The Holocene precipitation dipole pattern in the Asian drylands: mechanisms and processes from PMIP۴ simulations and paleo-proxy evidence

Asian drylands consist of arid Central Asia (ACA) and West Asia (WA), in which climatological water vapor transport is constantly controlled by the westerlies. Recent research has revealed the presence of dipole pattern in the hydroclimate changes during the Holocene between the ACA and WA, challenging prior notions of consistent hydroclimate changes in the westerlies-dominated mid-latitude of the Northern Hemisphere. However, the mechanisms behind the dipole pattern remain largely unknown. Here we show that PMIP۴ models faithfully replicated the dipole pattern, attributing it primarily to opposing spring precipitation variations. From the mid-to-late Holocene, intensified westerlies resulted in increased precipitation in ACA. Conversely, increasing spring solar insolation strengthened the subtropical high, resulting in decreased water vapor and descending motion in WA, which resulted in decreased precipitation in WA. Our study suggest that WA is a unique region within the westerlies-dominated mid-latitude, and the low-latitude process caused inconsistent Holocene precipitation variations.