Western Nepal has experienced consecutive and worsening winter drought conditions since 2000, culminating in a severe drought episode during 2008/09. In this study, the meteorological conditions and a historical perspective of the winter droughts in western Nepal were analyzed using instrumental records, satellite observations, and climate model simulations. Meteorological diagnosis using atmospheric reanalysis revealed that 1) winter drought in western Nepal is linked to the Arctic Oscillation and its decadal variability, which initiates a tropospheric short-wave train across Eurasia and South Asia; and that 2) the persistent warming of the Indian Ocean likely contributes to the suppression of rainfall through enhanced local Hadley circulation. Simulations from the phase 5 of the Coupled Model Intercomparison Project (CMIP5) sets of historical single-forcing experiments indicated that the increased loading of anthropogenic aerosols is also a compounding factor in the precipitation decline during the later decades. It is therefore conceivable that the recent spells of decadal drought in Nepal are symptomatic of both natural variability and anthropogenic influences. Given the observations that winter precipitation has declined to near zero while groundwater has hardly been replenished, appropriate management of western Nepal's water resources is both critical and necessary.

During 13-17 June 2013, heavy rainfall occurred in the northern Indian state of Uttarakhand and led to one of the worst floods in history and massive landslides, resulting in more than 5,000 casualties and a huge loss of property. In this study, meteorological and climatic conditions leading up to this rainfall event in 2013 and similar cases were analyzed for the period of 1979-2012. Attribution analysis was performed to identify the natural and anthropogenic influences on the climate anomalies using the historical single-forcing experiments in the Coupled Model Intercomparison Project Phase 5 (CMIP5). In addition, regional modeling experiments were carried out to quantify the role of the long-term climate trends in affecting the rainfall magnitude of the June 2013 event. It was found that (a) northern India has experienced increasingly large rainfall in June since the late 1980s, (b) the increase in rainfall appears to be associated with a tendency in the upper troposphere towards amplified short waves, and (c) the phasing of such amplified short waves is tied with increased greenhouse gases (GHGs) and aerosols. In addition, a regional modeling diagnosis attributed 60-90% of rainfall amounts in the June 2013 event to post-1980 climate trends.

The analysis of precipitation trends for Vietnam revealed that early-monsoon precipitation has increased over the past three decades but to varying degrees over the northern, central and southern portions of the country. Upon investigation, it was found that the change in earlymonsoon precipitation is associated with changes in the low-level cyclonic airflow over the South China Sea and Indochina that is embedded in the large-scale atmospheric circulation associated with a "La Niña-like" anomalous Sea Surface Temperature (SST) pattern with warming in the western Pacific and Indian Oceans and cooling in the eastern Pacific. The Community Climate System Model version 4 (CCSM4) was subsequently used for an attribution analysis. Over northern Vietnam an early-monsoon increase in precipitation is attributed to changes in both greenhouse gases and natural forcing. For central Vietnam, the observed increase in early-monsoon precipitation is reproduced by the simulation forced with greenhouse gases. However, over southern Vietnam the early-monsoon precipitation increase is less definitive where aerosols were seen to be preponderant but natural forcing through the role of the Interdecadal Pacific Oscillation (IPO) may well be a factor that is not resolved by CCSM4. Increased early-monsoonal precipitation over the coastal lowland and deltas has the potential to amplify economic and human losses.