Algorithms

Algorithms#

Listed algorithms (A1, A2, etc.) have submitted catalogues for Tier 1. Algorithm numbering is determined by overall alphabetical order with the first set of numbers assigned to developers who participated in the 1-month proof of concept (A1 – A15), see GMD paper, followed by Tier 1-only participation (A16-39).

Fig. 5 Algorithm Grid, by Christine Shields#

Alogrithms
(Click a name to veiw the alogrithm details)

Brands et al

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Brands et al	Condition	> 1500 km	Both Relative and Absolute IVT: 95^th(A16)/90^th(A23)/90^th(A24) percentile at point of detection, 90^th/85^th/85^th percentile along the AR structure, consider all months for threshold calculation with a min threshold of 240/500/250 kgm^-1s^-1. Spatial tracking guided by vector IVT.	Time slice	150°W to 30°E 30°N to 62°N	10.1007/s00382-016-3095-6

Gershunov et al^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Gershunov et al^b	Condition and Track	>= 1500km long	Absolute: 250kgm^-1s^-1 IVT 1.5cm IWV	Time stitching -18 hours (3 time steps for 6 hourly data)	Western U.S.	10.1002/2017GL074175

Goldenson^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Goldenson^b	Condition	> 2000km long and < 1000km wide Object recognition	Absolute: 2cm IWV	Time slice	Western U.S.	10.1175/JCLI-D-18-0268.1

Gorodetskaya et al

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Gorodetskaya et al	Condition	IWV > thresh. at the coast (within defined longitudinal sector) and continuously at all latitudes for ≥ 20° equatorward (length > 2000 km), within ± 15° longitude sector (width of 30° ~ 1000 km at 70°S; requirement of meridional extent)	Relative: ^aZN using IWV adjusted for reduced tropospheric moisture holding capacity at low temperatures (AR_coeff = 0.2)	Time slice	Polar (East Antarctica)	10.1002/2014GL060881

Guan and Waliser^bc

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Guan and Waliser^bc	Condition	Length >2000km and length width ratio >2; Coherent IVT direction within 45° of AR shape orientation and with a poleward component	Relative: 85^th percentile IVT; Absolute min requirement designed for polar locations: 100kgm^-1s^-1 IVT	Time slice	Global	10.1002/2015JD024257 10.1175/JHM-D-17-0114.1 tracker code

Hagos et al.^b (PNNL1)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Hagos et al.^b (PNNL1)	Condition	Dependent on threshold requirements to determine footprint; > 2000 km long and < 1000 km wide	Absolute: 2cm IWV 10ms^-1 wind speed	Time slice	Western U.S.	10.1175/JCLI-D-14-00567.1

Kashinath et al.^f (ClimateNet)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Kashinath et al.^f (ClimateNet)	Condition	Deep learning based segmentation. Trained on ~500 expert labelled images	Threshold free; input fields are IWV, U850, V850, SLP	Time slice	Global	10.5194/gmd-2020-72

Krinitsky et al. (SAIL)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Krinitsky et al. (SAIL)	Condition	Geometry reqirements Length >= 250km; Length-to-width >=5; Length is estimated along the “ridge” taking IVT into account. Width is the median of widths estimated in each point of AR ridge.	Relative: IVT-IVT_RM >_ 100. IVT_RM is climatological IVT running mean with 20-day windows	Time slice	Global	10.1088/1755-1315/606/1/012011

Lavers et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Lavers et al.	Condition	4.5° latitude movement allowed	Relative: ~85^th percentile determined by evaluation of reanalysis products	Time slice	UK, Western US	10.1029/2012JD018027

Leung and Qianb (PNNL2)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Leung and Qianb (PNNL2)	Track	Moisture flux has an eastward or northward component at landfall; tracks originating north of 25N and east of 140W are rejected	Absolute: mean IVT along track > 500 kgm^-1s^-1 and IVT at landfall > 200 kgm^-1s^-1; grid points up to 500km to the north and south along the AR tracks are included as part of the AR if their mean IVT > 300 kgm^-1s^-1	Time slice	Western U.S.	10.1029/2008GL036445

Lora et al.^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Lora et al.^b	Condition	Length >= 2000km	v1: Relative : IVT 100kgm^-1s^-1 above climatological area means for N. Pacific; v2:Relative/Absolute : IVT 225 kgm^-1s^-1 above time/latitude dependent threshold using 30-day running mean and zonal average of IWV	Time slice	v1 Global (A6) v1 North Pacific (A7) v2 (Global)	10.1002/2016GL071541 10.1016/j.epsl.2020.116293

Mahesh and O’Brien (CASCADE)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Mahesh and O’Brien (CASCADE)	Condition	Convolutional neural network to replicate ARTMIP mean	Threshold-free; IVT(A25) and IWV (A26) is the input, output is probability of AR presence	Time slice	Global	Experimental

