Study of Intra Annual and Intra Seasonal Variations of Indian Summer Monsoon during ARMEX Period

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1 Study of Intra Annual and Intra Seasonal Variations of Indian Summer Monsoon during ARMEX Period Bhanu Kumar, O.S.R.U., S.Ramalingeswara Rao and K.Muni Krishna Dept. of Meteorology & Oceanography Andhra University Visakhapatnam

Determination of onset of SW monsoon over Kerala using pentad NOAA OLR data Generally the onset dates over Kerala varied from 11 th May to 18 th June 25 Year Mean NOAA OLR for the 7 pentads

2 Determination of onset of SW monsoon over Kerala using pentad NOAA OLR data Generally the onset dates over Kerala varied from 11 th May to 18 th June 25 Year Mean NOAA OLR for the 7 pentads (13 th May, 18 th May, 23 rd May, 28 th May, 2 nd June, 7 th June and 12 th June). 25-Years mean 7 pentads from 13 May 12 June OLR minima is centered over Kerala (210W/m²) and Barma (190 W/m²)

1 st Pentad of June 2002 2June02 pentad minus 25-Years mean 7 Pentads

minus 25-Years mean 7 Pentads surrogates signal of date of onset over

3 1 st Pentad of June June02 pentad minus 25-Years mean 7 Pentads indicates no signal of Onset 2 nd Pentad of June June02 pentad minus 25-Years mean 7 Pentads surrogates signal of date of onset over Kerala. IMD declared onset date 11th June 2002, which is in this pentad.

minus 25-Years mean 7 Pentads surrogates signal of

4 Figure 12June03 pentad minus 25-Years mean 7 Pentads indicates no signal of Onset Figure 17June03 pentad minus 25-Years mean 7 Pentads surrogates signal of date of onset over Kerala. IMD declared onset date 8th June 2003

25-Years mean 7 Pentads surrogates signal of date of onset

5 Figure 13May04 pentad minus 25-Years mean 7 Pentads indicates no signal of Onset Figure 28May04 pentad minus 25-Years mean 7 Pentads surrogates signal of date of onset over Kerala. IMD declared onset date 18th May 2004, which is in this pentad.

Pentads surrogates signal of date of onset over Kerala.

6 28thMay05 pentad minus 25-Years mean 7 Pentads indicates no signal of Onset 2June05 pentad minus 25-Years mean 7 Pentads surrogates signal of date of onset over Kerala. IMD declared onset date 5th June 2005, which is in this pentad.

7 Examined the day oscillations for the region N and E.

Time-longitude cross-section of NOAA OLR - 2002 (5 day running mean, averaged 0 N 20 N) The probabilities of getting rain for 180, 220 and 240 w/m 2 are 0.9, 0.8 and 0.

8 Time-longitude cross-section of NOAA OLR (5 day running mean, averaged 0 N 20 N) The probabilities of getting rain for 180, 220 and 240 w/m 2 are 0.9, 0.8 and 0.7 respectively The active phases of ISOs identified over the ARMEX region were a. 20 day during 3 rd June to 24 th June b. 36 days during 28 th July to 5 th September.

9 Coastal Stations (Karwar, Vengurla, Honnavar) IMD rainfall during active phase of ISO These three stations received considerably good amount of rainfall during the above two active phases of ISOs namely a. 20 day 3 rd June to 24 th June b. 35 day during 20 th July to 5the September

Time-longitude cross-section of NOAA OLR - 2003 (5 day running mean, averaged 0 N 20 N) The active

10 Time-longitude cross-section of NOAA OLR (5 day running mean, averaged 0 N 20 N) The active phases of ISOs identified over the ARMEX region was 60 day ISO is in active phase during 8 th June to 8 th Aug.

11 Coastal Stations (Karwar, Vengurla, Honnavar) IMD rainfall during active phase of ISO Rainfall events were identified during active phases of ISOs

Time-longitude cross-section of NOAA OLR - 2004 (5 day running mean, averaged 0 N 20 N) The active phases of ISOs

12 Time-longitude cross-section of NOAA OLR (5 day running mean, averaged 0 N 20 N) The active phases of ISOs identified over the ARMEX region were a. 11 day during 5 th June to 16 th June b. 51 days during 28 th June to 20 th August.

Time-longitude cross-section of NOAA OLR - 2005 (5 day running mean, averaged 0 N 20 N) The active phases of ISOs

13 Time-longitude cross-section of NOAA OLR (5 day running mean, averaged 0 N 20 N) The active phases of ISOs identified over the ARMEX region were a. 54 days during 16 th June to 10 th Aug. b. 30 days during 25 th Aug. to 25 th Sept.

14 Validation of satellite rainfall and OLR data with IMD rain gauge Karwar station June September (2002) On validating rain gauge data with different satellite data sets it is found that 3B42 and 3B42RT are better than OLR data set over Karwar in the year 2002

15 Validation of satellite rainfall and OLR data with IMD rain gauge Honnavar station June September (2002) On validating rain gauge data with the satellite rainfall data sets, it is found that all the products are near similar

16 Validation of satellite rainfall and OLR data with IMD rain gauge Vengurla station June September (2002) On validating rain gauge data with different satellite data sets it is found that OLR was better than 3B42 and 3B42RT data set over Vengural in the year 2002

17 Validation of satellite rainfall and OLR data with IMD rain gauge Vijaydurg station June September (2002) On validating rain gauge data with different satellite data sets it is found that OLR and 3B42RT are better than 3B42 data set over Vijaydurg the year 2002

18 Validation of satellite rainfall and OLR data with IMD rain gauge Karwar station June September (2003) On validating rain gauge data with different satellite data sets it is found that 3B42 and 3B42RT are better than OLR data set over Karwar in the year 2003

19 Validation of satellite rainfall and OLR data with IMD rain gauge Honnavar station June September (2003) On validating rain gauge data with different satellite data sets it is found that 3B42 and 3B42RT are better than OLR data set over Honovar in the year 2003

20 Validation of satellite rainfall and OLR data with IMD rain gauge Vengurla station June September (2003) On validating rain gauge data with different satellite data sets it is found that 3B42 and 3B42RT are better than OLR data set over Vengural in the year 2003

21 Validation of satellite rainfall and OLR data with IMD rain gauge Vijaydurg station June September (2003) On validating rain gauge data with different satellite data sets it is found that all the products are near similar over Vijaydurg the year 2003

22 Conclusions Onset date can be studied using pentad OLR. Active phases of day oscillation from daily OLR cause good rain over ARMEX study region. On validating the OLR with rainfall, statistically significant inverse relationship identified for the study period. However NOAA OLR dataset is not able to show the extreme cases of rainfall. This is true because OLR is exclusively depends upon cloud top temperature.

23 Finally, daily 3B42 and 3B42RT merged precipitation dataset was validated with the rainfall over west coast of India. This validation is really better than 3B42 and NOAA OLR datasets with the rainfall.

Atmospheric Moisture during Monsoon 2002 ARMEX Phase I

Atmospheric Moisture during Monsoon 2002 ARMEX Phase I Anu Simon, K. Mohankumar, Aype Thomas and C.K. Rajan Department of Atmospheric Sciences Cochin University of Science and Technology Cochin-682 016