Evaluation of winter mean precipitation over North India in CMIP6 models

Evaluation of winter mean precipitation over North India in CMIP6 models

Nischal Sharma¹, Raju Attada¹*, A. R. Dandi², R. K. Kunchala³, Anant Parekh², J. S. Chowdary²

¹Department of Earth and Environmental Sciences - Indian Institute of Science Education and Research Mohali, Punjab – 140306

² Indian Institute of Tropical Meteorology, Pune, India

³Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, India

*E-mail of corresponding author: rajuattada@iisermohali.ac.in

 

Abstract

North India receives a significant proportion of annual precipitation during winter (December to February) through mid-latitudinal cyclonic perturbations (Western Disturbances) embedded in subtropical westerly jet stream. This region accounts for a paucity of available in-situ observations owing to complex topography which underpins the necessity of other non-conventional tools for precipitation estimation. Global Climate Models are an effective tool to investigate global monsoon systems and are being extensively used to better understand spatio-temporal characteristics of precipitation. In the present study, north Indian winter precipitation (NIWP) and its variability has been characterized in 30 CMIP6 historical simulations (1979-2014) and compared with IMD gridded data observations. Normalized biases in different models relative to observations have been used to categorize models as wet (11), dry (8) and normal (11) models and further composite analysis has been conducted for these model categories. Our findings suggest that all the models show highest precipitation orientation along the western Himalayan belt, with the normal model category showcasing quite similar results to observations. Wet models show highest variability, errors and positive bias over the region while dry models exhibit least variability and negative bias. Majority of the models show an overall good correlation with observations. The representation of winter mean dynamical and circulation patterns has been carried out using composite analysis of three model categories relative to observations. The composite analysis reveals an intensified jet in both wet and dry model categories, with a southward shift of the jet position in wet models.  Detailed results will be discussed.

Keywords: Global climate models, CMIP6, winter precipitation