J. Ocean Univ. China (Oceanic and Coastal Sea Research) DOI 10.1007/s11802-013-2168-y ISSN 1672-5182, 2013 12 (2): 253-259 http://www.ouc.edu.cn/xbywb/ E-mail:xbywb@ouc.edu.cn The Distribution and Variability of Simulated Chlorophyll Concentration over the Tropical Indian Ocean from Five CMIP5 Models LIU Lin * , FENG Lin, YU Weidong, WANG Huiwu, LIU Yanliang, and SUN Shuangwen Center for Ocean and Climate Research, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, P. R. China (Received October 9, 2012; revised November 12, 2012; accepted February 22, 2013) © Ocean University of China, Science Press and Springer-Verlag Berlin Heidelberg 2013 Abstract Performances of 5 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating the chloro- phyll concentration over the tropical Indian Ocean are evaluated. Results show that these models are able to capture the dominant spatial distribution of observed chlorophyll concentration and reproduce the maximum chlorophyll concentration over the western part of the Arabian Sea, around the tip of the Indian subcontinent, and in the southeast tropical Indian Ocean. The seasonal evolution of chlorophyll concentration over these regions is also reproduced with significant amplitude diversity among models. All of 5 mod- els is able to simulate the interannual variability of chlorophyll concentration. The maximum interannual variation occurs at the same regions where the maximum climatological chlorophyll concentration is located. Further analysis also reveals that the Indian Ocean Dipole events have great impact on chlorophyll concentration in the tropical Indian Ocean. In the general successful simulation of chlorophyll concentration, most of the CMIP5 models present higher than normal chlorophyll concentration in the eastern equatorial Indian Ocean. Key words Indian Ocean; chlorophyll concentration; climatology; seasonal variability; interannual variability 1 Introduction Primary production is an important part of the carbon cycle in the Earth system. However, it is difficult to quan- tify primary production at this scale because of the variety of habitats and the impact of weather conditions on the earth. Oceans occupy over 2/3 of the Earth’s surface and play an important role in climate (Li et al., 2006; Wang et al., 2009, 2012; Wang and Wang, 2012). In the ocean, the physical, chemical, and biological processes are closely linked (Tang et al., 2002; Xiu and Liu, 2006), which greatly influences ocean dynamics and air-sea interaction. Marine primary production can be assessed directly using field flux measurements. However, it can be costly to carry out these measurements. As an alternative, sea surface chlorophyll is often used in models of photosynthesis to study the marine primary production because of its easy accessibility from the world ocean database. Examples include a number of chlorophyll studies in the tropical Indian Ocean (Tang et al., 2002; Dey and Singh, 2003; Vinayachandran et al., 2004; Susanto and Marra, 2005; Sarma, 2006; Lévy et al., 2007; Sarangi et al., 2008; Liu * Corresponding author. Tel: 0086-532-88961173 E-mail: liul@fio.org.cn et al., 2012; Li et al., 2012). Similar to the Pacific Ocean, the Indian Ocean pos- sesses strong interannual variability. The Indian Ocean Dipole (IOD) is a basin-scale ocean–atmosphere coupled mode in the interannual time scale, characterized by a zonal contrast of a positive and a negative sea surface temperature anomaly (SSTA) along the equatorial Indian Ocean and a zonal wind anomaly over the central equato- rial Indian Ocean (Saji et al., 1999; Webster et al., 1999; Hu and Liu, 2005; Yu et al., 2005; Sun et al., 2010; Liu et al., 2011). A number of studies show that the convection associated with IOD exert great impact on the climate variability in Africa, South Asia, East Asia, and other re- mote regions (Saji and Yamagata, 2003a, b; Ashok et al., 2004; Behera et al., 2005; Matthew et al., 2006; Wang et al., 2006). IOD events are a key to understand the un- derlying mechanisms responsible for climate change as well as biochemical processes in the tropical Indian Ocean. Sarma (2006) pointed out the close relationships between chlorophyll and SSTA, and between chlorophyll and sea surface height anomaly in the Arabian Sea during IOD events. Rahul Chand Reddy and Salvekar (2008) and Wiggert et al. (2009) demonstrated the close relationships between chlorophyll concentration in the southeast, tropi- cal Indian Ocean and IOD events respectively. Although many researches have focused on chlorophyll