Tracing seasonal signals in dry/wet status for regions with simultaneous rain and heat from Eastern and Central Asia since the Last Glacial Maximum

Abstract. The global monsoon region with the summer precipitation regime and the Mediterranean climate region with the winter precipitation regime showed opposite dry/wet evolution since the Last Glacial Maximum (LGM). The remarkable difference in summer precipitation regime and winter precipitation regime reveal the seasonal signals of precipitation in multi-time scale climate change. Most studies revealed that the dry/wet status with the summer precipitation regime in Eastern and Central Asia (EA and CA) contradicted those with the winter precipitation regime in CA. Based on the comprehensive study of modern observation datasets, model outputs of eight climate models from the Paleoclimate Model Intercomparison Project phase 3 (PMIP3) and proxy records from EA and CA, here we show that seasonal signals of precipitation derived from the simultaneity of rain and heat periods could govern the difference and linkage in dry/wet status from EA and CA. EOF analysis results of mean annual precipitation uncover different precipitation regimes in EA and CA. However, the similarity between EA and the east of CA, indicated by EOF results of summer and winter precipitation, suggested seasonal signals of precipitation are the primary factor causing the linkage in dry/wet status at short-term timescales. In particular, summer and winter precipitation in EA and CA is associated with the Asian monsoon, westerlies, ENSO, NAO, and PDO. At long-term timescales, the compilation of 42 proxy records since the LGM in EA and CA reveals parallel dry/wet changes in EA and the east of CA as well, attributing to seasonal signals triggered by the insolation in different seasons. PMIP3 multi-model simulation between the LGM and Mid-Holocene (MH) in summer and winter visually was conducted to analyze paleoclimate mechanisms of difference and linkage in dry/wet status from EA and CA. Results show that summer insolation influences the meridional temperature gradient and sea level pressure in the summer, changing the intensity of the westerly winds and summer monsoon and further controlling the summer precipitation in EA and the east of CA. Meanwhile, winter insolation contributes to the general warming in EA and the core region of CA, and in turn results in lower relative humidity, which ultimately increases winter precipitation during the LGM. Overall, we suggest, in addition to the traditional difference caused by different precipitation regimes, that dry/wet status in EA and CA universally have inter-regional connections affected by seasonal signals of precipitation at multi-time scales.