SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "LAR1:gu ;pers:(Chen Deliang 1961)"

Sökning: LAR1:gu > Chen Deliang 1961

  • Resultat 1-10 av 203
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  •  
2.
  •  
3.
  •  
4.
  • Achberger, Christine, 1968-, et al. (författare)
  • The surface winds of Sweden during 1999-2000
  • 2006
  • Ingår i: International Journal of Climatology. - 0899-8418. ; 26:2, s. 159-178
  • Tidskriftsartikel (refereegranskat)abstract
    • This study aims at increasing our understanding of the regional wind climate in Sweden. Spatial and temporal patterns of the surface winds are presented for the years 1999-2000. Annual mean wind speeds range between 2 and 5 m/s with high values at exposed mountainous sites and on islands off the coast. Combining wind speed and direction into mean wind velocities shows that flow conditions are stronger and more coherent in space in southern Sweden than in central and northern Sweden. The spatial scale, defined as the distance between stations when the correlation for wind speed drops to similar to 0.37, was determined by pairwise correlations between all possible station pairs. Scales range from 38 to 530 km for wind speed and from 40 to 830 km for wind direction depending on the region. They tend to be smaller in central and northern Sweden, where the more pronounced relief has a larger influence on the local wind conditions. The strength and the timing of the annual and diurnal wind speed cycle have been estimated for each station. Amplitudes of the annual cycle are greater at exposed sites and correlate generally well with annual mean wind speeds. Monthly mean wind speeds peak in winter in southern Sweden, but peak in other seasons in the remaining regions. In winter, weaker pressure gradients over northern Sweden and surface-near temperature inversions contribute to weaker surface winds. Diurnal cycles vary in strength between summer and winter. Compared to the last normal climate period (1961-1990), 1999-2000 is characterized by the increased occurrence of westerly and southerly geostrophic flow. Copyright (C) 2005 Royal Meteorological Society.
  •  
5.
  •  
6.
  •  
7.
  •  
8.
  • Azorin-Molina, C., et al. (författare)
  • AVHRR warm-season cloud climatologies under various synoptic regimes across the Iberian peninsula and the Balearic islands
  • 2014
  • Ingår i: International Journal of Climatology. - 0899-8418. ; 35:8, s. 1984-2002
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we retrieved the spatial distribution of mid-afternoon clouds under various synoptic regimes across the Iberian Peninsula and the Balearic Islands for the warm/convective-season, from May to October. Accurate daily cloud masks were derived by applying a daytime over land multispectral convective cloud detection algorithm spanning 15 years (1997–2011) of Advanced Very High Resolution Radiometer (AVHRR) HRPT data. We processed a total of 2094 afternoon overpasses (between 1230 and 1720 UTC) corresponding to the NOAA-14, NOAA-16 and NOAA-18 spacecrafts, and stratified daily cloud masks as a function of: (1) the automated circulation-typing scheme of Jenkinson and Collinson and (2) the prevailing wind field at 850 hPa. The AVHRR warm-season cloud climatology with high spatial resolution (1.1-km) identified six representative areas (regions of interest; ROIs) with intensified cloud activity (hot spots). The results also revealed the typical spatial distribution of clouds for each synoptic regime across the whole region, identified the synoptic patterns and wind regimes under which high amounts of clouds occur for each ROIs, and showed that strong boundary layer winds in general increase the frequency of clouds. The regional cloud climatology presented here could be useful, e.g. to improve convective short-term forecasting by identifying active cloud areas for each atmospheric type.
  •  
9.
  •  
10.
  • Azorin-Molina, C., et al. (författare)
  • Trends of daily peak wind gusts in Spain and Portugal, 1961-2014
  • 2016
  • Ingår i: Journal of Geophysical Research-Atmospheres. - 2169-897X. ; 121:3, s. 1059-1078
  • Tidskriftsartikel (refereegranskat)abstract
    • Given the inconsistencies of wind gust trends under the widespread decline in near-surface wind speed (stilling), our study aimed to assess trends of observed daily peak wind gusts (DPWG) across Spain and Portugal for 1961-2014 by analyzing trends of (i) the frequency (90th percentile) and (ii) the magnitude (wind speed maxima) of DPWG. Wind gust series were homogenized on a daily basis, using MM5-simulated series as reference, resulting in 80 suitable station-based data sets. The average DPWG 90th percentile frequency declined by -1.49ddecade(-1) (p<0.05) annually. This showed marked seasonal differences: decreasing in winter (-0.75ddecade(-1); p<0.05) and increasing in summer (+0.18ddecade(-1); p>0.10). A negligible trend was calculated for the annual magnitude of DPWG (-0.005ms(-1) decade(-1); p>0.10), with distinct seasonality: declining in winter (-0.168ms(-1) decade(-1); p<0.10) and increasing in summer (+0.130ms(-1) decade(-1); p<0.05). Combined, these results reveal less frequent and declining DPWG during the cold semester (November-April) and more frequent and increasing DPWG during the warm semester (May-October). Large-scale atmospheric changes such as the North Atlantic Oscillation Index (negative correlations similar to-0.4--0.6; p<0.05) and the Jenkinson and Collison scheme (positive correlations mainly with Westerly regime: similar to+0.5-0.6; p<0.05) partly account for the decadal fluctuations of both frequency and magnitude of DPWG, particularly in winter. However, the North Atlantic Oscillation index-DPWG relationships are smaller in spring, summer, and autumn (similar to-0.1--0.2; p>0.10), especially for the frequency, suggesting the role of local-to-mesoscale drivers.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 203
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy