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decreases until midnight. 1600 1400 BLH estimations 16/06/2010 Backscatter Exp. Ideal. Vertical Critical 400 350 1200 300 Height [m] 1000 800 250 200 β [1/(10 8 srad m)] 600 150 400 100 200 50 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 Time of day 0 Figure 43: The backscatter coefficient measured with the ceilometer on June 16 2010. The coloured shading indicates the intensity of the backscattered light, blue shading indicates minimal scattering and white indicates negative backscatter values. BLH estimates indicated by different shapes and colours. Clouds have been filtered and interpolated with a nearest neighbour interpolation. The BLH detection methods generally detect the same BLHs, except the vertical gradient deviates slightly from the other methods. The nearest neighbour cloud filtering results in a discrete change of the backscatter profile approximately in the middle of the removed cloud. As the profile fitting methods and the critical threshold detect the non-smoothed backscatter profile, these methods are prone to detect the BLH in middle of the cloud (with three exceptions of the profile fitting methods). The vertical gradient is the only method that uses the smoothed backscatter profile for BLH detection. Therefore the BLH estimates of the vertical gradient method will deviate from the other methods. Data are available from the wind lidar this day. The standard deviations of the total wind field are used to calculate the vertical TKE profiles. The turbulence kinetic energy per unit mass is shown in Figure 44. Only signals where the CNR ≥ -22 dB are shown. The white area shows missing data. When compared with Figure 43 it is seen that the cut-off edge of the data follows the cloud top. Bands of strong turbulence are seen in the presence of the cloud, sometimes reaching from the first measuring height to the cloud top. In these cases the minimum TKE is at the cloud top. From 9:00–18:00 there is increased turbulence in the cloud, at heights ∼600–800 m. There are peaks of high TKE values at the cloud top from 9:00. There are relatively high TKE values near the surface from 9:00 to 15:00. From midnight the minimum TKE values follow the cut-off value until ∼7:00 where the cloud thickness has increased. After that the minima are scattered at different heights, from the near surface to cloud top. DTU Wind Energy Master Thesis M-0039 53
1400 BLH from minimum TKE 16 June 2010 4 1200 3.5 1000 3 2.5 Height 800 2 TKE [m 2 /s 2 ] 600 1.5 400 1 0.5 200 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 Time of day 0 Figure 44: The TKE measured with the wind lidar on June 16 2010. The coloured shading indicates the strength of the TKE, blue shading indicates minimal values and white indicates missing data. Pink circles indicate BLH estimates with the minimum TKE. 54 DTU Wind Energy Master Thesis M-0039
Page 1 and 2: DTU Wind Energy Master Thesis M-003
Page 3 and 4: Contents 1 Introduction 5 1.1 Thesi
Page 5 and 6: 1.1 Thesis contents The content of
Page 7 and 8: and Batchvarova, 1994; Stull, 1988)
Page 9 and 10: ∂ē ∂t = g w ′ θ v ′ − u
Page 11 and 12: 2.7 Boundary-layer clouds The prese
Page 13 and 14: the square root of the variance. Ro
Page 15 and 16: 3 Site and measurements In this sec
Page 17 and 18: occasionally use the term “radial
Page 19 and 20: Ultrasonic Wind Sensor uSonic-3 Sci
Page 21 and 22: 4 Boundary-layer height detection T
Page 23 and 24: 90/(10 8 m srad), respectively). Fo
Page 25 and 26: 1400 β profile 16/04/2010 11:40 14
Page 27 and 28: 24/04/2010 06:20 1000 σ w 1000 ē
Page 29 and 30: Decoupled Clouds Clouds that are no
Page 31 and 32: 1600 Zero filter 23/07/2010 22:00 N
Page 33 and 34: 5.2 Continuous and average data The
Page 35 and 36: of the error bars during the day. T
Page 37 and 38: also be explained by the shape of t
Page 39 and 40: increases from 19:00-20:00. A resid
Page 41 and 42: 1400 1200 BLH estimations 01/05/201
Page 43 and 44: 5.4 Cold front passage On April 8 2
Page 45 and 46: Wind vectors at 10m height. Metmast
Page 47 and 48: 0.3 The inverse Obukhov length 1/L
Page 49 and 50: Wind vectors at 10m height. Metmast
Page 51: 0.1 The inverse Obukhov length 1/L
Page 55 and 56: 70 60 Threshold night day Easterly
Page 57 and 58: Threshold Westerly winds Ideal prof
Page 59 and 60: 140 120 Threshold night day Easterl
Page 61 and 62: Threshold Easterly winds Ideal prof
Page 63 and 64: 400 300 Threshold night day Easterl
Page 65 and 66: 5.9 Intra-annual variation The BLH
Page 67 and 68: wind lidar (Sathe et al., 2011). Ho
Page 69 and 70: distributions. It is clear that the
Page 71 and 72: A Appendix Abbreviations ABL Atmosp
Page 73 and 74: References Batchvarova, E., X. Cai,
Page 75: Sinclair, V. A., S. Niemelä, and M

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