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Hadley Centre for Climate Prediction and Research
The Hadley Centre for Climate Prediction and Research, founded in 1990 within the UK Met Office, is the United Kingdom's primary source of climate change information and climate models.
Haematococcus pluvialis
Haematococcus pluvialis is a freshwater unicellular green microalga that accumulates astaxanthin in thick-walled resting cells under stress, making it the primary natural source for supplements.
Hail
Hail is precipitation in the form of ice pellets more than 5 mm across that falls from thunderstorms, causing about $10 billion a year in US damage.
Hailstorm
A hailstorm is a thunderstorm that produces hail, ice pellets that damage roofs, vehicles, and crops, causing about $10 billion a year in the United States.
Hakuhō earthquake
The Hakuhō earthquake (白鳳地震, also called the Tenmu earthquake) was a magnitude 8.3 earthquake that struck Japan on 29 November 684, the oldest recorded great earthquake along the Nankai Trough.
Half-graben
A half-graben is an asymmetric area of subsidence controlled by hanging-wall subsidence above a single basin-margin normal fault, and is the most common structure in syn-rift settings, typically 25 to 100 km long.
Halocline
A halocline is a layer of water where salinity changes rapidly with depth, separating fresher surface water from saltier water below and limiting vertical mixing.
Hanukkah Eve windstorm of 2006
The Hanukkah Eve windstorm of 2006 was a powerful windstorm that struck western Oregon, Washington, and British Columbia in December 2006, leaving 1.5 million customers without power.
Harmattan
The Harmattan, also called the doctor, is a dry, dust-bearing northeasterly wind over West Africa from late November to mid-March, carrying Saharan dust toward the Gulf of Guinea.
HARMONIE-AROME
HARMONIE-AROME is a kilometer-scale, non-hydrostatic numerical weather prediction model for limited-area regional forecasting in which convection is treated explicitly, built on the shared ALADIN-HIRLAM code framework.
Haruj
Haruj (Al Haruj, هروج) is a large intraplate basaltic volcanic field of about 45,000 km2 in central Libya, at the SW margin of the Sirt Basin, with ~150 volcanoes and K-Ar ages of 6-0.4 Ma.
Hasandag-Keciboyduran Volcanic Complex
The Hasandag-Keciboyduran Volcanic Complex (Hasandağ-Keçiboyduran volkanik kompleksi) is a volcanic field in Central Anatolia, Turkey, centered on Hasan Dağı, a double-peaked stratovolcano rising to 3253 m.
Hashemite (mineral)
Hashemite is a rare barium chromate mineral, Ba(Cr,S)O₄, isostructural with baryte, first described in 1983 from west-central Jordan and named for the Hashemite Kingdom of Jordan.
Hauterivian
The Hauterivian is a stage of the Early Cretaceous, spanning about 132.6 to 125.77 million years ago between the Valanginian and Barremian, named after Hauterive, Switzerland.
Hawaii Ocean Time-series
The Hawaii Ocean Time-series (HOT) is a quasi-monthly oceanographic program that has measured hydrography, chemistry, and biology at Station ALOHA, 100 km north of Oahu, since October 1988.
Hawaiian–Emperor seamount chain
The Hawaiian–Emperor seamount chain, also called the Hawaiian Ridge Emperor Seamounts, is a mostly submarine line of over 100 Pacific volcanoes spanning about 6,000 km.
Hawk Fire
The Hawk Fire was a wind-driven wildfire that burned on Peavine Peak northwest of Reno, Nevada, in August 2026, destroying 47 homes and prompting evacuations of roughly 90,000 people.
Haynesville Shale
The Haynesville Shale is an Upper Jurassic shale gas play more than 10,000 feet beneath northwestern Louisiana, eastern Texas, and southwestern Arkansas, producing natural gas at scale since 2008.
Hayward Fault Zone
The Hayward Fault is a major strike-slip branch of the San Andreas fault system running through Berkeley, Oakland, Hayward, and Fremont, with large earthquakes every 100 to 200 years.
Haze
Haze is a suspension of extremely small dry particles, such as dust, smoke, or pollution, that reduces visibility and gives the air an opalescent appearance.
HBV model
The HBV model (Hydrologiska Byråns Vattenbalansavdelning) is a conceptual rainfall-runoff model developed by Sten Bergström at the Swedish Meteorological and Hydrological Institute in 1972, converting precipitation and temperature into river discharge.
Health effects of climate change
The health effects of climate change include heat deaths, shifting infectious disease, degraded air, and food insecurity, with the WHO projecting 250,000 extra deaths yearly by the 2030s.
Heart Peaks
Heart Peaks: Pleistocene shield volcano with rhyolite lava domes in the Northern Cordilleran Volcanic Province, NW British Columbia, Canada; 2,012 m, no Holocene eruptions, low ash hazard, epithermal gold-silver prospect.
Heat dome
A heat dome is an exceptionally warm air mass trapped beneath a high-pressure system aloft, suppressing clouds and precipitation; the term became widespread during the June 2021 Pacific Northwest heatwave.
Heat index
The heat index, also called the humiture or temperature-humidity index, combines air temperature and relative humidity to estimate how hot conditions feel to a resting person in the shade.
Heat lightning
Heat lightning, also called summer lightning, is the light from a distant thunderstorm too far away for thunder to be heard, often seen as silent flickers on hot summer nights.
Heat wave
A heat wave is a period of unusually hot weather lasting several days, defined by local thresholds, and human-caused warming has made heat waves more frequent and intense.
Heave compensation
Heave compensation is the set of techniques that remove a vessel's wave-induced vertical motion from a suspended load or sensor, used in lifting and hydrographic surveying.
HEC-HMS
HEC-HMS (Hydrologic Modeling System) is a free hydrology program from the US Army Corps of Engineers' Hydrologic Engineering Center that converts precipitation into streamflow hydrographs, replacing HEC-1.
HEC-RAS
HEC-RAS, the Hydrologic Engineering Center's River Analysis System, is free hydraulic modeling software from the U.S. Army Corps of Engineers, first released in July 1995 and used for floodplain and dam safety studies.