เปรียบเทียบวิธี

	แบบจำลองการไหลเวียนทั่วไป	ดัชนีปริมาณน้ำฝนมาตรฐาน
สาขาวิชา	ธรณีฟิสิกส์	ธรณีฟิสิกส์
ตระกูล	Process / pipeline	Process / pipeline
ปีกำเนิด	1975	1993
ผู้ริเริ่ม	Syukuro Manabe and Richard Wetherald	Thomas McKee, Neil Doesken, and John Kleist
ประเภท	Deterministic coupled atmosphere-ocean simulation	Probabilistic drought indicator
แหล่งต้นตำรับ	Manabe, S., & Wetherald, R. T. (1975). The effects of doubling the CO2 concentration on the climate of a general circulation model. Journal of the Atmospheric Sciences, 32(1), 3-15.	McKee, T. B., Doesken, N. J., & Kleist, J. (1993). The relationship of drought frequency and duration to time scales. Proceedings of the Eighth Conference on Applied Climatology, 179-184.
ชื่อเรียกอื่น	GCM, Global Climate Model	SPI
ที่เกี่ยวข้อง	3	3
สรุป	A General Circulation Model (GCM), also called a Global Climate Model, is a three-dimensional numerical representation of the Earth's atmosphere, oceans, ice, and land surface that simulates physical processes governing weather and climate. Pioneered by Manabe and Wetherald in 1975, GCMs are the primary tools for understanding past climate, projecting future climate change, and investigating climate sensitivity to greenhouse gases and other forcings.	The Standardized Precipitation Index (SPI) is a climate index that quantifies precipitation anomalies relative to historical norms, standardized to account for differences in precipitation climatology across regions. Introduced by McKee, Doesken, and Kleist in 1993, SPI has become a primary tool for drought detection and characterization, adopted by meteorological agencies worldwide for operational drought monitoring and early warning systems.