# Presentation: 097225

## Intra-seasonal Variability of Mesoscale Convective Systems over the Indo-Pacific Region using TRMM Measurements

**Figure 2. Pentad time series of the MJO indices in the Indo-Pacific during December-January-February. Negative values on the Y-axis indicate active and positive values represent passive phase of MJO.**

**Intra-seasonal Variability of Mesoscale Convective Systems ****over the Indo-Pacific Region using TRMM Measurements**

**INTRODUCTION**
- The overall objective of the study is to diagnose the intra-seasonal variability of MCSs in the Indo-Pacific region, originated by the MJO, and its relation to climate prediction. The hypothesis adopted for this study is the MJO affects the organization, strength, intensity, and frequency of precipitation features.
- The study comprises the Indo-Pacific between 26oN to 26oS latitude and 50oE to 180oE longitude. TRMM data from December to February of 2001 through 2007 is selected for the study.
**DATA AND METHODS**
- The precipitation features used in this study is from TRMM algorithm 2A25. Primarily two analytical techniques- geographic information systems and kernel density distribution estimator are used for identifying ‘hot spots’ of MCS (ellipses in map).
- Six pentad MJO indices are downloaded from the National Weather Service’s Climate Prediction Center website. The indices are within the Indo-Pacific domain, centered at 70oE (Index 10), 80oE (Index 1), 100oE (Index 2), 120oE (Index 3), 140oE (Index 4) and 160oE (Index 5). Composites were constructed with the 5 most negative index values (70 neg, 80 neg, 100 neg, 120 neg, 140 neg and 160 neg) and 5 most positive index values (70 pos, 80 pos, 100 pos, 120 pos, 140 pos and 160 pos) for every month. Negative values indicate the convective phase of the MJO.

- ●There  are fewer MCS observed over the ocean during  positive MJO Januaries than for the negative
- ●The percentage of MCS observed over ocean increases from 120o east to 140o east though the west Pacific Ocean.
- ●Therefore, the development of MCSs increases over the ocean as MJO propagates eastward through the maritime continent

**Figure 1. Percentage of MCSs observed over ocean in January during phases of the MJO. Solid line denotes five pentads when the MJO index was most negative (active). Dashed line represents five pentads when the MJO index was most positive (passive phase). X-axis shows longitude and corresponding MJO indices are in parenthesis**

-  The intra-seasonal variability of MJO is higher during December–January–February
- The MJO index was most positive during January 2004 throughout the Indo-Pacific region, but especially in  the west Pacific region during January of 2004.
- The MJO index was observed negative (active) over the eastern Indian Ocean during January of 2002.

- 		**Ahmed Salahuddin**** ****	****	****	****Scott Curtis**
- 		Atmospheric Science Laboratory		Atmospheric Science Laboratory
- 		Coastal Resources Management 		Department of Geography
- 		East Carolina University 			East Carolina University
- 		Greenville, NC 27858 			Greenville, NC 27858
-    	 	Email: as0812@ecu.edu			Email: curtisw@ecu.edu

**Acknowledgement**: This study is funded by the Precipitation Measurement Mission NASA grant no. NN04GB35G.

***3******rd****** International TRMM Science Conference***
***4-8 February 2008, Los Vegas, Nevada, USA.***

**Figure 3. Pentad time series of the MJO indices during Januaries. Negative values on the Y-axis indicate active and positive values represent passive phase of MJO. **

**Figure 5. January MJO in relation to MCS, intensity proxies, volumetric rain, zonal wind**

**CONCLUSIONS**
**● ****There  are fewer MCS observed over the ocean during  positive MJO Januaries than for the negative**
**● ****The MJO index was most positive during January 2004 throughout the Indo-Pacific region**
**  ****The large number of MCSs count in January 2002, when the MJO index was negative (active) may be a precursor to the 2002-03 El Nino**
**  ****Increase in storm intensity as the MJO moves eastward from 120****o**** E to 140****o**** E**
**  ****Winds become more westerly with MJO activity as it moves eastward between latitudes 100****o**** E and 140****o****E.**
**  ****MCS density is evidently higher off the Indonesian coast when the MJO is in the eastern Indian Ocean but MCSs begin to populate the western Pacific region as the MJO moves eastward. The interesting feature consistent in all maps is that the major hot spots and MJO densities are primarily over the East Indian Ocean and Java Sea**

**Chuntao Liu**
- Department of Meteorology
- University of Utah
- Salt Lake City, UT 84112
- Email: liuct@met.utah.edu

- (a)

**Figure 4. Kernel density distribution differences and hotspots for boreal winter, December-Januray-February. Density difference (color) between five most negative and five most positive indices are presented below. The graduation of the colors denotes counts in intervals of one from red (positive) to green (negative). The ellipses represent hot spots for the negative (active) phase of MJO.**

- ● **During the active MJO composite MCS hot spots are predominantly located in the East Indian Ocean and in the MC but less frequent in the west Pacific Ocean.**
** ****A cluster of MCS points are seen in the west Pacific Ocean centered at 146****o**** East and 8****o**** South off the coast of Papua New Guinea **
** ****Active MJO composites and hot spots are largely located at the same location as 70****o****  and 80****o****  also another hot spot is found in the west Pacific Ocean **
** ****The MJO centered at 120****o**** East suggests that the positive density differences and hot spots have moved towards the east and are predominantly positioned over the Flores Sea.**
** ****The MCS density increases in the West Pacific and decreases in the Indian Ocean**
** ****When the active MJO is centered at 160****o**** East the densities and hot spots are shifted further to the east centered at 155****o**** East and 5****o**** South in the western Pacific Ocean**
**MCS density is evidently higher off the Indonesian coast when the MJO is in the eastern Indian Ocean but MCSs begin to populate the western Pacific region as the MJO moves eastward. **

**70°E**

**80°E**

**100°E**

**120°E**

**140°E**

**160°E**

**70****o**** E**

**80****o**** E**

**100****o**** E**

**120****o**** E**

**140****o**** E**

**160****o**** E**

- Ocean

- Land

- Ocean

- Ocean

- Ocean

- Ocean

- Ocean

- Ocean

- Ocean

- Ocean

- Land

- Land

- Ocean

- Ocean

- Ocean

- Land

- Land

- Land

- Land

- Land

- Land

*►**When the MJO is in the convective phase...*
-  the number of MCS increase over ocean as compared to the dry phase (highest correlation),
-  the intensity of the storms increases over land.
- ●The majority of the MCSs fall within -0.5 and +0.5 range of MJO.

*►**When the MJO is in the convective phase...*
-  the number of MCS increases.

- ►*When the MJO is in the convective phase...*
-  The median volumetric rainfall increases
-  The number of MCSs increases
-  The convective intensity increases (highest correlation)
-  The zonal wind becomes more westerly

*►**When the MJO is in the convective phase...*
-  the median volumetric rainfall increases over ocean
-  the convective intensity increases over ocean (highest correlation)
-  the zonal wind is more westerly over ocean
-  the median rainfall increases over land (highest correlation)
-  the convective intensity increases over land

*►**When the MJO is in the convective phase...*
- ●the median volumetric rainfall increases over ocean (highest correlation)
- ●the convective intensity increases over ocean (highest correlation)
- ●the zonal wind is more westerly over ocean
- ●the median volumetric rainfall increases over land
- ● the number of MCSs decreases over land
- ● the convective intensity increases over land

***►****When the MJO is in the convective phase...*
- ● the median volumetric rainfall increases over land
- ● the number of MCSs decreases over land
- ● the convective intensity decreases over land