Low-Pressure System (LPS) tracks over South Asia — v4.1

Region: South Asia (India, Sri Lanka, Pakistan; tracks may extend beyond these borders)
Data source: 3-hourly ERA5 reanalysis
Method: Automated LoG tracking following Hunt & Fletcher (2018, doi:10.1007/s00382-019-04744-x) and Hunt et al. (2016, doi:10.1175/MWR-D-15-0138.1)

Coverage

• Temporal span: 1940-01-01 to 2025-08-31 (inclusive)
• Frame epoch: frame is hours since 1940-01-01 00:00 UTC
• Timestep: hourly detections

Variables (columns)

• x — longitude (deg E)
• y — latitude (deg N)
• frame — hours since 1940-01-01 00:00 UTC (int)
• year, month, day, hour — UTC components of detection time
• max_vort — maximum relative vorticity within ~4° (~400–450 km) of the LPS centre from the 850–700 hPa mean; units 10⁻⁵ s⁻¹
• mean_vort_850, mean_vort_700, mean_vort_500 — mean relative vorticity within ~4° at each level; units 10⁻⁵ s⁻¹
• precip_1hr — mean precipitation rate within ~8° (~800–900 km) over the hour; mm h⁻¹ 
• precip_24hr — mean of the calendar-day 24-h precipitation sum within ~8°; mm day⁻¹
• mean_wind, max_wind — 10 m wind speed within ~4° (area-mean and maximum); m s⁻¹
• min_mslp — minimum mean sea-level pressure within ~4°; hPa
• mslp_contours — count of closed 2 hPa isobars that enclose the LPS centre (dimensionless)
• over_land — 1 if the centre is over land (Natural Earth 1:50 m), else 0
• category — intensity class (IMD-style): 1=L, 2=D, 3=DD, 4=CS, 5=SCS, 6=VSCS, 7=SuCS
• track_id — unique integer identifier for each track (all points with the same track_id belong to the same system)

Intensity category (category)

IMD-style classes, derived from the number of enclosing closed isobars and 10 m wind (over ocean) / combination with isobars (over land).
Mapping used in figures/legends:

• 1 = L (Low)
• 2 = D (Depression)
• 3 = DD (Deep Depression)
• 4 = CS (Cyclonic Storm)
• 5 = SCS (Severe Cyclonic Storm)
• 6 = VSCS (Very Severe Cyclonic Storm)
• 7 = SuCS (Super Cyclonic Storm)
  
  

Notes:

• Over ocean, thresholds follow IMD (knots converted to m s⁻¹): 17, 28, 34, 48, 64, 119 kt breakpoints.
• Over land, the number of enclosing closed isobars (2 hPa spacing) informs classification together with wind.