Lok Sabha Question No. 1284 (UNSTARRED), answered on 2018-07-25
Subject: Average Rainfall
Ministry: EARTH SCIENCES
Asked by: SANJAY JAISWAL

## GOVERNMENT OF INDIA

## MINISTRY OF EARTH SCIENCES LOK SABHA

## UNSTARRED QUESTION No. 1284 TO BE ANSWERED ON MONDAY, JULY 25, 2018

## AVERAGE RAINFALL

## 1284.  DR. SANJAY JAISWAL:

Will the Minister of EARTH SCIENCES be pleased to state:

- (a) whether the average rainfall has decreased in the country;
- (b) if so, the details thereof and the reaction of the Government thereto; and
- (c) the strategies and means his Ministry is using to measure and predict the rainfall?

## ANSWER

## MINISTER FOR MINISTRY OF SCIENCE AND TECHNOLOGY AND MINISTRY OF EARTH SCIENCES (Dr. HARSH VARDHAN)

- (a) No Sir. The average rainfall of the country has not shown any significant decrease, considering the rainfall data for the period from 1901 to 2017.
- (b) By the analysis of past data of more than 100 years, it has been reported by  several  scientists  including  IMD  scientists  that  All  India  rainfall  has multi decadal/epochal variability and currently it is in dry epoch. Analyzing past 117 years (1901-2017) data, it has been found that the all India Southwest monsoon seasonal rainfall as well as annual rainfall has no significant increasing/decreasing trend. However, if the period 19512017 is considered, it has been found that all India SW monsoon as well as annual rainfall has significant decreasing trend. The reason behind is that the initial decade i.e. 1951-1960 was a wet epoch and there after dry epoch  has  started.  Whereas,  during  the  period  1901-2017,  initial  few decades were dry epochs, then wet epochs again followed by dry epoch and as a result there was no significant decreasing trend.
- (c) The  monsoon  related  forecasts  are  prepared  by  the  Climate  Prediction group and are issued from the office of Climate Research and Services, IMD Pune. The tentative schedule for issuing various operational forecasts    for  rainfall  from  this  centre  in  tabular  form  is  given  in Annexure-1.

IMD uses State of the art statistical models developed through in house research and development work for monsoon related forecasting work. During the period from 1988 to 2002, operational forecast for monsoon seasonal  rainfall  over  for  the  country  as  a  whole  was  based  on  16 parameter  power  regression  and  parametric  models.  During  2003  to 2006, the operational forecast was issued using the 8 and 10 parameter models based on power regression and probabilistic discriminant analysis  techniques.  From  2007  onwards,  a  new  Statistical  Ensemble Forecasting  System  (SEFS)  based  on  the  ensemble  technique  is  being used for seasonal rainfall forecast for the country as a whole. The use of ensemble forecasting system has resulted in bringing down the average absolute  forecast  error  to  5.95%  of  Long  Period  Average  (LPA)  as compared to its value of 8.56% of LPA prior to its implementation.

From  2017  onwards,  IMD  started  using  State  of  the  art  dynamical forecasting  system  along  with  statistical  models  for  the  generation  of operational  monsoon  forecasts.  This  model  was  developed  under  the first  phase  of  National  Monsoon  Mission  (NMM)  project  of  Ministry  of Earth  Sciences  (MoES)  with  the  objective  to  have  a  State  of  the  art dynamical  prediction  system  for  the  monsoon  rainfall  in  different  time scales. The advanced dynamical prediction systems are now being used for  Seasonal  prediction  (mainly  for  SW  monsoon  season  of  June  to September); Extended range weather prediction (for next 20 days) and Short and Medium range weather prediction (up to 10 days).

## Annexure-1

|   Sr.No | Forecast for                                                      | Region for which forecast issued                                                                     | Issued in   |
|---------|-------------------------------------------------------------------|------------------------------------------------------------------------------------------------------|-------------|
|       1 | SW Monsoon Season (June to September) Rainfall                    | Country as a whole                                                                                   | April       |
|       2 | SW Monsoon Season (June to September) Rainfall                    | Country as a whole                                                                                   | June        |
|       3 | South-West Monsoon Onset                                          | Kerala                                                                                               | May         |
|       4 | SW Monsoon Season (June to September) Rainfall                    | Four broad geographical regions: Northwest India, Northeast India, Central India and South Peninsula | June        |
|       5 | SW Monsoon Monthly Rainfall for July and August                   | Country as a whole                                                                                   | June        |
|       6 | SW Monsoon Second half of the Season (August- September) Rainfall | Country as a whole                                                                                   | July        |
|       7 | September Rainfall                                                | Country as a whole                                                                                   | August      |
|       8 | NE Monsoon Season (October to December) Rainfall                  | South Peninsula                                                                                      | September   |