Low-pressure system (LPS) tracks in ERA5 over South Asia (1979-2025) v4.1

<h1>Low-Pressure System (LPS) tracks over South Asia &mdash; v4.1</h1> <p><strong>Region:</strong> South Asia (India, Sri Lanka, Pakistan; tracks may extend beyond these borders)<br><strong>Data source:</strong> 3-hourly ERA5 reanalysis<br><strong>Method:</strong> Automated LoG tracking following Hunt &amp; Fletcher (2018, doi:10.1007/s00382-019-04744-x) and Hunt et al. (2016, doi:10.1175/MWR-D-15-0138.1)<br><br></p> <h2>Coverage</h2> <ul> <li><strong>Temporal span:</strong> <strong>1940-01-01</strong> to <strong>2025-08-31</strong> (inclusive)</li> <li><strong>Frame epoch:</strong> <code>frame</code> is hours since <strong>1940-01-01 00:00 UTC</strong></li> <li><strong>Timestep:</strong> hourly detections</li> </ul> <h3>Variables (columns)</h3> <ul> <li><code>x</code> &mdash; longitude (deg E)</li> <li><code>y</code> &mdash; latitude (deg N)</li> <li><code>frame</code> &mdash; hours since 1940-01-01 00:00 UTC (int)</li> <li><code>year</code>, <code>month</code>, <code>day</code>, <code>hour</code> &mdash; UTC components of detection time</li> <li><code>max_vort</code> &mdash; maximum relative vorticity within ~4&deg; (~400&ndash;450 km) of the LPS centre from the <strong>850&ndash;700 hPa mean</strong>; units <strong>10⁻⁵ s⁻&sup1;</strong></li> <li><code>mean_vort_850</code>, <code>mean_vort_700</code>, <code>mean_vort_500</code> &mdash; mean relative vorticity within ~4&deg; at each level; units <strong>10⁻⁵ s⁻&sup1;</strong></li> <li><code>precip_1hr</code> &mdash; mean precipitation rate within ~8&deg; (~800&ndash;900 km) over the hour; <strong>mm h⁻&sup1;</strong>&nbsp;</li> <li><code>precip_24hr</code> &mdash; mean of the <strong>calendar-day</strong> 24-h precipitation sum within ~8&deg;; <strong>mm day⁻&sup1;</strong></li> <li><code>mean_wind</code>, <code>max_wind</code> &mdash; 10 m wind speed within ~4&deg; (area-mean and maximum); <strong>m s⁻&sup1;</strong></li> <li><code>min_mslp</code> &mdash; minimum mean sea-level pressure within ~4&deg;; <strong>hPa</strong></li> <li><code>mslp_contours</code> &mdash; count of <strong>closed</strong> 2 hPa isobars that enclose the LPS centre (dimensionless)</li> <li><code>over_land</code> &mdash; 1 if the centre is over land (Natural Earth 1:50 m), else 0</li> <li><code>category</code> &mdash; intensity class (IMD-style): 1=L, 2=D, 3=DD, 4=CS, 5=SCS, 6=VSCS, 7=SuCS</li> <li><code>track_id</code> &mdash; unique integer identifier for each track (all points with the same <code>track_id</code> belong to the same system)</li> </ul> <h3>Intensity category (<code>category</code>)</h3> <p>IMD-style classes, derived from the number of enclosing closed isobars and 10 m wind (over ocean) / combination with isobars (over land).<br>Mapping used in figures/legends:</p> <ul> <li><strong>1 = L</strong> (Low)</li> <li><strong>2 = D</strong> (Depression)</li> <li><strong>3 = DD</strong> (Deep Depression)</li> <li><strong>4 = CS</strong> (Cyclonic Storm)</li> <li><strong>5 = SCS</strong> (Severe Cyclonic Storm)</li> <li><strong>6 = VSCS</strong> (Very Severe Cyclonic Storm)</li> <li><strong>7 = SuCS</strong> (Super Cyclonic Storm)<br><br></li> </ul> <p><strong>Notes:</strong></p> <ul> <li>Over <strong>ocean</strong>, thresholds follow IMD (knots converted to m s⁻&sup1;): 17, 28, 34, 48, 64, 119 kt breakpoints.</li> <li>Over <strong>land</strong>, the number of enclosing closed isobars (2 hPa spacing) informs classification together with wind.</li> </ul>