Xianmei Lang

Last Glacial Maximum over China: Sensitivities of climate to paleovegetation and Tibetan ice sheet

[1] With the boundary conditions appropriate for the Last Glacial Maximum (LGM), including ice sheets, sea surface temperatures, sea-ice distribution, atmospheric CO2 concentration, the Earth’s orbital parameters, topography, and coastline, the atmospheric general circulation model of the Institute of Atmospheric Physics (IAP-AGCM) computes colder and drier conditions than for present day. Global annual-average surface temperature decreased by 5.3C, and terrestrial precipitation was down by 29%. It is shown that IAP-AGCM LGM simulation compares favorably to results from other AGCMs, and/but generally shows a weak terrestrial cooling when compared to paleoclimatic reconstructions in tropics. The 21 ka (ka: thousands of years ago) vegetation reconstruction is introduced into the model to study the regional climate response to the changes in vegetation and associated soil characteristics over China. The additional cooling due to these two changes reduces, to a certain degree, the model-data discrepancies. In addition, under the precondition of continental ice existing over part of the Tibetan Plateau at the LGM, the authors examine the regional climate response to the continental ice. It follows that the glacial-age environment over the Tibetan Plateau is a very important factor for 21 ka climate simulation in East Asia. INDEX TERMS: 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; KEYWORDS: last Glacial Maximum, climate, paleovegetation, Tibetan ice sheet

Last Glacial Maximum East Asian Monsoon: Results of PMIP Simulations

Abstract During glacial periods, the East Asian monsoon is typically thought to have been stronger in boreal winters and weaker in boreal summers. It is unclear, however, whether this view is true at larger scales and to what extent the East Asian monsoon responds to glacial conditions as a whole. Using all experiments conducted as part of the Paleoclimate Modeling Intercomparison Project (PMIP), this paper examines East Asian monsoon climatology during the Last Glacial Maximum (LGM), around 21 000 calendar years ago. In contrast to conclusions drawn from sparse proxy data, the intensity of the East Asian winter (December–February) monsoon (EAWM) during the LGM, as measured by regionally averaged meridional wind speed at 850 hPa, was found to vary both in sign and magnitude, with reference to baseline climate, across the PMIP simulations. It strengthened in 10 out of the 21 models but weakened in the remaining 11 models, with an average weakening of 4% for the 21-model ensemble mean (15% for the ensemble ...

Considerable Model–Data Mismatch in Temperature over China during the Mid-Holocene: Results of PMIP Simulations

Using the experiments undertaken by 36 climate models participating in the Paleoclimate Modeling Intercomparison Project (PMIP), this study examines annual and seasonal surface temperatures over China during the mid-Holocene. Compared to the present or preindustrial climate, 35 out of the 36 PMIP models reproduced colder-than-baseline annual temperature, with an average cooling of 0.4 K, during that period. Seasonal temperature change followed closely the change in incoming solar radiation at the top of the atmosphere over China during the mid-Holocene. Temperature was reduced (elevated) in boreal winter and spring (summer) in all of the PMIP models, with an average of 1.4 K (1.0 K) at the national scale. Colder (warmer)-than-baseline temperatures were derived from 14 of the 16 atmosphere-only (18 of the 20 coupled) models during the mid-Holocene boreal autumn. Interactive ocean was found to lead to a warming effect on annual (0.3 K), boreal winter (0.5 K), and boreal autumn (0.7 K) temperatures, with reference to the atmosphere-only models. Interactive vegetation had little impact in terms of six pairs of coupled models with and without vegetation effects. The above results are in stark contrast to warmer-than-present annual and winter climate conditions as derived from multiproxy data for the mid-Holocene. Coupled models generally perform better than atmosphere-only models.

Improving Extraseasonal Summer Rainfall Prediction by Merging Information from GCMs and Observations

Abstract A new prediction approach for summer (June–August) rainfall in China was designed by considering both preceding observations and numerically predicted summer rainfall through a multivariate linear regression analysis. First, correlation analyses revealed close relationships between summer rainfall in parts of China with the Antarctic Oscillation (AAO), the Arctic Oscillation (AO), and sea surface temperatures (SSTs) in the preceding winter (December–February). The Huang-Huai Valley, two subregions of the Jiang-Huai Valley, the southern Yangtze River, south China, and southeastern Xinjiang were then chosen as targets for their regional climate characteristics. Following this, an extraseasonal (one season in advance) regression prediction model for regionally averaged summer rainfall was constructed by using these three climate factors and a 3-month lead-time forecast of summer rainfall, undertaken by an atmospheric general circulation model (GCM) forced by observed SSTs, as predictors region by re...