An analysis of forecast data based on three climate models suggests the country will have a normal monsoon in July — 3 millimetres above the 1996-2013 average
Northern and eastern India would likely witness a below-average monsoon in July while Peninsular India will mostly see above average rainfall in various states and meteorological subdivisions, according to an analysis. The monsoon is expected to be 3 millimetres above the 1996-2013 average.
The analysis — carried out by Akshay Deoras, climate scientist at the University of Reading, the United Kingdom — took stock of three climate models (UK Meteorological Office, European Centre for Medium-Range Weather Forecasts and National Centers for Environmental Prediction) and combined them to get mean values.
Down To Earth has accessed the raw data and quantified it.
Analysis: Akshay Deoras; Graphic: Pulaha Roy
Unlike administrative boundaries like states and districts, meteorological subdivisions are demarcated after considering their similarity in climatic patterns. While Mumbai comes under Maharashtra, the region’s climate is similar to that of the Konkan coast (as shown in the map).
El Nino phenomenon is expected to influence the rainfall this monsoon. The United States’ National Oceanic and Atmospheric Administration (NOAA) has already declared an El Nino on June 8, 2023, but the India Meteorological Department (IMD) has not declared it yet.
India usually gets below-average rainfall during El Nino years. So, the question remains on its effect on the monsoon this time, even as climate models are predicting a normal July monsoon?
“The El Nino effect can’t disappear overnight and there are no reasons why its effect in July would be lesser than previously predicted. The focus needs to be on the dry signal over parts of the monsoon core zone since that is consistent with the known impact of El Nino,” Deoras said.
The core monsoon zone is a region in India that stretches from Gujarat in the west to West Bengal in the east. IMD demarcates it as an agricultural region where cropping is mostly rainfed.
But will the July monsoon in India be actually normal or is there any bias projection by the climate models?
“There was a similar forecast for June 2023, but Kerala received large deficient rainfall whereas coastal Karnataka has received deficient rainfall so far. The entire west coast where above average rainfall was simulated has received below average rainfall, so we need to be cautious about such wet biases in models,” Deoras added as a word of caution.
While the scientist pointed out how climate modeling is not precise, he also added how climate researchers are always looking at large-scale patterns or signals rather than the final outcome of forecast data. A case in point would be the forecast on the monsoon core zone which he pointed out.
“The climate models from these three particular centers outperform others given their superior performance over India,” Deoras said.
In June, while the three climate models had forecasted above average rainfall in Kerala and coastal Karnataka. Kerala and coastal Karnataka received large deficient to deficient rainfall as of June 26, 2023, according to IMD.
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