Norton_8th_COPS_WS by wuxiangyu

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									   SNAPSHOT OF WIND PROFILER MEASUREMENTS
            DURING CSIP AND COPS.




        Emily Grace Norton 1,Alan Blyth 2,Andrew Russell 1,Geraint Vaughan1, Dave Wareing1,Catherine Gaffard 3
                             1. School of Earth Atmospheric and Environmental Sciences, University of Manchester, UK
                              2. School of Earth and Environment, University of Leeds, UK, 3. Met Office, Reading, UK

Abstract
The FGAM (Facility for Ground based Atmospheric Measurements) wind profiler is a 1290 Mhz ‘clear’ air weather radar manufactured by
Degreane Horizon. It is a mobile instrument and has been regularly deployed as part of many field campaigns, including CSIP (Convective
Storm Initiation Project) and COPS (Convective and Orographically-induced Precipitation Study). During CSIP and COPS the wind profiler was
surrounded by a screen to reduce interference caused by ground clutter. The electromagnetic radiation from the wind profiler is sensitive to both
Rayleigh scattering, from hydrometeors and Bragg scattering from refractive index inhomogenieties, on a scale of half a wavelength. In the
lower troposphere the irregularities in refractive index are mainly caused by humidity fluctuations and to a lesser extent temperature changes.
During field campaigns the wind profiler provides a picture of the meteorology over the site by providing detailed profiles of the three
components of wind between altitudes of 75m and 3.5 km, depending on atmospheric conditions. During CSIP and COPS the wind profiler
provided a particularly important role in identifying the altitude of temperature inversions that acted as lids to convective development. On
occasions the wind profiler was used to resolve thermals as they drifted over the wind profiler. In addition, the location and strength of the
turbulence was inferred from the spectral width of the Doppler signal. This poster shows some snap shots of measurements from the wind
profiler during CSIP and COPS.
 Specifications of the FGAM wind profiler
The FGAM mobile wind profiler is a ‘clear-air’ UHF Doppler radar manufactured by Degreane Horizon. It operates at frequency of 1290 MHz
twenty four hours a day. The wind profiler consists of three antennas one vertical and two orthogonal at an elevation of 73 o . The Doppler shift
associated with the turbulence provides a direct measurement of the mean radial velocity along the radar beam. Measurements in three
independent directions enable full wind vectors (zonal, meridional and vertical) to be calculated.




                                                                                                                            DEGREANE
                                                                                                                            HORIZON




 Figure 1: a) Outside view of the                    Figure 2: a) Scale drawing plan of the                Figure 3: A typical plot of radial
 Clutter screen built during CSIP to                 clutter screen. b) Photo of the wind                  velocity verses altitude during
 surround the wind profiler. It consisted
 of a 2 m high curved clutter screen                 profiler at Achern during COPS                        COPS. Note there is very little
 made out of corrugated metal from an                surrounded by clutter screen made                     ground clutter evident
 old silage container b) View of the                 from wood and ½ inch steel wire
 inside of the clutter screen.                       mesh. The sides are angled at 170 from
                                                     vertical
Thermals observed during CSIP – 13th July 2005 - IOP 8
   Convection developed in the CSIP area on 13 July 2005 in a region of high moisture just north of Chilbolton near the wind profiler site. Cumulus
   congestus clouds eventually grew to 5 km, but only a few light showers were observed north east of the CSIP area. A sea breeze front advanced
   northwards from the south coast. Convection became deeper along the front, but the clouds were still not deep enough to produce
   precipitation. Convection was suppressed behind the front. Winds were light on this day, so thermals and cumulus clouds drifted slowly over the
   wind profiler and could be detected with the 2-min averaging.




Figure 4 a) Shows the minimum signal to noise ratio (SNR) of the three beams as a function of altitude over a half hour perio d. An inverted cup pattern
was observed as the thermal drifted over the wind profiler. There are sharp abrupt changes in the humidity at the edges of thermals and cumulus clouds
due to mixing and this causes sharp gradients of refractive index that results in the strong Bragg-scattering signal. The cores are more uniform as they
are protected from entrainment and mixing hence Bragg scattering is weak. b) Shows the vertical velocity as a function of altitude over the same time
period. The updraft in the core of this thermal, typical of the day, reached a maximum of 1.3 m s-1. The updrafts typically lasted approximately 7
minutes. From the average wind speed (2-3 m s-1) the horizontal extent of this updraft was estimated to be approximately 850-1260 m. The vertical
extent of the updraft was approximately 1.4 km corresponding to the height of the cloud base which corresponded to a temperature inversion
suppressing the convection The downdraughts associated with the thermals were weaker, approximately -0.8 m s-1and less distinct than the up draught.
            Thermals observed during COPS 15th July 2007 – IOP 8b




Wind profiler plots of vertical velocity
         On the 15th July 2007 deep convection developed east of the Black Forest crest, although convective available potential energy was moderate and
         convective inhibition was high.
         Figure 5 a) A plot of the signal to noise ratio of the clear air echo shows a layered structure to the planetary boundary layer. b) A plot of the vertical
         velocity show a series of updrafts as they drift over the site. Notice at 15:20 the updraft penetrates the capping inversion of the planetary boundary layer
         and extends to a vertical height of more than 3.8 km.
             Combining the strengths of UMIST and
             The Victoria University of Manchester
19th July 2007 – IOP 9b
A large scale mesoscale convective system (MCS) was affecting the COPS region 6-12 UTC. The orography of the region had a significant
effect on the modulation and the precipitation distribution of the system. After passing the COPS region strong convective ce lls were triggered
in south East Germany.