Mahoney et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Mahoney et al.	Condition and Track	Length >= 1500km, Width <=1500km	Absolute: ARDT-IVT 500kgm^-1s^-1 for SEUS.	See Wick	Southeast U.S.	10.1175/MWR-D-15-0279.1 (uses Wick)

Mattingly

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Mattingly	Condition	Length >= 1500km; Length to width ratio > 1.5	Relative: 85^th percentile IVT (relative to 31 day centered climatological mean); Absolute min requirement designed for polar locations: 150 kg/m/s IVT: vIVT must be poleward unless feature is poleward of 66.56 N/S (Arctic/Antarctic Circle)	Time slice	Global coverage poleward of 10N/S; parameters tuned for polar focus (allows non poleward vIVT for features poleward of 66.56 N/S	10.1029/2018JD028714

Mundhenk

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Mundhenk	Condition	>1400km length, aspect ratio 1:4, lat limit >16N/S, axis orientation based on IVT	Relative IVT percentiles and/or anomalies both temporal and spatial	Time slice	Global	10.1175/JCLI-D-15-0655.1

Muszynski et al. (ML_TDA)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Muszynski et al. (ML_TDA)	Condition	Topological analysis and machine learned	Threshold-free	N/A	Western U.S., adaptable to other regions	10.5194/gmd-12-613-2019

Nellikkattil et al. (SCAFET)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Nellikkattil et al. (SCAFET)	Condition and Track	Local geometric shape	Threshold free on IVT but precipitation > 1 mm/day	Time slice	Global	In preparation

O’Brien et al. (teca_bard_v1.01 = CASCADE_bard_v1)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
O’Brien et al. (teca_bard_v1.01 = CASCADE_bard_v1)	Condition	^eMinimum area	^eRelative threshold (based on spatial percentile for each timestep). An inverted Gaussian filter is applied at the equator to damp out the ITCZ	Time slice	Global	10.5194/gmd-13-6131-2020

PanLu

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
PanLu	Condition	1) Length>2000km; 2) Length-Width ratio>2; 3) sum of turning angle<360; 4) percentage within tropics < 95%; 5) 50% < percentage within tropics < 95% or percentage with IVT direction smaller than 15 degrees <50%	Two relative thresholds. Local threshold: smoothed 85% quantile IVT field using the Gaussian kernel density smoothing technique; regional threshold: the 80% quantile of IVT for all grids within 80N and 80S.	Time stitching: last for at least 18 hours	East Asia & Global	10.1029/2018WR024407 10.1029/2020GL089477

Payne and Magnusdottir^bc

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Payne and Magnusdottir^bc	Condition	Length > 1200km, landfalling only	Relative: 85^th Percentile of maximum IVT (1000-500mb) Absolute: IWV >2cm, 850mb wind speed > 10m/s	Time stitching (12-hour minimum)	Western U.S.	10.1002/2015JD023586 10.1002/2016JD025549

Ralph et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Ralph et al.	Condition	Length >= 2000km, Width <= 1000km	Absolute: IWV 2cm	Time slice	Western U.S.	10.1175/1520-0493(2004)132

Ramos et al.^bc; Blamey et al.^*

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Ramos et al.^bc; Blamey et al.^*	Condition	Detected for reference meridians, length >=1500km (1800km^*), latitudinal movement <4.5°N	Relative: IVT 85th percentile (1000-300mb)	Time slice, but 18-hour minimum for persistent ARs	Western Europe, South Africa^*, adaptable to other regions	10.5194/esd-7-371-2016 10.1175/JHM-D-17-0111.1

Reid et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Reid et al.	Condition	Length > 2000km; Length-Width ratio > 2; orientation angle >10°	= Absolute. IVT > 250 kg/m/s; IVT > 500 kg/m/s	Time slice	Global	10.1029/2020JD032897

Rutz et al.^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Rutz et al.^b	Condition	Length >= 2000km	Absolute: IVT (surface to 100mb) = 250kgm^-1s^-1	Time slice	Global, low value on tropics	10.1175/MWR-D-13-00168.1

Shearer et al.(AR-CONNECT)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Shearer et al.(AR-CONNECT)	Track	Object identification	Absolute: Absolute: IVT thresholds used = 700 for seeding, 300, for region growing	Time stitching, minimum 24-hour period	Global weighted centroid of AR event must be outside tropics (23.25 N - 23.25 S)	10.1029/2020JD033425

Sellars et al.^b (CONNECT)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Sellars et al.^b (CONNECT)	Track	Object identification	Absolute: IVT, thresholds tested = 300 (A11), 500 (A12), 700 (A13) kgm^-1s^-1	Time stitching, minimum 24-hour period	Global	10.1002/2013EO320001 10.1175/JHM-D-14-0101.1

Shields and Kiehl^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Shields and Kiehl^b	Condition	Ratio 2:1, length to width grid points min 200km length; 850mb wind direction from specified regional quadrants, landfalling only	Relative: ^aZN moisture threshold using IWV; Wind threshold defined by regional 85^th percentile 850mb wind magnitudes	Time slice	Western U.S. Iberian Peninsula, UK, adaptable but regional specific	10.1002/2016GL069476 10.1002/2016GL070470

