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5.5 Ideal daily evolution of the ABL On April 11 2010, ideal cloud free conditions, with easterly winds are observed. Figure 36 indicates the backscatter intensities and BLH estimates with the four different detection methods. The backscatter intensity is generally low this day. Notice the different scale on the colour bar compared with previous backscatter intensity figures. At midnight the backscatter intensity is below 40/(10 8 m srad) above the surface, so no BLH estimates are made. After 3:00 the backscatter intensity increases slightly. The BLH detection methods generally show a similar BLH. After 7:00 the BLH increases rapidly and reaches its maximum at ∼800 m at noon. After 18:00 the BLH begins to decrease and the residual layer is visible between 18:00–21:00. 1600 1400 1200 BLH estimations 11/04/2010 21:30 Backscatter Exp. Ideal. Vertical Critical 180 160 140 120 Height [m] 1000 800 100 80 β [1/(10 8 srad m)] 600 60 400 40 200 20 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 Time of day 0 Figure 36: The backscatter coefficient measured with the ceilometer on April 11 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. Figure 37 topmost shows the inverse Obukhov lenght measured at 10 and 100 m. From midnight to 7:00 there are observed stable conditions at 10 and 100 m, though the measurements at 100 m show large fluctuations until 2:00. Between ∼7:00–17:00 unstable conditions are observed at both measuring heights and after 17:00 both heights show stable conditions until midnight. The bottom figure shows the solar radiation from the pyranometer. Radiation values larger than 1 W/m 2 are measured from 5:30–19:20. The radiation peaks at noon showing values just below 700 W/m 2 . DTU Wind Energy Master Thesis M-0039 47
0.3 The inverse Obukhov length 1/L 0.2 0.1 0 −0.1 −0.2 −0.3 1/L 10m 1/L 100m −0.4 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00 Time of day 700 Pyranometer 600 Radiations [W/m 2 ] 500 400 300 200 100 0 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00 Time of day Figure 37: Upper: The inverse Obukhov length derived from sonic anenometer measurements at 2 m and 100 m. Lower: The solar radiation measured with the pyranometer. Measurements from April 11 2010. 48 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: Wind vectors at 10m height. Metmast
Page 49 and 50: Wind vectors at 10m height. Metmast
Page 51 and 52: 0.1 The inverse Obukhov length 1/L
Page 53 and 54: 1400 BLH from minimum TKE 16 June 2
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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