# Presentation: 172068

## Takahisa Kobayashi 
 Kazuhiko Masuda  
Meteorological Research Institute Japan

-  Kazuhiko Masuda
- Meteorological Research Institute Japan

-  Retrieval of cloud-precipitation characteristics by a combined radar and visible/IR scanner technique

- We measured cloud – precipitation interaction using TRMM to improve our understanding of indirect effects of aerosols on climate

_**3**__**rd**__** TRMM Conf.**_

## Effects of aerosol on climate

_**/ **__**MRI **__**/**_

**1. Atmospheric aerosols **
** ****directly impact the radiation balance and climate**
**      “ **_**Direct effect of aerosols**_**”**
**2. Atmospheric aerosols also **
**  ****act as CCN and affect climate by modifying  **
**  ****cloud/precipitation properties**
**      “ **_**Indirect effect of aerosols**_**”**
**The indirect effect  is one of  the largest **
**sources of unknowns in the climate studies.  **
**We need  ****cloud/precipitation****  interaction studies.**

_**3**__**rd**__** TRMM Conf.**_

## Indirect effects of aerosols

_**/ **__**MRI **__**/**_

** ****Increases in aerosol concentration**
**   ****---> Increases in condensation nuclei**
**    ****--- >Decreases in cloud drop size**
**        ****--- > **_**Increases in Cloud albedo**_
**         ****“ ****First indirect effect”****    ****Many studies**
**        ****--- > **_**Suppression of precipitation**_** **
**          ****“ **_**Second indirect effect**_**”****   ****Few studies****!**_** **_**            **
_**What size of cloud drops-> suppression?**_

_**3rd TRMM Conf.**_

## Critical size :Dc

_**/ **__**MRI **__**/**_

- <r0>=9 um

- Pruppacher and Klett (1998)

- <r0>=13 um

**Rain formation models suggest that  there **
**     ****exists a  ****critical size**** of cloud drops below **
**     ****which precipitation hardly forms. **
**Dc is a **_**key**_** factor for 2****nd**** indirect effect . **** **

_**3**__**rd**__** TRMM Conf.**_

##  Objectives

_**/ **__**MRI **__**/**_

**Questions:**
** ****Does the critical size really exist in nature? **
** ****What is the value of the critical size?**
**     ****Observation?   Model :  14-20 um (models)    **

**To answer these, we measured cloud drop size for **
**    ****non-precipitating clouds (NPC)   and        **
**    ****precipitating clouds         (PRC)**
**using the TRMM satellite.**** **

**Dmax****npc**** < Dcritical <<Dmax****prc**

_**3**__**rd**__** TRMM Conf.**_

## TRMM Tropical Rainfall Measurement Mission

_**/ **__**MRI **__**/**_

**It measures both clouds and rain and is well suited to our objects.**
_**Rain rate near surface**_** :**
**  ****  ****2A25 data from **_**PR**_** (Precipitation Radar)**
**    ****resolution     :****Δ****Z=125m,****Δ****X=5km**
_**Cloud drop size (Effective radius)**_** :**
**    ****from **_**VIRS**_** **_**(**_**Visible and Infrared Scanner)   **
**    ****1B01 radiance cH1 (0.63****μ****m) , cH3 (3.8****μ****m)**
**    ****resolution    :   ****Δ****X=2.4km, swath=830km **

_**3**__**rd**__** TRMM Conf.**_

## Effective size of cloud drops: Re

_**/ **__**MRI **__**/**_

** ****   ****We derived the effective radius of clouds  **
**    ****droplets from radiances at 0.63 and 3.8 um.**
**             ****R       : radius**
**          ****N (r ) : drop size distribution**
**   **

_**3**__**rd**__** TRMM Conf.**_

## Theoretical diagram of reflection Retrieval of  Re 

_**/ **__**MRI **__**/**_

**Observation**

**Re=10 um**
**Opt.depth= 16**

_**3rd TRMM Conf.**_

**N(r ):Log-Normal**

##  Data

_**/ **__**MRI **__**/**_

**Date****:2002 12/5--15      2003  6/11—20**
**         ****daytime (10—16 LST)**
**We intend to analyze mrine water clouds.**
**  ****Following data were selected.**
**   ****1) 273K < brightness Temp. <290K**
**   ****2) BT(ch4: 10.8)-BT(ch5: 12.0) <1**** **
**  **

_**3**__**rd**__** TRMM Conf.**_

## TRMM orbit (daytime)

**PR 1 Granule : 256 MB   3.8GB/day **
**VIRS              :  97  MB   1.5 GB/day**

_**3**__**rd**__** TRMM Conf.**_

## Rain rate and Effective Radius

**Re**

**Rain rate**

**Large Re,  rain**

**Small Re, No rain**

_**3**__**rd**__** TRMM Conf.**_

## Scatter Plot of Rain and Re

- Surface Rain

- Effective Radius

_**3**__**rd**__** TRMM Conf.**_

## Sequential Plot of Re and rain rate

**Rain rate**

**Re**

_**3**__**rd**__** TRMM Conf.**_

## Re Jump 

- Rain rate

**Precipitating cloud**

**Non-precipitating cloud**

- Re Jump

-  June

_**3**__**rd**__** TRMM Conf.**_

##                Re Jump                  Dec.

-                Re Jump                  Dec.

**PR**C

**NPC**

_**3**__**rd**__** TRMM Conf.**_

**NPC**

**PRC**

## Frequency of Effective Radius h3:0605

**NPC**

**PRC**

_**3**__**rd**__** TRMM Conf.**_

## Brightness Temp.

_**3**__**rd**__** TRMM Conf.**_

##  Conclusions 

**1) We derived Re for NPC and PRC by **
**      ****combined use of the TRMM PR and VIRS.**
**2) Largest size was 20 um for NPC. It increased  **
**    ****30um for PRC. A sudden jump was observed at **
**    ****the boundary of NPC and PRC.  **
** ****3) The jump suggests that cloud drops of 20-30um    **
**      ****are short of life and grow to raindrops rapidly,   **
**      ****that is the critical size of cloud droplets.**
**4) **** ****TRMM is very useful for cloud-precipitation****  ****            ****studies****                                    **** ****Geophys. Res. Lett, 2007**** **

_**/ **__**MRI **__**/**_

_**3**__**rd**__** TRMM Conf.**_

##  Thank you for attention! 

_**3**__**rd**__** TRMM Conf.**_