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The first experiment studying the effect of irrigation on pre‐monsoon rainfall in India using a high‐resolution convection‐permitting model has been carried out. This study includes both short (3‐day) experiments and month‐long free‐running simulations, enabling investigation of the effect of irrigation on mesoscale circulations and associated rainfall. In the pre‐monsoon, it is found that irrigation increases rainfall in our simulations. Intriguingly, the rainfall increase found in the high‐resolution model mostly occurs on the mountains near the irrigation rather than over the irrigated region itself. This is because our applied irrigation is in low‐lying regions, and so it enhances the mountain‐valley flows leading to enhancement of diurnally driven orographic rainfall. Because Ganges basin irrigation occurs near mountains which already have some of the highest rainfall rates in the world, and which are subject to flash flooding and landslides, this has significant implications for hazards in mountainous regions during the pre‐monsoon and early monsoon period. [ABSTRACT FROM AUTHOR]

The Plant-Craig stochastic convection parameterization (version 2.0) is implemented in the Met Office Regional Ensemble Prediction System (MOGREPS-R) and is assessed in comparison with the standard convection scheme with a simple stochastic element only, from random parameter variation. A set of 34 ensemble forecasts, each with 24 members, is considered, over the month of July 2009. Deterministic and probabilistic measures of the precipitation forecasts are assessed. The Plant-Craig parameterization is found to improve probabilistic forecast measures, particularly the results for lower precipitation thresholds. The impact on deterministic forecasts at the grid scale is neutral, although the Plant-Craig scheme does deliver improvements when forecasts are made over larger areas. The improvements found are greater in conditions of relatively weak synoptic forcing, for which convective precipitation is likely to be less predictable. [ABSTRACT FROM AUTHOR]