# Presentation: 910935

## CLOUD/AEROSOL/SO2 Working Group

**CLOUD/AEROSOL/SO****2**** Working Group**
**Steven T Massie**
**NCAR**
**AURA Science Team Meeting**
**Columbia, Maryland**
**October 27-30**

## Outline 

_**Outline**_

**Cloud Detection**
**Retrieval Improvements**
**Extinction Comparisons**
**	****Sulfate**
**	****Cirrus**
**Comparison to CLAES and CALIPSO data**
**Conclusions**

## Methodology

**Methodology**

**Clouds are detected outside of the retrieval**
**	****Look for cloud radiance perturbations**
**	****Assign cloud flags**
**	****	****0 (clear), 1(unknown), 2(cirrus layer),**
**	****	****3(PSC), 4(opaque)**
**	****Determine cloud top pressure after T,P retrieved**
**Issue: for O****3**** intrusions, cloud artifacts were**
**present in previous retrieval code**
**Now we use 2 HIRDLS channels to detect clouds**
**Note: gas retrieval assumes no cloud along the tangent**
**ray path**

## Methodology

**Methodology**

**a) Gas retrieval assumes **_**no cloud**_** along the tangent**
**ray path.**
**If clouds are present, then the retrieved gas (e.g. O****3****)**
**mixing ratio is too large.**
**b) The retrieval of the extinction coefficient (km****-1****) uses**
**the retrieved P,T profile and gas (O****3****,H****2****O etc) mixing**
**ratio profiles from climatology**
**In the presence of clouds, ****β****(clouds) > ****β****(gas)**

## HIRDLS Detector Array

**HIRDLS Detector Array**

**21 detectors in 3 (columns) x 7 (rows)**
**12 micron detector is in the middle column**
**O****3**** detectors are in the 1****st**** column**
**~ 17km separation between the columns **
**O****3**** cloud structure sometimes differs from**
**the 12 micron cloud structure**

## ~17 km Horizontal Variation in Cloud Structure

**Detector 12****	****	****	****	****Detector 6**

- 16 km
- Cloud top

- 17 km
- Cloud top

**~17 km Horizontal Variation in Cloud Structure**

**Diamond symbols denote average radiance curve**

## A

**A = average radiance curve**
**O = observed radiance curve**
**Since there are significant variations**
**in O****3**** along a line of latitude,**
**the differences between the**
**average radiance curves and**
**observations are larger than **
**those for detector 6 (which is**
**primarily driven by temperature).**
**For the O****3**** detector the average**
**radiance curve is not used. We just**
**use the observed radiance profile.**

**A**

**O**

## Extrapolate 

**P = predicted**
**radiance**
**O = observed**
**radiance**

**1**
**2**
**3**

**O**

**P**

**Extrapolate **
**using points **
**1,2,3 to **
**point P.**
**Compare to O**

**Diamond symbols denote **
**average radiance curve – they are not used in fitting.**

## Use the optically thin O3 detector 12 to determine

**Use the optically thin O****3**** detector 12 to determine**
**the cloud top altitude in detector 12.**
**Determine the detector 6  (12 μm) cloud top altitude**
**Find out which cloud top is higher – this becomes**
**the adopted cloud top that is assigned to detectors**
**1-21, except for detector 6.**
**Cloud top pressure is based on the higher cloud top.**

**New Algorithm**

## Retrieval Improvements

**Retrieval Improvements**
**Example of cirrus observation**

## X(i+1) = X(i)+ dx

**X(i+1) = X(i)+ dx**
**dx =  (S****x****a****-1**** +K****T****S****y****-1****K)****-1  ****{ K****T****S****y****-1**** [y-f(x(i))] – S****x****a****-1****(x(i)  - x****a****) }**
**Graph dx for each iteration i **
**One can then see how the solution converges**
**Note that x is the natural log of a retrieved variable**

