# Presentation: 609856

## Fast Forward Radiative Transfer 
Modeling for Microwave Radiance Assimilation 

Albin J. Gasiewski
Alex G. Voronovich
Bob L. Weber
Dean F. Smith
Timothy L. Schneider
Jian-Wen Bao

NOAA Environmental Technology Laboratory

**Modeling for Microwave Radiance Assimilation**
- Albin J. Gasiewski
- Alex G. Voronovich
- Bob L. Weber
- Dean F. Smith
- Timothy L. Schneider
- Jian-Wen Bao
- NOAA Environmental Technology Laboratory

## NOAA/ETL RT Modeling Group

**Personnel**
- Dr. Al Gasiewski (~0.2 EFT) - PI*, JCSDA Tech Liaison
- Dr. Alex Voronovich (~0.1 EFT) - Algorithm Development
- Dr. Bob Weber (~0.7 EFT) - Code Development
- Dr. Dean Smith (~0.5 EFT) - Code Assessment
- Tim Schneider (~0.2 EFT) - RT Modeling Science
- Dr. Jian-Wen Bao (0.1 EFT) - NWP Modeling
- Dr. Gary Wick (~0.1 EFT) - Satellite Data Analysis
- Dr. Boba Stankov (~0.1 EFT) - RT Graphics
- Dr. Marian Klein (~0.1 EFT) - RT Modeling Science
-     Total: ~2.1 EFT contributing
- *Also, PI for NESDIS Geostationary Microwave Pathway Study

## All-Weather Microwave Assimilation

**   ****Potential capabilities include:**
- Extended thermodynamic information 	(water vapor and temperature fields) within the  forecast-sensitive and economically important cloud-covered regions
- Improved accuracy of cloud and radiation products
- Short-term prediction of mesoscale convection for warnings with high specificity
- Tracking of latent heat exchange within precipitation

## Fast Scattering-Based Jacobian Algorithm*

** ****Planar stratified atmosphere**
** ****Liebe MPM 87 & 93 gaseous absorption model**
** ****Polydispersive Mie solution for five phase of water: **
**  ***Cloud (liquid), Rain (liquid), Graupel (liquid + solid),*
*  **Snow (solid), Cloud Ice (solid)*
** ****Discrete-ordinate layer-adding solution**
** ****Incremental response to changes in bulk absorption**
**  ****and scattering coefficients and temperature**
** ****Efficiency compatible with satellite data streams**
** ****Applicable for arbitrary wavelengths**
** ****Henyey-Greenstein hydrometeor phase matrix, being**
**  ****extended to incorporate an exact Mie library**
** ****Interface to JCSDA CRTM developed**

- 	* Voronovich, A., A.J. Gasiewski, and B.L. Weber, "A Fast Multistream
-         Scattering-Based Jacobian for Microwave Radiance Assimilation,"
-         *IEEE Trans. Geosci. Remote Sensing*, August 2004.

## ETL DOTLRT Radiative Transfer Model (v2.0)

**Numerical Weather Prediction Model**

**CRTM Profile Setup Routine**

**DATA**

**Dielectric constant**
**     ****ε****(f,T, t****j****), ∂****ε****/∂T**

*DOTLRT v2.0*

**Exact Mie Library**

***Consists of two files:***
***LIBNAME.CAT***
***and***
***LIBNAME.LIB***

**Calculation of scattering**
**(phase) matrix ****S**** as well **
**as its derivatives  ****S****T ****, S****Λ**

***Calculates Mie***
*** ******solution and ***
***averages it over***
***azimuthal angles***
***and exponential***
***size distribution***
***for each***
***hydrometeor ***
***phase***

***Calculates ***
***brightness***
***temperatures***
*** ******T******B******V****** , T******B******H****** ***
***along with RT***
*** ******Jacobian***

**Level = 1**

***Layer = 1***

**OPTRAN**

## S

******S**

******a**

- TB

## S

******S**

******a**

- TB

## Practical Implications(Radiation Jacobian)

|  # Layers  |  # Streams | CPU Rate
(GHz) | Calculation                       Time (ms) |
| --- | --- | --- | --- |
|          60 |           8 | 1.8 |        4.2 |

