| 1. |
- Lopez-Moreno, J. I., et al.
(författare)
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Air and wet bulb temperature lapse rates and their impact on snowmaking in a Pyrenean ski resort
- 2019
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Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 135:3-4, s. 1361-1373
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Tidskriftsartikel (refereegranskat)abstract
- A set of 17 air temperature and relative humidity sensors were used to analyze the temporal variability of surface air temperature (Tair), wet bulb temperature (Twb), and daily snowmaking hours (SM, number of hours per day with Twb<-2 degrees C), lapse rates, and the occurrence of thermal inversions at the Formigal ski resort (Spanish Pyrenees) from December to March during three consecutive ski seasons (2012-2013, 2013-2014, and 2014-2015). The Tair and Twb lapse rates showed strong hourly and daily variability, with both exhibiting almost identical temporal fluctuations.The Twb exhibited average lapse rates that were slightly steeper (-5.2 degrees C/km) than those observed for Tair (-4.9 degrees C/km). The less steep lapse rates and most thermal inversions were observed in December. Days having less (more) steep Tair and Twb lapse rates were observed under low (high) wind speeds and high (low) relative humidity and air pressure. The temporal dynamics of the SM lapse rates was more complex, as this involved consideration of the average Tair in the ski resort, in addition to the driving factors of the spatio-temporal variability of Twb. Thus, on a number of cold (warm) days, snowmaking was feasible at all elevations at the ski resort, independently of the slopes of the lapse rates. The SM exhibited an average daily lapse rate of 8.2h/km, with a progressive trend of increase from December to March.Weather types over the Iberian Peninsula tightly control the driving factors of the Tair, Twb, and SM lapse rates (wind speed, relative humidity, and Tair), so the slopes of the lapse rates and the frequency of inversions in relation to elevation for the three variables are very dependent on the occurrence of specific weather types. The less steep lapse rates occurred associated with advections from the southeast, although low lapse rates also occurred during advections from the east and south, and under anticyclonic conditions. The steepest Tair and Twb lapse rates were observed during north and northwest advections, while the steepest rates for SM were observed during days of cyclonic circulation and advections from the northeast.
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| 2. |
- Navarro-Serrano, F., et al.
(författare)
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Air temperature measurements using autonomous self-recording dataloggers in mountainous and snow covered areas
- 2019
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Ingår i: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 224, s. 168-179
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Tidskriftsartikel (refereegranskat)abstract
- High mountain areas are poorly represented by official weather observatories. It implies that new instruments must be evaluated over snow-covered and strongly insolated environments (i.e. mid-latitude mountain areas). We analyzed uncertainty sources over snow covered areas including: 1) temperature logger accuracy and bias of two widely used temperature sensors (Tinytag and iButton); 2) radiation shield performance under various radiation, snow, and wind conditions; 3) appropriate measurement height over snow covered ground; and 4) differences in air temperature measured among nearby devices over a horizontal band. The major results showed the following. 1) Tinytag performance device (mean absolute error: MAE approximate to 0.1-0.2 degrees C in relation to the reference thermistor) was superior to the iButton (MAE approximate to 0.7 degrees C), which was subject to operating errors. 2) Multi-plate radiation shield showed the best performance under all conditions ( > 90% samples has bias between +/- 0.5 degrees C). The tube shield required wind ( > 2.5 m s(-1)) for adequate performance, while the funnel shield required limited radiation ( < 400 W m(-2)). Snow cover causes certain overheating. 3) Air temperatures were found to stabilize at 75-100 cm above the snow surface. Air temperature profile was more constant at night, showing a considerable cooling on near surface at midday. 4) Horizontal air temperature differences were larger at midday (0.5 degrees C). These findings indicate that to minimize errors air temperature measurements over snow surfaces should be carried out using multi-plate radiation shields with high-end thermistors such as Tinytags, and be made at a minimum height above the snow covered ground.
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