                                                                       Figure 6: a) Plot of the minimum signal to noise ratio (SNR) of the
                                                                       radar echoes such as these are useful for identifying lids in the
                                                                       atmosphere and defining the planetary boundary layer.
                                                                        b) Plot of wind speed with wind direction arrows superimposed. This
                                                                       plot shows low winds beneath higher winds. The winds below 2km on
                                                                       this day changed from south easterly to southerly to westerly between
                                                                       6:00 UTC and 14:00 UTC.
                                                                       c) Plot of the vertical velocity calculated from the wind profiler. The
                                                                       black areas on this plot show bands of precipitation. The red areas
                                                                       show updrafts and the blue areas show the down drafts.
23rd July 2007 – IOP 10
•   Figure 7: Time series of signal to noise ratio of the radar echos on 23 rd July 2007. a) shows data from the high mode b) shows data
    from the low mode. The plots highlight the advantage of having two measurement modes.


                                             a) High mode




                                              b) Low mode
                                        }


                                  Melting layer at 3km
Map right to show the deployments the FGAM
wind profiler.




 The map above shows CSIP measurement sites. The wind
 profiler was run continuously between during both parts of
 CSIP 6th July to 22nd July 2004 for the pilot campaign
 and16th June to 19th August 2005 for the main campaign.
 During the main CSIP campaign the wind profiler was
 located at Linkenholt (latitude 51.314 N, longitude1.475 W)
 approximately 18 km north of Chilbolton shown as the green    The map above shows the locations of the COPS supersites. The wind
 spot on the main map.                                         profiler was run continuously between 13th June and 6th August 2007 during
                                                               COPS at supersite R. Supersite R is located at Achern, Southern Germany
 During the pilot campaign the wind profiler was at
                                                               (latitude 48.6 N, longitude 8.06 E) in the lowlands of the Rhine valley. This
 Ashmansworth close to Linkenholt.
                                                               area is characterised by mainly homogeneous surfaces, the only landscape
                                                               differences arising from variations in land use.
Papers to date from CSIP using the wind profiler data.
Convection forced by a descending dry layer and low-level moist convergence Author(s): Russell A, Vaughan G, Norton EG, Ricketts HMA, Morcrette CJ, Hewison TJ, Browning KA, Blyth AM, Source:
TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY Volume: 61 Issue: 2 Pages: 250-263 Published: MAR 2009

Observations of the development of convection through a series of stable layers during the Convective Storm Initiation Projec t Author(s): Bennett LJ, Blyth AM, Browning KA, Norton EG Source:
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY Volume: 134 Issue: 637 Pages: 2079-2091 Part: Part B Published: OCT 2008

Convective inhibition beneath an upper-level PV anomaly Author(s): Russell A, Vaughan G, Norton EG, Morcrette CJ, Browning KA, Blyth AM Source: QUARTERLY JOURNAL OF THE ROYAL
METEOROLOGICAL SOCIETY Volume: 134 Issue: 631 Pages: 371-383 Part: Part B Published: JAN 2008

Application of the Aventech AIMMS20AQ airborne probe for turbulence measurements during the Convective Storm Initiation Project Author(s): Beswick KM, Gallagher MW, Webb AR, Norton EG, Perry F
Source: ATMOSPHERIC CHEMISTRY AND PHYSICS Volume: 8 Issue: 17 Pages: 5449-5463 Published: 2008

The Convective Storm Initiation Project Author(s): Browning KA, Blyth AM, Clark PA, Corsmeier U, Morcrette CJ, Agnew JL, Ball ard SP, Bamber D, Barthlott C, et al Source: BULLETIN OF THE
AMERICAN METEOROLOGICAL SOCIETY Volume: 88 Issue: 12 Pages: 1939-+ Published: DEC 2007

Variable cirrus shading during CSIP IOP 5. II: Effects on the convective boundary layer Author(s): Marsham JH, Blyth AM, Parker DJ, Beswick K, Browning KA, Corsmeier U, Kalthoff N, Khodayar S,
Morcrette CJ, Norton EG Source: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY Volume: 133 Issue: 628 Pages: 1661-1675 Part: Part A Published: OCT 2007

Secondary initiation of multiple bands of cumulonimbus over southern Britain. I: An observational case-study Author(s): Morcrette CJ, Browning KA, Blyth AM, Bozier KE, Clark PA, Ladd D, Norton EG,
Pavelin E Source: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY Volume: 132 Issue: 617 Pages: 1021-1051 Part: Part B Published: APR 2006

Multi-sensor observations of a wave beneath an impacting rear-inflow jet in an elevated mesoscale convective system
John Marsham, Keith Browning, John Nicol, Emily Norton, Alan Blyth, Doug Parker et al.




Acknowledgements
All the many participants of CSIP, COPS and Philipp Currier from Degreane.
Funding from NCAS, NERC
Data storage British Atmospheric Data Centre (BADC)


 http://www.cas.manchester.ac.uk/research/facilities/ufam/instrumenttable/windprofiler/
 http://www.ncas.ac.uk/fgam/
Combining the strengths of UMIST and
The Victoria University of Manchester

								
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