TEMPEST^b

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
TEMPEST^b	Track	^dLaplacian IVT thresholds most effective for widths >1000km; cluster size minimum = 120000km²	dIVT >=250kgm^-1s^-1	Time stitching	Global, but latitude >=15°	10.1029/2020JD033421 10.5194/gmd-10-1069-2017 10.1029/2019JD031977 10.1029/2020JD033421

Viale et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Viale et al.	Condition	Length >2000km (>1500km north of 35°S) and length-width ratio>2; Coherent IVT direction within 45° of AR mean direction and with a poleward component	Relative: 85^th percentile IVT; Absolute min requirement designed for subtropical locations: 100kgm^-1s^-1 IVT; a frontal zone intercept or locate south (up to 50 km), i.e., mag. of the horizontal gradient of the 1000-850hPa thickness > 5 m 100 km^-1)	Time slice	Southwestern South America	10.1175/JHM-D-18-0006.1

Walton et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Walton et al.	Condition and Track	Length >= 2000 km	Relative: IVT > 250 kg/m/s + daily IVT climatology	Time stitching, minimum 24-hour period	Western U.S.	Experimental

Wick et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Wick et al.	Condition and Track	>=2000km long, <= 1000km wide object identification involving shape and axis	Absolute: ARDT-IWV >2cm	Time slice and stitching	Regional	10.1109/TGRS.2012.2211024

Wille et al.

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Wille et al.	Condition	Length > 20° (2000 km) equatorward with no breaks. Defined as AR landfall if AR shape overlaps a land grid cell.	Relative > 98^th percentile IWV(A28) or vIVT(29) based on monthly climatological means	Time slice	Polar: Antarctic(37.5°-78°S; Arctic(37.5°-80°N	Antarctic 10.1029/2020JD033788 Arctic: Experimental

Xu et al. (IPART)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Xu et al. (IPART)	Condition and Track	Length >= 1500 km, area in range [5010⁴, 180010⁴ km²], L/W ratio>=2, isoperimetric quotient < 0.7, centroid latitude > 20 N, < 80 N.	Threshold free;Select transient IVT plumes standing out from a temporal scale of 8 days;Spatial scale of ~ 1000 km	Time slice and stitching	Northern Hemisphere	10.5194/gmd-13-4639-2020

Zhang, Tung, & Cleveland^g (Purdue)

Developer	Type	Geometry Req.	Threshold Req.	Temporal Req.	Region	DOI/Reference
Zhang, Tung, & Cleveland^g (Purdue)	Multifactorial Conditions and Track	(Length >= 1500, 1800, OR 2000 km) AND (Length/average Width >= 2)	Relative: (75^th, 85^th, OR 95^th monthly percentile applied at every gridpoint, in ENSO neutral and weak ENSO years) (IVT, IWV, OR IVT+IWV)	(Persistent Duration >=12, 18, OR 24 hours) AND (Break < 24 hours)	Regional: West-Coast landfalling region: located between 33-48.5N and 124.375-114.375W; Midwest region is between 37-47N and 94-84W	10.1029/2020JD033667

^aZN relative threshold formula: $Q >= Q$ _{zonal_mean} + AR_coeff (Q_zonalmax – Q_zonamean) where Q = moisture variable, either IVT (kg m^-1s^-1) or IWV(cm). AR_coeff = 0.3 except where noted (Zhu and Newell, 1998). The Gorodetskaya method uses Qsat, where Qsat represents maximum moisture holding capacity calculated based on temperature (Clausius-Clapeyron), an important distinction for polar ARs. Additional analysis on the ZN method can be found in Newman et al., 201

^bMethods used in a 1-month proof-of-concept test (Section 5). These methods are assigned an algorithm id, i.e. A1, A2, etc.

^cThese 1-month proof-of-concept methods apply a percentile approach to determining ARs. A3 and A8 applied the full MERRA2 climatology to compute percentiles. A9, applied the Feb 2017 climatology for this test only. For the full catalogues, A9 will apply extended winter and extended summer climatologies to compute percentiles. Please refer to individual publications (DOI reference column in this table) for climatologies used in earlier published studies by each developer. The climatology used to compute percentile is often dependent on the dataset (re-analysis or model data) being used.

^dTempest contains both an absolute threshold (typically set at IVT>250) and a relative threshold (which uses a local Laplacian of IVT, typically set at del² IVT < -50k).

^eThe O’Brien et al. Bayesian AR Detector (BARD) algorithm runs 1,024 AR detectors simultaneously. Percentile threshold, minimum area, and filter latitude width are all sampled from a posterior distribution that is designed to optimize global AR counts relative to a dataset of AR counts from a set of experts.

^fThe DL model presented in the paper and the one used to produce the catalogue use slightly different architectures (DeepLab3+ vs CGNet)

^gThe Purdue indices consist of 81 indices for the land-falling West-Coast ARs and 81 indices for the inland Midwest ARs.