+-----------------------------------+-----------------------------------+
| a\) Dec, Jan, Feb                 | b\) Mar, Apr, May                 |
| ![](media/image1.pct) = -1.7 W m  | ![](media/image3.pct) **=** -4.8  |
| ^--2^                             | W m ^--2^                         |
|                                   | ![](media/image4.                 |
| ![](media/image2.                 | pct){width="3.0506944444444444in" |
| pct){width="3.0506944444444444in" | height="1.3576388888888888in"}    |
| height="1.3576388888888888in"}    |                                   |
+-----------------------------------+-----------------------------------+
| c\) Jun, Jul, Aug                 | d\) Sep, Oct, Nov                 |
| ![](media/image5.pct) = -5.1 W m  | ![](media/image7.pct) **=** -2.3  |
| ^--2^                             | W m ^--2^                         |
|                                   |                                   |
| ![](media/image6.                 | ![](media/image8.pct)             |
| pct){width="3.0506944444444444in" |                                   |
| height="1.3576388888888888in"}    |                                   |
+-----------------------------------+-----------------------------------+
| e\) *ω*~.55~ = 0.9                | f\) *ω*~.55~ = 1.0                |
| ![](media/image9.pct) = -3.5 W m  | ![](media/image11.pct) = -4.8 W m |
| ^--2^                             | ^--2^                             |
|                                   |                                   |
| ![](media/image10.                | ![](media/image12.                |
| pct){width="3.0590277777777777in" | pct){width="3.0590277777777777in" |
| height="1.3597222222222223in"}    | height="1.3597222222222223in"}    |
+-----------------------------------+-----------------------------------+
| g\) *ω*~.55~ = 0.9                | h\) *ω*~.55~ = 1.0                |
| ![](media/image13.pct) = -0.8 W m | ![](media/image15.pct) = -1.1 W m |
| ^--2^                             | ^--2^                             |
|                                   |                                   |
| ![](media/image14.                | ![](media/image16.                |
| pct){width="3.0590277777777777in" | pct){width="3.0590277777777777in" |
| height="1.3597222222222223in"}    | height="1.3597222222222223in"}    |
+-----------------------------------+-----------------------------------+
| ![](media/image17                 |                                   |
| .pct){width="4.016666666666667in" |                                   |
| height="0.31666666666666665in"}   |                                   |
+-----------------------------------+-----------------------------------+

> **-10 -8 -6 -4 -2 0**

**Net Flux Change (W m ^--2^)**

**Figure 1**. Aerosol-induced change in net shortwave flux at tropopause
(λ \< 4 µm). Results were obtained by combining the AVHRR-derived
aerosol midvisible optical depths of Husar et al. (1997) with aerosol
intensive properties determined primarily in TARFOX. Values above each
frame are averages for the 25^o^-60^o^ N region, excluding African dust.
(a-d) seasonal average with single scattering albedo ω(550)=0.9. (e-f)
annual average (no clouds) for ω(550)=0.9 and ω(550)=1.0. (g-h) annual
average (ISCCP clouds). (Bergstrom and Russell, 1999)

![](media/image18.pct){width="5.833333333333333in"
height="4.402777777777778in"}

**Figure 2.** Sunphotometer channel wavelengths (vertical lines with
arrows) in relation to atmospheric spectra. The spectra of ln(1/T) were
calculated for the transmission T of the direct solar beam at sea level
using MODTRAN-3/Version 1.2 with a US Standard atmosphere, a
spring-summer tropospheric aerosol model, and the sun at the zenith.
Current center wavelengths of channel filters are 380.3, 448.3, 453.0,
499.4, 524.7, 605.4, 666.8, 711.8, 778.6, 864.4, 939.5,1018.7, 1059.0,
1557.5 nm for AATS-14 and 380.1, 450.7, 525.3, 863.9, 941.4, 1020.7 nm
for AATS-6. Filter full widths at half-maximum (FWHM) are 5 nm, except
for the 448, 453, and 1558 nm channels, which have FWHM 0.94, 2.17, and
30 nm, respectively.