sensitive to the cloud optical depth as over a dark surface. So, it is difficult to use AVHRR channel 1 for the retrieval of τ over snow/ice surfaces. The reflectance in channel 2 (0.725–1.10 μ m) is more sensitive to the cloud optical

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Katja Friedrich, Jeffrey R. French, Sarah A. Tessendorf, Melinda Hatt, Courtney Weeks, Robert M. Rauber, Bart Geerts, Lulin Xue, Roy M. Rasmussen, Derek R. Blestrud, Melvin L. Kunkel, Nicholas Dawson, and Shaun Parkinson

from the seeding track ( Fig. 20 ). Degree of riming determines how fast snow falls out. Snow fell out within 15–40 min on days (20 and 31 January) with greater LWC along and downwind of the seeding track, and widespread occurrence of supercooled drizzle. In summary, the greatest amount of LESnow, largest area covered by snowfall, and highest peak snowfall produced through seeding occurred on the day (31 January) with the largest and most widespread occurrence of supercooled drizzle, highest wind

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Gerd Wendler

mainly used for melting of the snow cover. For the hill station the heat fluxe~ are generally smaller. The only source is the radiation balancecal cm'~), wh/ch is only 40% of the value found for the valley station. The latent heat flux is much smaller(- 19 cal cm"I), a~d the surface temperature on the hill is higher. The sensible heat flux is slightly negative(-2 cal cm~), meaning that the air will be warmed by the surface only slightly for an average day overa year in contrast to the valley

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Arthur T. DeGaetano, Michael D. Cameron, and Daniel S. Wilks

assumption is made that the average daily air temperature is representative of the temperature of the snow surface. The snow depth ( Z s ) gives the thickness of the first layer in the snow/soil system ( Fig. 1 ). In the absence of snow cover, the air temperature is assumed to equal the temperature at the upper surface of a 1.0 × 10 −3 -m laminar layer, the thermal properties of which are characteristic of still air. To avoid the assumption of equality between the air and soil surface temperature, the

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Qiuhong Tang and Taikan Oki

again occur over regions classified by the USGS as having wooded tundra. The standard deviations of R 2 values are the largest, indicating uncertainty, over water bodies and wooded tundra. The R 2 values remain higher than 0.5 over the well-vegetated land uses mentioned above. The lower R 2 values over wooded tundra suggest that frozen surface soil and snow cover may disturb the relationships between the NCI and observed cloud indices. Figure 6 shows that the weakest relationships for both

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Junsei Kondo and Jianqing Xu

present study, by employing a soil model that makes use of daily routine meteorological data, the daily and seasonal variation of heat and water balances in different climatic regions have been simulated. The following themes are investigated: the variations in the heat balance and the soil-water content under different climatic conditions, such as in moist, semiarid, and arid regions; the relationship between soil type and water balance;and the effect of snow cover on the heat and water balances. The

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Elizabeth E. Ebert

help identify surface and cloud types. Cirrus, cumulus, and stratocumulus clouds have significantly different macro- and microtextural characteristics whichcan be quantitatively measured (Welch et al. 1988; Kuoet al. 1988). Features such as cold, bumpy cloud tops,cloud shadows on the snow, illumination of cloud sides,and cracks and leads in the sea ice can aid the humanobserver in distinguishing cloud cover from sea ice andsnow in satellite imagery (Kukla 1984; Welch et al.1989). Ebert (1987) used

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Gary A. Maykut and Phil E. Church

-yearperiod between 1962 and 1966. Data on incoming shortwave radiation, albedo, incoming longwave radiation,and net total radiation are summarized in the form of monthly and annual averages. Due to the prevalenceof summer clouds, incident shortwave radiation (Q) reaches a peak in early ~une with maximum flux valuesin excess of 50 mW cm-a. Increasing cloud cover throughout the snow-free period results in a distributionfor Q which is asymmetric about the summer solstice. Atmospheric transmissivity averages vary

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J. R. Wang, W. C. Boncyk, L. R. Dod, and A. K. Sharma

. Retrieved high refiectivities over land surface at 90 GHz and 183 GHzare presumably related to snow cover on the ground. This suggests that radiometric measurements at thesefrequencies could be used to map snow at high-latitude regions.1. Introduction The radiometric measurements near the strong watervapor absorption line of 183.3 GHz have in the pastbeen used mostly for retrieval of atmospheric watervapor profiles (Schaefer and Wilbeit 1979; Rosenkranzet at. 1982; Kakar 1983; W,?ng et ai. 1983

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Xin Jin, John M. Hanesiak, and David G. Barber

slightly cloudy skies are common during this period. Moreover, the obvious difference between CFs from the ceilometer and manobs indicates more high clouds in this stage. It is reasonable to assume that MODIS misrepresented the snow-covered background as clouds under clear or high-cloud events. However, after April, both MODIS products had very good agreement with manobs, indicating the good performance of MODIS cloud detection algorithms during the daytime. The monthly averaged CF deviations from the

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