_**Recourses:**_
- Further simplified treatment of non-scattering layers (acceleration factor ~ 2-3x)
- Parallel processing 2.8 GHz 100-nodes (acceleration ~ 200x)
- Statistical: ~10% scattering cloud cover (acceleration ~10x)
-                  => **~1 usec** per channel-profile (anticipated)
- e.g., NPOESS CMIS data rate: ~30 channels every ~12 msec
** **=> **~400 usec** per channel-profile

## DOTLRT Development Pathway

| Code Attribute                                                DOTLRT version > | v1.0 | v1.1 | v2.0 | v2.1 |
| --- | --- | --- | --- | --- |
| Atmospheric radiation and geophysical Jacobians; Mie spherical scatterer model | x | x | x | x |
| Five hydrometeor phases / exponential size distribution | x | x | x | x |
| Henyey Greenstein phase function | x | x |  |  |
| Fast Mie lookup library |  | x |  | x |
| Full Mie scattering phase function |  |  | x | x |
| Full Stokes Capability |  | * | * | * |
| Interface with CRTM | x |  |  | x |
| Distribution | Jan 2005 |  |  | Sep 2005 (est) |

*** Proposed**

## Precipitation Correlation Length

**- TRMM vs GCI, Active Months -**

**TRMM PR>0.1 mm/hr**

**GCI T****B,IR****<240K**

**TRMM PR>1 mm/hr**

- Land/water continuity vindicates GPROFS maritime classification scheme
- Short scale lengths over land, longer over water
- Short scale behavior within ITCZ and over "maritime" continent

## NWP Precipitation “Locking”

**NWP Precipitation “Locking”**

## NWP Precipitation “Locking” 

- To realize “locking” of an NWP model onto precipitation, observations are needed at time and space scales of order ~5-15 km and ~15 minutes.
- Locking is analogous to phase-locked loop in electrical engineering wherein linear phase differencing is achieved only when oscillator and signal remain within same phase cycle.
- Similarly, linear NWP model updates can be achieved provided that the cloud and precipitation state does not decorrelate between satellite observations.

## Sampling Requirements for NWP Precipitation Locking

-    The sampling requirements for all-weather microwave assimilation using near-term NWP models (especially regional models) are well satisfied by a large-aperture geosynchronous microwave sounder.

## GMSWG  Concept SummaryGEosynchronous Microwave (GEM) Sensor

** Geosynchronous Microwave Sounder *
*  **Working Group, Chair: D.H. Staelin (MIT)*

**Baseline system using 54, 118, 183, 380, and 424 GHz with ~2 m diameter Cassegrain antenna. **
**~16 km subsatellite resolution (~12 km using oversampling) above 2-5 km altitude at highest frequency channels.**
**The 380 and 424 GHz channels selected to map precipitation through most optically opaque clouds at sub-hourly intervals. (Gasiewski, 1992)**
**Temperature and humidity sounding channels penetrate clouds sufficiently to drive NWP models with hourly data.**
**Estimated 2005 costs: $36M non-recurring plus ~$34M/unit.**

## GeoSTAR Concept2-D Geostationary Sounder/Imager 

**Y-Array of ~300-600 receiver elements and tens of thousands of one-bit correlators in each of three bands: 50-56, 89, and 183 GHz**

**GeoSTAR spatial response pattern **
**for 298 elements with 2.8****l****spacing **
** ****~50 km spatial resolution **
** ****Full disk image every one hour**
** ****No moving parts**
** ****~2.5m maximum baseline**
** ****NASA/JPL concept**

## Summary

- FAST RT Jacobian development for multiphase precipitation including scattering (DOTLRT)  Focus is on microwave bands, but applicable to IR also.
- Extension to include full Mie library underway
- Extension to full Stokes vector proposed
- Precipitation erorr covariance model development underway
- Geostationary Microwave Sounder system studies and simulations underway
- All-weather microwave radiance assimilation observing system experiments - focus on AMSU using the WRF regional model.
- Minimal funds received in FY04; no funding received yet in FY05