Inter‐Model Uncertainty in Projecting Precipitation Changes Over Central Asia Under Global Warming

• Published in: Geophysical research letters 2024-12, Vol.51 (24), p.n/a
• Main Authors: Yao, Mengyuan, Tang, Haosu, Huang, Gang
• Format: Article
• Language: English
• Subjects: Advection; Antarctic front; Climate; Climate change; Cooling; Dipoles; Future climates; Global warming; Jets; Livelihoods; Moisture; Moisture budget; Phase variations; Polar fronts; Precipitation; Relative vorticity; Soil temperature; Soil water; Temperature gradients; Thermal winds; Uncertainty; Uncertainty analysis; Vorticity; Water demand; Water shortages; Wetting; Winds; Winter; Winter precipitation; Zonal winds
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL111989

The impact of global warming on Central Asian precipitation suffers from huge uncertainties, yet their origins remain largely unidentified. This study investigates the inter‐model spread in the projection of winter Central Asian precipitation (WCAP) using models from the Coupled Model Inter‐comparison Project Phase 6. The results reveal a homogenous wetting trend in WCAP, with the primary source of uncertainty in its magnitude stemming from the dynamic component of vertical moisture advection. This dynamical uncertainty is further attributed to an out‐of‐phase variation between two Eurasian westerly jets, which can enhance the upward motion over Central Asia through positive relative vorticity advection and warm temperature advection. The opposing variation between two westerly jets can be traced to cooling in the North Pacific, which alters jet intensity through changes in the meridional temperature gradient. This study informs policy and adaptation strategies to better cope with future climate shifts in Central Asia. Plain Language Summary Central Asia (CA) faces high water demand for agriculture and livelihoods, but struggles with scarce precipitation and dry soils. Therefore, accurate simulation and projection of precipitation in CA are crucial. Based on Coupled Model Inter‐comparison Project Phase 6 models, this study shows a consistent wetting trend in winter precipitation across CA under global warming, with an 8.84%/K increase projected under the SSP5–8.5 scenario. The moisture budget analysis reveals that the primary source of uncertainty in precipitation projections comes from the dynamic component of vertical moisture transport. The strengthened ascending motion over CA is further attributed to an enhanced Eurasian polar front jet (EAPJ) and a weakened Eurasian subtropical jet (EASJ) through positive relative vorticity advection and warm temperature advection. The intensity changes of these two jets can be traced back to cooling in the North Pacific, which results in dipole meridional temperature gradient (MTG) changes over CA. Negative (positive) MTG changes in northern (southern) CA enhance (reduce) the mean‐state MTG and increase (decrease) upper‐level zonal winds according to the thermal wind relation, thereby intensifying (weakening) the EAPJ (EASJ). This study advances the understanding of uncertainties in precipitation projection and informs policymakers on addressing water shortages in the climate‐sensitive CA. Key Points Winter precipit