# Presentation: 888594

## NASA Ames Solar Spectral Flux Radiometer (SSFR)

- wavelength range:
- 	300 nm to 1700 nm
- spectral resolution ~
- 	8-12 nm
- simultaneous zenith
- 	and nadir viewing
- hemispheric FOV
- Accuracy: ~ 3%; precision: 0.5%
- Missions: FIRE/SHEBA, DOE ARM UAV (1999, 2000, 2002), PRIDE, SAFARI-2000, ACE-Asia, CRYSTAL-FACE, DOE Aerosol IOP

**Notes:**
Instrument specs; we measure flux/irradiance with hemispheric fov for radiation budget analysys. Narrow fov more appropriate for remote sensing.

## radiative transfer model

- Cloud:
- Mie theory (, g)
- ri, i

- extraterrestrial solar irradiance

- state variables
- P, T, RH

- surface spectral albedo

- tables of spectral irradiance

- SSFR

- measured spectral irradiance

- best fit

**Notes:**
First step: what if we reteive Re, tau from SSFR. Here is the model. Input is ext. sol. Irr., P,T, RH, sfc. Albedo; scattering properties from Ping Yang, same as for MAS/MODIS.
Calculate down/up spectral irradiance for clouds of varying size distribution (12) and tau (15); compare with SSFR 

## RT Model

- 300 - 1700 nm in 10 nm intervals
- k distribution; 16 g points per interval
- 38 layers
- instrument filter function (correlation in g space)
- Kurucz solar source function (correlation in g space)
- HITRAN with Giver corrections
- DISORT
- spectral surface reflection

## Cloud Retrievals: J-31

## Cloud Retrievals: P-3

## CRYSTAL-FACE Solar Radiation/Remote 								Sensing

- 1835 UTC

- 1901 UTC

**radiance -> flux**

**cloud/atmo properties -> energetics**

- 350 nm

- 1700 nm

- Albedo

- SSFR

- CRYSTAL-FACE Solar Radiation/Remote 								Sensing

**Notes:**
Motivation to compare with MAS (Platnick). MAS derives cloud properties; SSFR measure spectral irradiance, important for energetics. Can we reproduce irradiance fields from MAS retrievals. 

## 2002.07.09 flight 02948, track 6, scanlines 0-5780

**RGB:**
**1.61;0.66;1.87**

**Cloud top P(mb)**

**Optical Thickness**

**Effective Radius (μm)**

*Platnick and Wind, 2003*

**Notes:**
MAS retrievals for a case study on Jul. 9; t, eff. Radius. Although SSFR measures irradiance, we can define a footprint as the half power point, shown here; 90% power point is here so SSFR does integrate outside the MAS domain.

## 9 July 2002Reflectance: SSFR/MODEL Comparison

**Notes:**
Comparison of measured/modeled spectrum. Use 5 wavelengths in the retrieval routine to find the best fit; for the most part the entire spectrum matches very well. There greates residual is right in the stronget ice absorption band in this regions, at around 1500 nm. Does not really effect retrieval.

## 9 July 2002Reflectance: SSFR-MODEL Residuals 

**Notes:**
Residuals in r-tau space. Unique, well-defined minimum. About the magnitude of measurement uncertainty.
How do we compare with MAS? Very well.

## DOE ARM AIOP

**SGP **

**Notes:**
Another test of the measurements, methodology: look at water clouds

MODIS RGB composite image on 17 May 2003.  The SGP CART is at the trailing (western) edge the cloud system.

## SSFR/Model Comparison

**Notes:**
Upper panel: Comparison between SSFR measured albedo (solid, blue) and best-fit modeled cloud albedo (dashed, red). Lower panel: measurement-model residuals in re- space showing a unique, well defined minimum.

## ~19:05 UTC

**Twin Otter, FSSP data**

- ~5km

- re

- Nd

- LWC

- Time, s

| optical depth | re (m ) | LWP 
(g m-2) |
| --- | --- | --- |
| 21.3 | 6.2 | 98 |

**MODIS**

**Notes:**
Comparison between in situ (FFSP on Twin Otter, left panels) and surface and aircraft remote sensing (right panels). The Twin Otter was approximately 30 km from SGP at the time of penetration (1905 UTC; circled in surface remote sensors time series) and was directly over the site at 1930 UTC (circled in SSFR time series).

## Satellite Comparisons

- quantify 3-D effects by comparing *pdf’s* of re and  from SSFR, MODIS.
- 2-D cloud field from MODIS retrieved re, 
- 3-D RT to simulate spectral irradiance; agree with SSFR?
- 3-D *pdf’s* of LWC?
- Schmidt, S., 2004: *Influence of cloud inhomogeneities on solar radiation.** *