# Presentation: 498337

## Comprehensive study of 150 Tropical storms observed by TRMM-PR

**Comprehensive study of 150 Tropical storms observed by TRMM-PR**

**Direk Khajonrat and V. Chandrasekar**
**Colorado State University**

** ****The 3rd International TRMM Science Conference**
**4-8 February 2008, Las Vegas, NV.**

**Notes:**
Good morning ...My name is Direk Khajonrat,,,from Colorado State University. 
Today I am going to present our work on comprehensive study of 150 tropical
Storms observed by TRMM precipitation radar.

## Tropical Storm Data observed by TRMM-PR over 4 years

|         Year

    Storms | 2000 |  | 2002 |  | 2003 |  | 2004 |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | Number of storms | Number of profiles | Number of storms | Number of profiles | Number of storms | Number of profiles | Number of storms | Number of profiles |
| Hurricanes | 8 | 37632 | 4 | 53799 | 6 | 43774 | 8 | 36974 |
| Typhoons | 15 | 176215 | 12 | 172273 | 14 | 176251 | 21 | 286251 |
| Cyclones | 11 | 45754 | 17 | 70783 | 18 | 107686 | 14 | 67686 |

**Tropical Storm Data observed by TRMM-PR over 4 years**

** ****Total :  **
** ****150 tropical storms**
**  ****28 Hurricanes**
**  ****62 Typhoons**
**  ****60 Cyclones**

**Notes:**
Tropical storm data set that we used in our analysis was collected over 4 years by TRMM-PR. The data includes Hurricane over North Atlantic, Typhoon over North Western pacific and cyclones over South Indian Ocean, as shown in this figure. 
In total, we had 28 hurricanes, 62 Typhoons, 60 cyclones. 
I would like to note that by the time we submitted our abstract we analyzed data for 3 years which is 107 storms.  We were be able to finish one more year of analyzing data, and will be presenting today.
To our knowledge, We believe this is the biggest data set ever analyzed and hence we hope our study will enhance our understanding on characteristics of vertical profiles of tropical storm and their associated drop size distribution. 

This table shows detail of number of storm in each year, and also number of vertical profiles.

## Outline

-   - DSD gamma model and algorithm used to estimate its parameters
-   - RR-Nw and Do-RR relations
-   - Comparison  above relations with those existing in
-      literatures
** ****Vertical profile of reflectivity (VPR) of Tropical  storms**
-   - Classification of VPR using Self Organizing Map (SOM)
-   - Illustrate characteristic VPRs and their corresponding
-     DSD parameters  as well as rainfall rate.
-   - Estimated DSD map on the hurricane Katrina.

**Outline**

**Notes:**
This is the outline of the presentation.

In this study we generally focus on two aspects of tropical cyclones for each
 different regions as mention in previous slide.

First thing we look into is  Rain Drop Size Distribution or simply DSD, and how to estimate its governing parameters. 

And we compared the relation between DSD parameters  we estimated  and rainfall rate with those relation existing in literatures.

Another thing we look into is vertical profile of reflectivity (VPR) of the storms

and their corresponding DSD parameters

## Literature used for DSD

**Comparison**
- Sekhon and Srivastava (SS), 1971
-    Instrument : C-band Doppler radar (vertical pointing)
-              Data  : Continental thunder storms
- 2. Willis and Tattelman (WT), 1989
-     Instrument : Optical spectrometer system on aircraft
-                Data  : hurricanes and tropical storms

##  Model of Rain Drop Size Distribution (DSD)

- Normalized gamma model (Bringi and Chandrasekar, 2001 : Testud *et al*. 2001)

- Procedure developed by Chandrasekar et al. (2003) is used to estimated *N**w* and *D**o*

-  The key of the procedure is making use of  adjusted alpha coefficient in TRMM-PR
-    Rain profiling algorithm (Iguchi et al. 2000).

- and

- μ is shape parameter.
*D**o* is the median volume diameter in mm.
*N**w* =  intercept parameter ( mm-1mm-3)
- If μ is fixed. *N(D)* is controlled
- by *D**o* and *N**w*

- where

- where

**Notes:**
This slide give a short description of DSD model used in the DSD parameters estimation 

Normalized gamma model is used in this work and can be expressed in this form. There are 3 parameters in the distribution. However in this work we assumed one parameters fixed, which mu (shape parameter) and Do and Nw to be estimated. 

