Community-based wind erosion monitoring across Australia 1

DustWatch Report December 2018 Dust activity Dustiest December in DustWatch records Wind strength Windier that 10-year average for December Groundcover Very low and further declining Rainfall Dry in the west, some rain in the east Land management Reduced harvest activity due to failed crops

Dust activity December 2018 saw the dust highest dust activity of any December since our records began in 2005 (Figure 1). Dust was predominantly raised by thunderstorm downdrafts. Some events travelled from west to east right across New South Wales (Figure 10). Most dust activity was in the north of New South Wales (Figure 2). Downdrafts can lead to spectacular rolling dust storms and this was well documented on social media. Literally, hundreds of images and reports have been posted on Instagram and Facebook during December 2018 using the tag #DustStorm. Figure 1 Area of Western Local Land Services with above

50% cover (orange line) and hours of dust (blue line) – December data only

Figure 2 Hours of dust activity (number in brackets) at each DustWatch site in December 2018

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Community-based wind erosion monitoring across Australia 2

Groundcover Groundcover has declined further from last month. The area above 50% groundcover (yellow and green colours in Figure 3) in the Western Local Land Services (LLS) has dropped to the lowest level since 2001 (Figure 1 and Table 1). Only 24% of the area had above 50% groundcover.

Figure 3 Groundcover for December 2018 as determined from MODIS by CSIRO Table 1 Percentage of each NRM with cover >50% for November 2017 to December 2018

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Nov 2017 95 94 100 100 94 97 83 51 100 Dec 2017 92 86 99 99 92 93 78 44 100 Jan 2018 90 90 99 100 92 92 81 44 100 Feb 2018 88 91 98 99 93 91 81 47 100 Mar 2018 89 92 98 99 93 92 83 49 100 Apr 2018 92 94 99 100 95 94 86 56 100 May 2018 94 95 99 99 95 98 91 62 100 June 2018 95 98 100 100 95 99 95 66 100 July 2018 94 98 100 100 94 99 93 62 100 Aug 2018 90 98 99 100 93 98 91 53 100 Sept 2018 85 95 98 100 91 94 84 43 100 Oct 2018 79 89 96 100 89 91 75 39 100 Nov 2018 69 78 90 98 84 78 66 31 100 Dec 2018 59 62 79 92 81 64 56 24 99

Note: The MODIS bare ground data processing has changed in January 2019 leading to small (<5% cover) differences in historic maps and results.

Community-based wind erosion monitoring across Australia 3

Groundcover change The area above 50% cover has dropped between September 2018 and December 2018, especially in the Local Land Services Riverina and Murray regions (Figure 5) and across the border in the North Central and Mallee Catchment Management Areas where large areas the groundcover has dropped between 20 and 40% (orange colours in Figure 4).

Overall groundcover values are comparable to the 2008 and 2009 years (Figure 5).

Figure 4 Groundcover change between August 2018 and December 2018 as determined from MODIS

Figure 5 Percentage area of NRM with more than 50% cover since December 2005 as determined

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Community-based wind erosion monitoring across Australia 4

Groundcover across large parts of New South Wales in December 2018 was 20 to 40% lower than in December 2017 (orange and red colours in Figure 6). When comparing December 2018 to December 2009, the year of the ‘Red Dawn’ dust storm, groundcover values this year are lower in the Local Land Services North West and Central West regions (red colours in Figure 7). Groundcover is better in the south of New South Wales (green colours in Figure 7) and north and west of Broken Hill.

Figure 6 Groundcover change between December 2017 and December 2018 as determined from

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Figure 7 Groundcover change between December 2009 and December 2018 as determined from

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Community-based wind erosion monitoring across Australia 5

Rainfall December 2018 saw some welcome rainfall in the south west of New South Wales and into northern Victoria (Figure 8). Falls exceeding 100mm were recorded in the Mallee and North Central CMA areas. The remainder of the state remained dry or had very little rainfall. This rainfall was usually low for this time of the year with large areas ending up in the driest 10% of Bureau of Meteorology records (Figure 9a). 2018, as a whole, ended up well below average rainfall for the south east of Australia (Figure 9b).

Updates on the latest drought status across the state can be found on the Department of Primary Industries website at: Latest NSW Drought maps.

Figure 8 Rainfall totals for December 2018 (source: Bureau of Meteorology)

Figure 9 Rainfall deciles for December 2018 (a) and 1 January 2018 to 30 December 2018 (b)

Community-based wind erosion monitoring across Australia 6

VIIRS fires and MODIS satellite image The number of fires in December 2018 (1173 pixels with temperature anomalies on VIIRS satellite) was higher than December 2017 (886 pixels – Figure 11). The increased number of thunderstorms in the Western and Central West Local Land Services (LLS) has likely caused the larger number of fires. The MODIS satellite image also shows the large-scale dust storm in north west New South Wales that occurred on 13 December 2018 (Figure 10).

Figure 10 Pixels (375m) with active burning fires in December 2018 as determined from VIIRS satellite

Figure 11 Number of 375 m pixels with active burning fires between January 2016 and December 2018.

The DustWatch team Contact us at dustwatch@environment.nsw.gov.au Dust data supplied by the Office of Environment and Heritage Rural Air Quality network. The MODIS image is courtesy of MODIS Rapid Response Project at NASA/GSFC; the VIIRS fire data is courtesy of the Fire Information for Resource Management System (FIRMS) and the rainfall maps are from the Australian Bureau of Meteorology. This project would not be possible without funding from: The National Landcare Programme, Riverina, Western, Central West, Central Tablelands and Murray Local Land Services (LLS) in NSW; the NSW EPA, the Mallee and North Central CMAs in Victoria and Murray Darling Basin NRM in South Australian, CSIRO, TERN and the Australian National University. We particularly thank our many DustWatch volunteers who provide observations and help maintain the instruments.

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