Supplementary material to "Evaluation of tropospheric ozone and ozone precursors in simulations from the HTAPII and CCMI model intercomparisons – a focus on the Indian Subcontinent"

Abstract

India receives nearly 70% of its annual rainfall from the southwest monsoon, 5% during winter and 25% during pre and post monsoon seasons combined. During winter, most of the rainfall is in the northern part of India due to western disturbances (Yadav et al., 2010). Precipitation during winter is not included in this analysis. The spatial spread of precipitation is very less during the pre and post monsoon season. In this study we have considered precipitation rates during the monsoon season only. Earlier studies have shown that TRMM overestimates the rainfall over higher mean rainfall regimes against the gridded gauge-based data over India, except for the orographic regions of Western ghats on the western coast of India and the foothills of Himalayas (Prakash et al., 2015). Figure S1.b shows the magnitude of bias in model simulated precipitation rates with respect to TRMM data for the monsoon season. Models in general overestimate surface precipitation over this region. High biases are observed in the northeastern part of India. This can be attributed to the higher uncertainty in the satellite based precipitation estimates in the mountainous regions reported in several studies (Aghakouchak et al., 2012). The annual area average of surface precipitation as simulated by the models show a positive bias of 15-30 over land when compared to surface precipitation rates from TRMM. However, CCMI-UKCA shows a negative bias of-0.5 to-7.5 over central and southern part of India. Since, TRMM overestimates surface precipitation over this region, models must also overestimate surface precipitation over this region. S1.a) TRMM mean precipitation rates for June, July, August, September (JJAS), monsoon months, for the years 2008-2010 and Model simulated mean surface precipitation for JJAS for the year 2009.