Procedure developed by Chandrasekar et al. (I2003) is used to estiamted Nw and Do.   The key of this procedure is making use of adjust alpha coefficient in TRMM-PR rain profiling algorithm  described in Iguci et al 2000)

I am not going to go through detail of the procedure. At the end Do and Nw can be expressed in this forms.  I want to note that the rain profiling using hybrid method allow us to adjust only one parameter, as a result, our estimated Nw will be assumed constant for along rain profile.

## Year 2000

## Strat.

- Conv.

**Hurricanes 2000**

- At 1 km. altitude

**RR-Do**

**RR-Nw**

## Strat.

- Conv.

**RR-Do at 2 km.**

**RR-Do at 3 km.**

**Hurricanes 2000**

## Strat.

- Conv.

**RR-Nw**

**Typhoons 2000**

- At 1 km. altitude

**RR-Do**

## Strat.

- Conv.

**RR-Do at 2 km.**

**Typhoons 2000**

**RR-Do at 3 km.**

## Strat.

- Conv.

**RR-Nw**

**Cyclones 2000**

- At 1 km. altitude

**RR-Do**

## Strat.

**Strat.**

**Conv.**

**RR-Do At 2 km.**

**RR-Do at 3 km.**

**Cyclones 2000**

## Year 2002

## Hurricane 2002

**RR-Nw**

**Hurricane 2002**

**RR-Do**

- At 1 km. altitude

- Strat.

- Conv.

## Hurricane 2002

**Hurricane 2002**

**Strat.**

**Conv.**

**RR-Do At 2 km.**

**RR-Do at 3 km.**

## Hurricane 2002 : Nw and Do at various latitudes

**                             ****at 2 km. altitude**

- RR-Nw

- RR-Do

## Strat.

- Conv.

**RR-Nw**

**Typhoon 2002**

- At 1 km. altitude

**RR-Do**

## Strat.

- Conv.

**Typhoon 2002**

**RR-Do At 2 km.**

**RR-Do at 3 km.**

## Typhoons 2002

**: Nw and Do at various latitude**
**  ****at 2 km. altitude**

- RR-Nw

- RR-Do

## Strat.

- Conv.

**RR-Nw**

**Cyclones 2002**

- At 1 km. altitude

**RR-Do**

## Strat.

- Conv.

- at 2 km. altitude

**Cyclones 2002**

- : RR-Do

- at 3 km. altitude

## Cyclones 2002

**: Nw and Do at various latitude**
**  ****at 2 km. altitude**

- RR-Nw

- RR-Do

## Distribution of Do and Nw of hurricanes for 

**Distribution of Do and Nw of hurricanes for **
**different rain rate value interval**

- Do

- Nw

- Default value for stratiform rain

- Default value for
- Convective rain

**Log10(Nw)**

## Vertical profile of reflectivity (VPR) 

- of precipitation and associated DSD study

## Vertical profile of reflectivity (VPR) classification technique

**: Self Organizing Map (SOM)**

-  Observing the vertical profile of reflectivity (VPR) of
-   precipitation is the key potential  of the  of TRMM-PR.
-  VPR is well-know for extensive spatial variation in global scale
-  It’s useful to classify VPR into a number characteristics profiles and then
-   global study can be done through such profiles.

**Self Organizing Map (SOM)**
**( ****Kohonen T., 1997)**
-  Unsupervised learning  neural network
-  A  non linear mapping of the data into
-   a two-dimensional map grid.

