SABAKURAKU — Drylands

Deserts are on the move. SABAKURAKU teaches the science of drylands — how dunes take shape, how water balance decides what becomes desert, and which global forces create deserts — through beautiful, hands-on simulations. A companion to HYOURAKU (the cryosphere) in the "Raku" series, it covers Earth's other extreme; after all, Antarctica is a "cold desert." Six topics span high-school geography and earth science up to introductory geomorphology, hydrology, and climatology. [Challenges: predict, then test] 30 challenges, 5 per screen. Pick one with the flag button and predict the outcome (1 of 2 choices). Then work the controls and hold the target state for a few seconds while it plays. "Cleared!" shows whether you predicted right, with a short explanation, and "Next challenge" leads on. Progress (n/5) shows on each home card and is saved only on your device. [Six Modules] - Dune Formation Adjust the sand supply, the wind regime (one, two, or many directions), and the wind strength to grow barchans, transverse ridges, linear (seif) dunes, and star dunes, computed with Werner's 1995 cellular automaton. Watch dunes march downwind, lower the sun for long shadows, and fast-forward at x1, x4, or x16. - Water Balance and Desertification Change rainfall and temperature to move the aridity index, classed by UNEP from hyper-arid to humid. Raise grazing pressure until the vegetation suddenly collapses (a tipping point), then see that easing off does not bring it back (hysteresis) — the same mechanism as Ice-Albedo Feedback in HYOURAKU. - Oases and Groundwater Set the mountain recharge and the number of wells. Pump more than they supply and the water table falls until the spring dries up. A graph tracks water-table depth and soil salinity, with events like "Spring dried up in year 12." Irrigation leaves salt in the fields; add drainage and compare. - Flash Floods (Wadis) Pick rain intensity, storm length, and upstream surface (bare crust, grass, or sand), then make it rain. Rain that exceeds the infiltration capacity (Horton's equation) runs off down the dry riverbed. A hydrograph shows the peak flow at the downstream village and when the water arrives — a flood under clear skies. - Why Dry Belts Form Particles trace the Hadley circulation and the sinking air that puts many great deserts near 30° latitude. Step through the months to follow the ITCZ and the Sahel's rainy season, and add a cold offshore current to see why the Atacama and the Namib get fog but almost no rain. - Rain Shadow Moist air climbing a mountain cools at the dry adiabatic rate (about 1°C per 100 m), then at the moist rate (about 0.5°C) once clouds form, dropping its rain on the windward side. Change the mountain height and upwind humidity and temperature to see the cloud base, rainfall on each side, and the warm, dry foehn that turns the lee into desert. [Features] - Principle / explanation sheet in every module - 9 languages (Japanese, English, Chinese Simplified/Traditional, Spanish, Portuguese (BR), Korean, German, French) - Easy start: a new screen opens paused with a big play cue and its main control highlighted until touched; the home screen marks Dune Formation "Start here" - A one-line "how to try" guide on every simulation screen - Play / pause button with a clear label - Reset can be undone for a few seconds ("Undo") - Supports portrait and landscape, text at 200%, and VoiceOver (spoken summaries of each simulation) - About screen with privacy policy and support links - Same simulation speed on any display refresh rate - Every feature free (banner ads only; no in-app purchases or subscriptions) - Realistic desert visuals on a dark theme [Great for] - Students of geography, earth science, geomorphology, hydrology, or climatology - Anyone curious about dunes, groundwater, dry climates, or news on desertification, drought, and water shortages - Teachers looking for classroom material - HYOURAKU users ready to explore the dry extreme too