Development of Synoptic Analogue Model for Quantitative Precipitation Forecast over Cauvery basin, India

Abstract

Daily Average Areal Precipitation (AAP) data of South West Monsoon Season for 2012 to 2020 in respect of sub-basins of Cauvery river basin were collected alongwith synoptic systems causing rainfall in the sub-basins. Five synoptic systems namely Depression/Deep Depression, low/well marked low(WML) pressure area, Upper air cyclonic circulations(UAC), off-shore trough(OST)/OST with embedded cyclonic circulations, east-west shear zone  are considered in the study. Rainfall(AAP) caused by these systems considered are 11-25mm, 26-50mm, 51-100mm and > 100mm. Number of days for which these systems caused rainfall under each range was computed. The rainfall range with highest frequency for the particular system is taken as Synoptic Analogue Model. OST/OST with embedded cyclonic circulation has contributed significantly to rainfall in all the sub-basins. Depression/Deep Depression over Rayalaseema, Tamil Nadu and Pondicherry, South Interior Karnataka or North Interior Karnataka provides > 50mm rainfall in Harangi basin. Depression/Deep Depression over Rayalaseema, Tamil Nadu and Pondicherry, South Interior Karnataka or North Interior Karnataka provides > 50mm rainfall in Harangi basin. Low/Well Marked Low over Telangana provides > 50mm rainfall in Hemavathy basin. Upper Air Cyclonic circulation(UAC) over Rayalaseema provides > 50mm rainfall in Kabini basin. UAC over Rayalaseema, South East Bay of Bengal or West Central Bay of Bengal off Coastal Andhra Pradesh leads to >100 mm rain in Harangi. UAC over Coastal Karnataka and North Interior Karnataka or OST from Konkan Goa/Maharashtra to Karnataka leads to >100 mm rain in Upper Vaigai.

Key words- Aerial Average Precipitation, QPF, Cauvery river basin, Synoptic Analogue Model