- The update rule for the prototype vectors

**The Gaussian neighborhood function**

## Classification of 100 profiles of hurricanes 

- Classification of 100 profiles of hurricanes

## Do, Nw and Rain Rate associated with profiles : Year 2003

**Do, Nw and Rain Rate associated with profiles : Year 2003**

## Profiles of hurricane, typhoon 

**Profiles of hurricane, typhoon **
**and cyclone that produce **
**high mean rainrate**

**Hurricane**

**Typhoon**

**Cyclones**

-  Hurricane : RRhigh = 48.8 mm/hr
-  Typhoon   : RRhigh = 47.72 mm/hr
-   Cyclone   : RRhigh = 38.41 mm/hr
- Do : between 1.3 – 1.5 mm.
- Nw : between 4.5 – 4.7

## Profiles of hurricane, typhoon and cyclone

**Profiles of hurricane, typhoon and cyclone**
** ****that produce large mean Do**

-  Hurricane : Dohigh = 1.81 mm
-                    : log10(Nw)     =  3.77
-  Typhoon   : Dohigh = 1.87 mm
-                    : log10(Nw)     =  3.87
-   Cyclone   : Dohigh = 2.08 mm
-                    : log10(Nw)     =  3.6

**Cyclones**

**Hurricane**

**Typhoon**

## Do and Nw map

- Hurricane Katrina case

## Hurricane Katrina observed by TRMM-PR : Aug 28-29, 2005

## Reflectivity and

**Reflectivity and**
**DSD map of **
**hurricane**
**Katrina**

- Reflectivity
-     map

- Do map

- Nw map

## Conclusion

-   RR-Do relation of tropical storms in year 2000 agree well with existing
-      model  for stratiform rain, whereas RR-Do for convective shows smaller value .
-   Year 2002 to 2003, and 2004 for intense rain rate, Do appears to become
-      relative small compared to those existing RR-Do models, while Nw appears
-      to be relatively large.
-   Do in stratiform and convective rain exhibit different trend change as
-      rainrate  become more intense
-   Do at higher altitude is found to be larger than that at lower altitude,
-      suggesting drop breakup  while falling.
-   Reflectivity profiles that produce heavy rain has found to have small Do
-      and large Nw, whereas very tall profiles is  to associate with large Do.

## Thank you 

## Back up slides

## 1) Analysis of TRMM-PR  observation ( Continue ....) 

- 1.2) Drop Size Distribution (DSD parameters)

- The drop-size-distribution (DSD) is
-  based on the normalized gamma model:

- μ is shape parameter.
*D**o* is the median volume diameter in mm.
*N**w* =  intercept parameter ( mm-1mm-3)
- If μ is fixed. *N(D)* is controlled
- by *D**o* and *N**w*

_***D***__***o***__** **__**and **__***N***__***w***__*** ***__**estimate using TRMM-PR observation**_

- Normalized by Nw and get new coefficient

- where

## Vertical profile type and Do Map

- Reflectivity  **( top view at 2 km. altitude)**

- Location of each
- vertical profile type
- in a hurricane cell

## Reflectivity viewed from top

- at altitude of 2 km.

- 6 vertical profile types

- Median volume diameter, Do

## Do, Nw and Rain Rate associated with profiles : Year 2002

**Do, Nw and Rain Rate associated with profiles : Year 2002**

## Bright band (BB)  structure 

**Bright band (BB)  structure**** **

-  **Typhoon**

**Cyclone**

**Hurricane**

** ****Hurricane : Bright band structures in year 2000 **
**                       ****are similar **
**                       **
** ****Typhoon : Bright band structures are similar for**
**                     ****all years**
** ****Cyclone : Bright band structures are fairly similar **
**                    ****for all years**

**Note: Bright band structure study in stratiform**
**           ****rain used bright band peak as the reference.**

## BB characteristics

_**BB characteristics**_

**Three characteristics of BB are studied.**
**Height of BB peak from sea level (a)**
**Reflectivity of BB peak (b)**
**BB thickness (c)**

- (a)

- (b)

- (c)

** ****Height of BB peak: H,T and C have similar distribution **
**   ****(while peaking at different heights ) for; but they have different **
**   ****distribution from Generic Oceanic Storms.**
** ****Reflectivity of BB peak: All storms have similar distribution**
** ****BB thickness : All have similar distribution. H has the thickest BB**.

## CDF of reflectivity of tropical storm over 3 years

**CDF of reflectivity of tropical storm over 3 years**

## Bright Band structure classification

## Reflectivity (dBZ)

## Reflectivity (dBZ)