# Presentation: 497205

## Measurements and Retrievals from a New 183-GHz Water Vapor Radiometer in the ArcticM.P. Cadeddu1, J.C. Liljegren1 and A. Pazmany21Argonne National Laboratory, Argonne, IL2Prosensing, Inc., Amherst, MA

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Overview of the instrument

Data analysis

Retrieval algorithm

Retrieval results

Conclusions

- Data analysis
- Retrieval algorithm
- Retrieval results
- Conclusions

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## SBIR Phase II prototype

Deployment in Barrow 4/14/2005

Successful data stream collection and processing

- Deployment in Barrow 4/14/2005
- Successful data stream collection and processing

- Instrument

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## 4 double side-band channels at 1, 3, 7, 14 GHz from 183.3 GHz

Bandwidth 0.4, 1.0, 1.4, 2.0 GHz

Measurement Rate: ~4/minute including calibration

- Bandwidth 0.4, 1.0, 1.4, 2.0 GHz
- Measurement Rate: ~4/minute including calibration

- GVR Design

- Instrument

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## One year of operation has been useful to:

Investigate RFI interference.

Identify hardware-related issues.

Check quality of calibration.

Assess data quality.

Based on the operations of the past year, the instrument will be sent back to Prosensing Inc. this summer for improvement of initial prototype.

- Investigate RFI interference.
- Identify hardware-related issues.
- Check quality of calibration.
- Assess data quality.
- Based on the operations of the past year, the instrument will be sent back to Prosensing Inc. this summer for improvement of initial prototype.

- Instrument

- Data

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Comparison of measured (lines) and modeled (squares) brightness temperatures in January. 

| Freq./GHz | Mean | SD |
| --- | --- | --- |
| 183.3 ± 1 | -3.81 | 2.03 |
| 183.3 ± 3 | -2.77 | 2.08 |
| 183.3 ±7 | 3.03 | 2.90 |
| 183.3 ± 14 | 1.49 | 3.87 |

- Comparison of measured (lines) and modeled (squares) brightness temperatures in January.

- TBGVR-TbmonoRTM mean and SD (clear sky; N=31)

- Data

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Clear-sky brightness temperature measured by the GVR (top) and MWR (bottom).

- Cloudy measurements

- Data

- Retrieval

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Gauss-Newton method: Find a maximum probability state by finding the zero of the gradient of the cost function J:

- Gauss-Newton method: Find a maximum probability state by finding the zero of the gradient of the cost function **J**:

- Retrieval

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## xa, Sa, E

**x**a, **S**a, **E**

- x0(1)=0.05
- x0(i)=RH from MWRP
- T(i) = T from MWRP
- y(j) from GVR

- Radiative transfer model
- MonoRTM

**y**n, K(i,j)     **x**n+1

- Check convergence

- no

- yes

- Retrieval

- Convergence criteria:
- xn+1(1) - xn(1) < 1
- xn+1(i) - xn(i) < 2    i=2,27

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Error in x = Smoothing error + Forward model error + Retrieval Noise.

**S****x**** = S****O****+S****N**
**S****N ****= S****x****-1****K****T****E****-1****KS****x**

- PWV (*p*) is computed from RH profile by using the MWRP-provided temperature profile.
- Total retrieval error covariance

- Retrieval

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Assuming Gaussian error pdf:

- Covariance of retrieved PWV (Sp):

- Estimated retrieval error:
- PWV ~ 0.1 mm
- LWP ~ 0.006 mm

- Retrieval

- Results

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## GVR and MWR retrievals of LWP (top) and PWV (middle) for two weeks in January.

- PWV measured by radiosonde and retrieved (N=47 cases).

- Results

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Difference between retrieved and measured PWV as a function of measured PWV.

- Less spread in GVR data LWP<3mm

- Results

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## Retrieved LWP distribution during clear sky (IRT224 K) in January 2006 (N=499).

- Results

- Lower SD during clear sky

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006

## CONCLUSIONS

**Instrument working for the past year. Several hardware/ RFI problems identified during trial period.**
**Satisfactory agreement with MonoRTM model.**
**Estimated PWV accuracy~0.1 mm (PWV<3mm). **
**Clear case LWP distribution: ********=0.004 mm, SD = 0.002 mm.**
- Data available from the Archives!

- Sixteenth ARM  Science Team Meeting, Albuquerque, NM, March 27-31, 2006