Published on: June 2, 2022

PRE-MONSOON RAINFALL

PRE-MONSOON RAINFALL

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Karlskrona As the southwest monsoon made its entry into Karnataka, the Karnataka State Disaster Management Authority’s (KSDMA) data revealed that the pre-monsoon showers were 105% above normal.

Highlights of the data revealed by KSDMA

  • Marked by high-intensity rainfall in short periods of time for the most part, the pre-monsoon rain had wreaked havoc in many parts of the State, causing flooding and loss of lives, infrastructure and standing crops.
  • The KSDMA data show that the departure from normal (1960-2010) for rainfall received between March 1 and May 31 this year is far higher than that in recent years; in 2021, the pre-monsoon rainfall was 44% above normal, and in 2020, 3% above normal rainfall.
  • The average temperature has shown an increasing trend, whereas the RH had a decreasing trend in most regions
  • Thunderstorms and lighting events have occurred more frequently in recent years, while the variability of south-west monsoon rainfall has increased significantly since 1960. Several districts are seeing an increase in prolonged dry periods with low or no rainfall or intermittent with short, intense spells of rainfall.
  • “The analysis of the temperature and relative humidity data series for 2002 to 2020 shows an increasing trend in average temperature, while the relative humidity showed a decreasing trend. The State has experienced drought for 15 years in the last two decades. Karnataka also experienced severe floods, and the last four years have been consecutive flood years for the State. The recurrence of droughts and changing rainfall patterns are detrimental to the surface and groundwater recharge and pose a significant challenge to water security

237 mm rainfall

  • The State as a whole received 237 mm rainfall for this period, which, is the highest in 51 years (since 1971). As many as 27 districts recorded large excess rainfall, three excess rainfall, and one district recorded normal rainfall (Bidar).
  • Karnataka’s normal annual rainfall is 1,153 mm; the southwest monsoon brings in 74%, 16% is received during the northeast monsoon and 10% during pre-monsoon.
  • As the southwest monsoon arrives, having recorded large departures from normal in recent years
  • The variability of southwest monsoon rainfall has also increased significantly since 1960. “Several districts are seeing an increase in prolonged dry periods with low or no rainfall or intermittent with short, intense spells of rainfall.
  • The study of long-term climate data series for the last 58 years shows that there has been a considerable shift in rainfall patterns over Karnataka.
  • The quantum, intensity and distribution of rainfall have varied across the regions in the State from the 1960-1990 period (P1) to 1991-2017 (P2)

Highs and lows

  • Kodagu, Kalaburagi, Yadgir, Dakshina Kannada and Uttara Kannada districts show a reduction in annual rainfall, while and an increase in rainfall has been observed over Shivamogga and Hassan districts from P1 to P2.
  • A significant increase in the rainfall is observed in Kolar for the pre-monsoon season, and a decreasing trend is observed in northeast monsoon for the north interior Karnataka (NIK) region.

Reasons for changing climatic conditions in the state

  • The main reason for these extreme events can be attributed to the active phase of monsoon season coupled with La Nina and positive / Neutral Indian Ocean Dipole (IDL) conditions over the State
  • At the same time, there is a reduction in the amount of annual rainfall and a marginal increase in the number of rainy days in NIK and coastal regions,