Management of spray drift through inversion risk awareness

Transcription

1 Management of spray drift through inversion risk awareness The Spray-Keys to knowing GO/CAUTION/EXTREME CAUTION/STOP Weather conditions for night spraying Research conducted by Graeme Tepper and Warwick Grace

2 5 PAWS: good resources for 2 million hectares Likely effective area Applies to flat and gently undulating country 2 million hectares (20,000 sqkm) For each element (i.e. wind speed) 10 million observations have been analysed.

3 The research integrates spray and air pollution science that describes surface layer motion, stability and dispersion Wind speed at 10m: 7kph Weak turbulence and drainage winds Wind speed at 10m: CALM Adapted from -

4 The research focuses on the conditions that keep pesticides suspended at high concentrations near the surface Turbulence may not vanish as the wind speed appears to become CALM Weak turbulence, confined in layers, has the potential to keep in suspension small aerosols (~<50µm) for considerable time and for long distances.

5 Turbulence intensity controls the dispersion rate of the spray cloud 5 between 3 and 32m (CSIRO) 5 in 32m Weak turbulence in an inversion condition causes 32µm droplets to remain suspended as they float across the paddock 32µm IMAGE: adapted from

6 17.0 Clear-sky inversion with Nyabinglocal-drainage winds 22/08/2014 to 24/08/2014 Inversion onset 1655, sunset Inversion onset 1703: sunset m T 10m T Inversion burnt of to 10m by 0714: sunrise kph 1.25 T pulsing 18:00 22 Aug Drainage winds 0:00 23 Aug 6:00 Synoptic winds 12:00 18:00 Drainage winds 0:00 24 Aug 6:00 Ave 10m Temperature (degc) Ave 1.25m Temperature (degc) Ave WndSpd (m/s)

7 18.0 Inversions can coexist with high-wind speed Katann10 16/06/2014 to 17/06/ Inversion onset 1655, sunset 1708 w s 9 kph Inversion 22kph 12.0 I 0746, sr kph 14kph kph :00 16 Jun 20:00 7kph 0:00 17 Jun 4:00 8:00 Ave 10m Temperature (degc) Ave 1.25m Temperature (degc) Ave WndSpd (m/s)

8 The decline and rise of turbulence Ongeru /06/2014 to 17/06/ Inversion (variable risk) unstable Very stable ~ Neutral unstable kph 10kph 4kph 7kph 22kph 30kph 16:00 16 Jun 20:00 0:00 17 Jun Ave 10m Temperature (degc) Ave 1.25m Temperature (degc) Ave WndSpd (m/s) Wind speed 10m (w ) (m/s) 4:00 8:

9 Deposition of aerosol or fine droplets is dominated by turbulence (CSIRO) ULV aerosol applicators: VMD <25μm and where 90% of the spray volume is < 50μm Armed Forces Pest Management Board TECHNICAL GUIDE NO. 13 Very unstable Very stable Dispersing Weak dispersion EXTRAPOLATION OF DROPLET CATCH MEASUREMENTS IN AEROSOL APPLICATION TREATMENTS (2011) Lav R. Khot,1 David R. Miller,2 April L. Hiscox,3 Masoud Salyani,1, ToddW.Walker,4 & Muhammad Farooq4

10 Traditional and GTR Stability indices and turbulence intensity Stability Scheme PG PG (numb) Correspondence between Stability Classification Schemes and with Turbulence Description Pasquill-Gifford Approx n to Gradient Richardson Number Stability Scheme Turbulence Ri Yates SR L, m GTR σs m/s Monin-Obukhov ~ Very Unstable VU A 1 < < < -0.2 Unstable U B to to -0.5** to to 1 or Slightly Unstable Sl U C to to to more Neutral N D to to +0.1 ± to Weakly Stable Wk S E to to to to 0.5 Strongly Stable S F **Extremely Stable XS G n/a * Yates has no Slightly Unstable class: a division at -0.5 is used to assign uniformity. ** Not commonly used. Table compiled from several sources. The two rightmost columns are from Katanning fieldwork and analysis by Tepper & Grace.

11 From Stull Meteorology for Scientists and Engineers Pasquill-Gifford is outmoded Replaced by TKE and Velocity variance more stable more unstable Pasquill-Gifford Classifications [warmer with height] [cooler with height] Vertical temperature difference R= function of surface heating and wind shear

12 Deposition of aerosol or fine droplets is dominated by turbulence (CSIRO) Fits Stull Wind speed km/h Spray-Key contours (based on turbulence intensity as indicated by velocity variance) Original diagram source: Warwick Grace more stable more unstable Stability classifications based on GTR 0 [warmer with height] Vertical temperature difference [cooler with height]

13 kph Spray-Keys Flag conditions Katanning and warns of Risk Levels sunset 7:20pm : Ws 20km/h 20:00 26 Dec 7:50pm Inversion onset Ws 19km/h 22:00 26/12/2014 w to 27/12/2014 Spray-Keys need not be regulatory to be useful GO C STOP Inversion 0:00 27 Dec Ws 7km/h EC Ave 10m Temperature (degc) Ave 1.25m Temperature (degc) StdDev WndSpd (m/s) Ave WndSpd (m/s) 2:00 Spray- Key Calm 4:00 EC Sunrise :

14 ACHIEVED Applicable to the broad acres around Katanning 1. Proven that PAWS provide detailed and reliable inversions detection 2. Proved not all inversions pose the same risk 3. PAWS provide data for inversion-risk analysis and advice. 4. Tentatively identified Spray-Keys (Indices), that match traditional stability/dispersion indices, for real-time guidance Go/Caution/Extreme Caution/Stop 1. Shown that over simple terrain that strong stability causes significantly different paddock wind conditions and weak turbulence 2. Although inversion intensity varies across the region; Inversion risks are similar 3. It would be practical for a third party such as (BOM, CSIRO or a university, or commercial weather provider) to forecast inversion-risk advice

15 Need - National Accreditation How well do the current research outcomes translate nationally Test various configurations of PAWS for cost effective rollout Opportunity for - add on sensors frost soil temperature and moisture - rainfall Establish national Australian Standard inversion risk Use data from diverse regions to support Nationally relevant recommendations for: An inversion risk management project expected to include PAWS networks and resources delivered direct from PAWS and from 3 rd parties (forecasts) to Growers. A review of label requirements to the APVMA to include scientific evidence gathered across diverse regions to ensure national integrity.

16 Conclusions Not all inversions pose the same risk Inversion risks need to be quantified PAWS provide accurate and immediate observation of inversions and risks. Forecast advice is feasible for inversions exists and for Spray-Keys. Factoring Spray-Keys into spray planning and spray practices could lead to greater spray opportunity and less drift.

17 Our research aims to provide knowledge and resources to Combat Inversion Risks Thank You Graeme Tepper and Warwick Grace Image Source: Pete Nikolaison - Masterton