Detailed comparison of NAAPS data to AERONET Sun photometer data

INTRO: These files contain graphical and statistical comparison of aerosol optical depth (AOD) measured by Sun photometers in the AERONET network to AOD values generated from the 3-D analysis of aerosol concentration produced by the Navy Aerosol Analysis and Prediction System. The specific emphasis of these graphs and statistics is to demonstrate the impact of the Navy Variational Data Asssimilation System (NAVDAS-AOD), which uses assimilated optical depth data from MODIS to adjust the initial conditions of the model before each forecast timestep. In their current configuration, these plots and statistics also permit quick evaluation of the smoke aerosol in NAAPS, which uses the Fire Locating and Monitoring of Burning Emissions (FLAMBE) fire monitoring system.

CONTENTS: from top to bottom, the information on each page is as follows:

I. AERONET site information: This includes the latitude and longitude of the site, as well as its name, corresponding to the official site name in the AERONET database.

II. Site data statistics: This includes the mean AOD measured by the sunphotometer during the period of comparison, the number of valid AERONET AOD values during the time period, and the mean 'eta', corresponding to the fraction of AOD in the fine mode, as estimated using the algorithm developed by Norm O'Neill at U. Sherbrooke (see references below).

III. Plot 1 (time series of fine-mode fraction). This shows the time series of the fraction of AOD in the fine mode, estimated from AERONET data using Norm O'Neill's algorithm (references below). The X-axis is time, and is matched to the two time series plots below.

IV. Plots 2&3 (AOD time series plots). The legend for these plots is as follows:
     - AOD from AERONET is plotted as black dots;
     - AOD from NAAPS is shown as solid gray bar;
     - AOD from the biomass burning tracer in NAAPS is shown as a solid red bar in front of the gray bar representing NAAPS total AOD from all species.
     The UPPER time series plot uses results from the NAAPS model run with no AOD data assimilated. The LOWER time series plot shows NAAPS results with data assimilation. Both plots show the T=0 analysis.

V. Plots 5-8 (AOD scatter plots). The legend for these plots is as follows:
     - AOD from the model and AERONET, paired in space and time, is shown as small 'x's.
     - The green line shows the ordinary least squares (OLS) regression of the AOD data.
     - The red line shows a tolerance of +/- (0.05 + (AOD(AERONET)*0.2)). This tolerance is used in statistics at the bottom of the page.
     - The gray line is the 1:1 line.
     Data for plots are as follows, from left to right:
     1) Y=NAAPS total AOD, X=AERONET total AOD. No Data Assimilation.
     2) Y=NAAPS total AOD, X=AERONET total AOD. with NAVDAS-AOD.
     3) Y=NAAPS smoke AOD, X=AERONET fine-mode AOD. No Data Assimilation.
     4) Y=NAAPS smoke AOD, X=AERONET fine-mode AOD. With NAVDAS-AOD.

V. Statistics (fixed-font text at bottom of page). Statistics given are as follows, from left to right:
     - N = number of AOD observations from AERONET;
     - Mean NAAPS AOD;
     - Fraction of NAAPS AOD > 0.2;
     - Fraction of NAAPS AOD > 1.0;
     - Mean AOD Bias (NAAPS – AERONET);
     - RMS error of NAAPS – AERONET;
     - Errors relative to tolerance of +/-(0.05 + (AOD(AERONET)*0.2)): Percent below, within, above;
     - Slope and intercept of OLS regression of AOD;
     - Regression coefficient r-squared.
     Data for statistics is as follows, from top to bottom:
     - (1-4) These use the same data as the scatter plots above;
     - (5-8) These use the same data as (1-4), but with the AOD values averaged weekly before calculation of statistics.


RESOURCES:

NRL Aerosol home page: http://www.nrlmry.navy.mil/aerosol_web/
FLAMBE home page: http://www.nrlmry.navy.mil/flambe/
AERONET home page: http://aeronet.gsfc.nasa.gov/

REFERENCES:

NAVDAS-AOD:
Zhang, J. L., Reid, J. S., Westphal, D. L., Baker, N., and Hyer, E. J.: A System for Operational Aerosol Optical Depth Data Assimilation over Global Oceans, Journal of Geophysical Research, 113, doi:10.1029/2007JD009065, 2008.

FLAMBE:
Reid, J. S., Hyer, E. J., Prins, E. M., Westphal, D. L., Zhang, J. L., Wang, J., Christopher, S. A., Curtis, C. A., Schmidt, C. C., Eleuterio, D. P., Richardson, K. A., and Hoffman, J. P.: Global Monitoring and Forecasting of Biomass-Burning Smoke: Description of and Lessons From the Fire Locating and Modeling of Burning Emissions (FLAMBE) Program, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2009, in press.

AERONET:
Holben, B. N., Eck, T. F., Slutsker, I., Tanre, D., Buis, J. P., Setzer, A., Vermote, E., Reagan, J. A., Kaufman, Y. J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET - A federated instrument network and data archive for aerosol characterization, Remote Sens. Environ., 66, 1-16, 1998.