Impacts of global warming on changes in the East Asian monsoon and the related river discharge in a global time-slice experiment

Abstract

Changes in the East Asian monsoon and the related river discharge under global warming conditions are investigated using 2 time-slice simulations of the IS92a scenario with a T106 atmospheric general circulation model (ECHAM4) for 1971 to 1980 and 2041 to 2050. Daily runoff and drainage calculated by the land-surface scheme are used as input to a hydrological model to diagnose changes in the Yangtze River and Zhujiang River discharges. In the future climate, the simulated annual cycle of precipitation over the southeastern coastal area of China is systematically shifted about 1 mo ahead compared with the present-day climate, and the rainy season starts 1 mo earlier for the Yangtze River Valley and North China. In line with the surface-warming distribution change, the East Asian summer monsoon (EAM) flow strengthens. This causes increased precipitation in North China. In winter, the subtropical part of the EAM flow strengthens and leads to a large increase in rainfall over the EAM region. The discharges of the Zhujiang and Yangtze rivers in the future climate decrease in the late summer and autumn, to which both increased evaporation and an early retreat of the monsoon rainfall contribute. In the early and mid-summer, the Yangtze River discharge increases, mainly due to the large increase in precipitation in the preceding months, which has been stored in the catchment. KEY WORDS: Global warning · East Asian monsoon · Time-slice experiment · River discharge Resale or republication not permitted without written consent of the publisherClim Res 24: [47][48][49][50][51][52][53][54][55][56][57] 2003 rently, 3 techniques are available to compensate for this problem:• dynamical downscaling via time-slice simulations with global high-resolution models; • dynamical downscaling using high-resolution regional models; • statistical downscaling. The advantages and limitations of these methods have been discussed in Cubasch et al. (1995), Lal et al. (1997), Rummukainen (1997) and IPCC (2001). In this study, we employ the time-slice simulation method (Bengtsson et al. 1995, Cubasch et al. 1996, Wilby & Wigley 1997, Déqué et al. 1998, Jones et al. 1998, May & Roeckner 2001, which uses a global atmosphere model with a horizontal resolution of 1.1°× 1.1°. Details of the model and the design of the time-slice experiments can be found in Section 2.The present-day interannual and interdecadal variability of the EAM have been extensively studied by many investigators (Ding 1991, Yasunari 1991, Lau 1992, Nitta & Hu 1996, Ji et al. 1997, Chen & Graf 1998, Bueh & Ji 1999a, Lu & Chan 1999, Samel et al. 1999, Kripalani & Kulkarni 2001. However, the EAM change under global warming conditions has hardly been investigated. Wang & Ye (1993) and Nitta & Hu (1996) found from observational data a pronounced warming trend in North China.Using observational data, Hulme et al. (1994) concluded that coinciding with warming in the last century, East Asian precipitation increased with a trend of 0.54% decade -1 , which is larger than...

Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950–2000

“…3 and 7). The strengthening of the EASM is consistent with analyses of coupled climate model simulations by Hu et al (2000) and Bueh et al (2003), who showed that increased future greenhouse gas concentrations intensify the EASM because of an enhanced land-ocean temperature gradient due to larger warming over land. In our experiments, near-surface summer temperatures over Asia increased under increasing greenhouse gases while the SSTs were fixed to climatological values, so that the land-ocean (surface) temperature gradient was enhanced, resulting in a stronger EASM.…”

Climate change impact on the hydrological balance of the Itaipu Basin

“…On an annual basis, the simulated runoff decreased by 0.3% in 2010–2040 and 2.5% in 2070–2100 with respect to the baseline period, corresponding to an expected monetary loss of 0.37 and 1.43 million US$ per month, respectively. However, on a seasonal scale the results indicated that climate change will affect the regional water regime by increasing spatial and temporal variability of water resources, as observed also in other regions (Bueh et al , 2003; Graves and Chang, 2007; Bae et al , 2008). In the present period, rainfall distribution in the study area presents a slight seasonality, where the drier periods occur in autumn–winter and wetter periods in spring–summer.…”

Observed trends of precipitation amount, frequency, and intensity in China, 1960–2000

“…[21] Previous studies based on climate model simulations projected that the Asian monsoons would weaken in winter and strengthen in summer under greenhouse gas -induced global warming due to the land-sea thermal contrast [Intergovernmental Panel on Climate Change, 2001;Bueh, 2003;Bueh et al, 2003]. However, some recent studies based on instrumental measurements did not support the model projections.…”