1. Simultaneous Presence of 30 and 60 days ISO modes in Indian Summer Monsoon Observed from TRMM Merged Rainfall Data M S Narayanan National Atmospheric Research Laboratory, Gadanki Shivani Shah, C.M. Kishtawal, V. Sathiyamoorthy Meteorology & Oceanography Group (MOG), SAC M. Rajeevan India Meteorological Department, Pune R. H. Kriplani Indian Institute of Tropical Meteorology, Pune 3 rd ISRO – CNES joint Workshop on Megha Tropiques 19 th October 2005

2.  Instantaneous Rainfall – over oceans and Land 19, 22, 37, 85 GHz  Less utility – because of poor temporal sampling (3-4 per day)  Rainfall highly variable in space and time Megha – Tropiques – MADRAS MW sensors

3. Products from TRMM Project – (Predecessor to Megha Tropiques)  24 hr accumulated daily rainfall at 1° x 1° produced in combination with IR / Vis data from Geostationary satellite - 3B42 version 5 (global) from 1998 to 2003 (now version 6)  3B43 monthly rainfall

4. Merged Rainfall from MW (TRMM), Meteosat (IR) & Gauge Rain-rate : CTT Threshold, Texture based C/S Separation Rain-rate : MW Emission/ Scattering algorithms Tuning of Vis/IR Rain algorithm Using MW and gauge rain Tuning Parameters for Merger Rainfall Observations from Gauge Network TRMMTRMM Meteosat Merged  Such data set for TRMM available from 1998 to date  Also GPCP 1DD from 1996 to date

5. OBJECTIVES  Validation of daily TRMM merged rainfall over Indian land mass, and  Studying Monsoon ISO oscillations in rainfall

6. 1 2 3 333 grids  TRMM data for 1998 to 2003

8. 19982002 2001 Frequency Distribution

9. 1998 2002 2001 199820012002 (b) : Grids in which IMD analysis shows 1 mm or more rain and 3B42 has no rain (c) : Average percentage of days (all six years – monsoon months) in which 3B42 shows no rain, for cases when IMD shows 1 mm or more rain (a) : Grids in which 3B42 shows 1 mm or more rain and IMD analysis shows no rain

10. 2001 y = 0.1996x + 5.2187 CC = 0.33 y = 0.2754 x + 4.2841 CC = 0.54 IMD (a) Individual days (b) Seasonal mean

11. 15 July 2001 - IMD15 July 2001 – 3B42Difference – 15 July 2001 July 2001 Seasonal 2001 23 rd July 2001

12. Seasonal variance in daily rainfall in 3B42 and IMD for 2001 and 2002

13. 3  x 3  5  x 5  1  x 1  Box1 -2001 y = 0.5355x + 1.5158 CC = 0.63 y = 0.7442x + 0.4822 CC = 0.83 y = 0.7632x + 0.3377 CC = 0.87

14. MINICOY PORTBLAIR Comparison over the oceans ( 5 day running mean) – Minicoy and Port Blair y = 0.6907x + 2.2288 cc = 0.69 y = 0.4648x + 3.3735 cc = 0.72

15. For studying Intra Seasonal Periodicities

16. IMD - daily3B42 - daily IMD – 5 day running mean3B42 – 5 day running mean Time series of all India daily and running mean pentad rainfall 2001

17. YearObserved3B42 199890.387.6 199984.078.4 200080.876.1 200180.777.5 200271.263.6 200389.887.4 All India Seasonal Rainfall (cm) YearJuneJulyAugustSeptember IMD3B42IMD3B42IMD3B42IMD3B42 1998227158328278288245213193 1999211152317251245211187170 2000231190294243261195141133 2001257224317239234184127 200220617816712626923914093 2003218174324302235232145166 Monthly All India average rainfall

18. 1 June – 30 September Time series of IMD and 3B42 rain at all India scale for 2003 Rain Rate

19. IMD – All India - 2003TRMM – All India - 2003 2 4 8 16 32 64 ModeMode 2 4 8 16 32 64 ModeMode Wavelet showing various modes in IMD and 3B42 rainfall

20. PowerPower Year PowerPower Contribution of 10 – 20 day mode Contribution of 30 - 60 day mode Contribution of 10 – 20 day and 30 – 60 day modes in different years

21. IMD – All India - 2003TRMM – All India - 2003 2 4 8 16 32 64 ModeMode 2 4 8 16 32 64 ModeMode Wavelet showing various modes in IMD and 3B42 rainfall

22. IMD – All India - 2003TRMM – All India - 2003 Significance of the various periodicities at 95 % confidence 2 64 16 32 8 4 Global Wavelet Variance (mm 2 ) 2 64 16 32 8 4 Global Wavelet Variance (mm 2 )

23. 1998

24. 2001

25. 2003

26. Rainfall over the oceans

27. Buoy TMI DS 3 2000 Bay of Bengal 2 4 8 16 32 64 2 4 8 16 32 64 Period (Day) Oceanic Winds

28. Buoy TMI DS 1 1998 Arabian Sea 2 4 8 16 32 64 2 4 8 16 32 64 Period (Day) SST

29. Water Vapour over the oceans

30. Global Wavelet Variance (m/s 2 )

31. Hovmollor plot showing propagation characteristics of the ~ 30 and ~ 60 day modes : for rainfall and NCEP 850 mb winds for the year 2001

32. 2003 : No clear propagation for wind or rainfall 1998 : Northward for 30 day for both wind and rainfall Overall : Inconclusive – but both parameters show similar trend in both modes

33. GPCP 3B42 1° x 1° deg Version -5 3B42 0.25° x 0.25° deg Version - 6 IMD Mean July - 1998

34. Conclusions & Future Work * 3B42 limitation in picking variability & high rainfall * Differences in Specific boxes IR estimates also to be improved for merged rainfall Comparison with version 6 and GPCP 1DD * Useful for studying ISO / IAV * Simultaneous ~ 30 and ~ 60 days modes seen in some years * Linkage with Interannual Variations