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Proxy-based precipitation reconstruction is essential to study the inter-annual to decadal variability and underlying mechanisms beyond the instrumental period that is critically needed for climate modeling, prediction and attribution. Based on 2912 annually resolved proxy series mainly derived from tree rings and historical documents, we present a set of standard precipitation index (SPI) reconstructions for each year (November–October), covering the whole of Asia, and for the wet season (i.e., November–April for western Asia and May–October for the others) since 1700, with the spatial resolution of 2.5 ∘. To screen the optimal candidate proxies for SPI reconstruction in each grid from available proxies in its connected region with a homogeneous rainfall regime and similar precipitation variability, a new approach is developed by adopting the grid-location-dependent division derived from the instrumental SPI data. The validation shows that these reconstructions are effective for most of Asia. The assessment of data quality compared with gauge precipitation before calibration time indicates that our reconstruction has high quality to show the precipitation variability in most of the study areas, except for a few grids in western Russia, the coastal area of southeast Asia and northern Japan. The full dataset can be obtained from https://doi.org/10.57760/sciencedb.01829 (Y. Liu et al., 2022). [ABSTRACT FROM AUTHOR]

This study discusses the interannual variation of spring precipitation in Northeast China (NECSP) from 1980 to 2016 and its relationship with Arctic sea ice based on observation data and numerical experiments. The observed results reveal that the leading mode of NECSP mainly exhibits a homogenous pattern with a significant interannual variation. The NECSP has a significant negative correlation with the preceding winter Barents Sea ice concentration (BSIC) at the interannual scale. In the preceding winter, the decreased BSIC resulted in positive geopotential height anomalies over the polar region, which could weaken the polar vortex and westerly winds, forming a cyclonic anomaly indirectly over West Siberia. The circulation anomalies resulted in a zonal dipole pattern of preceding winter snow water equivalent (SWE) anomalies in the mid‐high latitudes of Eurasia with less SWE over Eastern Europe and more SWE over West Siberia. The SWE anomalies in winter could persist to the subsequent spring and facilitate more precipitation over Northeast China (NEC) by local thermal processes affecting circulation anomalies over Eurasia. On the other hand, the negative preceding winter BSIC anomalies can persist to spring, increasing the NECSP by strengthening the cyclonic anomalies over NEC. In this study, the response of the atmosphere to the thermal effect of SWE is further verified by using the linear baroclinic model (LBM). The response of NECSP to BSIC loss is tested by using the Community Atmosphere Model version 5.3 (CAM5.3). [ABSTRACT FROM AUTHOR]

The potential causes of megadroughts over North China (NC) in the preindustrial period were investigated using eight climate models evolved using CMIP5/PMIP3 and multiple proxy data. The full forcing experiments driven by both external forcing and internal variability show that megadroughts in NC were accompanied by extensive decadal drying over the Northern Hemisphere (NH), particularly in most of North America and Europe. The spatial pattern of hydroclimate matched well with the proxy-based illustration. However, such hydroclimate conditions over NH were difficult to reproduce in control experiments driven solely by internal variability. This finding suggests that external forcing may be a crucial factor leading to megadroughts in NC and simultaneous decadal drying over the NH. Moreover, external forcing may lead to climate cooling. Climate cooling weakened the pressure gradient from the West Pacific to East Asia and hence reduced the water vapor to land; meanwhile, local vertical downward movement occurred in the cooling climate background, which was unfavorable to air convection over NC. Both reduced water vapor and weakened air convection led to less precipitation. Meanwhile, there was a negative NAO, which intensified the eastward wave train at mid-latitudes. Consequently, the North American trough and European trough deepened, the northerlies in the post trough pattern intensified, and the water vapor from the high-latitude continent or polar areas was low, which was unfavorable to precipitation. This study implies that the megadrought in NC and simultaneous hydroclimatic spatial pattern over the NH may be underestimated in the CMIP5 climate prediction, which excludes external forcing. • Megadrought in North China co-occur with extensive dry anomaly over North Hemisphere. • The dry-anomaly hydroclimate pattern occurs in global cooling, declined water vapor. • Abnormal external forcing, e.g., volcanic eruption, is necessary for the dry-anomaly. • Effects of abnormal external forcing may be active through negative NAO pattern. [ABSTRACT FROM AUTHOR]

Large-scale palaeoclimate reconstructions can be very sensitive to the proxy records they are based on, and hence to the criteria used to select proxy records. Data selection rarely follows objective criteria that are applicable to all types of proxies, including both low- and high-resolution records. Thus, there is a need for a uniform and transparent approach to assess the suitability of input proxy data for a reconstruction. Here, we develop classification criteria that are applicable to multiple proxy types and evaluate different selection strategies using a network of 62 millennium-long terrestrial hydroclimate proxy records from Monsoon Asia. Our results reveal that robust evidence for a coherent climate signal and high dating accuracy are important criteria for benchmarking the suitability of each proxy record. We determine these criteria by reviewing the literature for each record (rather than screening against instrumental data). We show that the proposed selection approach can yield a network with a stronger common signal. By evaluating the uncertainty and centennial variability of composite reconstructions, from differently selected subsets of the proxy network, it appears beneficial to use suitable proxies stemming from different archives, as well as having a dense network of proxy sites. We suggest that future large-scale palaeoclimate reconstructions might be improved by evaluating proxy networks according to the universal categories presented here and, if indicated, removing less suitable records. This will strengthen the climate signal in the final reconstruction, allowing more precise inferences about past climate variability and more robust comparisons with climate model simulations. • Suitability of proxy records should be estimated based on literature review. • Semi-quantitative criteria: evidence for climate signal and dating accuracy. • Proposed selection approach can yield a network with a stronger common signal. • Multi-proxy approach is beneficial to preserve various frequency domains. [ABSTRACT FROM AUTHOR]