**Standard Application**

## Solution blows

**Solution blows**
**up at the 1****st**
**iteration**

**Ouch !!**

## X(i+1) = X(i)+ ( F(i) dx)

**X(i+1) = X(i)+ ( F(i) dx)**
**dx =  (S****x****a****-1**** +K****T****S****y****-1****K)****-1  ****{ K****T****S****y****-1**** [y-f(x(i))] – S****x****a****-1****(x(i)  - x****a****) }**
**F(i) is a scalar, i is the iteration number**
**F(i) = 0.1 for iterations i=1,4**
**F(i) =1.0 for iterations i=5,6,7,..**
**This is done   only  for the aerosol-cloud  extinction solution**

**Modified application**

## Better

**Better**
**first step**

## Example of cirrus retrieval

**Example of cirrus retrieval**

**6         -5        -4        -3         -2      log****10**** (Extinction)**

**Cirrus Layer**
** ****is retrieved**

## 65 % at 100 hPa			85% at 100 hPa

- 65 % at 100 hPa			85% at 100 hPa

- Previous			New

## Mie calculations:

**Mie calculations:**
**2 Deshler sulfate size distributions **
**Tisdale H****2****SO****4**** indices of refraction (75% H2SO4)**
_**HALOE **__****_**	****	**_**Theory HALOE / HIRDLS(12 μm)**_
**1901****	****cm****-1****	****	****	****0.47,  0.47**
**2890****	****	****	****	****0.24,  0.24**
**4081****	****	****	****	****3 - 6**
**Compare HIRDLS to HALOE extinction at 1901 cm-1 **
**Multiply HALOE 1901 cm****-1**** extinction values by 0.47**
**Average data in latitude bins**

**Sulfate Extinction **

## HIRDLS (squares)   HALOE (diamonds)     v20419

**HIRDLS (squares)   HALOE (diamonds)**    ** v20419**

**Ratio of HIRDLS to HALOE extinction**
**June – July - August 2005, 30 – 50 hPa**

- 0 Latitude

- -40 Latitude

## 2

**Ratio**
**HIRDLS/HALOE**

**-50****	**** 0        50      Latitude**

**2**
**1**
**0**

**Ratio of HIRDLS to HALOE extinction **
**June - July - August 2005, 30 – 50 hPa**

## Comparison to CLAES Cirrus Extinction

**Comparison to CLAES Cirrus Extinction**

_**CLAES**_
**	****Extinction profiles archived at 11.9 μm**
**	****Vertical resolution is 2.5 km (HIRDLS is 1 km)**
**	****CLAES (1 year average May 1992 – May 1993)**
_**HIRDLS**_
**	****Extinction profiles archived at 12.1 μm ****	**
_**Compare zonal averages**_
**	****Select ****β**** > 9 10****-4**** km****-1**** for both instruments**
**	****This threshold for cloud detection was determined by**
**	****     ****Mergenthaler et al., JGR, 104, 22183-22194, 1999**

## Slide 21

## Slide 22

## Clouds (cirrus, PSCs) are indicated by:

**Clouds (cirrus, PSCs) are indicated by:**
**a) 12.1MicronCloudAerosolFlag (0,1,2,3,4)**
**b) Cloud Top Pressure (hPa)**
**c) 12.1MicronExtinction (km****-1**** units)**

**Cloud Products**

## Pressure range : 20 – 177 hPa

**Pressure range : 20 – 177 hPa**
**Extinction range : 10****-5**** to 0.01 km****-1**
**Precision range: 0 – 100 %**
**Use extinction data in a qualitative manner, i.e. data**
**can be used to indicate the geographical distributions**
**of clouds**

**Data Usage**

## Conclusions

**Conclusions**

**More clouds are being detected by the HIRDLS experiment**
**(helps with O****3**** intrusion studies)**
**More cloud extinction is being retrieved (85% at 100 hPa)**
**Extinction (****β****) comparisons: factor of 2 agreement, with**
**	****HIRDLS ****β**** being on the high side**
**CALIPSO and HIRDLS cirrus morphology agrees very well**