HAL · Physics
Hail
NASA PMHAILCLIM satellite hail-signature climatology (TRMM/GPM passive microwave) sets where hail forms; one global function of the ERA5 environment (freezing level, elevation, 700–500 hPa lapse rate, 0–6 km shear), fitted once on US ground radar (NOAA MRMS MESH) and six Australian Bureau of Meteorology radars, sets how often that becomes MESH ≥ 25 mm; one measured constant sets the severity tail — position, region and continent are never inputs · v1.0 · 2026-10
North American Plains — 100-year MESH hail size (mm)
Global hail screening on a 0.05° (~5 km) grid carrying ~28 km of information, with a measured transfer error of ×/÷1.65 on level and ×/÷1.93 on severity at every pixel. Sizes are MESH — the ground-radar estimate of the largest hailstone aloft, not a measured stone on the ground (above ~45 mm the typical reported ground stone is smaller). Tested against radar only in the US and Australia; the coverage flag reads 0.5 where the function extrapolates (deep tropics, high plateaus), and cells filled from observed convection are untested against radar. The 50-year probability saturates near 1 across the great hail regions (US Plains, Argentina, South Asia, central Africa) — use the Returns line to rank them. No detail below 0.25° is claimed; nodata beyond ±68° latitude, where the satellite anchor does not observe.
What ships
Surfaces — P(radar-defined hail, MESH ≥ 25 mm, at a point within 50 years) with a five-class cut, uncertainty and a coverage flag (1.0 inside the fitted range, 0.5 where the function extrapolates). Returns — MESH hail size in millimetres at rp10/25/50/100/250/500 with rp100 low/high bands, plus annual exceedance probabilities for MESH ≥ 25 / 51 / 76 mm; 0 means below 25 mm, not no hail.
Every release: 0–1 score · 5-class band · per-pixel uncertainty · input-coverage mask · STAC item · methodology doc.
Inputs
NASA GHRC PMHAILCLIM (Bang & Cecil 2019), NOAA MRMS MESH 2020–2026, Bureau of Meteorology radar volumes 2010–2025, ERA5, lightning + ERA5 convective environment for sparse satellite cells
Version history
What changed between releases — the same notes that ship with the data. Newest first.
Surfaces
v1.0
2026-10
current
- First release. Global (±68°) probability of radar-defined hail (MESH) ≥ 25 mm at a point within 50 years, with classification, uncertainty and a coverage flag (1.0 inside the fitted support of the level function / 0.5 extrapolating), on a 0.05° grid (information at 0.25°).
- The level is one global function of ERA5 environment fitted once on US and Australian ground radar; the severity tail is one measured constant. No region carries its own constant.
- Every land cell between ±68° carries a value: 2° satellite cells with no or few hail signatures are filled from observed convection (lightning, ERA5 environment) through the same global function everywhere, weighted by each cell's own sampling; well-sampled cells are unchanged.
- The 50-year probability saturates in the world's most hail-prone regions; the Returns line separates them.
Returns
v1.0
2026-10
current
- First release. Global (±68°) return-period MESH hail size at 10–500 years, plus annual exceedance probabilities for MESH ≥ 25 / 51 / 76 mm, on a 0.05° grid (information at 0.25°).
- Sizes are radar-defined (MESH, hail aloft). A ground-size transform was tested and could not be calibrated from hail reports; the product says so rather than applying one.
- One rule for every pixel: the level is one global function of ERA5 freezing level, elevation, mid-level lapse rate and deep-layer shear, fitted once on US and Australian ground radar, with a measured ×/÷ 1.65 band on every pixel; the severity tail is one measured constant. No region carries its own constant, and a per-pixel coverage flag marks where the function extrapolates.
- Every land cell between ±68° carries a value: 2° satellite cells with no or few hail signatures are filled from observed convection (lightning, ERA5 environment) through the same global function everywhere, weighted by each cell's own sampling; well-sampled cells are unchanged.
Other hazards
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